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As a practical contribution to the energy transition from fossil to renewable energy, this paper addresses a wellness product with high energy demand: the sauna. The overall goal of the presented research project is to develop and demonstrate a so-called Zero-Energy-Sauna. In this paper, the development by means of numerical simulations is discussed. In a preliminary study, multiple concepts have been systematically derived and assessed. One innovative concept has been patented and an extended version of this concept is being implemented in this research project. The implemented concept utilizes solar energy and applies two types of thermal energy storage: a pressurized, stratified hot water storage and a closed low-pressure adsorption storage. The main purpose of the hot water storage is the heat supply, while the purpose of the adsorption storage is to provide steam. We formulate and investigate two numerical models for these thermal energy storages. For the hot water storage, an one-dimensional model is applied which considers the effect of natural convection. With this model, different charging and discharging scenarios are examined, proving the applicability of this type of hot water storage for a Zero-Energy-Sauna. For the adsorption storage, a previously developed and published model is adopted and extended by a metal plate for manual steam generation. Based on this model, various configurations of the adsorption storage are studied, revealing an optimum design for maximum steam generation. The storage designs derived by numerical simulation serve as blueprints for the two thermal energy storages. Both thermal energy storages are currently being implemented and experimentally investigated in the Zero-Energy-Sauna of the ongoing research project.

As an efficient energy storage material, phase change material can be combined with lightweight buildings to reduce the energy consumption of the building envelopes effectively, while it is often accompanied by phase change hysteresis(PCH) and supercoiling (SC) phenomena during the phase transition. SC means that the nucleation does not solidify at the theoretical solidification temperature and needs to be nucleated at a lower temperature. PCH indicates the difference between the melting temperature and the solidification temperature of the phase change materials (PCMs). So far, a lot of research on SC has been done and there is still a lack of research on PCH. On the one hand, the PCH is proportional to the energy loss of the system, the latent heat of PCMs cannot be exploited if PCH is beyond the operating temperature range of the system. On the other hand, when PCMs are combined with building envelopes, the greater the hysteresis temperature, the better the thermal performance of the wall. It’s vital to use the hysteresis temperature to improve the performance of the system. Especially, PCMs are equipped in building envelopes, the hysteresis phenomenon of incomplete phase transition will be more obvious because of large temperature fluctuation outside. The hysteresis effect of PCMs in building envelopes is discussed in this paper, the numerical simulation methods and experimental research of PCH are reviewed and analyzed from two aspects of complete and incomplete phase transition. It showed that the PCH should be considered when simulating the thermal behavior of PCMs in building envelopes. The results would be more accurate if two enthalpy-temperature curves (H(T) curve) are used to represent the melting and solidification process, respectively. In addition, the nucleation mechanism of PCH has not been discussed in previous articles and there is no explanation about whether the hysteresis phenomenon is caused by the properties of the material itself or is affected by experimental measurement conditions. Therefore, the related issues are discussed in this paper, it is considered that the PCH is not only related to the properties of the materials but also affected by the experimental measurement conditions.

The goal of this paper is to identify the effects of in-pore transport of liquid water and water vapor as well as phase changes on the hygrothermal behavior of earthen buildings. Indeed, one of the main assets used to promote these constructions is their role in moisture buffering hence temperature and relative-humidity quality controlling. However, there is no clear consensus yet concerning the impact of these phenomena on the global energy performance of the buildings. A coupled model is therefore proposed in this paper, based on heat and mass balances inside the earthen walls, in order to clarify this question. This model considers separately the kinematics of each phase (e.g. liquid water, vapor, dry air and solid matrix), in interaction with each other. It also takes into account the impact of pore water confinement on the liquid-to-vapor phase change, in particular on the resulting latent heat released or absorbed. The model is successfully compared to experimental results on instrumented full-scale rammed earth wall subjected to temperature cycles. It eventually allows identifying the singular hygrothermal behavior of earth material by testing the range of applicability of the simplifying assumptions which are commonly made in function of the permeability of the tested material.

In winter, a large amount of icing and snowing occurs in outdoor equipment and systems, which adversely affects their lifespan. The melting process is divided into two parts: convection melting and gravity shedding melting. This paper is based on an experiment with a real high-speed train unit, and it establishes a three-dimensional computational fluid dynamics model of the bogie area to validate the mathematical model of the winter ice melting experiment. A numerical simulation was used to calculate the airflow in the baffle-enclosed space and to predict the effects of interactions between air and the ice body on heat transfer and phase change. The influence of air velocity and temperature on the heat transfer was analyzed. The computational simulation effectively quantifies the amount of heat transfer and energy consumption under different conditions. This paper also presents a research method for the simulation of gravity shedding in complex models. These models provide information for the construction of similar ice melting models. This paper has suggested that for thin ice bodies, convection melting was the dominant strategy. For thick ice bodies, however, gravity shedding melting became dominant. The study also confirmed that enclosed hot-air ice-melting systems gave a better energy performance than unenclosed systems.

Ice storage systems are capable of shifting the electricity demand from on-peak hours to off-peak hours, and ice slurry becomes more widely used as an efficient cooling medium for replacing the traditional ice-on-coil system. However, ice blockage is a severe problem threatening the transportation safety of ice cooling systems. In this paper, a method for determining the critical velocity for safe transportation is proposed. Moreover, mechanical analysis is carried out to find out the stratification mechanism. This paper focuses on numerical simulation of ice slurry flow, and aims to find out influences of the following factors on transportation safety: ice packing fractions, ice particle size, additive concentrations and pipe size. According to the simulation, the IPF is suggested to be 20–25%; ice particle diameters are suggested to be within 100 μm; ethanol concentrations are suggested to be in the range of 5–10 wt%. In addition, reducing pipe diameters is beneficial to transportation safety. The results and proposed guidelines are of significance for predicting the critical velocity for safe transportation and guiding the safety design and operation of ice cooling systems.

The paper presents the experimental measurements and numerical simulation of a ground source heat exchanger operating at a cold climate for a passive house ventilation system. The investigated passive house is a detached single-family house without a basement, occupied by a four head family, located in the South of Poland. The measurements cover over one year period and CFD (Computational Fluid Dynamics) simulations are reported for February when system operates at typical for this period and location cold climate conditions. The calculations were made with the CFD ANSYS FLUENT software package. The house and its components are fitted with a data acquisition system that is operational from 2011 and records 139 points at an interval of 1 min. The data reported in the paper were recorded during winter in the year 2011/2012 by an onside located meteorological station and temperature sensors placed at different depths in the ground and at the outlet of the ground heat exchanger.

International audience; An experimental investigation has begun concerning the hygrothermal behaviour of wooden frame houses. The experimental set-up, consisting in a full-scale wooden frame house exposed to natural exterior climate is presented in the paper. It is located in Grenoble (South-East of France), and is equipped with over 150 sensors in order to collect a large amount of data (temperatures, relative humidity). The experimental data presented in the paper enable to get better understanding of coupled hygrothermal phenomena, and can be used to allow the validation of numerical models for heat, air and moisture transfers in wooden frame buildings. The analysed results demonstrate the importance of temperature-driven moisture diffusion from hygroscopic panelling.

In this paper, a calculation method for the floor surface temperature in radiant floor heating/cooling system is proposed, a new formula is derived to estimate the floor surface temperature. The floor is divided into two layers. The correlation for the thermal conductivity of the lower layer is developed based on the numerical model of the radiant floor system built in this paper. The results show that the floor surface temperature values from the proposed method are in agreement with the experimental and numerical values.

This paper is the second part of a two-part investigation of a novel approach to optimally control commercial building passive and active thermal storage inventory. The proposed building control approach is based on simulated reinforcement learning, which is a hybrid control scheme that combines features of model-based optimal control and model-free learning control. An experimental study was carried out to analyze the performance of a hybrid controller installed in a full-scale laboratory facility. The first paper introduced the theoretical foundation of this investigation including the fundamental theory of reinforcement learning control. This companion paper presents a discussion and analysis of the experiment results. The results confirm the feasibility of the proposed control approach. Operating cost savings were attained with the proposed control approach compared with conventional building control; however, the savings are lower than for the case of model-based predictive optimal control As for the case of model-based predictive control, the performance of the hybrid controller is largely affected by the quality of the training model, and extensive real-time learning is required for the learning controller to eliminate any false cues it receives during the initial training period. Nevertheless, compared with standard reinforcement learning, the proposed hybrid controller is much more readily implemented in a commercial building.

This paper reports on the improvement and application of a new method for the prediction of earth-contact heat transfer. In previous studies the new method was claimed to be fast, accurate and flexible as a result of incorporating elements of the response factor method into a finite volume technique based numerical model. Initially, a ‘pre-processing’ procedure is required to generate a certain number of hours for use as a time-series by the response factor technique in the second stage of the method. This paper shows that, it is possible to further improve the speed and accuracy of the ‘pre-processing’ procedure without losing the advantage of flexibility that the numerical models provide in the design of such cases. The improvement of the new method is presented which makes use of a ‘time-stepping control scheme’. A simple ‘extrapolation’ technique has been demonstrated previously. This method proved to be accurate and fast in solving the three-dimensional earth-contact heat transfer, which may involve a certain number of heating zones (rooms) interacting with several different temperature profiles. A multi-room configuration is utilised in this study and simulations are performed over one or more years according to the initial ground domain temperature conditions.

In this paper, we consider a special case of the one dimensional heat diffusion across a homogeneous wall. This physical system is modeled by a linear partial differential equation, which can be thought of as an infinite dimensional dynamic system. To simulate this physical system, one has to approximate the underlying infinite order system by a finite order approximation. In this paper we first construct a simple and straight forward approximate finite order model for the true system. The proposed approximate models may require large model order to approximate the true system dynamics in the high frequency regions. To avoid the usage of higher order models, we use a scheme similar to singular perturbations to further reduce the model order.

This paper describes how a model-based feedforward control scheme can improve control performance over traditional PI(D) and detect faults in the controlled process. The scheme uses static simulation models of the system under control to generate feedforward control action, which supplements a conventional PI(D) feedback loop. The feedforward action reduces the effect of plant non-linearity on control performance and provides more consistent disturbance rejection as operating conditions change. In addition to generating feedforward control action, the models act as a reference of correct operation. Faults that occur in the system under control cause the PI(D) loop to provide a greater than normal control action to compensate for fault-induced discrepancies between the feedforward models and the controlled process. By monitoring the level of feedback compensation, faults can be detected in the controlled process. The paper presents results from testing the controller with a simulated dual-duct air-handling unit. We also discuss recent experiences of implementing the control scheme in a real building using the BACnet communication protocol.

To facilitate multi-variate performance appraisal all aspects of a building must be treated simultaneously. This paper gives examples of how the principal technical domains relating to a building's environmental performance are coupled within the ESP-r integrated simulation package. Essentially, the equation-sets defining each domain are processed by customised solvers, while the domain interactions are handled by ensuring that the equation-sets for a given domain are established and solved as a function of information defining the evolution of any coupled domains. An earlier version of this paper appears in the proceedings of Building Simulation'99 [J.A. Clarke, Proc. Building Simulation'99, 1999] [1].

This paper describes the concept of using simulation as a tool for performance validation and energy analysis of HVAC systems. Recent advances in control system technology, including the development of open protocols such as BACnet™ have made sensor and control signal information from various components and subsystems in a building more accessible. This development has created significant potential for improving the monitoring and supervision of building systems in order to optimize operational performance. The paper describes one way of making use of this new technology by applying simulations, configured to represent optimum operation, to monitored data. The idea is to use simulation predictions as performance targets with which to compare monitored system outputs for performance validation and energy analysis. The paper presents results from applying the concepts to a large dual-duct air-handling unit installed in an office building in San Francisco.

This paper describes the present state of the project SNOW-SIM at Narvik Institute of Technology. The project is aimed at finding methods for simulations of wind and snowdrift around building construction. The purpose of this project is to develop an integrated planning environment suitable for determining wind loads and snow deposition in planning construction in the cold climate areas. Such problems are now mostly solved by using wind tunnel experiments, rough assumptions or by experience. Calculations in two and three dimensions are performed on commercial fluid dynamic software based on Navier-Stokes equations. This paper deals with wind loads on buildings, ventilation of the attic of a small house, and flow patterns around groups of buildings. The velocity is shown as a vector plot around the structures, and the wind pressure is given as characteristics pressure values on surfaces. Flow patterns around buildings are visualized by streamlines. Simulations of snow accumulations are done with a generalized drift-flux model which is described in the paper. Drifts around snow fences are simulated in two dimensions and compared with full-scale measurements. Three-dimensional snow deposition is calculated around a group of houses with snow deposition expressed as surfaces.

Solar heating should be recommended strongly for domestic buildings in the Qinghai–Tibetan plateau due to the area's high intensity radiation. In this paper, a novel hybrid solar heating system is presented, that includes a solar kang system, a Trombe wall and a direct gain window. The effects of five combined solar heating operation modes on the indoor hourly temperature for one case domestic building located in the Qinghai–Tibetan plateau were investigated by field measurement and numerical simulation. The optimal operation mode for improving the indoor thermal environment was determined. Furthermore, the effectiveness of each operational mode on the east room was quantitatively evaluated and ranked. The results show that the numerical simulation and field experimental results were well agreed, although there were some differences in specific values. In addition, the results it indicated that a solar kang running all days and Trombe wall running daytime played a significant role in improving the indoor thermal temperature. These relevant findings could provide a reference for solar heating system design and indoor thermal comfort improvement for rural domestic buildings in the Qinghai–Tibetan plateau.

This paper investigates the efficiency of a naturally ventilated double-skin facade (DSF) built in a test cell focusing on the airflow and heat convection of the cavity formed by DSF. The study covers measurements of the test cell and their numerical simulation. DSFs have been widely researched worldwide, since they contribute to the thermal performance of the internal environment and to energy savings by eliminating mechanical conditioning systems. For data acquisition, type K surface thermocouples are installed on the wall faces of the test cell and the additional facade, that is, on the inner and outer face of the wall of the test cell and the inner face of the external one. Furthermore, hot wire anemometers are positioned so as to obtain the air velocity in the lower and upper openings of the cavity, which has an air layer thickness of 0.1 m. The results show that the DSF presence contributes to a decrease of the temperature inside the environment because it inhibits the direct solar radiation. Measurement of the faces shows that at 4:00 p.m. the temperature reaches their maximum values. These values are equal to 25.6 °C on the inner face of the facade and 23.6 °C on the inner face of the test cell, while the outdoor temperature presents values equal to 23.1 °C at this time.

The development of energy-saving technologies for buildings is an important means of achieving carbon neutrality. The respiration-type double-layer glass curtain wall (RDGCW) is a kind of enclosure structure with natural air circulation and a shading function. The RDGCW provides energy saving, and it is being widely promoted and used in China. However, there is still a lack of relevant research on the energy-saving effects and operating strategies of the RDGCW throughout the year. In response, this paper describes experimental evaluation and numerical simulation. First, the energy-saving effects in an office building using an RDGCW in Tianjin during the winter were studied experimentally, and the real-time temperature changes in the RDGCW and the room were measured with high accuracy under different operating strategies. Second, because the temperature distribution and energy consumption in a room is affected by the air flow in the RDGCW and by outdoor meteorological parameters in a complex manner, this investigation developed a coupled model on the basis of TRNSYS and CONTAM. The simulation results were in good agreement with the experimental results. Third, the verified model was used to evaluate the annual energy-saving effects of the RDGCW under dynamic outdoor meteorological conditions in Tianjin. When the optimal operating strategy was adopted, the energy-saving effect of the RDGCW in comparison with single skin facade (SSF) reached 32.8% under summer conditions and 38.3% under winter conditions. Finally, the RDGCW system in typical cities (Changchun, Shanghai, Guangzhou, Kunming and Tianjin) in five climate zones in China was simulated for the whole year. Under the optimal strategy, the RDGCW achieved good energy-saving effects. The energy saving was 27.7–49.2% in summer and 25.6–46% in winter, in comparison with SSF.

Heat transfer through external walls plays a significant role in building energy saving. This paper tries to investigate the thermal and energy performance of a novel lightweight steel-bamboo wall structure. A testing residential building was constructed using the prefabricated steel-bamboo composite wall and field measurement was carried out to determine the heat transfer coefficient, time lag and decrement factor of the steel-bamboo wall. Numerical simulation was conducted in order to further evaluate its performance improvement compared to two commonly used wall structures in this climate region. The results show that the steel-bamboo wall has a high thermal performance with an improvement of U value by up to 26.1%–48.4%, indicating a lower heating demand compared to common wall structures in winter. Meanwhile, it has a high resistance to outdoor air temperature fluctuation with a low decrement factor of 0.022. The relatively low time lag (2 h) contributes to a lower indoor temperature during summer nighttime and thus reduces cooling energy demand. The improvement of total energy performance reaches 27.1%–40.9%, indicating a great potential of applications of this steel-bamboo wall in residential buildings in hot summer and cold winter zone. However, the main drawback of the steel-bamboo structure is that its indoor thermal performance during the hottest hours in summer is poorer than conventional walls.

This paper analyses annual energy performance of atrium type hotel building in Belgrade. The objective is to examine the impact of the atrium on the hotel building's energy demands for space heating and cooling. Integrated approach through numerical simulations that include Belgrade climate data and thermal comfort parameters, indicates an optimal model of hotel building with atrium for this area. Building energy simulation is carried out using EnergyPlus simulation engine, as a basic tool in the process of building energy optimization. The methodological approach includes the creation of a hypothetical model of an atrium type hotel building, numerical simulation of energy performances of several design alternatives of the hotel building with atrium, and comparative analysis of the obtained results. The main task of analysis is to change certain parameters in the particular model (for example, building structure, orientation, etc.) and to observe how the changes influence energy performance of the building. The goal of this research is to show that the atrium contributes to the heating and cooling energy savings in the rest of the building, but also that the atrium itself demands a lot of energy for its air-conditioning. The most sustainable solution should be to cover energy demands for atrium by using the renewable energy sources. In this case, the atrium can contribute to the energy efficiency of the hotel building in Belgrade climatic conditions, thus reducing its negative impact on the environment. This is the peer-reviewed version of the article: Vujošević, M., Krstić-Furundžić, A., 2017. The influence of atrium on energy performance of hotel building. Energy and Buildings 156, 140–150. [https://doi.org/10.1016/j.enbuild.2017.09.068] Supporting dataset is available: [https://doi.org/10.1016/j.dib.2018.01.040]

With the increasement of worldwide population, high-rise buildings of multi-dwelling units have been widely used as a residential building, especially in China, United States and India etc. At present, most of cooking exhaust shafts in high-rise residential building takes the form of central exhaust system. However, the mal-distribution of exhaust flow in central exhaust system often leads to oil fumes reflux and odor migration, which decreasing the performance of kitchen hoods. This study is conducted in a 32-storey residential building which employed central exhaust system. Static pressure and velocity distribution were investigated in central exhaust shaft with uniform cross section. In addition, Computational Fluid Dynamics was adopted to analyze flow characteristics and validated by comparing the simulation results with experimental data. The emphasis of this study lies in the effects of temperature differences and equally spaced operating rates of kitchen hoods on flow characteristics in central exhaust shaft. The results showed that when the temperature difference varies from −12 °C to 30 °C, the locations of maximum static pressure gradually moved downwards and presented a low-high-low distribution. The maximum occurred in the middle-low storeys under different operating rates. This paper is valuable for HVAC engineers to improve the design of central cooking exhaust shafts in high-rise residential buildings, and solve the mal-distribution problems of exhaust flow in central exhaust systems.

This paper proposes an enhanced-convection overhead radiant floor heating system (EORFHS), which adds holes to an existing overhead radiant floor heating system (ORFHS). In addition, the heat flow and heat transfer of these systems were analyzed. By experimental investigations in an artificial climate chamber, the heat storage and release characteristics of the two systems were investigated and compared. The results indicated that the floor surface temperature and the room temperature were more responsive in the EORFHS during the preheating period. For the ORFHS, the pipe spacing has the strongest effect on the preheating time, whereas the pipe spacing and pipe water temperature have the same effect on the preheating time for the EORFHS. The relationship between the two systems for the intermittent period and the preheating period was also obtained. For the EORFHS, the number of holes per floor unit has a minimal effect on the floor surface temperature. The outlet air experienced natural convection with an average wind speed of 0.1 m/s. The numerical simulation method was proven to be accurate; the error between the numerical simulations results and the experimental results was less than 9%.

Recently, the energy pile has been introduced as a viable alternative to the conventional closed-loop vertical ground heat exchanger (GHEX). The energy pile contains a heat exchange pipe inside the pile foundation and allows a circulation of working fluid through the pipe inducing heat exchange with the ground formation. In this paper, a series of thermal performance tests was conducted on two coil-type cast-in-place energy piles with different coil pitches, 200 mm and 500 mm, to evaluate the effect of coil pitch on the heat exchange performance of energy piles. Thermal performance tests were carried out by applying intermittent (8 h operating–16 h pause) artificial cooling and heating loads with the aid of a constant-temperature water bath. The experimental result indicated that the heat exchange rate per pile length was not directly proportional to the installed pipe length because the tight coil pitch caused thermal interference between each pipe loop. In addition, a parametric study was conducted by computational fluid-dynamic (CFD) simulations to assess the effect of coil pitch and thermal interference on the thermal performance. The CFD model was verified by comparing the numerical simulation results with the field test data. Finally, an optimum coil pitch in the test bed condition was proposed considering the thermal performance and the economic feasibility of coil-type cast-in-place energy piles.

In China, more than 100 million people live in earth-based dwellings currently. However, there have been few studies on measures for improving indoor thermal environment and decreasing energy consumption of adobe buildings systematically. So, this paper studied the measures mentioned above. Firstly, parameters such as indoor thermal environment, PMV, thermal properties and thermodynamic disfigurement of building envelope were measured and analyzed on a quadrangle adobe dwelling in Gansu, China. Then, three optimization schemes (transforming layout only, transforming external walls only and changing the two simultaneously) were put forward. Finally, the thermal environment and energy consumption of the optimization schemes were analyzed by numerical simulation, and the cost benefit analysis of them was carried out. Among those schemes, scheme of changing layout and external walls simultaneously leads to the best performance in both the two respects mentioned above, while scheme of transforming layout only gives the worst performance. But, when both taking consideration of economy and energy saving, the preferred plan is scheme of changing layout only, and the worst is scheme of transforming layout and external walls simultaneously. This study has been conducted to give guidance when constructing or reconstructing quadrangle adobe dwelling, which is distinctive and historical in China.

Nowadays, energy simulation in many respects assists researchers and engineers in the design phase, as well as in the buildings operational phase. Reliability of the integrated simulation model and the knowledge and experience of the user are the cornerstones of good quality simulation prediction result. This study was preceded by a detailed and long-term experimental analysis of the building with a double-skin ventilated facade [10] . The paper presents results of the measurement, fine-tuning process and validation of the numerical simulation model. The simulation software tool, EnergyPlus in combination with Airflow Network Algorithm algorithm was used for the cavity air temperature and velocity prediction. When the model was verified, the criterion of eligibility were defined with the recommended statistical indicators. In order to achieve the better assessment, the validation process was done trifold: for winter, transitional and summer season. Overall, the research results highlight a very good agreement and a high level of matching between measured values and simulated results, which is a confirmation of the applied energy simulation tool.

Mathematical models can be used to evaluate the health impacts of housing energy efficiency interventions. However by their nature, models are subject to uncertainty and variability, which are important to quantify if used to support policy decisions. Models that are used to assess the impacts on health of housing energy efficiency interventions are likely to be based on a pair of linked component models: a building physics model which calculates changes in exposures and whose outputs then feed into a health impact model. Current methods to propagate uncertainty in a series of models, where the outputs of one model are inputs to another, invariably use Monte Carlo (MC) numerical simulation. In this paper, two methods are used to quantify the uncertainty in the impact of draught proofing on childhood asthma: the MC simulation method and a semi-analytical method based on integral transforms. Both methods give close results but it is argued that the semi-analytical method has some advantages over the MC method, particularly in quantifying the uncertainties in the main outputs of the building physics model before propagating them to the health model.

The ground heat exchanger is an important part of a ground source heat pump system. The site selection and arrangement affect the thermal performance of the entire system. A horizontal (shallow) ground heat exchanger has lower initial cost than a borehole heat exchanger. However, it has a larger physical footprint and its thermal performance is strongly affected by surface heat flux and rainfall infiltration. The capillary mat heat exchanger comprises small parallel capillary tubes and provides larger effective heat transfer area per unit footprint installation area. Additionally, it is more easily prepared and installed. This paper reports experimental result and numerical validation of ground source heat pump cooling application using shallow horizontal capillary mat ground heat exchangers. From the experiment, it was found that the installed capillary mat heat exchangers provide sufficient heat rejection rate for the heat-pump's thermal load. A numerical model for capillary mat heat exchangers is developed and the numerical result are validated using experimental data, within 1.54% root-mean-square error. A new and simple numerical relationship is also proposed to express the rate of heat transfer from capillary pipes to the surrounding soil. The extended numerical simulation found that currently installed ground heat exchangers can provide higher thermal load. The estimation of the pressure drop suggests that for a given pressure drop and flow rate, a single capillary mat having a surface area of 13.18 m2 is equivalent to a 40-m high-density polyethylene pipe with a standard diameter of 3.2 cm and a surface area of 8.05 m2.

This paper deals with the methodology of sizing a sustainable heating–cooling system, which consists of a heat pump, thermo-solar collectors and underground water tank, as a seasonal thermal energy storage. The methodology is based on successive and coupled energy balancing of all system elements for time intervals of 1 h, during one representative calendar year. The starting assumption for the calculation contains the size of the underground storage tank, its burial depth, the size of building that is heated or cooled, and the temperature of air in the building. To make the calculation, it is necessary to know the so-called dynamic boundary conditions during a calendar year, comprising the following: hourly outdoor air temperature, hourly insolation (received solar radiation energy) and hourly temperature of the ground surface. The calculation result is the size of the thermal–solar collectors surface, which will ensure the sustainability of the system, i.e. it will ensure that after one year of operation this system is restored to the original conditions, without disturbing natural environment in which it is used. For the purpose of presenting the methodology and checking the influence of individual parameters of the system's operation, a numerical simulation was performed and required surfaces of thermo-solar collectors were determined for one of the system models. Analyses of the influence of the underground tank burial depth, tank size and the initial water temperature in the tank on the required size of thermal–solar collectors were also performed.

In this paper a new modeling of an indirect evaporative cooling system (IEC) with consideration of wall longitudinal heat conduction (LHC) and effect of spray water temperature variation along the exchanger surface in a cross-flow configuration is presented. The resultant coupled equations of heat and mass transfer are discretized using finite difference method (FDM) and solved by an iterative method. Comparing the numerical results of the presented simulation against experimental data revealed excellent agreement with them, this shows a small margin of error in the calculation (around 3%). After validation, this mathematical model is used in a two-stage system of indirect/direct evaporative cooling system, which shows that a two-stage indirect/direct evaporative cooling system in comparing to a one-stage IEC has around 50%higher wet-bulb effectiveness with the same parameters of inlet air and exchanger. Furthermore, the presented model is used for numerical simulation of a counter-flow regenerative evaporative cooler which shows around 60%higher wet-bulb effectiveness in comparing to a one-stage IEC. The numerical results of this study show applicability of the presented model for both sub-and above-wet bulb cooling applications.

A numerical simulation model of a two-stage compression refrigeration system with vapor injection using R-32 as refrigeration is newly presented in this paper. The middle chamber state of the twin rotary compressor with vapor injection was simulated. Based on that, the whole system model was set up and it was validated by comparing the predictions with measured data. The results show that, compared with No-injection cycle, R-32 vapor injection system provides very significant performance improvements for cooling performance. The most suitable volume ratio of the high-pressure cylinder to low-pressure is between 0.65 and 0.78; Compared with the single-stage compression system, the cooling capacity and COP of the two-stage compression system can improve 5–15% and 10–12%, respectively; The optimum vapor injection pressure corresponding to the comprehensive cooling performance was 1.3–1.8 MPa.

The aim of this paper is to provide a numerical simulation for giving a technical answer to some problems that a structural engineer has to solve when designing a timber building based of Platform Frame technology, i.e., composed of light-frame timber shear walls. For a fully anchored wall, a finite element model, aimed at determining wall stiffness, strength and ductility, is presented. The shear wall is considered as lacking of any constructive imperfection.

An updated method for the dynamic simulation of ground coupled heap pump (GCHP) system was proposed. The method developed an analytical heat transfer model for the borehole heat exchanger (BHE) with considering the variation of fluid temperature along borehole length and thermal interference between two adjacent legs of U-tube. Based on the BHE model, the borehole heat exchange effectiveness (BHEE) was put forward and defined, and then the influences of borehole thermal resistance, fluid thermal capacity and borehole depth on the BHEE were investigated. By quoting the BHEE in the system simulation, the inlet and outlet fluid temperature of BHE can be calculated directly by the BHEE rather than by the calculation of average fluid temperature of BHE, this can overcome the disadvantage of former model that the average fluid temperature must be calculated previously to determine the inlet and outlet temperature of BHE. Validation of the model was undertaken by comparison with the variable heat flux cylindrical source model validated experimentally and theoretically. The experimental validation was also conducted by a model experimental facility, and the results show that the model developed in this paper has a good predicted precision, and the predicted relative error is less than 3%.

Seawater heat pump (SWHP) systems are considered as an ideal approach to heat and cool buildings in coastal areas due to its attractive advantages of high efficiency, low carbon emission and using renewable energy instead of electricity for heating and cooling. A great many of SWHP systems have been applied in residential and commercial buildings successfully. In this paper, models describing the coupled seepage and heat transfer process of beach well infiltration intake systems for a SWHP were established and validated by field experiment. In addition, the performance of the beach well infiltration intake system was simulated. And effect of the parameters related to the beach well and the operation of the system on pumping water temperature was explored through a series of simulations. As a result, application of SWHP systems with beach well infiltration intake system in coastal areas in China is feasible due to the favorable geographical conditions and environment.

This research aims to further improve the thermal performance and the heat charge and discharge efficiency of the developed vertical phase change thermal energy storage device (VPCTESD) in order to adapt the application of VPCTESD in solar energy utilization technology and waste heat utilization technology. Based on the developed heat transfer model of VPCTESD, with experiment and numerical simulation methods, this paper proposes the optimization design parameters of VPCTESD filled with PCMs (called DX-53), including the gap between DX-53 slabs, the velocity of HTF (water) in heat transfer unit's flow passage, the thickness of DX-53, the filling height of DX-53 and divergent length of entrance region. The research result provides the reference methods for evaluation of the thermal performance of VPCTESD.

Energy consumption of buildings depends significantly on the criteria used for the indoor environment and building design and operation. The environmental factors that define the indoor environmental quality are: thermal comfort, indoor air quality, acoustic comfort and visual comfort. This paper approaches the numerical prediction of thermal comfort in closed spaces on the basis of PMV–PPD model, and its testing to asymmetric or nonuniform thermal radiation, as well as the indoor air quality simulation and control. The following are developed: a computation and testing model of thermal comfort in buildings, a computational model for indoor air quality numerical simulation, as well as a methodology to determine the outside airflow rate and to verify the indoor air quality in rooms, according to the European Standard CEN 1752. Also, the thermal comfort criteria for design of heating systems, the relationship between thermal environment and human performance, as well as the influence of carbon dioxide on human performance and productivity are presented. The performance of the developed computational models, implemented in two computer programs, is illustrated by using some numerical comparative applications for two building construction types.

This paper reports on a recently developed numerical simulation method (NGRFs, numerical generation of response factors method) for the prediction of earth-contact domain temperatures under multi zone structures. It will be studied the way that a typical multi-room slab-on-ground floor influences soil's and other underground components’ temperature with time and depth. In order to validate the NGRF solution when is applied in multi zone cases the analysis of the way that rooms interact each other is explained.

Complaints on thermal comfort and confusions on cooling load calculation are still two main issues for the design of stratified air distribution (STRAD) system. This paper investigated these two issues for STRAD systems applied in a large space lecture theatre. The simulation results revealed that best satisfied thermal environment was obtained when supplied air from floor level, terrace and desk-edge mounted grilles simultaneously. A new method for the calculation of the occupied zone cooling load, which is based on CFD (computational fluid dynamics) simulation was proposed and tried. The effective cooling load factor concept was further clarified, which can be conveniently used to calculate the occupied zone cooling load and then determine the supply airflow rate. The concepts of occupied zone cooling load reduction and the associated but different cooling coil load reduction were differentiated, and it was illustrated that cooling coil load reduction up to 16.5% of the space cooling load can be achieved with split location of return and exhaust grilles. These simulation works provide a good basis for full-scale experimental validation of the key energy saving features of a well-designed stratified air distribution system.

It is a challenge to estimate the ventilation rate of a natural ventilated livestock building in varied wind conditions. Both experiment and numerical simulation approaches can be applied. In this paper, numerical simulations using computational fluid dynamics (CFD) and experiments using the pressure method and tracer gas method are compared. The simulations were based on five two-equation RANS turbulence models. A building model with two different sizes of the ridge openings was investigated in a wind tunnel. Results indict the simulated overall ventilation rate through building space by standard k–ω model has the closest agreement with experiment. However, there lies a large discrepancy between simulation and experiment as the ridge opening size become larger. The discrepancy may come from shortcoming of using pressure method, especially the network method, in calculating the ventilation rate in larger ridge opening, or lack of reliable technique to measure the wind pressure at the ridge opening. As for the tracer gas method, a generally good fit was found comparing with simulation results; however, the variance still exists as the wind direction was more perpendicular to the building sidewall. The discrepancy is expected to be reduced by the improvement of measurement accuracy of experiment.

Active transparent facades constitute a building envelope component that is becoming more and more common in high-rise office buildings. Many designers have opted for a ventilated facade, claiming that this technology is sustainable, reduces energy consumption and enhances indoor comfort conditions, but these claims have often proved to be wrong. From the thermofluid-dynamic analysis point of view, few design procedures or sufficiently detailed, reliable and easy to use simulation software are available for ventilated facades. A numerical model that has been developed to simulate the thermal behaviour of mechanically ventilated active transparent facades is presented in this paper. The model, developed in the Simulink/Matlab® environment, simulates the facade in both steady-state and transient conditions and provides the temperature of the different layers of the facade structure and the corresponding heat fluxes as output data. The model has been validated by comparing the simulation results with experimental data obtained in the laboratory. A test has also been performed on a real facade under actual operating conditions. The model performance has resulted to be quite promising. The accuracy of the prediction of the temperature is good, while the simulations of the heat fluxes are slightly less reliable for some operative conditions.

Natural ventilation, which is in line with the concepts of sustainability and green energy, is widely acknowledged nowadays. Prevailing winds in urban areas are unavoidably modified by the increasing number of closely placed high-rise buildings that significantly modify the natural ventilation behaviour. This paper explores the effects of building interference on natural ventilation using computational fluid dynamics (CFD) techniques. The cross-ventilation rate (temporal-average volumetric airflow rate) of hypothetical apartments in a building cluster under isothermal conditions was examined using the standard two-equation k − ɛ turbulence model. The sensitivity of ventilation rate to wind direction, building separation and building disposition (building shift) was studied. Placing buildings farther away from one another substantially promoted the ventilation rate, cancelling the unfavourable interference eventually when the building separation was about five times the building width (the optimum separation). The characteristic flow pattern leading to this behaviour was revealed. With the adoption of building disposition, the optimum separation could be reduced to three times the building width. In addition, the airflow rates could be doubled with suitable shifts. Building disposition is therefore one of the feasible solutions to improve the natural ventilation performance in our crowded environment.

Dew point evaporative cooling system is an alternative to vapor compression air conditioning system for sensible cooling of ventilation air. This paper presents the theoretical performance of a novel dew point evaporative cooling system operating under various inlet air conditions (covering dry, moderate and humid climate) and influence of major operating parameters (namely, velocity, system dimension and the ratio of working air to intake air). A model of the dew point evaporative cooling system has been developed to simulate the heat and mass transfer processes. The outlet air conditions and system effectiveness predicted by the model using numerical method for known inlet parameters have been validated with experimental findings and with recent literature. The model was used to optimize the system parameters and to investigate the system effectiveness operating under various inlet air conditions.

The recent rise in the environmental and economic costs of energy demands a need to design and build more sustainable building systems. Curtain wall assemblies show great promise—the spandrel panels within them can be natural solar collectors. By using a solar dynamic buffer zone (SDBZ) in the spandrel cavity, solar energy can be efficiently gathered using the movement of air. There is a need for a numerical model capable of predicting performance of this system. This paper presents the quantification of a prototype SDBZ curtain wall system through experimental testing in a laboratory environment. Results from the experimental testing were used to validate a one-dimensional numerical model of the prototype. This research shows a SDBZ curtain wall system as an effective means of reducing building heating energy consumption. The numerical model showed good correlation with experimental results in the expected operating range of the system. Given the lack of published literature for similar systems, this research acts to validate a simple, innovative approach to collect solar energy that would otherwise be lost to the exterior using already existing components within a curtain wall. This research shows the SDBZ curtain wall has the potential to act as a significant solar collector.

This paper deals with the numerical three-dimensional prediction of the induced flow patterns around and inside a building, which is cross-ventilated in a natural way. The air change rate is controlled by two opposite openings on the building envelope, as a function of wind velocity and its incidence angle. The numerical methodology is based on the finite volume numerical solution of the Navier–Stokes equations, using the CFD commercial code FLUENT. The numerical results are compared with available experimental data regarding the refresh rate of the building's room and the relative velocity profiles at the window openings, indicating a good agreement. Furthermore, a detailed description of the natural ventilation process is provided, whilst additional information regarding the induced velocity and pressure field is presented; information which cannot be easily extrapolated by experimental methodologies. Finally, the impact of the inner topology of the building on the induced flow field is investigated.

This paper presents the experimental study and numerical simulation of a semi-indirect evaporative cooler (SIEC), which acts as an energy recovery device in air conditioning systems. The numerical simulation was conducted by applying the CFD software FLUENT implementing a UDF to model evaporation/condensation. The numerical model was validated by comparing the simulation results with experimental data. Experimental data and numerical results agree for the lower relative humidity series but not for higher relative humidity values.

This paper briefly reviews the primary parameters for a double skin facade (DSF) design. The research presents an integrated and iterative modeling process for analyzing the thermal performance of DSF cavities with buoyancy-driven airflow by using a building energy simulation program (BESP) along with a computational fluid dynamics (CFD) package. A typical DSF cavity model has been established and simulated. The model and the modeling process have been calibrated and validated against the experimental data. The validated model was used to develop correlations that can be implemented in a BESP, allowing users to take advantage of the accuracy gained from CFD simulations without the required computation time. Correlations were developed for airflow rate through cavity, average and peak cavity air temperature, cavity air pressure, and interior convection coefficient. The correlations are valuable for “back of the envelope” calculation and for examining accuracy of zonal-model-based energy and airflow simulation programs.

This paper analyses the ventilation airflow pattern in a two-bedded hospital room. The whole space of the room is divided in modules by means of curtains and internal partition walls. This configuration has many advantages from the point of view of comfort and medical assistance, but it implies an important restriction as far as ventilation is concerned. The ventilation system consists of an induction unit placed inside the hall ceiling blowing into the room and an exhaust fan in the bathroom. Numerical model solves mass, momentum and mean age of air equations assuming isothermal and stationary flow. Ventilation is evaluated analysing the age of air and the velocity fields inside the room. The results with the initial architectural design of the room show a very deficient ventilation at the patients site. Alternative configurations have been studied, allowing for correct ventilation without renouncing to the assistance advantages. Finally, the optimum configuration of the room is provided, regarding both the comfort of the patients and the cost of execution.

Ground-source heat pump (GSHP) systems can achieve a higher coefficient of performance than conventional air-source heat pump (ASHP) systems. For the design of a GSHP system, it is necessary to accurately predict the heat extraction and injection rates of the heat exchanger. Many models that combine ground heat conduction and heat exchangers have been proposed to predict heat extraction/injection rates from/into the ground in the research field of heating, ventilation and air-conditioning systems. However, most analysis models are inaccurate in their predictions for long periods because they are based on a thermal conduction model using a cylindrical coordinate model or an equivalent diameter model. In this paper, a numerical model that combines a heat transport model with ground water flow and a heat exchanger model with an exact shape is developed. Furthermore, a method for estimating soil properties based on ground investigations is proposed. Comparison between experimental results and numerical analysis based on the model developed above was conducted under the conditions of an experiment from 2004. The analytical results agreed well with the experimental results. Finally, the proposed model was used to predict the heat exchange rate for an actual office building in Japan.

As an application of the super-hydrophilicity of a photocatalyst (TiO2) coating, buildings are cooled by sprinkling water on their external surfaces coated with TiO2. This is a new cooling technology that was recently developed in Japan. In order to make better use of this cooling system, quantitative prediction and evaluation of the cooling effect on the urban/built environment is required during design. In an attempt to provide a computer-aided simulation tool for supporting the above-mentioned design, we introduce a thermal simulation tool that was developed previously by the authors’ group. The goal of the present study is to develop a numerical model by which to predict the temperature of a TiO2-coated surface with a water film and integrate the calculation algorithm into the simulation tool. The availability of the proposed model was discussed in the present paper. Various urban districts in downtown Tokyo were selected for a discussion of the availability of the simulation tool in which the proposed model is integrated. Simulations were performed to quantify the thermal improvement effect of the cooling system in terms of surface temperature reduction, mean radiative temperature (MRT), heat island potential (HIP), indoor air temperature, and cooling load reduction.

There are few countries in the world where they have special characteristics including weather conditions, wind direction, and topography. In other words, some countries have multi-climate regions, and needed to be investigated more precisely. Based on these conditions, several cooling systems can be used for each region. In this study, the potential of the direct evaporative cooling (DEC) systems, indirect evaporative cooling (IEC) systems, desiccant wheel (DW) with DEC systems, and combination of theses methods for cooling in the cities of Iran are investigated. In the remaining regions, mechanical cooling systems and absorption systems can be used. According to weather condition and natural resources for water in Iran, DEC can be considered as a serious alternative for cooling. In this paper, based on numerical simulation and long-term meteorological measurements, general set of criteria is obtained. Results show that according to population dispersal DEC systems can provide comfort conditions for 53% of people of Iran. IEC, DW, combination of these systems, and mechanical cooling systems can supply comfort condition in remaining major cities of Iran consequently. Moreover, for showing the uniqueness of weather condition which leads to these varieties of climates, other important cities in the neighboring countries are compared with this numerical simulation code.

As a new-style building, the thermal performance of double skin facade with the venetian blind cannot be predicted for the absence of suitable tool. In the paper, a detailed analysis of the thermal process in glass double facade with venetian blind was made. The governing equations were solved by comprising CFD, optical and heat balance model for multi-layer transparent system. It is shown that the more complex natural ventilation exists in the two air gaps divided by venetian blind, which cannot be reflected with the simplified model. Comparing the simulation results with the experiment data in the literature, a good agreement was achieved. Hence, it can be used as a reliable tool to analyze the ventilation in the double skin facade with a venetian blind.