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A silica gel-water adsorption chiller driven by low-grade heat is developed. System configuration without any vacuum valves includes two sorption chambers, a 4-valve hot/cooling water coupled circuit and a 4-valve chilled water circuit. Each sorption chamber is composed of one adsorber, one condenser and one evaporator. The design of this chiller, especially the design of modular adsorber, is suitable for low-cost industrial production. Efficient and reliable heat and mass recovery processes are also adopted. This chiller is tested under different conditions and it features the periodic variations of temperatures and cooling power. Through the experimental study, the optimal cooling time, mass recovery time and heat recovery time are 720 s, 40 s and 24 s, respectively. Besides, the obtained cooling power, COP and SCP are 42.8 kW, 0.51 and 125.0 W kg −1 , respectively, under typical conditions of 86/30/11 °C hot water inlet/cooling water inlet/chilled water outlet temperatures, respectively. [ABSTRACT FROM AUTHOR]

Decarbonization and resilience to heat waves have recently become high priorities for building and district energy systems. Geothermal coupled district heating and cooling systems that operate a water loop near ground temperature gain increasing adoption to support decarbonization. In these systems, vapor-compression machines, distributed in the energy transfer stations, lift the temperature up or down to the needs of the particular building. In principle, these systems can provide low-power, free cooling from the geothermal bore field during heat waves when electricity is often scarce. However, the performance of such a resilience operation mode and its implication on the energy system configuration and the sizing of the bore field and HVAC equipment is not yet understood. Consequently, we are assessing their resilience, power use and design implications under a scenario of a heat wave on five working days during which chillers are switched off to reduce electrical consumption. Our analysis is based on high-fidelity, coupled dynamic models of district energy, building-side HVAC and actual control logic, with whole building energy simulation used to assess thermal conditions in a 2004 vintage multi-zone office building in Chicago, IL. The results show that relying only on waterside economizer cooling, the indoor thermal conditions can be maintained in a tolerable range for the majority of the building zones with half the electrical energy compared to standard chiller operation. Thermal comfort in the hottest zones can be further improved by oversizing the cooling coil. However, the waterside economizer has significant implications on the system configuration and sizing: The geothermal bore field needs to be sized about 30% larger than the upper limit of the range observed for conventional geothermal systems. Nevertheless, if a central chiller plant is added, the bore field can be downsized to the typical design range. The latter configuration still allows compressor-less cooling during the heat wave with peak power reduced by 60% compared to the standard design and chiller operation. [Display omitted] • Geothermal coupled energy systems improve resilience of buildings during heat waves. • Demonstrated acceptable thermal comfort in typical office building during heat wave. • Integrated waterside economizer in ETS of ambient loop district energy network. • Used model-based HVAC and controls co-design for economic and reliable operation. [ABSTRACT FROM AUTHOR]

Heating, ventilation and air conditioning (HVAC) systems in battery production are a main component of the technical building services (TBS) and ensure the required low moisture conditions in dry rooms for battery cell assembly. In fulfilling these functions, they contribute significantly to the overall energy demand and are among the main energy consumers in battery production. In this context, model-based approaches to support the sizing and planning of these systems are increasingly interesting, as they enable the consideration of the system dynamics of the involved components. Furthermore, few data with regard to energy requirements of TBS in the context of battery cell production is available. We propose in this paper a 5-step planning procedure to address both of these problems. The planning procedure structures the planning process for the design of relevant TBS components in the context of battery cell production by using an inside-out planning approach. Moreover, we publish in this paper comprehensive data sets to evaluate the energy demand of battery cell production in dry rooms at 22 different locations and 10 different plant size with three different internal loads of moisture and heat per size and explain how to use the proposed procedure in this case. Our planning procedure enables planners to better size HVAC systems and evaluate alternative system designs in the context of battery cell production. We illustrate the application of the planning procedure with a case study. The goals of the case study are to assess, whether the air or cooling supply should be centralized or decentralized and to correctly dimension the TBS to supply the two dry rooms using the proposed planning procedure. The results of the case study show that the supply of the dry room with conditioned air via the HVAC system should be realized using two decentralized HVAC system, which saves up to 7.4% of final energy compared to the centralized variant. However regarding the cooling supply, constant base loads of min. 15 % occur through-out the year and since modern chillers usually have high efficiencies at partial load, a central supply is preferable for the cooling supply. The provided data sets of the 660 considered simulation cases can be used to assess the energetic demand to operate dry rooms for battery production at different locations, scales and internal loads, which is a considerable added value in the context of life-cycle assessment of the battery production. With the data sets, supply air volume flows of 5500 m 3 / h - 99000 m 3 / h can be considered, which covers plant sizes from laboratory to industrial size scales. • Model-based planning of technical building services for battery production • Proposition of 5-step inside out planning procedure for technical building services. • Evaluation of centralized and decentralized supply systems for dry room operation. • Publication of data sets to evaluate 660 cases at different locations, scales and internal loads of dry rooms. • Provision of evaluation scripts to simplify the assessments from user's point of view. [ABSTRACT FROM AUTHOR]

A comparative thermodynamic analysis and optimization is presented for two different designs of geothermal energy-based tri-generation systems. The two considered systems are distinguished by their power generation units, as organic Rankine cycle is employed in one system while Kalina cycle is used in the other system. To provide cooling and heating loads, a LiBr/water absorption chiller and a water heater are coupled to the Organic Rankine and Kalina cycles. To assess the systems’ performances, thermodynamic models are developed and a parametric study is carried out prior to the optimization with respect to the second law efficiency, as the objective function. Also, an exergy destruction modeling is conducted to identify the major sources of irreversibilities within the components of the considered systems. The Kalina cycle-based system is found to be more efficient as its maximum second law efficiency is 50.36% while the organic Rankine cycle-based system has a maximum second law efficiency of 46.51%. The results also indicate that, for a heat source temperature of 120 °C, the Kalina cycle-based system can produce more power than the other system by around 12.2%, under the optimized conditions. [ABSTRACT FROM AUTHOR]

We consider the problem of electricity demand shifting for the cooling needs of a large institution, using a thermal energy storage (TES) tank. The system is comprised of a number electric chillers with varying capacity and performance, as well as a tank that can store significant amount of chilled water but not enough for the whole day. The approach outlined here selects the number of chillers, and their time of operation, to minimize the costs, primarily by shifting the demand to the overnight period for which the electricity costs are lower and, due to lower ambient temperatures, the chillers are more efficient. The main goal is to develop a reliable and fast algorithm, through solving a linear or convex optimization problem, that operates the chillers at their peak efficiency and avoids excessive start-up and shut-down of chillers. [ABSTRACT FROM AUTHOR]

The present work was aimed to investigate the possibility of incorporating vegetable gums as binders in nuggets prepared from freshwater catfish, Pangasius pangasius. Guar gum and gum Acacia, which are well-known texturising agents were added in varying quantities during the preparation of the nuggets. Proximate analysis indicated that moisture content decreased from 78.9 to 74.0%, with increasing concentration of gum (0 – 2%), and so did fat content, from 6.1 to 5.4%. Protein content went up from 15.5% in control to 19.3% in treated sample. Control sample underwent maximum cooking loss (≈3.5%), whereas both treatments T4 (2% guar gum, w/w) and T7 (2% gum Acacia, w/w), exhibited minimum loss (≈ 2.7%). CIE L*a*b* values indicated significant lightening of the product during prolonged storage at 0 0C). Textural and sensory evaluation data also indicated that vegetable gums could be incorporated successfully in fish nuggets to improve their texture and sensory attributes. In all the treated and stored samples (0 0C, 60 days), the presence of bacteria, yeast and mould were well within permissible limits (≤ 3.0 x 102 cfu/g and ≤ 2.8 x 101 cfu/g, respectively). [ABSTRACT FROM AUTHOR]

Temperature and humidity independent control (THIC) systems demonstrate promising energy-saving potential compared with the conventional air conditioning systems. One type of THIC systems is proposed to use dual cooling sources with different temperatures since they could be produced easily by traditional vapor compression refrigeration chillers. This paper investigates the applicable condition of the THIC system based on dual cooling sources (DCSTHIC system). It is found that the DCSTHIC system has limited conditions (such as scopes of the heat moisture ratio and the fresh air rate) when applied, otherwise the indoor air temperature and humidity can’t be fulfilled, and further available scope of the heat moisture ratio realized by the DCSTHIC system is disclosed for air conditioned spaces. The minimum realized heat moisture ratio depends on the temperature of low-temperature cooling sources ( t LCS ). A parametric study is also conducted to analyze effects on the energy efficiency of DCSTHIC systems. These parameters include the heat moisture ratio ( ε ) and temperatures of dual cooling sources. Results show that DCSTHIC systems show more significant energy-saving potential in the air conditioned spaces with higher ε . The system COP improvement ranges from 3.1% to 17.5% compared with conventional air conditioning systems when the heat moisture ratio changes from 8000 kJ/kg to 15,000 kJ/kg. This study helps to guide the design and optimization of DCSTHIC systems. [ABSTRACT FROM AUTHOR]

The performance of two adsorbent bed silica gel-water adsorption chiller and the influences of its adsorbent bed dimensions, the velocity of heat exchange fluid and the adsorbent particle diameter on the transient distributions of the solid phase temperature, adsorbate concentration and the pressure are numerically examined in this study. A transient two-dimensional local thermal non-equilibrium model that takes into account both internal and external mass transfer resistances is developed to simulate the adsorption chiller considered herein. The internal and external mass transfers are predicted by the linear driving force (LDF) model and Darcy's equation, respectively. It is found that an increase in the adsorbent particle diameter results in the decrease in both the coefficient of performance (COP) and specific cooling power (SCP) of the adsorption chiller. On the other hand, the system performance is nearly independent from the variation of velocity of heat exchange fluid. An increase in the bed thickness leads to an increase in COP and a decrease in the SCP. The influence of adsorbent bed length on the performances of system can be neglected. The results of our simulations provide useful guidelines for the design of this type of adsorption chillers. [ABSTRACT FROM AUTHOR]

This paper presents a performance analysis of air-cooled chillers with evaporatively cooled condenser in 3 different cities of Turkey with the help of meteorological data provided from the Turkish State Meteorological Service (TSMS). The aim of the study is to determine the effects of evaporative cooling on inlet air of the condenser unit under various humidity and temperature conditions, and therefore on cooling performance (COP) of the air conditioning system. Considering the summer season between June and September for 4 months, it is assumed that the cooling requirements are provided by the direct expansion air-conditioners and the condenser inlet air is cooled by evaporative cooler with 70% effectiveness. The results show that after the evaporative cooling the highest COP increase of the chillers is occurred in most arid city as 40.5%, while the lowest increase was in the most humid city as 15.5%. This improvement increased the cooling capacity by 14.3% and 5.56%, correspondingly. In addition, the mean electrical consumption is considerably decreased as 9.97%, 15.49% and 6.97% for 3 different cities. The highest water consumption was around 5 tons per day for 10 hours of operation and 1400 m3/min mean air flow rate. [ABSTRACT FROM AUTHOR]

Replacement of air-cooled chillers with water-cooled chillers for air-conditioning plants in existing buildings can yield a significant amount of energy savings, especially in a sub-tropical climate. However, due to variations in weather conditions and building operation patterns, the amount of actual energy saving is often uncertain in these retrofits. These uncertainties impose a risk of saving shortfalls when Energy Service Companies (ESCOs) guarantee building owners for a certain amount of energy savings in Energy Performance Contracting (EPC) projects. This study presents a probabilistic approach to estimating a range of possible energy savings with the associated confidence levels for chiller replacement in existing buildings, taking into account the annual variations in the influential parameters affecting energy savings. The influential factors include building cooling loads, system control and operation systems, as well as chiller plant characteristics. The proposed approach involves: the use of correlation analysis for identifying influential parameters; EnergyPlus for simulating energy use of chiller plant; and a Monte Carlo approach for simulating the probability of post-retrofit energy savings. A commercial building where the air-cooled chillers were replaced with water-cooled chillers is used to illustrate the proposed approach. Results show that the variations in annual energy savings for chiller replacement projects can be estimated with a defined degree of certainty. In the case study project, the possible annual energy savings during the post-retrofit period range from 1,149,000 kWh (37.6% of baseline consumption) to 1,504,000 kWh (49.2% of ditto) at 90% statistical significance. The risk mitigation measures for this type of energy retrofit are discussed as well. [ABSTRACT FROM AUTHOR]

The present research conducted a parametric study on an embossed plate heat exchanger (plate HX) type adsorption chiller with SWS-1L and water pair, using a numerical method. The plate HX has a relatively high heat transfer capacity and compact size, and this study is a first attempt to apply the plate HX as a new type of adsorption chiller, as an improved alterative to the fin-tube type heat exchanger. A feasibility study was conducted on the base model and the result is comparable to the value for existing fin-tube type adsorption chillers. Furthermore, a parameter study was conducted for seven important design parameters, embossing diameter ratio, embossing height, embossing pitch, bed thickness, plate thickness, heating temperature and heat transfer fluid velocity. The results provided guidelines for the optimal designs of plate HX type adsorption chiller. The optimal values of COP and SCP were 0.5118 and 662.8 W kg −1 , respectively. [ABSTRACT FROM AUTHOR]

In the current paper we quantified and evaluated the energy saving potential in air conditioners and chiller systems. We also showed how to reduce the cost of air conditioners and chiller systems in existing facilities on the basis of payback periods. Among the measures investigated were: 1) installing higher efficiency air conditioners, 2) installing higher efficiency chillers, 3) duty cycling air conditioning units, and 4) utilizing existing economizers on air conditioning units. For each method, examples were provided from Arizona, ÜSA. In these examples, the amount of saved energy, the financial evaluation of this energy, and the investment cost and pay back periods were calculated. [ABSTRACT FROM AUTHOR]

Solar driven air conditioning systems can cope with solar collectors working in a wide range of temperatures. Sorption systems, including absorption and adsorption refrigeration systems, are among the best choices for solar cooling. Five systems including modular silica gel–water adsorption chiller, single/double effect LiBr–water absorption chiller, 1. n effect LiBr–water absorption chiller, CaCl 2 /AC (activated carbon)–ammonia adsorption refrigerator, and the water–ammonia absorption ice maker with better internal heat recovery were presented. The above five sorption chillers/refrigerators work under various driven temperatures and fulfill different refrigeration demands. The thermodynamic design and system development of the systems were shown. All these systems have improvements in comparison with existing systems and may offer good options for high efficient solar cooling in the near future. [ABSTRACT FROM AUTHOR]

The switching time is an important operating condition that must be correctly anticipated for an effective adsorption cooling system. Before the adsorption (or desorption) process begins, time is required to cool down (or heat up) the bed temperature so that the bed pressure reaches the evaporator pressure (or condenser pressure). During the switching time, the supplied heat is reduced and pressure overload conditions can be avoided. The switching time cannot be estimated early on, and an improper switching time degrades the system performance. Thus, this study provides guideline with which to determine the required time to open this valve, i.e., the switching time, and carefully examines the thermo-physical behavior in the adsorption bed during this period. A two-dimensional numerical method with the composite sorbent of SWS-1L and a water pair is applied to a fin-tube type adsorption chiller. Three cases of no switching time, the optimal switching time and a double the optimal switching time are examined. The results show that no consideration of the switching time overestimates the performance of the adsorption cooling system in terms of the Coefficient of performance (COP) and the Specific cooling power (SCP). On the other hand, if the switching time exceeds the optimal value, the performance of the adsorption cooling system is also reduced compared to that when using the optimal switching time. The dependency of the optimal switching times on various design parameters, such as the fin pitch, fin height and heating temperature, is also examined. [ABSTRACT FROM AUTHOR]

The present work investigates the feasibility of solar heating and cooling (SHC) absorption systems based on combining three types of LiBr–H 2 O absorption chillers (single-, double-, and triple-effect) with common solar thermal collectors available on the market. A single-effect chiller is coupled with evacuated tube collectors (ETCs) – SHC1. A double-effect chiller is integrated with parabolic trough collectors (PTCs), linear Fresnel micro-concentrating collectors (MCTs) and evacuated flat plate collectors (EFPCs) respectively – SHC2, SHC3, and SHC4. PTCs are employed to provide high-temperature heat to a triple-effect absorption chiller (SHC5). Although triple-effect chillers have been around for a while, this paper represents the first system-level analysis of these chillers coupled with high-temperature solar concentrating collectors for air-conditioning applications. A simulation model for each configuration is developed in a transient system simulation environment (TRNSYS 17). Furthermore, a unique, comprehensive perspective is given by investigating the impact of characteristic solar beam radiation to global radiation ratios on the techno-economic performance of the proposed SHC plants for a wide variety of climatic regions worldwide. The results of parametric study suggest that a storage volume of around 70 L/m 2 is a good choice for SHC1, while 40–50 L/m 2 storage capacity is sufficient for the other configurations (SHC2 to SHC5). The simulation results reveal that when the fraction of direct normal irradiance (DNI) is less than 50%, SHC2, SHC3, and SHC5 require larger collector area compared to SHC1, showing there is no advantage in using concentrating collector powered multi-effect chillers over solar single-effect chillers in climates with low DNI level. However, in climates with DNI fractions above 60%, the smallest solar field is achieved by SHC5, followed by SHC2. SHC4, which benefits from both relatively high COP of double-effect chiller and the diffuse component in the solar field, results in the most reasonable trade-off between energetic and economic performance of the system in a wide range of climatic conditions. [ABSTRACT FROM AUTHOR]

Cooling Load based Control (CLC) for the chiller sequencing is a commonly used control strategy for multiple-chiller plants. To improve the energy efficiency of these chiller plants, researchers proposed various CLC optimization approaches, which can be divided into two groups: studies to optimize the load distribution and studies to identify the optimal number of operating chillers. However, both groups have their own deficiencies and do not consider the impact of each other. This paper aims to improve the CLC by proposing three new approaches. The first optimizes the load distribution by adjusting the critical points for the chiller staging, which is easier to be implemented than existing approaches. In addition, by considering the impact of the load distribution on the cooling tower energy consumption and the pump energy consumption, this approach can achieve a better energy saving. The second optimizes the number of operating chillers by modulating the critical points and the condenser water set point in order to achieve the minimal energy consumption of the entire chiller plant that may not be guaranteed by existing approaches. The third combines the first two approaches to provide a holistic solution. The proposed three approaches were evaluated via a case study. The results show that the total energy consumption saving for the studied chiller plant is 0.5%, 5.3% and 5.6% by the three approaches, respectively. An energy saving of 4.9–11.8% can be achieved for the chillers at the cost of more energy consumption by the cooling towers (increases of 5.8–43.8%). The pumps’ energy saving varies from −8.6% to 2.0%, depending on the approach. [ABSTRACT FROM AUTHOR]

Detecting the faults at the incipient stage is important for keeping chiller systems healthy and saving energy and maintenance cost. Traditional principle component analysis (PCA) and support vector data description (SVDD) methods are insensitive to two common faults, condenser fouling (CdF) and refrigerant leakage (RfL). To improve the fault detection performance, this study proposed a PCA-R-SVDD based method. Instead of principle component subspace (PCs), it develops a SVDD model in the residual subspace (Rs) using the PCA modeling residual data. The SVDD based distance based monitoring statistic was used for fault detection. The proposed method shows significant improvement comparing with the traditional methods due to the better fault data distribution and tighter monitoring statistic. It is sensitive to six common faults. At least 50% of the fault data can be correctly detected even at the least severe fault level. Centrifugal chiller experimental data from the ASHRAE Research Project 1043 (RP-1043) was used to evaluate the methods. [ABSTRACT FROM AUTHOR]

This paper presents the energy assessment of a water/water R744 chiller/heat pump, working according to a transcritical cycle, used for winter heating, summer cooling and tap water production. The different functions (heating, cooling, hot water) are managed water side. The analysis of the R744 chiller/heat pump is based on an original simplified method, which is able to predict the energy performance of the unit based only on its performance data at the nominal rating conditions. The method was validated against experimental data. A comparison with a state-of-the-art R410A unit is presented. The monthly analysis shows that the CO 2 unit is very efficient in hot water production, but penalised in heating and cooling service. The adoption of an ejector in place of the expansion valve makes the CO 2 system reach the same energy consumption as the R410A unit, despite the presence of the water loop only in the R744 lay-out. [ABSTRACT FROM AUTHOR]

This paper presents an algebraic solution of erroneous sensor's undetectable boundary to evaluate the sensitivity of chiller sensor fault detection based on principal component analysis. Q -statistic of PCA is normally applied as a collective statistical index to detect sensor fault by comparing its value with the threshold. However, Q -statistic has no specific physical meaning and cannot evaluate the sensitivity of the provided method for sensor fault detection. We analyzed the definition of Q -statistic and derived the numerical value of the minimum range not to detect sensor fault. Bias sensor fault of a fielded screw chiller was studied for each sensor in PCA model by introducing different severity levels. Results showed that each sensor has different fault detection sensitivity using the same PCA model. The undetectable boundary can be a criterion used to evaluate the detection sensitivity of PCA-based method easily. [ABSTRACT FROM AUTHOR]

This paper presents a statistical training data cleaning strategy for PCA-based chiller sensor Fault Detection, Diagnosis and Data Reconstruction method. Finding and removing outliers from the original training data set, the training data quality can be improved by the presented data-cleaning strategy. This can enhance the efficiency of the fault detection and increase the accuracy of the data reconstruction. Outliers cannot be easily found in the original data set used for training the PCA model. These outliers would severely affect the projection directions of PCA's two orthogonal subspaces (PC subspace and Residual subspace). Therefore, the threshold of Q -statistic is changed by the unexpected projection subspaces so that the detection efficiency of the sensor fault is decreased. The Euclidean distance was employed as an index to detect outliers from the original training data. In order to achieve optimal training data for the sensor FDDR, the z -scores of each sample's Euclidean Distance were employed as the key to remove the outliers. A field measured data set of a screw water-cooled chiller was used to validate the presented strategy. Results demonstrate that the quality of the training data is optimized and sensor fault detection efficiency, as well as the reconstruction data accuracy, is improved when compared to the normal PCA method. [ABSTRACT FROM AUTHOR]

In recent years, the use of air conditioning systems based on cycles driven by thermal energy has increased. These cycles utilize renewable energy or waste heat energy from industrial processes. However, the complexity associated with such facilities makes the simulation of these systems with regard to sizing and performance advisable in many cases. This paper develops a simulation model under the EES environment for a 17.6 kW Yazaki WFC-SC5 simple effect LiBr–H 2 O absorption chiller. In this study, the heat transfer areas and coefficients of each heat exchanger, the circulating solution flow rate and the properties of the LiBr–H 2 O solution have been considered. Once the model is created, real data are used to validate the obtained results, providing a high level of correlation between real and simulated data. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical analyses of a novel high-temperature solar cooling system based on innovative flat-plate evacuated solar thermal collectors (SC). This is the first solar cooling system, including a double-effect absorption chiller, which is based on non-concentrating solar thermal collectors. The aim of the paper is prove the technical and economic feasibility of the system, also presenting a comparison with a conventional technology, based on concentrating solar thermal collectors. To this scope, an experimental setup has been installed in Saudi Arabia. Here, several measurement devices are installed in order to monitor and control all the thermodynamic parameters of the system. The paper presents some of the main results of this experimental campaign, showing temperatures, powers, energies and efficiencies for a selected period. Experimental results showed that collector peak efficiency is higher than 60%, whereas daily average efficiency is around 40%. This prototypal solar cooling system has been numerically analysed, developing a dynamic simulation model aiming at predicting system performance. For a representative operating period, numerical data were compared with the experimental one, showing an excellent accuracy of the model. A similar system, equipped with Parabolic Trough solar thermal collectors (PTC) was also simulated in order to compare the novel solar collectors with such reference technology. For both systems a detailed thermo-economic model has been implemented in order to perform such comparison also from the economic point of view. Results showed that the rated energy performance of the prototypal solar cooling system featuring new collectors is better than that of the reference system. In particular, the difference between the novel and the reference solar cooling system becomes more and more significant, when considering the effects of dust and defocusing related to the tracking mechanism of concentrating collectors in harsh environments. Finally, from the economic point of view, results showed that the novel prototype was able to achieve a good profitability. [ABSTRACT FROM AUTHOR]

Thermodynamic optimization of single-stage water–LiBr absorption system was performed earlier both from first- and second-law points of view. However, a realistic comparison between the two approaches is essential to identify the superior one. Hence a theoretical model is developed to optimize the absorption chiller for identifying conditions corresponding to maximum system coefficient of performance (COP) and minimum entropy generation rate. Optimum generator temperature for minimum entropy generation is found to be lower than that corresponding to maximum COP, with absorber having a dominant role in enhancing irreversibility in system. Optimal generator temperature decreases with increasing evaporator temperature and decreasing condenser temperature. Thus, it is possible to identify optimum value for any combination of condenser and evaporator temperature from both the energy and entropy points of view. Concerned contour maps are presented. Adoption of an entropy-optimized map is suggested, owing to higher sensitivity of entropy generation to the changes in condition compared to COP. [ABSTRACT FROM PUBLISHER]

High temperature and mass flow rate of the exhaust gases of submarine diesel engines provide an appropriate potential for their thermal recovery. The current study introduces a combined cooling, heating and power system for thermal recovery of submarine diesel engines. The cooling system is composed of a mixed effect absorption chiller with two high and low pressure generators. The exhaust of the diesel engine is used in the high pressure generator, and the low pressure generator was divided into two parts. The required heat for the first and second compartments is supplied by the cooling water of the engine and condensation of the vapor generated in the high pressure generator, respectively. The power generation system is a Rankine cycle with an organic working fluid, which is considered a normal thermal system to supply hot water. The whole system is encoded based on mass stability, condensation and energy equations. The obtained findings showed that the maximum heat recovery for the power cycle occurs in exhaust gas mass ratio of 0.23–0.29 and working fluid mass flow rate of 0.45–0.57 kg/s. Further, for each specific mass ratio of exhaust gas, only a certain range of working fluid mass flow rate is used. In the refrigerant mass flow rate of 0.6 kg/s and exhaust gas mass ratio of 0.27, the power output of the cycle is 53 kW, which can also be achieved by simultaneous increase of refrigerant mass flow rate and exhaust gas mass ratio in a certain range of higher powers. In the next section, the overall distribution diagram of output water temperature of the thermal system is obtained according to the exhaust gas mass ratio in various mass flow rates, which can increase the potential of designing and controlling the thermal system. The effect of parameters of this system on output water temperature was also analyzed. Finally, the performance of mixed effect absorption chiller was examined and the findings indicated that in the exhaust gas mass ratio of 0.375, the system has a coefficient of performance equal to 0.94. The output water temperature of evaporator in this state is 3.64 °C and the cooling system power is 176.87 kW. [ABSTRACT FROM AUTHOR]

This paper sets out to make a dynamic analysis of a single-effect, lithium bromide–water (LiBr/H 2 O) absorption chiller. A mathematical model has been developed based on conserving mass, energy, and species, which considers the correlations of the convective coefficients of absorption refrigeration processes so as to determine the overall heat transfer coefficients of the heat exchangers of chillers. The implementation of this mathematical model was built on the Matlab platform, and resolved the system of non-linear equations by making explicit use of the finite difference method. The model has the ability to simulate and predict the behavior of internal and external parameters such as temperature, concentrations and pressures when these are subjected to disruptions in the power supply and thermal load. The largest absolute differences found when validating the model by means of the experimental numerical values in the water circuits were approximately 1.0 °C, 0.7 °C and 0.2 °C for hot, chilled and cold water, respectively. In terms of relative error, these divergences represent a maximum of 5% and a minimum of 0.3%. The model showed good results when subjected to disturbances in the load and power source, as it reproduced the behavior of the temperature parameters and the Coefficient of Performance (COP), in line with the comparisons made with the data provided by the manufacturer, the COP being approximately 0.7 for operating conditions. [ABSTRACT FROM AUTHOR]

We designed, built and experimentally assessed the cooling power and the coefficient of performance (COP) of a chemisorption chiller that used a consolidated composite made of NaBr impregnated in expanded graphite as sorbent and ammonia as refrigerant. The influence of the operation conditions on the COP and the cooling power was calculated through the values of inlet and outlet water temperature and water mass flow across the chiller’s heat exchangers. From the experimental results, we concluded that the utilization of mass recovery simultaneously to heat recovery improved the COP and cooling power up to 11.7% and 15.4%, respectively, when compared to the values obtained when only heat recovery was employed. Regarding the influence of the heat source temperature, maximum cooling power and COP were obtained when that temperature was, respectively, 75 °C and 65 °C. As for the influence of the cycle time, the highest values of COP were obtained with an 88 min cycle, whereas the highest values of cooling power were obtained at different cycle time, depending on the value of other operation conditions. When the chiller was driven by hot water at 70 °C, and the inlet water temperature in the evaporator was not kept constant, it cooled water from 23 °C to 10 °C in 90 min with mean cooling power of 1400 W and COP 0.33. [ABSTRACT FROM AUTHOR]

The paper describes a new automation system developed to control and monitor a refrigeration system used for industrial experimental tests. The equipment owner it is a certificated laboratory for experimental tests in thermodynamics, aeronautics and vibrations. One of the laboratory activities is the products and equipment certification. During the certification process, the ambience temperature is a factor that needs to be controlled. The paper presents the SCADA system developed to monitor and control the water temperature of a refrigeration system used in the climate chambers. The system was successfully tested and is currently in operation in a shaker's temperature control. The project it was developed in cooperation between academia and industry. It is a case study that demonstrates the potentialities of knowledge transfer between both actors. [ABSTRACT FROM AUTHOR]

The performance of two adsorbent bed silica gel-water adsorption chiller and the influences of its adsorbent bed dimensions, the velocity of heat exchange fluid and the adsorbent particle diameter on the transient distributions of the solid phase temperature, adsorbate concentration and the pressure are numerically examined in this study. A transient two-dimensional local thermal non-equilibrium model that takes into account both internal and external mass transfer resistances is developed to simulate the adsorption chiller considered herein. The internal and external mass transfers are predicted by the linear driving force (LDF) model and Darcy's equation, respectively. It is found that an increase in the adsorbent particle diameter results in the decrease in both the coefficient of performance (COP) and specific cooling power (SCP) of the adsorption chiller. On the other hand, the system performance is nearly independent from the variation of velocity of heat exchange fluid. An increase in the bed thickness leads to an increase in COP and a decrease in the SCP. The influence of adsorbent bed length on the performances of system can be neglected. The results of our simulations provide useful guidelines for the design of this type of adsorption chillers. [ABSTRACT FROM AUTHOR]

A steady-state simulation model of a commercial 3-ton ammonia/water absorption chiller is developed and validated using the flow-sheeting software Aspen-Plus. First an appropriate thermodynamic property model for the ammonia/water fluid mixture is selected. To this purpose nine methods from the software library are pre-selected and tested, but none of the methods predicts the VLE (vapour–liquid equilibrium) with sufficient accuracy. The interaction parameters of these models are then determined by fitting the equations of state (EOS) to VLE data. It is finally found that the Boston–Mathias modified Peng–Robinson EOS with fitted parameters predicts most accurately the VLE for the temperature and pressure ranges encountered in commercial chillers. A simulation model of the machine is then developed. The simulation results are found to be in good agreement with data from literature at a cooling air temperature of 35 ºC. The heat transfer characteristics ( UA ) of the various heat exchangers of the machine are then determined and the model modified to make it accept these ( UA ) as input parameters. The comparison of the simulation predictions at cooling air temperatures of 26.7 and 38 ºC with the bibliographical data showed good concordance. The proposed model could be very useful for the analysis and performance prediction of the commercial absorption chiller. [ABSTRACT FROM AUTHOR]

Adsorption technology enables construction of chillers that can be driven with a low temperature cogeneration, solar or waste heat source. As compared with absorption chillers, the adsorption devices have the unique advantages like the utilization of heat source characterized by lower temperature. The paper presents the thermodynamic model of a three-bed adsorption chiller of a cooling capacity equal to 90 kW. The chiller has been commissioned at Wrocław Technology Park and is instrumented in a way allowing a full identification of important thermodynamic and operational parameters like COP (coefficient of performance), switching time, temperatures and pressures of adsorption and desorption processes as well as water condensation. The chiller provides cooling power at two temperature levels of about 13 and 8 °C. Experimental results of a long-term chiller investigation are presented. The dependence of the chiller COP on the adsorption bed regeneration temperature in the range from 45 °C to 70 °C has been identified. It has been demonstrated that the chiller can be driven with a hot water of 65 °C, what is a typical cogeneration heating temperature in distributed systems. It allows the utilization of cogeneration heat in trigeneration mode, what is especially important for distributed heating systems in summer time. [ABSTRACT FROM AUTHOR]

Small-scale solar air conditioning systems based upon thermally activated chillers offer great potential for cooling houses with minimal demands upon the central electrical system. Building performance simulation can be used to assess the potential of the technology and to explore the impact of system design (e.g. type and area of solar collectors, volume of hot and cold thermal stores, operating strategies), but only if appropriate models calibrated with accurate and reliable data are available. Experiments were conducted on a commercially available lithium bromide–water absorption chiller under a controlled set of operating conditions. Instrumentation was selected, calibrated, and installed in order to derive quantities of interest at acceptable levels of measurement uncertainty. Over this range of experiments, the cooling capacity varied from 6.9 kW to 40.5 kW, and the thermal coefficient of performance ranged from 0.56 to 0.83. A quasi-steady-state model suitable for use in building performance simulations that expressed the chiller’s performance was developed. Based upon statistical significance testing, it was found that the rates of heat transfer to both the generator and the evaporator could be expressed as linear functions of the generator inlet temperature, absorber/condenser inlet temperature, and flow rate of water to the generator. The validity of the calibrated model was then tested using measurements from a disjunct experiment whose data were not used to calibrate the model. [ABSTRACT FROM AUTHOR]

Only a few electrical solution-pumps are available on the market suitable for ammonia/water absorption heat pumping systems with an evaporator capacity lower than 20 kW. In order to improve this, a “thermally-driven” solution-pump is proposed, offering several advantages, as e.g. an oil-free, simple and leak-proof design. “Thermally-driven” means this pump is driven by a power process within the absorption heat pumping-cycle instead of electricity. The experimental analysis of this novel pump operating in a commercially available ammonia/water-absorption chiller shows that it can be easily integrated and works without any relevant operating limits. However, the measured COP of the considered chiller is decreased by at least 0.1 (15%) by this thermal-pump compared to the existing electrical-pump. Nevertheless, thermal energy (e.g. cost and CO 2 -free waste heat) can be used to drive this pump and due to lower production cost it can be an interesting alternative from an economical and ecological point of view. [ABSTRACT FROM AUTHOR]

Displacement ventilation (DV) flows are more complex than conventional overhead mixing systems since the stratified room environment cannot be modeled using the traditional fully mixed room air approach. A successful DV designer must be able to control the vertical room temperature profile and manage the position of the lower boundary of the upper air layer that contains heat and pollutants. The inclusion of a chilled ceiling (CC) in the DV system increases the complexity by adding the need to manage the CC cooling power so that it does not disrupt the DV stratification. This paper presents the extension of an existing DV nodal model so that the effects of the CC in room airflow and air temperatures can be predicted. The model uses three air nodes and focuses on the thermal plumes as the drivers of the airflow and room air heat exchange. The proposed model is validated using twelve different test chamber configurations from three independent experimental studies. When compared with existing models the proposed model achieves improved precision and model flexibility while using less air nodes. The last section of the paper presents a set of CC/DV design charts that can assist system designers in early design phases. [ABSTRACT FROM AUTHOR]

More than a quarter of the non-residential buildings in Europe are public buildings and their energy consumption is forty percent higher than that of residential buildings. Therefore, promoting a public policy to increase energy efficiency of the HVAC systems in public buildings will have a significant impact in reducing global energy consumption. In order to have a precise estimation of the impact of the substitution of the HVAC systems in a large number of public buildings, it is essential to have accurate data of the performance of these systems in specific buildings, beyond the technical specifications stated by the manufacturers. In this paper the substitution of the wide-spread, conventional air-condensed chiller (ACC) for a water-condensed chiller (WCC) with a dry-adiabatic cooler in a public administration building is analyzed in terms of energy efficiency, economic return of the required investment and environmental implications. The influence of external factors as well as the load effect are quantified. The results show that the seasonal Energy Efficiency Ratio of the WCC is near twice that of the ACC, making the replacement of the ACC for the WCC an interesting option. The results obtained in this study could be extrapolated to other non-residential public buildings. [ABSTRACT FROM AUTHOR]

The fault detection and diagnosis (FDD) of centrifugal chillers is always a complex difficulty in HVAC systems. This paper develops an online fault detection and diagnosis strategy based on non-linear radial basis function (RBF) to online detect and diagnose the fault of centrifugal chillers. The RBF is adopted to develop the reference feature parameter (FP) models. Exponentially-weighted moving average (EWMA) residual control charts of FP is used to detect the faults. A rule-based diagnostor is developed to online identify the fault. Seven common faults are taken in account for typical centrifugal chillers. The FDD strategy proposed was validated by using the experimental data from the ASHRAE RP-1043 project and the operating data of a centrifugal chiller in an office building of Hong Kong. The test results show that the RBF-EWMA method has achieved significant improvements in accuracy and reliability by comparing with the previous method with SVR-EWMA. The proposed RBF-EWMA method is robust for fault detection and diagnosis in centrifugal chiller systems. [ABSTRACT FROM AUTHOR]

Solar air-conditioning (AC) is an attractive AC system but it has intermittent output, and therefore, a conventional heater is needed as a backup. This study presents the effect of ratio of heat delivered by solar (Qsolar) to the total heat delivered to an adsorption chiller (Qsolar "P Qhearer) or solar fraction (SF) on the economic and environmental peiformance of a solar AC. This solar AC is not a solar-assisted AC, and therefore, it needs to fully cover the cooling load. The cooling demand of an office building in Kuala Lumpur, and the performance of flat-plate collectors and the adsorption chiller were calculated by equest and watsun software and by a mathematical model, respectively. Economic performance was analyzed by life-cycle cost analysis, whereas the environmental peiformance was analyzed by using typical emissions rate of energy systems used. It was found that a boiler was a better solution than an electric heater as a backup heater. Furthermore, the net profit (NP) at lower SF was higher because of its lower capital investment, but more emissions were released compared to the conventional AC because of the boiler operation. Thus, when economic and environmental performance were fairly considered, it is appropriate to have solar AC with an SF around 0.74. [ABSTRACT FROM AUTHOR]

Nowadays, the increasing demand of summer cooling is typically covered by electric chillers, often determining electric peak loads and black-outs. Thus, a wide interest is spreading in small scale natural gas-fired cogenerators driving desiccant-based air-conditioning systems, which represent interesting alternatives to conventional systems based on vapor compression cooling only. In this article, experimental tests performed on an air handling unit (AHU) equipped with a desiccant wheel (DW), coupled to a small scale cogenerator and an electric chiller are described. A new layout of the desiccantbased AHU is investigated, considering a third flow (the cooling air), besides the process air flow and the regeneration one. A cross-flow heat exchanger between process air and cooling air is used; the cooling air, cooled by an adiabatic humidifier, is aimed to precool the process air exiting the DW. The relevant influence of the heat exchanger and of the humidifier, as well as that of the chiller performance, on global primary energy requirements, water consumption and CO2 equivalent emissions of the system is experimentally evaluated. [ABSTRACT FROM AUTHOR]

A comparison of absorption and desorption is conducted using a detailed model describing heat and mass transfer. First, the influences of various assumptions have been evaluated. Second, typical conditions for both absorption chillers and heat transformers have been defined. The performance of absorption and desorption processes have been analysed for a flow length of 0.1 m. In an absorption chiller, during desorption, the viscosity is lowered and the mass diffusivity is increased. These circumstances cause a 46% higher transfer rate as compared to absorption. Thus, the overall performance of the process is determined by the absorber component. In a heat transformer, during absorption at an elevated pressure and temperature level, the viscosity is lower and mass diffusivity is higher as compared to desorption. Therefore, the transfer rate of during absorption is 10% higher as compared to desorption. Hence, the desorber performance is somewhat more influential to the overall system performance. [ABSTRACT FROM AUTHOR]

A variable effect LiBr–water absorption chiller is studied in this paper based on a real developed 50 kW prototype. The chiller is designed specifically for the high-efficient utilization of the solar power with variable temperature. It can obtain the optimized COP and cooling power under different heat source temperatures. The construction, circulation and testing system of the chiller were introduced. A typical running condition of the chiller from the starting to the steady operating was given to show the dynamic performance. Several groups of the temperatures and COPs were given to show the steady state performance. These data showed that the COP increased from 0.69 to 1.08 under generation temperature from 95 °C to 120 °C. Besides, the effects of chilled water temperature, cooling water temperature, pump frequency and opening of valve on COP and cooling power were analyzed respectively. [ABSTRACT FROM AUTHOR]

This paper presents a multivariable Newton-based extremum seeking control (ESC) scheme for efficient operation of a chilled-water plant. A MODEUCA-based dynamic simulation model of the chilled-water plant consists of one screw chiller and one counter-flow cooling tower was adopted for evaluation of proposed two-input Newton-based ESC controller. The ESC controller takes the total power of the chiller compressor, the cooling-tower fan, and the condenser water (CW) pump as feedback signal and discovers the optimum outputs of cooling-tower fan speed and the condenser-loop water flow rate to maximize the power efficiency in real time with the cooling load being satisfied. Remarkable energy saving is observed for several testing conditions. [ABSTRACT FROM AUTHOR]

Adsorption working pairs are the vital main components in the adsorption refrigeration machines. Therefore, the key for the further development is focusing on the adsorption pairs, which lead to the improvement of the adsorption refrigeration machines. In this study, an overview of both classical and modern adsorption pairs of the adsorption refrigeration systems is presented, compared and summarized. It was found that the maximum adsorption capacity for the classical working pairs was 0.259 kg/kg for activated carbon/methanol pair and that for the modern working pairs was 2 kg/kg for maxsorbIII/R-134a pair. This study concluded that, further investigations are still necessary to improve the performance of the adsorption working pairs of adsorption cooling systems as well as to develop the adsorption pairs with higher sorption capacity while with low or no impact on environment, in order to build compact, efficient, reliable, and long-life adsorption chillers. It was additionally found that activated carbon powder adsorbent has not been paid much attention so far, and hence, the study and application of it are to be of great interest. Further researches need to be focused on designing the adsorption system that provides efficient heating and cooling for the adsorbent materials by distributing the adsorbent material over heat exchanger surface, to allow good heat and mass transfer between the adsorbent and the refrigerant. [ABSTRACT FROM AUTHOR]

The scheduling of both absorption cycle and vapour compression cycle chillers in trigeneration plants is investigated in this work. Many trigeneration plants use absorption cycle chillers only but there are potential performance advantages to be gained by using a combination of absorption and compression chillers especially in situations where the building electrical demand to be met by the combined heat and power (CHP) plant is variable. Simulation models of both types of chillers are developed together with a simple model of a variable-capacity CHP engine developed by curve-fitting to supplier's data. The models are linked to form an optimisation problem in which the contribution of both chiller types is determined at a maximum value of operating cost (or carbon emission) saving. Results show that an optimum operating condition arises at moderately high air conditioning demands and moderately low power demand when the air conditioning demand is shared between both chillers, all recovered heat is utilised, and the contribution arising from the compression chiller results in an increase in CHP power generation and, hence, engine efficiency. [ABSTRACT FROM AUTHOR]

Multiple-chiller plant is commonly employed in the heating, ventilating and air-conditioning system to increase operational feasibility and energy-efficiency under part load condition. In a multiple-chiller plant, chiller sequencing control plays a key role in achieving overall energy efficiency while not sacrifices the cooling sufficiency for indoor thermal comfort. Various sequencing control strategies have been developed and implemented in practice. Based on the observation that ( i ) uncertainty, which cannot be avoided in chiller sequencing control, has a significant impact on the control performance and may cause the control fail to achieve the expected control and/or energy performance; and (ii) in current literature few studies have systematically addressed this issue, this paper therefore presents a study on robustness analysis of chiller sequencing control in order to understand the robustness of various chiller sequencing control strategies under different types of uncertainty. Based on the robustness analysis, a simple and applicable method is developed to select the most robust control strategy for a given chiller plant in the presence of uncertainties, which will be verified using case studies. [ABSTRACT FROM AUTHOR]

A novel residential micro-combined cooling heating and power system (CCHP) incorporating a proton exchange membrane fuel cell (PEMFC) stack, a single effect absorption chiller and accessories is proposed. The proposed CCHP system can provide electric power, hot water and space heating/cooling for family demand simultaneously. A steady-state mathematic model of overall system is developed, and validated by reference data. For parametric analysis, the effects of operating parameters (i.e.: inlet gas temperature and pressure, fuel cell operating temperature and current density) on system performance are analyzed, especially, the relationship of stack and absorption chiller performance is discussed. Furthermore, the performances of CCHP system in summer and winter are compared. The maximum efficiency of CCHP system can reaches 70.1% in summer, while 82% in winter. [ABSTRACT FROM AUTHOR]