Search

Heat recovery in rooftop units can generate significant energy savings, leading to an improvement in the overall performance of the system. These systems are mainly based on heat recovery from the exhaust air and incorporate other elements to utilize its energy. In this paper, we model with Modelica and IMST-ART several recovery systems to simulate their operation integrated in a rooftop unit with a reversible heat pump operating in both cooling and heating mode. With the generated model, we are able to analyze how the system operates. We compare the performance of the rooftop unit with each of the modeled heat recovery systems with the Seasonal Energy Efficiency Ratio (SEER) and the Seasonal Coefficient of Performance (SCOP) calculated according to the standard EN 14825. In conclusion, the heat recovery system that presents the best performance is a combination of a rotary wheel heat exchanger together with thermodynamic heat recovery. Belén Llopis-Mengual acknowledges the Spanish “Ministerio de Universidades” through the “Formación de Profesorado Universitario” program ref. FPU 19/04012. This publication has been carried out in the framework of the project “DECARBONIZACIÓN DE EDIFICIOS E INDUSTRIAS CON SISTEMAS HÍBRIDOS DE BOMBA DE CALOR”, funded by the Spanish “Ministerio de Ciencia e Innovación (MCIIN)” with code number PID2020-115665RB-I00.

This paper presents experimental results on the study of the effects of ejector adiabatic absorber on heat and mass transfer of binary nanofluid with heat transfer additives (2-ethyl-1-hexanol and gum Arabic). In this case, H2O/lithium bromide-alumina nanofluid was suggested due to a growing interest in absorption heat transfer working fluid for solar energy application. An experimental setup — ejector test rig — was designed to study the absorption, heat, and mass transfer rate as a result of refrigerant vapour mass flow entrained by the ejector adiabatic absorber. The study was carried out at different solution mass flowrate (0.051 to 0.17 kg/s) with three prepared sample solutions, which include pure LiBr solution, LiBr-Alumina nanofluid without heat transfer additives, and LiBr-Alumina nanofluid with heat transfer additives. The absorption rate, mass transfer coefficient, heat transfer rate, and heat transfer coefficient for the three samples were reported. On the other hand, the percentage enhancements for all the parameters — at a suitable flow rate of 0.085 kg/s — due to the addition of alumina without and with heat transfer additives were recorded. The absorption rate enhancements were 25% and 96%, the enhancement rates of mass transfer coefficient recorded were 20% and 82%, the heat transfer rate enhancements were 85% and 183%, and the heat transfer coefficient enhancements obtained were 72% and 156% with addition of alumina nanoparticles only and alumina nanoparticles with heat transfer additives respectively. Material mass balance analysis suggests that mass inflow in the ejector equals to the mass outflow from the ejector, indicating a complete absorption of the entrained refrigerant vapour beyond which falling film absorption can occur due to concentration. This article also presents experimental evidence of the capability of ejector as strong adiabatic absorber, heat, and mass transfer component, which were earlier reported using numerical models.

This article presents an analysis of rotary heat exchangers (RHE) used as heat recovery units in building ventilation systems in cold climates. Usually, heat exchangers with the highest heat transfer efficiency are the preferable option for this purpose. However, such exchangers usually have the highest media pressure drop, thus requiring the highest amount of energy for media transportation. In this study, the problem is solved by analysing the lifecycle cost (LCC) of the RHE including both the recovered heat and the electricity consumed in the fans of the air handling unit (AHU). The purpose of the investigation was to determine the optimal set of geometrical characteristics such as the exchanger’s length, foil thickness, the height and width of the air channel. Two hundred and seventy different combinations were examined using analytical dependencies and ANSYS simulations. The results are compared with experimental data obtained earlier at the KOMFOVENT laboratory. The results show that the best overall energy efficiency is obtained in heat exchangers that do not offer the best heat recovery efficiency, and LCC differences in the same climatic and economic conditions can go as high as 31 %, mainly due to the geometrical parameters of the heat exchanger.

In the emergence of new technologies to harness renewable energy, industrial-scale storage of heated water in a geothermal system is a promising technique. A porous, permeable medium, bounded by a poorly thermally conductive/convective overburden and underburden, can be used for transient subsurface thermal storage. The reservoir in this concept forms a geothermal battery. As a very simplified scenario, consider a single well injecting and producing hot water diurnally or seasonally. The source of the hot water could be solar-heated water, for example, or possibly even water heated from the excess regional electricity supply. For that situation, this study investigates the influence of spatial permeability heterogeneity on heat recovery, and the distributions of temperature and pressure inside the reservoir. Four heterogeneous models are created from lognormal distributions of permeability by varying the standard deviations while keeping the mean absolute permeability at 100 mD. The injection pressure experienced while pumping into a candidate formation is affected by heterogeneity; higher bottom hole pressure is required to inject water into a more heterogeneous reservoir. The spatial distribution of temperature is less affected by permeability heterogeneity. In the simulations carried out, 91% of the heat is recovered after the 30th cycle of injection/production operation in all cases proving less impact of heterogeneity on heat recovery for fixed injection and production rates.

The residential sector is currently responsible for approximately 30% of the final energy consumption and 12% of direct CO2 emissions in Italy, mainly due to the heating and cooling of buildings and the use of domestic hot water. Such figures show a significant potential for reducing non-renewable primary energy utilization to comply with the decarbonization constraints of the European Union. In this context, the purpose of this work is to provide a quantitative assessment of the effect of a different number of actions (eight for energy savings, four for energy efficiency and two for the installation of renewable energy plants) that could be implemented at the national level to reduce the consumption of natural gas in the residential sector. Two typical residential buildings are dynamically simulated using Trnsys®, and the savings from energy, economic and CO2 emissions points of view are evaluated in the different climatic zones of Italy. The most effective action foresees the replacement of natural gas boilers and old air conditioners with modern heat pumps and air/air chillers as well as the installation of a controlled mechanical ventilation system with heat recovery. This solution allows for non-renewable primary energy savings of 58% and an economic savings on annual energy costs of 72%.

Metal hydride (MH) hydrogen storage needs an external heat source to release the stored hydrogen. To enhance the thermal performance of MHs, the incorporation of phase change materials (PCM) is a way to preserve reaction heat. This work proposes a new MH-PCM compact disk configuration (i.e., a truncated conical MH bed surrounded by a PCM ring). An optimization method is developed to find the optimal geometrical parameters of the MH truncated cone, which is then compared to a basic configuration (i.e., a cylindrical MH surrounded by a PCM ring). Moreover, a mathematical model is developed and used to optimize the heat transfer in a stack of MH-PCM disks. The optimum geometric parameters found (bottom radius of 0.2, top radius of 0.75 and tilt angle of 58.24) allow the truncated conical MH bed to reach a faster heat transfer rate and a large surface area of higher heat exchange. Compared to a cylindrical configuration, the optimized truncated cone shape enhances the heat transfer rate and the reaction rate in the MH bed by 37.68%.

In thermally modernised buildings, sharing of ventilation heat loss becomes more significant. In the case of the application of ventilation with heat recovery, especially during transitional periods, there arises a question of whether an air system makes it possible to maintain the required indoor air temperature without the necessity of using a basic hydronic heating system. This paper presents the application of a simple thermal network model of a building zone to simulate indoor air temperature in a single room of a multi-storey building with a mechanical ventilation system with heat recovery. Ventilation air was supposed to be the only heat source and its ability to maintain the required indoor air temperature was checked in simulations and then compared with measurements. The 5R1C thermal network model of a building zone was used for simulations. Comparison with measurements showed the Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) of indoor air calculation to be 2.37 °C and 2.45 °C, respectively. When including heat flux from the bottom storey through the floor, MAE = 1.28 °C and RMSE = 1.38 °C were obtained.

Most industrial processes generate raw heat. To enhance the efficiency of industrial operations, this raw heat is recovered. Thermoelectric generators (TEG), as solid state devices, provide an excellent application of heat recovery in the form of most manageable electrical power. This work presents a novel MPPT controller based on the Mud Ring Optimization algorithm for a centralized Thermoelectric Generator (TEG) under dynamic thermal gradients. The existing stochastic optimization algorithm for Maximum Power Point Tracking (MPPT) control in renewable energy systems exhibits several limitations that affect its performance in MPPT control. The convergence speed, local minima trap, hyper parameters’ sensitivity toward the population size, acceleration coefficients, and the stopping criterion all impact the convergence stability. In addition to these limitations, sensor noise sensitivity in measurement fluctuates the control system leading to reduced performance. Therefore, the careful design and implementation of the MRO algorithm is crucial to overcome these limitations and achieve a satisfactory performance in MPPT control. The results of this study contribute to developing more efficient MPPT control of TEG systems and implementing renewable energy technologies. The algorithm effectively tracks the maximum power point in dynamic thermal environments and increases the power output compared to conventional MPPT methods. The findings illustrate the efficacy of the proposed controller providing a higher power output (Avg. 99.95%) and faster response time (220 ms) under dynamic thermal conditions achieving 38–70% faster tracking of the GM in dynamic operating conditions.

The analysis of heat exchange processes during cooling of the heated surface of the process equipment is carried out on the basis of the equations contained in the ANSYS Fluent package. When modeling heat exchange processes, the following boundary conditions are adopted: the temperature of the heated surface; the coil heat exchanger is located at a distance from the heated surface of the process equipment. From these results, we can draw the following conclusions: the increase in the temperature of the heated surface leads to the increase of the heating zone of the refrigerant with high capacity and, hence, to increase heat capacity; increasing the refrigerant flow rate, the lower the temperature of the refrigerant at the exit, but increases the thermal capacity; increasing the pressure of the heated refrigerant increases the thermal; this design of the heat exchanger allows you to achieve the necessary power for the operation of the drive by: changing the flow rate of the refrigerant, the excess pressure of the refrigerant, the number of elbows, as well as by installing a heat-reflecting casing

The paper presents energy and exergy analysis of a typical dwelling ventilation system with heat recovery for Ukrainian climatic conditions using a quasi-steady state approach over 24-hour time-steps. Evaluation of such systems on the base of the first law of thermodynamics demonstrates that heat recovery is beneficial for the whole variety of operational modes. Such methodology identifies as a thermodynamic inefficiency only energy losses to the surroundings with the exhaust air. The exergy-based analysis can detect additional inefficiencies due to irreversibilities within the components of the system. As a result the exergetic investigations show that for the ventilation systems there are operating conditions for which heat recovery increases exergy of fuel expended to provide the ventilation air compared to cases without bringing any recovery of heat and additional power consumption to drive the air flow by the fans. For the specified system, in case of switching ventilation unit to the operation mode of lower values of spent fuel exergy it is possible to provide annual saving of the primary energy sources from 5 to 15%.

The aim of this paper is studied experimentally the effect of using oscillating heat pipe heat exchanger as a heat recovery device in the air conditioning system to enhance the dehumidification capability of the cooling coil. Water and Methanol and binary fluid of Water/Methanol used as working fluids with 50% filling ratio. The dehumidification capacity of cooling coil can be enhanced by using oscillating heat pipe heat exchanger by enhancement ratio 25%, 21%, and 17% for Methanol, Binary, and Water respectively. The maximum total energy saved can be reached at 1645 W, 1849 W, and 1932 W for Water, Binary, and Methanol respectively.

Absorption refrigeration technology was introduced to address some serious issues such as the energy crisis, increased fuel prices, and environmental problems associated with the conventional compression refrigeration systems. It has attracted an increasing deal of interest thanks to such advantages as utilization of low-grade heat sources and environment-friendly working fluid pairs. Nevertheless, this technology suffers from two major obstacles including the usually too large size of the cooling unit and the low coefficient of performance (COP), preventing the absorption systems from being commercially successful. Numerous research works have been done to develop strategies in order to improve the COP of the absorption systems, so as to make the absorption refrigeration technology more competitive with the conventional compression refrigeration systems. In this paper, it is intended to conduct a literature review on various technologies implemented to improve the COP of absorption refrigeration systems. Among effective and promising workarounds for increasing the COP of absorption refrigeration systems, this work refers to cycle design improvement, heat recovery method, development of new working pairs, adding sub-components, and improvement of operating conditions.

Endüstriyel ve tarımsal ürünler, doğal ve teknik yöntemler kullanılarak kurutulabilir. Kurutma maliyetini sıcak kurutma havasını elde etmek için harcanan enerji oluşturur. Bu çalışmada, kurutmanın enerji problemine çözüm üretmeye yönelik ısı borulu düzlemsel güneş kollektörlü ve ısı geri kazanımlı bir kurutma sistemi tasarlanmıştır. Karabük ili iklim şartlarında, sabit 1 m/s kurutma hızında, farklı ışınım değerlerinde, kuruma havası sıcaklığının değişimleri, ürün kütle kaybı ve kalitesi, ısı geri kazanımının sisteme katkısı deneysel olarak incelenmiş ve teorik analizleri yapılmıştır. Sistemde kapalı çevrimde içerisine ürün konulmadan yapılan deneyde sabit hava hızında ve ortalama 770 W/m2 ışınım değerinde kurutucu sıcaklığının dış hava sıcaklık değerinin yaklaşık olarak %49’luk bir artışla ortalama 14,63 °C üzerine çıktığı belirlenmiştir. Ürün ile kurutma deneyinde kivi meyvesi kullanılmıştır. Etüv fırınında kurutulan kivilerde yaş baza göre hesaplanan nem miktarı 0.83 g su/g yaş madde, kuru baza göre hesaplanan nem miktarı 4.94 g su/g kuru madde ve kuru madde miktarı %16,8 olarak belirlenmiştir. Kurutma işlemine, son üç ağırlık değerleri eşit çıkana kadar devam edilmiş ve nem değeri 0,03 g su/g kuru madde olana kadar kurutma gerçekleştirilmiştir. Ölçümler sonucunda ortalama 39.4 g değerine kadar kurumanın gerçekleştiği ve ürün ağırlığının %80 azaldığı belirlenmiştir. Sistemin genel verimi 4 Eylül saat 15:50’de 694,3 W/m2 ışınım değerinde maksimum %39, ısı borulu kollektörün ortalama verimi %24 ısı geri kazanım ünitesinin verimi %28’dir. Kurutma işleminde harcanan enerjinin %27’si ısı geri kazanım ünitesi, %73’ü de ısı borulu kollektör tarafından karşılanmıştır., Industrial and agricultural products can be dried using natural and technical methods. The energy spent to obtain the hot drying air constitutes the drying cost. In this study, a heat recovery drying system with heat pipe, planar solar collector and heat recovery is designed to solve the energy problem of drying. Changes in drying air temperature, product mass loss and quality, contribution of heat recovery to the system in Karabük province climatic conditions, constant 1 m/s drying rate, different irradiation values, were experimentally examined and theoretical analyzes were made. In the experiment, which was carried out in the closed cycle without putting the product inside the system, it was determined that the dryer temperature increased to an average of 14.63 °C with an increase of approximately 49%, at a constant air speed and an average irradiance value of 770 W/m2. Kiwi fruit was used in the drying experiment with the product. In the kiwis dried in the oven, the moisture content calculated according to the wet base was 0.83 g water/g wet matter, the moisture content calculated according to the dry basis was 4.94 g water/g dry matter and the dry matter amount was 16.8%. The drying process was maintained until the last three weight values became equal and drying was carried out until the final moisture value was 0.03 g water/g dry matter. As a result of the measurements, an average drying was determined as 39.4 g and the weight of the product decreased by 80%. The general efficiency of the system at 15:50 on September 4, at an irradiation value of 694.3 W/m2, is maximum 39%, the average efficiency of the heat pipe collector is 24%, and the efficiency of the heat recovery unit is 28%. 27% of the energy consumed in the drying process was met by the heat recovery unit and 73% by the heat pipe collector.

Energy efficiency is extremely significant for industrial processes and technologies. Rising energy prices, depleting fossil fuels, as well as tightening regulations that impose the need to reduce GHG emissions incentivize companies to look for energy-efficient solutions. This also applies to wastewater treatment plants, which, on the one hand, are consumers of very large amounts of energy, and on the other hand, have significant potential to retrieve waste energy in the form of heat accumulated in wastewater. The authors of this publication have recognized the benefits of managing this heat. However, they have also pointed out several problems and difficulties associated with this process. By means of measured data, this publication provides a comprehensive analysis of the heat that can be recovered from wastewater treatment plants. As a result of the analyses, the locations of sites for collecting heat from wastewater have been determined, and potential technologies for this purpose have been identified. Moreover, the impact of the proposed heat recovery technology on the process of biological wastewater treatment has also been analyzed. As a result of the research, the authors developed generalized guidelines for selecting an optimal heat recovery site and the technological system designed for this purpose.

Large amounts of waste heat during the cooling process of supermarket refrigeration systems (SRS) would be released. A heat recovery strategy potentially contributes to reducing the supermarket's heating costs related to buying heat from a district heating system (DHS). This paper explores the techno-economic feasibility of heat recovery for a real SRS integrated with a heat recovery unit (HRU) in terms of designing a dynamic heat recovery control (HRC) and business models. A cost-effective HRC is firstly developed for HRU to optimally manipulate the amount of heat recovered, thereby minimizing the real-time heat recovery cost. Furthermore, the business models of heat recovery under a long-term operation are proposed based on two transactional strategies between the SRS and DHS. A field test of the dynamic heat recovery for a remote SRS in Copenhagen Nordhavn area is conducted which demonstrates the proposed HRC algorithm can have a benefit of 0.49€ from a 3-h heat recovery operation. Moreover, the one-year operation of the SRS is also simulated which proves the developed two business models of heat recovery can achieve significant savings of 93% and 41% in energy costs.

The vast majority of the energy consumed for urban water services is used to heat tap water. Heat recovery from wastewater is consequently an area of rapidly growing concern, both in research and by commercial interest, promoting the path towards a circular economy. To facilitate a system-wide evaluation of heat recovery from wastewater, this paper compares two one-dimensional models (mechanistic and conceptual) that can describe wastewater temperature dynamics in sewer pipe systems. The models are applied to successfully predict downstream wastewater temperature for sewer stretches in two Swedish cities (Linköping and Malmö). The root mean squared errors for the mechanistic model (Linköping Dataset1 – 0.33 °C; Linköping Dataset2 – 0.28 °C; Malmö – 0.40 °C) and the conceptual model (Linköping Dataset1 – 0.32 °C; Linköping Dataset2 – 0.20 °C; Malmö – 0.44 °C) indicate that both models have similar predictive capabilities, encouraging the use of conceptual models to reduce data requirements and model calibration efforts. Both models are freely distributed and can be easily integrated with wastewater generation and treatment models to facilitate system-wide wastewater temperature dynamics analysis. HIGHLIGHTS Modelling tools to study energy recovery possibilities from wastewater are needed.; Mechanistic and conceptual models for temperature dynamics in sewer system are developed.; The models are applied for sewer pipes in two Swedish cities – Linköping and Malmö.; Both models offer similar prediction capabilities.; Further studies should include case studies outside Sweden and longer time periods.

Orientador: Arai Augusta Bernardez Pecora Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica Resumo: Neste trabalho foi realizado o estudo experimental da geração de entropia em um trocador de calor, o qual opera com leito fluidizado raso e recupera o calor contido na areia proveniente de um incinerador. Este trocador de calor é caracterizado por apresentar dois fluidos (ar e água) que ganham energia das partículas sólidas (areia). O objetivo foi analisar a influência dos fatores que afetam o desempenho do trocador de calor, visando determinar as condições operacionais ótimas do mesmo. Para isso foi realizado um planejamento experimental fatorial 23 com três pontos centrais, o qual permitiu a identificação dos fatores estatisticamente significativos sobre a variável de resposta. Os fatores estudados foram: a área de transferência de calor (A), analisada em 3 níveis diferentes (0,066 ; 0,1 04 e 0,130 m2); o número de chicanas (No) no casco (O, 3, e 6); e a razão entre as capacidades caloríficas do material sólido e da água (C) que variou também em 3 níveis (0,05; 0,075 e 0,1). A variável de resposta estudada foi o número de unidades de geração de entropia (Ns). Também foram analisadas as seguintes variáveis de resposta: eficiência exergética (N=:), eficiência energética (Ecne) e efetividade do trocador de calor (E). A aplicação do método de minimização de geração de entropia (EGM) e da análise exergética nos resultados obtidos experimentalmente, mostrou que a melhor configuração para o trocador de calor estudado ocorreu quando o diâmetro do tubo imerso no leito estava em seu valor médio, enquanto o número de chicanas e a razão entre as capacidades caloríficas estavam em seus valores máximos. A análise estatística dos resultados mostrou que o número de chicanas e a área de transferência de calor possuem influência significativa sobre o Ns. Verificou-se também que as melhores condições de operação (Ns mínimo e Nc:xe máximo) ocorreram quando a variação da exergia do sólido foi unifonnemente distribuída entre os fluxos de ar e de água. A análise de primeira lei refletida através da eficiência energética do sistema, foi um indicador interessante mas insuficiente para a análise do sistema. Quando esta análise é combinada com a análise exergética e o método de minimização de geração de entropia, os critérios de otimização e a adequada operação do sistema podem ser atingidos. A definição de efetividade do trocador de calor (E), usada tradicionalmente na avaliação deste tipo de equipamento, mostra-se adequada quando só a água é o produto útil, mas quando a intenção é o uso posterior dos fluxos de ar e de água esta definição pode levar a conclusões incompletas Abstract: This work presents an experimental study of the entropy generation in a fluidized bed heat exchanger used for heat recovering of contained sand particles discharged ftom an incinerator. This heat exchanger is characterized by presenting two fluids (air for fluidization and water flowing inside an immersed tube) that gains energy ITom solid particles (sand). The objective was to analyze the influence of the factors that affect the heat exchanger performance, being aimed to determine the best operational conditions for the equipment. A factorial experimental planning 23 with three central points was developed, in order to obtain the identification of the statistically significant factors about the reply variables. The studied factors were: heat transfer area (A), analyzed in 3 different levels (0.066; 0.104 and 0.130 m2); number ofbaflles immersed in the fluidized bed (Nc=0,3, and 6); and rate between the calorific capacities of solid material and water (C) that also varied in 3 levels (0.05; 0.075 and 0.1). The first studied reply variable was the number of units of entropy generation (Ns). Also the following reply variables had been analyzed: exergetic efficiency (Nexe), energy efficiency

Alginate lyase possesses wide application prospects for the degradation of brown algae and preparation of alginate oligosaccharides, and its degradation products display a variety of biological activities. Although many enzymes of this type have been reported, alginate lyases with unique properties are still relatively rare. In the present work, an alginate lyase abbreviated as Alyw203 has been cloned from Vibrio sp. W2 and expressed in food-grade Yarrowia lipolytica. The Alyw203 gene consists of an open reading frame (ORF) of 1,566 bp containing 521 amino acids, of which the first 17 amino acids are considered signal peptides, corresponding to secretory features. The peak activity of the current enzyme appears at 45°C with a molecular weight of approximately 57.0 kDa. Interestingly, Alyw203 exhibits unique heat recovery performance, returning above 90% of its initial activity in the subsequent incubation for 20 min at 10°C, which is conducive to the recovery of current enzymes at low-temperature conditions. Meanwhile, the highest activity is obtained under alkaline conditions of pH 10.0, showing outstanding pH stability. Additionally, as an alginate lyase independent of NaCl and resistant to metal ions, Alyw203 is highly active in various ionic environments. Moreover, the hydrolyzates of present enzymes are mainly concentrated in the oligosaccharides of DP1–DP2, displaying perfect product specificity. The alkali suitability, heat recovery performance, and high oligosaccharide yield of Alyw203 make it a potential candidate for industrial production of the monosaccharide and disaccharide.

Orientador: Antonio Carlos Bannwart Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica Resumo: Este estudo teve como objetivo a análise de processos industriais, os mais abrangentes possíveis, visando sua otimização do ponto de vista energético-econômico. Neste intento, buscou-se apresentar não apenas um único ponto de otimalidade, mas um conjunto de opções que permita a um decisor escolher a situação mais conveniente. No desenvolvimento deste estudo foram utilizados um conjunto de Métodos de Otimização, dentre os quais podem ser destacados a Metodologia Pinch de Recuperação de Energia, baseada em uma redistribuição de potenciais térmicos dentro do processo analisado, e os Métodos originários da Programação Matemática, em especial a Programação Linear. Analisou-se em profundidade o caso, relativo à lndúsrtria de refino de Petróleo, de uma etapa de Craqueamento Catalítico da Refinaria de Paulínia, da PETROBRÁS. Entretanto, o conjunto de procedimentos aplicados neste trabalho mostrou-se eficiente quando da análise de outros segmentos industriais, em particular das lndústrias Química, de Alimentos e Petroquímica, como apresentado no decorrer deste trabalho. Este estudo mostra que é perfeitamente possível fazer-se uma análise energética e uma avaliação econômica de sua implantação, de uma maneira muito satisfatória e rápida Abstract: This work deals with the industrial process analysis, includingvarious types and sizes, looking for their optimization fiom the economic and energetic point of view. Not only a single point of optimality was searched but a set of options which could permit to a decision maker to choose the best situation in each case. ln the development of this study were utilized a set of Optimization Methods, among which it can be mentioned the "Pinch Point Methodology" to heat recovery in networks, which is based in a redistribution of the thermal potentials of the process analyzed, and the methods originated tfom the Mathematics Programming, in special the Linear Programming. A deep analysiswas made on the case relative to an oil refinery.More precisely a part ofthe catalytic cracking of the Paulinia's Oil Refinery of PETROBRAS. The set of procedures applied in this work, it can be shown efficient when the analysis is applied to other industrial branches, in particular in the Chemistry, Food and Petrochemistry industries, as shown in throughout this work. This study shows that is possible to make an energetic analysis and an economic cost evaluation on the implementationof a process, in a fast and sactisfatory manner Doutorado Térmica e Fluídos Doutor em Engenharia Mecânica

To significantly decrease fossil carbon emissions from oil refineries, a combination of climate mitigation options will be necessary, with potential options including energy efficiency, carbon capture and storage/utilization, biomass integration and electrification. Since existing refinery processes as well as many of the potential new processes are characterized by large heating demands, but also offer large opportunities for process excess heat recovery, heat integration plays a major role for energy efficient refinery operation after the implementation of such measures. Consequently, the process heat recovery systems should not only be able to handle current operating conditions, but also allow for flexibility towards possible future developments. Evaluation of the flexibility of process heat recovery measures with both these perspectives enables a more accurate screening and selection of alternative process design options. This paper proposes a new approach for assessing the trade-off between total annual cost and potential operating flexibility for the heat exchanger network in short-as well as in long-term perspectives. The flexibility assessment is based on the evaluation of a flexibility ratio (similar to the conventional flexibility index) to determine the range in which operating conditions may vary while at the same time achieving feasible operation. The method is further based on identification of critical operating points to achieve pre-defined flexibility targets. This is followed by optimization of design properties (i.e., heat exchanger areas) such that feasible operation is ensured in the critical operating points and costs are minimized for representative operating conditions. The procedure is repeated for a range of different flexibility targets, resulting in a curve that shows the costs as a function of desired flexibility ratio. The approach is illustrated by an example representing a heat exchanger network retrofit at a large oil refinery. Finally, the paper illustrates a way to evaluate the cost penalty if the retrofit is optimized for one operating point but then operated under changed conditions. Consequently, the presented approach provides knowledge about cost and flexibility towards short-term variations considering also changes in operating conditions due to long-term development.

The energy efficiency of the drying section of paper machine is determined by the technology of heat flows arrangements in it. Paper drying is the most energy-consuming stage of paper production. The thermal mode of the drying section is provided by the steam condensate system which is a part of it. Analysis of exergy increments shows that almost all elements of the drying thermal process are characterized by low exergy efficiency. The main ways for increasing the degree of thermodynamic perfection of the processes occurring in the drying section of the paper machine are identified based on the exergy analysis. It is assumed that the deep internal heat recovery of the steam-air mixture for heating the source air will increase the exergy efficiency of the heat recovery plant and reduce heat removal to the environment. The effectiveness of development and implementation of a closed cycle use of steam-air mixture in the drying section was examined. Building a closed cycle provides that the air mainly has a process duty, that is, it is a transport agent for the transfer of moisture and heat along a closed circuit. The calculations show that the exergy efficiency of the processes in the recovery unit of the drying section of the paper machine of the existing production is 28.6% against 66.29% for the proposed method.

[EN] This paper compares and quantifies the energy, environmental and economic benefits of various control strategies recovering heat from a CO2 booster system in a supermarket for space heating with the purpose of understanding its potential for displacing natural gas fuelled boilers. A theoretical steady-state model that simulates the behaviour of the CO2 system is developed and validated against field measurements obtained from an existing refrigeration system in a food-retail building located in the United Kingdom. Five heat recovery strategies are analysed by modifying the mass flow and pressure level in the condenser. The model shows that a reduction of 48% in natural-gas consumption is feasible by the installation of a de-superheater and without applying any advanced operating strategy. However, the CO2 system can fully supply the entire space-heating requirements by adopting alternative control strategies, albeit by penalising the coefficient of performance (COP) of the compressor. Results show that the best energy strategy can reduce total consumption by 32%, while the best economic strategy can reduce costs by 6%. Findings from this work suggest that heat recovery systems can bring substantial benefits to improve the overall efficiency of energy-intensive buildings; nevertheless trade-offs need to be carefully considered and analysed on a site by site basis before embarking on such initiatives., This research was supported by funds provided via the Imperial-Sainsbury's Supermarkets Ltd. partnership. This work also was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) [grant number EP/P004709/1]. Emilio J. Sarabia gratefully acknowledges financial support from Universitat Politecnica de Valencia Fellowship. Data supporting this publication can be obtained on request from cep-lab@imperial.ac.uk

To achieve energy efficiency and lower carbon emissions, building envelopes have become tighter and more insulated. These buildings must have mechanical ventilation with high efficient heat recovery to provide adequate indoor air quality using low energy in cold climates, and requirements for heat recovery efficiency are expected to increase. Today’s aluminum heat wheels, one of the most commonly used heat recovery systems, may not be capable of providing such a high efficiency due to the presence of longitudinal heat conduction. This study focuses on developing highly efficient heat wheels by reducing the longitudinal heat conduction and enhancing heat transfer in different channel shapes and matrix materials for heat wheels. Previously often neglected, but in large heat wheels, the longitudinal heat conduction can result in a significant efficiency reduction effect. The highly efficient heat wheels are sought via parametric analysis, experimental verification, and optimization in this study. Reducing matrix wall thickness for high conductive materials and using low conductive materials can significantly improve temperature efficiency. The calculated and experimental results show that the developed plastic and stainless steel heat wheels can exhibit high temperature efficiency of over 90% with acceptable pressure drops. However, stainless steel's high cost and stiffness may limit its use in heat wheels. Wheels made of plastic with circular channels that are symmetrical could be a promising solution to meet the high temperature efficiency needs of the future. Additionally, the optimization shows that the temperature efficiency of plastic heat wheels is more sensitive to design parameters than aluminum or stainless-steel wheels.

The improvement of water and energy use is an important concern in the scope of improving the overall performance of industrial process plants. The investment in energy efficiency comprehended by the most recent sustainability policies may prove to be an effective response to the fall of energy intensity rates associated with the economic crisis brought by the COVID-19 pandemic. The improvement in water efficiency may also prove to be a potential approach due to its interdependencies to energy use, whose exploitation comprises part of the study of the water-energy nexus. Waste heat recovery and water reclamation practices have been exploited to improve water and energy efficiency. A specific method designated “Combined Water and Energy Integration” has been applied to water recycling as both an additional water source and a heat recovery source in a set of water-using processes. In scientific and industrial domains, there is still a need for integrated approaches of water-using and combustion-based processes for overall water and energy efficiency improvements in industrial plants. In this work, an innovative approach for a simultaneous improvement of water and energy use is proposed based on process integration and system retrofitting principles. This proposal is based on the delineation of two innovative concepts: Water and Energy Integration Systems (WEIS) and Water-Heat Nexus (WHN). A review on existing technologies for waste heat recovery, thermal energy storage and heat-driven wastewater treatment is performed, following a conceptualisation design.

Hydrogen extraction from nature is a time-consuming and energy-intensive procedure. Most of the current methods of extracting H2 are not eco-friendly, and the thermochemical copper-chlorine (Cu-Cl) cycle is a promising alternative since the ingredients are continuously recycled within the cycle without discharging pollutants into the atmosphere. In this study, the heat recovered from molten cuprous chloride (CuCl) salt produced in one of the reactors and quenched in a water bath is analyzed numerically to determine the amount of thermal energy that can be recovered and improve the efficiency of the Cu-Cl cycle. The quenching cell is simulated in an inert atmosphere since CuCl is highly reactive in the presence of oxygen. The interactions of various diameters of CuCl droplets within nitrogen (N2) are numerically modeled in COMSOL Multiphysics. Silver chloride (AgCl) is also used in this study to validate the phase-change process. It was discovered in this study that during the free fall, the outer surface of the molten droplets solidifies, and the phase change of droplets slowly propagates radially inwards, which slows down the energy dissipation. It was also determined that the average internal temperature of the droplet does not change substantially with droplet diameter or quenching height. Based on this study, the net energy recovered after quenching was calculated to be around 23 kJ during 1 kg of H2 production.

Residential dishwashers typically consume domestic hot water, heat it further with electric resistance heating elements, and drain the soiled heated water before each subsequent water fill. During the final rinse, the water is heated to a temperature of approximately 54.5–57.2°C (130–135°F) to heat the load and promote passive drying after the final drain event. In this work, the energy consumption, water consumption, and drying performance of a conventional dishwasher were measured under test conditions similar to U.S. energy efficiency test standards but with an unsoiled load. These measurements were considered baseline performance metrics. The dishwasher was then experimentally modified to recover heat from the drain water utilizing thermoelectric (TE) heat pump modules and a thermal storage component. The TEs were also used during the drying phase to improve the drying of the load. The novel dishwasher was operated in the laboratory under the same conditions as the baseline unit, and its energy consumption, water consumption, and drying performance were measured. The results demonstrated a 14.5% reduction in energy consumption, with the same amount of water consumption, and improved drying by 60% compared to the baseline.

В данной статье рассматривается технология рекуперации тепла из «серых» стоков, осуществля-емая непосредственно с применением рекуперативного теплообменного аппарата, проводится разра-ботка конструкции основных узлов рекуператора и математическое моделирование его работы., This article discusses the technology of heat recovery from “gray” wastewater, carried out directly with the use of a recuperative heat exchanger, the design of the main units of the recuperator and mathematical modeling of its operation are being developed.

Heat recovery systems based on thermoelectric micro-generators (µ-TEGs) can play a significant role in the development of wireless, energetically autonomous electronics. However, to date, the power density recovered for low temperature differences using µ-TEGs is limited to a few micro-watts or less, which is still insufficient to power a wide-range of wireless devices. To develop more efficient µ-TEGs, material, device and system requirements must be considered simultaneously. In this study, an innovative design of an in-plane µ-TEG integrating bismuth telluride forming sinusoidal-shaped trenches is reported. Using 3D numerical modelling, the influence of boundary conditions, parasitic effects (electrical and thermal contact resistances), and transport properties of thermoelectric materials on the output power of these µ-TEGs are investigated in detail for a small temperature difference of 5 K between the hot and cold sources. Compared to wavy-shaped trenches, this novel shape enables enhancing the output power. The results show that either the thermal conductivity or the Seebeck coefficient of the active n- and p-type semiconductors is the key parameter that should be minimized or maximized, depending on the magnitude of the parasitic effects.

The ZoneFlow™ reactor is an annular structured reactor that offers lower pressure drop and significantly better heat transfer than standard pellets used in Steam Methane Reforming. The annular ZoneFlow™ reactor is particularly suited for use in a bayonet configuration. The produced syngas then returns via the central tube, the so-called bayonet, allowing counter-current heat exchange between the return gas and the gas reacting in the ZoneFlow™ reactor. As such, the heat supplied by the furnace can be maximally used for the reactions and steam export can be reduced. To intensify the heat transfer between the gas in the bayonet and in the annulus, an insert is installed inside the bayonet, forming a second annulus that forces the gas to flow close to the bayonet wall at high velocity. In the present work, the pressure drop and heat transfer resulting from various bayonet configurations are experimentally measured at commercial scale reactor dimensions and air flow rates equivalent to commercial conditions. Correlations for the friction factors and the heat transfer coefficients are derived from the data. The correlations are then used to simulate a commercial scale ZoneFlow™-bayonet reactor and optimize the design.

There is a strongly growing interest for wastewater heat recovery (WWHR) in Sweden and elsewhere, but a lack of adequate tools to determine downstream impacts due to the associated temperature drop. The heat recovery potential and associated temperature drop after heat recovery on a building level is modelled for a case study in Linköping, Sweden. The maximum temperature drop reaches 4.2 °C, with an annual recovered heat of 0.65 kWh · person−1 · day−1. Wastewater temperature out from the heat exchanger was 18.0 °C in winter at the lowest. The drinking water source type can be an important factor when considering wastewater heat recovery.

[EN] In the present paper, a numerical investigation of a jet-ejector is carried out using a real gas model of R1234yf. The prototype under investigation works with specific operating conditions of a jet-ejector refrigeration system intended for waste heat recovery in an internal combustion engine (ICE). In the first instance, the geometry optimization involving nozzle exit diameter, mixing chamber diameter, and nozzle exit position (NXP) is performed. Once the optimum geometry has been obtained, the jet-ejector prototype is tested with different operating pressure ratios to determine its off-design performance. The flow structure in relevant cases has been examined with an emphasis on critical and subcritical modes. The flow phenomena occurring during expansion, entrainment, and mixing processes are discussed so performance degradation can be directly related to physical processes. The analysis has been completed fitting simulated points to critical and subcritical planar surfaces. The results in terms of goodness of fit are satisfactory so the jet-ejector performance in off-design operating conditions can be reflected through simple mathematic models. When the overall cycle is assessed by using previous computational fluid dynamics (CFD) maps, it is observed that the achievable cooling drops significantly when an ambient temperature of 31 degrees C is exceeded., The authors want to acknowledge the institution "Conselleria d'Educacio, Investigacio, Cultura i Esport de la Generalitat Valenciana" and its grant program "Subvenciones para la contratacion de personal investigador de caracter predoctoral" for doctoral studies (ACIF/2018/124).

[ES] Un porcentaje significativo de la energía se destina a la producción de Agua Caliente Sanitaria (ACS) en el sector comercial y residencial. Además, la mayor parte de la energía que contiene el agua se desperdicia en el ambiente tras su uso. Las bombas de calor han sido identificadas por su capacidad de producir ACS con una alta eficiencia y son una gran alternativa hacia la descarbonización de las ciudades. Además, son capaces de utilizar como fuente de calor, el calor contenido en el agua que actualmente se desperdicia. Sin embargo, la aplicación del uso de bombas de calor para ACS recuperando el calor de las aguas residuales presenta unas características diferentes a las usuales en bombas de calor. Por tanto, es necesario un análisis del problema más profundo y se require mayor investigación al respecto con el fin de lograr un desarrollo eficiente de la misma: 1. Un diseño de bomba de calor capaz de operar con alta eficiencia ante los grandes saltos de temperatura que tienen lugar en esta aplicación (ACS). 2. Un diseño de bomba de calor capaz de operar con alta eficiencia ante saltos de temperatura del fluido secundario variables (recuperación de calor). 3. La integración de esta bomba de calor en un sistema de ACS completo (estrategias de recuperación de calor, componentes, tamaño y estrategia de control). Normalmente, los ciclos transcríticos han sido considerados como una de las mejores soluciones para la producción de ACS (donde se tienen grandes saltos de temperatura en el agua, 10-60°C). Sin embargo, este tipo de ciclo presenta dos desventajas principales, la necesidad de altas presiones en la instalación y la dependencia de la eficiencia con el salto de temperatura del agua en el condensador. Sin embargo, los ciclos subcríticos han demostrado un gran potencial para saltos de temperatura del agua variables si se aplica un control del subenfriamiento adecuado. El objetivo de esta tesis es investigar la bomba de calor agua-agua más eficiente trabajando con un ciclo de refrigerante subcrítico para la producción de ACS utilizando como fuente de calor el calor disponible en las aguas residuales (a baja-media temperatura) para determinar el sistema más eficiente para este tipo de aplicación. El trabajo se divide en dos partes diferenciadas: ¿ Diseño de la bomba de calor El desarrollo de la bomba de calor es una continuación del trabajo realizado en la tesis de M. Pitarch [1]. En dicha tesis, se investigó el papel del subenfriamiento en una bomba de calor subcrítica para la apliación de ACS. Se desarrolló un prototipo de bomba de calor con el diseño de dos configuraciones distintas en función del modo en el que se realizaba el subenfriamiento. Los resultados permitieron concluir que este tipo de bombas de calor (subcríticas) eran capaces de operar con eficiencias similares a las de las bombas de calor basadas en ciclos transcríticos si se opera con un grado de subenfriamiento óptimo. Sin embargo, en ambas configuraciones se requiere un componente más que en las bombas de calor convencionales. En esta tesis, se ha realizado un estudio y análisis teórico de la bomba de calor. Se ha desarrollado e implementado una estrategia de control para el subenfriamiento y se ha construído el prototipo de bomba de calor propuesto en [1]. De todo este trabajo se ha obtenido el diseño de bomba de calor basada en ciclos subcríticos más interesante para este tipo de aplicaciones. ¿ Diseño e integración de la Bomba de Calor y el sistema de ACS La integración del prototipo seleccionado en un sistema para la producción de ACS con recuperación del calor de las aguas residuales ha sido analizada.El sistema más simple y eficiente necesario para este tipo de aplicaciones (producción de ACS con recuperación de calor de las aguas grises) se compone de un intercambiador de calor (recuperador), una bomba de calor con subenfriamiento optimizado y dos depósitos de almacenamiento., [CA] Un percentatge significatiu de l'energia es destina a la producció d'Aigua Calenta Sanitària (ACS) en el sector comercial i residencial. A més, la major part de l'energia que conté l'aigua es malgasta en l'ambient després del seu ús. Les bombes de calor han sigut identificades per la seua capacitat de produir ACS amb una alta eficiència i són una gran alternativa cap a la descarbonització de les ciutats. A més, són capaços d'utilitzar com a font de calor, el calor contingut en l'aigua que actualment es desaprofita. Contribuint així, a aconseguir un sector energètic més respectuós amb el Medi Ambient. No obstant això, l'aplicació de l'ús de bombes de calor per a ACS recuperant el calor de les aigües residuals presenta unes característiques diferents de les usuals en bombes de calor. Per tant, és necessari una anàlisi del problema més profund i es requereix una major investigació al respecte amb la finalitat d'aconseguir una alta eficiència: 1.Un disseny de bomba de calor capaç d'operar amb alta eficiència davant dels grans salts de temperatura presents en aquesta aplicació (ACS). 2.Un disseny de bomba de calor capaç d'operar amb alta eficiència davant de salts de temperatura del fluid secundari variables (recuperació de calor). 3.La integració d'aquesta bomba de calor en un sistema d'ACS complet (estratègies de recuperació de calor, components, grandària i estratègia de control). Normalment, els cicles transcrítics han sigut considerats com una de les millors solucions per a la producció d'ACS (on es tenen grans salts de temperatura en l'aigua, 10-60°C). No obstant això, aquest tipus de cicle presenta dos desavantatges principals, la necessitat d'altes pressions en la instal·lació i la dependència de l'eficiència amb el salt de temperatura de l'aigua en el condensador i evaporador. L'objectiu d'aquesta tesi és investigar la bomba de calor aigua-aigua més eficient treballant amb un cicle de refrigerant subcrític per a la producció d'ACS utilitzant com a font de calor el calor disponible en les aigües residuals (a baixa-mitja temperatura) per a determinar el sistema més eficient en aquest tipus d'aplicació. El treball es dividix en: ¿ Disseny de la bomba de calor El desenvolupament de la bomba de calor és una continuació del treball realitzat en la tesi de M. Pitarch [1]. En aquella tesi, es va investigar el paper del subrefredament en una bomba de calor subcrítica per a l'apliació d'ACS. Es va desenvolupar un prototip de bomba de calor amb el disseny de dues configuracions distintes en funció de la manera en què es realitzava el subrefredament. Els resultats van permetre concloure que aquests tipus de bombes de calor (subcrítiques) eren capaços d'operar amb eficiències semblants a les de les bombes de calor basades en cicles transcrítics si s'opera amb un grau de subrefredament òptim. No obstant això, en ambdues configuracions es requereix un component més que en les bombes de calor convencionals. En la present tesi, es va realitzar un estudi i anàlisi teòric de la bomba de calor. Es va desenvolupar i implementar una estratègia de control per al subrefredament i es va construir el prototip de bomba de calor proposat en [1]. De tot aquest treball s'ha obtingut el disseny de bomba de calor basada en cicles subcrítics més interessant per aquest tipus d'aplicacions. ¿Disseny i integració de la Bomba de Calor i el sistema d'ACS La integració del prototip seleccionat en un sistema per a la producció d'ACS amb recuperació de el calor de el calor de les aigües residuals ha sigut analitzada.El sistema més simple i eficient necessari per a aquest tipus d'aplicacions (producció d'ACS amb recuperació de calor provinent d'aigües grisas) està compost per un bescanviador de calor (recuperador), una bomba subrefredada i dos depòsits d'emmagatzemament., [EN] A significant percentage of energy is destined to produce Domestic Hot Water (DHW) within the building sector. Furthermore, most of that energy contained in the water is wasted to the ambient after its use. Heat pumps have been clearly identified as an efficient technology for DHW production, and as a main vector towards future de-carbonization of cities. In addition, they could use the heat from the wastewater as a heat source. Thus, contributing in two ways towards a more environmentally friendly energetic sector. However, the use of heat pumps for DHW recovering heat from wastewater faces several challenges that require further analysis and development: 1. A heat pump design capable to operate with high performance when variable secondary temperature lifts at the heat sink take place. 2. A heat pump design capable to operate with high performance when variable secondary temperature lifts at the heat source take place. 3. The integration of the heat pump within a system (heat recovery strategies, components, sizing, operation strategy). Usually, transcritical cycles have been considered the most suitable cycle for DHW production (high temperature lifts of the heat sink, 10-60°C). However, this cycle involves several drawbacks as for instance the requirement of high pressures in the installation or a significant reduction of the performance with the increase of water inlet temperature at the condenser. Instead, subcritical cycles have demonstrated great potential for DHW applications if a proper control of subcooling is performed. The objective of this thesis is to investigate the most efficient water-to-water heat pump working with a subcritical cycle for DHW production using as a heat source wasted heat at medium-low temperature and to determine the most efficient system based on heat pumps for this application. The work is divided in two differentiated parts: ¿ Heat pump concept This development is a continuation from the PhD work of M. Pitarch [1]. In that PhD work, the role of the subcooling in the performance of a subcritical heat pump for DHW applications was investigated. Two different configurations of a heat pump prototype were designed based on the way subcooling was made. The results showed that a subcooling optimized subcritical heat pump was able to provide comparable performance than present HPs employing transcritical cycles. However, both configurations require one more component than usual heat pumps. Thus, a new prototype based only on the typical components (compressor, condenser, expansion valve and evaporator) was proposed as future work. In this thesis, a theoretic analysis of the heat pump was done. A subcooling control methodology was developed and tested. The proposed prototype in [1] has been built and characterized. From all the results, the most convenient heat pump design was obtained. ¿ Integral Heat pump-DHW system The integration of the most convenient heat pump prototype within a system for the DHW production based on heat recovery from wastewater has been analyzed. The research has included the development of a model of the entire system in Trnsys and the optimization of the main components of the system: their sizing and their operation with the objective of reaching the maximum global efficiency of the complete system. Due to the complexity of the problem, the analysis was performed in three main steps: first, a study of the direct heat exchange,second, an study focusing on the condenser side, that is, the consideration of an infinite heat source (large availability of sewage water for instance) and third, the focus was done on the evaporator side. That is, the optimization of the complete system in which a finite heat source is considered (grey waters collected from the building for instance). The simplest and most efficient system required in DHW production and heat recuperation from wastewater has been determined., Esta tesis se enmarca dentro del proyecto “APROVECHAMIENTO DEL CALOR RESIDUAL A BAJA TEMPERATURA MEDIANTE BOMBAS DE CALOR PARA LA PRODUCCION DE AGUA CALIENTE” a través de una beca FPI del Ministerio de Economía y Competitividad.

Resumen. El presente proyecto parte del estudio y análisis de una central de cogeneración perteneciente a una instalación industrial, la cual demanda una cantidad significativa de energía térmica y eléctrica para la fabricación de un producto, posteriormente vendido a nivel internacional. La planta de cogeneración se compone de un generador de vapor de super – presión que emplea carbón como combustible principal, y abastece un turboalternador de contrapresión con extracción, del cual se obtiene energía eléctrica y vapor sobresaturado, empleados en procesos de fabricación. Por otra parte, cuenta con instalaciones de producción de vapor auxiliares neutras en emisiones, cuyas variables se han tenido en cuenta para el estudio de forma secundaria. El proyecto comienza con una exposición de la normativa y fundamentos teóricos, seguida de un análisis y presentación de las instalaciones existentes desde un punto de vista analítico, detallando determinados aspectos técnicos a modo didáctico. A partir de los datos conocidos y un cálculo previo orientativo, se han planteado una serie de modelos termodinámicos de ciclo combinado, sustituyendo parte de las instalaciones de la planta existente, llevados a cabo mediante el software ThermoFlex, junto a la extensión GT Pro, y obteniendo unos resultados próximos a los de una planta real. El modelo termodinámico escogido se compone de las redes de consumo de vapor de la fábrica, junto al turboalternador principal, sustituyendo las instalaciones de generación de vapor por una instalación compuesta por una turbina de gas y una caldera de recuperación de gases, produciendo vapor sobrecalentado a tres niveles distintos de presión, y energía eléctrica para el autoconsumo y venta a red eléctrica. De forma complementaria, se ha realizado una breve descripción de las disposiciones constructivas genéricas de los componentes de la instalación propuesta. El proyecto se ha planteado con el objetivo de lograr una reducción de emisiones en el proceso productivo, y un ahorro de energía primaria “AEP” derivado de la producción de energía eléctrica adicional correspondiente a la instalación tipo. Abstract. This project starts from the study and analysis of a cogeneration power plant of an industrial facility, which requires a significant amount of thermal and electrical energy to manufacture a product, subsequently sold internationally. The cogeneration plant is made up of a super-pressure steam generator that uses coal as its main fuel, and supplies a back pressure turbocharger with extraction, from which electrical energy and supersaturated steam are obtained, used in manufacturing processes. On the other hand, it has emission-neutral auxiliary steam production facilities, whose variables have been considered for the study in a secondary way. The project begins with an exposition of the regulations and theoretical foundations, followed by an analysis and presentation of the existing facilities from an analytical point of view, detailing certain technical aspects in a didactic way. Based on the known data and a preliminary calculation, a series of combined cycle thermodynamic models have been proposed, replacing part of the existing plant installations, carried out using the ThermoFlex software, together with the GT Pro extension, and obtaining results close to those of a real plant. The thermodynamic model chosen is made up of the factory's steam consumption facilities, together with the main turbo-alternator, replacing the steam generation boiler with an installation consisting of a gas turbine and a heat recovery steam generator, producing superheated steam at three different levels of pressure, and electricity for self-consumption and sale to the electricity grid. In addition, a brief description has been made of the generic constructive provisions of the components of the proposed installation. The project has been proposed with the objective of reducing emissions in the production process, and a primary energy saving “PES” due to the production of additional electrical energy corresponding to the type of installation Grado en Ingeniería Marítima

International Transaction Journal of Engineering, Management, & Applied Sciences & Technologies, 11, 13, 11A13E: 1-6

Producción Científica, Hospitals are highly energy demanding buildings, where simple actuations can involve large savings. However, energy efficiency actions must comply with the high safety standards. Operating rooms demand continuous ventilation despite the short activity periods. Setback during non-occupation of the operating rooms can reduce ventilation loads but must not hinder indoor overpressure to avoid infiltrations. Besides, it prevents any existing heat recovery system from operation. This work evaluates setback ventilation in operating rooms at a case study in Spain, from two approaches: its effect on indoor overpressure and its preference to an existing coil heat recovery (runaround) loop. It bases on monitored data of two operating rooms under setback and normal ventilation with operation of the heat recovery system. Seven tests are performed throughout the year, whose comparison to estimated results enables extrapolation to yearly operation. Results show that indoor overpressure maintain at 15 Pa under setback, thus meeting current and coming standards. Setback turned to be always preferable to hear recovery under cooling needs. Estimated heating and electric yearly supply energy savings reach 29 MWht and 262 MWhe, the latter accounting for 2% of the total electric energy consumption of the hospital during 2019., Junta de Castilla y León (grant EREN_2019_L2_UVA)

With the growing share of ventilation heat loads, the heat recovery over the mechanical ventilation systems appears as one of the key solutions to reduce heat loss and generate energy savings. Finland's long-term renovation strategy aims for a highly energy-efficient and almost carbon-free building stock by 2050. One of the greatest potentials for energy savings relates to those built between the 1960s and 1980s where no heat recovery exists. This study addresses the wasted heat potential of apartment buildings in the Kymenlaakso region in Finland and how EAHPs can utilize it. The wasted heat potential was mapped by selecting buildings of different ages in Kotka from the 1950s to 2010 and for which the thermal energy balance was determined. The apartment buildings with mechanical exhaust ventilation in Kymenlaakso were surveyed. If all the mapped exhaust air waste energy could be utilized by EAHPs, it could produce the thermal energy combined from different decades up to 18.7 GWh/a in Kotka and 36.8 GWh/a in Kouvola. The calculated annual reduction in CO2 emissions might be about 590 and 944 tCO2 in Kotka and Kouvola, respectively. The calculated payback periods varied from 7 to 13 years for the selected buildings.

A computational network heat transfer model was utilised to model the potential of heat energy recovery at multiple locations from a city scale combined sewer network. The uniqueness of this network model lies in its whole system validation and implementation for seasonal scenarios in a large sewer network. The network model was developed, on the basis of a previous single pipe heat transfer model, to make it suitable for application in large sewer networks and its performance was validated in this study by predicting the wastewater temperature variation across the network. Since heat energy recovery in sewers may impact negatively on wastewater treatment processes, the viability of large scale heat recovery was assessed by examining the distribution of the wastewater temperatures throughout a 3000 pipe network, serving a population equivalent of 79500, and at the wastewater treatment plant inlet. Three scenarios; winter, spring and summer were modelled to reflect seasonal variations. The model was run on an hourly basis during dry weather. The modelling results indicated that potential heat energy recovery of around 116, 160 & 207 MWh/day may be obtained in January, March and May respectively, without causing wastewater temperature either in the network or at the inlet of the wastewater treatment plant to reach a level that was unacceptable to the water utility.

Dual or multisource heat pumps were conceived to obviate to the defects of a single source, outside air or ground or solar radiation. Many studies simulated the possible behavior of combination of sources, but only few experimental results based on long term surveys on operating buildings are available in literature. A long term survey on a multisource heat pump system for the heating of a school building located in northern Italy gives the possibility of an evaluation based on real data. The main design features of the building incorporate a well insulated envelope, and a space heating and ventilation system driven by an innovative multisource heat pumps system. The latter incorporates outdoor air, ground, solar radiation, and heat recovery as heat sources, so enhancing the performance in terms of heating capacity and overall efficiency. The surveyed period concerns the last five heating seasons (2012–2017) allowing an assessment of the energy performance of the system based on real data monitored. The analysis permitted to identify incorrect settings, bad operation of the plant and heat pumps underutilization. The heating service was all the same assured, and the natural gas demand, almost steady if not in slight decrease, did not worry the management. Only the availability of data records and a careful analysis allowed to identify the bad working of the plant and the failure to achieve potential energy savings. The main novelty of this work is the highlighting of the paramount importance of monitoring and carefully analyzing recorded data as a guide to the plant management to keep correct operations, particularly when the plant integrates many different technologies even in the long term.

The increasing penetration of intermittent and aleatory RES such as photovoltaics and wind power poses new challenges in terms of grid stabilization. Surplus electric energy needs to be stored, if not curtailed. From this point of view, chemical storage can pave the way for a long-term shift between demand and production, together with sector interconnection. Hydrogen as an energy vector has been deeply studied but it has difficulties in asserting itself due to its low energy density at environmental conditions and lack of infrastructure. In previous papers, an innovative plant for the conversion of biomass and fluctuating electric power into substitute natural gas and stable electricity has been designed and analysed in terms of its overall performances. The adoption of an electrolyser for hydrogen production allows to use part of the oxygen for the biomass gasification and the syngas oxy-combustion. The resulting combustion products have high carbon dioxide concentration, which avoids energy consuming separation equipment. This paper analyses in detail the plant performances in terms of energetic and exergetic efficiencies, components by components. The plant is simulated with the commercial software AspenONE® V9. Losses allocation and optimum operating conditions are identified. The proposed heat recovery strategies allow consistent energy savings, making this plant competitive with other energy storage conversion devices in terms of energy efficiency.

© 2018 Elsevier B.V. As one of the latest emerging HVAC technologies, the Variable Refrigerant Flow (VRF) system with heat recovery (HR) configurations has obtained extensive attention from both the academia and industry. Compared with the conventional VRF systems with heat pump (HP) configurations, VRF-HR is capable of recovering heat from cooling zones to heating zones and providing simultaneous cooling and heating operations. This can further lead to substantial energy saving potential and more flexible zonal control. In this paper, a novel model is developed to simulate the energy performance of VRF-HR systems. It adheres to a more physics-based development with the ability to simulate the refrigerant loop performance and consider the dynamics of more operational parameters, which is essential for representing more advanced control logics. Another key feature of the model is the introduction of component-level curves for indoor units and outdoor units instead of overall performance curves for the entire system, and thus it requires much fewer user-specified performance curves as model inputs. The validation study shows good agreements between the simulated energy use from the new VRF-HR model and the laboratory measurement data across all operational modes at sub-hourly time steps. The model has been adopted in the official release of the EnergyPlus simulation program since Version 8.6, which enables more accurate and robust assessments of VRF-HR systems to support their applications in energy retrofit of existing buildings or design of zero-net-energy buildings.

The most significant factors of indoor air quality – besides temperature and humidity – are the concentrations of carbon-dioxide (CO2) and radon (222Rn). Radon seepage is caused by and affected by the materials used in walls and floors, the quality of insulation, cracks and even the amount of pipes running through the walls. The amount of CO2 is predominantly affected by the biological processes of the inhabitants, and possibly by potentially faulty HVAC systems. The energy efficiency related upgrades to family homes, which often only extend to window replacements and better insulation have a significant effect and could potentially increase concentrations of both radon and CO2 which has a significant effect on the well-being of the inhabitants. Our tests conducted in Hungary have proven that by using automated heat recovery ventilation (HRV) both energy efficient operation and low concentrations of radon and CO2 are achievable. Our results prove the significance and prevalence of the issue of higher concentrations of these pollutants, and offer a viable solution.

Styrene is a valuable commodity for polymer industries. The main route for producing styrene by dehydrogenation of ethylbenzene consumes a substantial amount of energy because of the use of high-temperature steam. In this work, the process energy requirements and recovery are studied using Exergy analysis and Heat Integration (HI) based on Pinch design method. The amount of steam plays a key role in the trade-off between Styrene yield and energy savings. Therefore, optimizing the operating conditions for energy reduction is infeasible. Heat integration indicated an insignificant reduction in the net energy demand and exergy losses, but 24% and 34% saving in external heating and cooling duties, respectively. When the required steam is generated by recovering the heat of the hot reactor effluent, a considerable saving in the net energy demand, as well as the heating and cooling utilities, can be achieved. Moreover, around 68% reduction in the exergy destruction is observed.

There are currently trends in the world to transfer and adapt traditional solutions to contemporary needs. This applies, inter alia, to mobile shelters used by nomadic peoples. The article is devoted to the research on the quality of internal air in the yurt and the possibilities of its adaptation to high contemporary quality and environmental requirements, while maintaining its characteristic sustainable values. The tested traditional Mongolian yurt was moved from the dry and cold climate of the Asian steppe to the temperate climate of Central Europe and has been significantly modified. The outer shell materials have been changed, replacing natural materials with modern tight insulating foils. The wood-fired stove has been replaced with an electric heater and the roof opening has been firmly closed. All of these modifications resulted in far-reaching changes in the quality of the internal environment in the yurt. The conducted measurements and simulations of CO2 concentration in the modified yurt proved that the efficiency of ventilation system is not sufficient and that the air quality is very poor (even for a single user). In the case of a larger number of users, the concentration of CO2 has already reached a level that was dangerous to health. The simplest method of improving the air quality in the yurt is its careful unsealing to the required level. Striving for a low energy demand, however, would require a completely different approach (for example, in the form of forced ventilation with a heat recovery unit, ultimately powered with a PV array). Such a solution is very different from the traditional yurt model but is close to modern expectations and environmental requirements.

Global optimization of industrial plant configurations using organic Rankine cycles (ORC) to recover heat is becoming attractive nowadays. This kind of optimization requires structural and parametric decisions to be made; the number of variables is usually high, and some of them generate disruptive responses. Surrogate models can be developed to replace the main components of the complex models reducing the computational requirements. This paper aims to create, evaluate, and compare surrogates built to replace a complex thermodynamic-economic code used to indicate the specific cost (US$/kWe) and efficiency of optimized ORCs. The ORCs are optimized under different heat sources conditions in respect to their operational state, configuration, working fluid and thermal fluid, aiming at a minimal specific cost. The costs of 1449.05, 1045.24, and 638.80 US$/kWe and energy efficiencies of 11.1%, 10.9%, and 10.4% were found for 100, 1000, and 50,000 kWt of heat transfer rate at average temperature of 345 °C. The R-square varied from 0.96 to 0.99 while the number of results with error lower than 5% varied from 88% to 75% depending on the surrogate model (random forest or polynomial regression) and output (specific cost or efficiency). The computational time was reduced in more than 99.9% for all surrogates indicated.

Cold start is one of the most difficult combustion phases of a diesel engine; and a large percentage of pollutants are produced during this period. Therefore, the present study focuses on proposing a numerical investigation of a novel design of an air preheating system to warm up the engine intake air at ambient air temperatures of 273 and 268 K. The preheating system consists of nano-enhanced phase change materials (NEPCM) housed in a plate heat exchanger. A comprehensive thermal model was developed and validated using experimental data from the literature. The model couples the transient turbulent fluid flow of the engine exhaust gases with the melting and solidification processes in the NEPCM domain. The effect of nanoparticle type, nanoparticle weight fraction, engine rotational speed, and ambient temperature were investigated. At 2000 rpm, the charging time was reduced by 34.88%, 30.23%, and 25.58% when using 5 w.t% of SiO2, Al2O3, and CuO nanoparticles, respectively. During the discharging process, in less than 1 min, the cold intake air can be heated from ambient temperatures of 273 and 268 K to 301.8 and 300.6 K, respectively.