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• Hydronic heating/cooling systems and GCHP performance indicators are briefly described. • Performances of various heating/cooling systems connected to a GCHP are tested in laboratory. • An energy efficiency comparison of radiator heating and radiant heating/cooling is provided. • A comparison of thermal comfort achieved with analysed heating/cooling systems is reported. • Two simulation models of thermal useful energy and COP of these systems are developed in TRNSYS. The method used in this study consists of evaluating different terminal heating/cooling systems in an experimental office at the Polytechnic University of Timișoara, Romania, through experimentation and numerical simulation. This paper is focused on the energy efficiency exploratory research of various low- and very low-temperature hydronic radiant heating/cooling systems (floor, wall, ceiling, combined floor-ceiling) and of the medium-temperature radiator heating system, connected to a vertical ground-coupled heat pump (GCHP) in double U-tube borehole heat exchanger (BHE) configuration. The main performance parameters are obtained for five weeks of operation in heating mode and three weeks in cooling mode, and a comparative analysis of these parameters together with indoor thermal comfort is carried out. The four simple heating systems (radiator, floor, wall, ceiling) have relatively small differences (maximum 7.4 %) in their coefficient of performance (COP) values, but the number of starts/stops in the case of radiator heating is twice that of floor heating, which leads to greater wear and tear on the heat pump equipment. Under the same operating conditions, the CO 2 emission of the radiator heating system are 0.7–16 % higher than those of the heating system with radiant panels (floor, wall, and ceiling). The floor-ceiling combined radiant heating system has the highest COP syst of 5.45 as well as the lowest CO 2 emission value of 2.15 kg. The predicted mean vote (PMV) index (pair 1.1 met-0.29 clo) has values approximately equal to 0 only in the case of the floor-ceiling heating, when the percent of likely dissatisfied with the thermal comfort is 5 %. The three cooling radiant systems show differences in their energy performance, namely the radiant ceiling cooling system has the best COP syst , 39.8 % higher than that of the radiant floor and only 5.9 % higher than that of the radiant wall. The values of the PMV index (pair 1 met-0.9 clo) for the radiant wall cooling system are 31–41 % lower than those of the radiant floor and 10.4–14.2 % lower than those of the radiant ceiling. Finally, numerical simulations of the useful thermal energy and the system COP in heating and cooling modes are performed with TRNSYS software for a duration of 8760 h and then analysed and compared with the experimental tests to validate the simulation models. [ABSTRACT FROM AUTHOR]

The negative environmental impacts of burning fossil fuels have forced the energy research community seriously to consider renewable sources, such as naturally available solar energy. Thermally powered refrigeration technologies are classified into two categories: thermo-mechanical technology and sorption technology (open systems or closed systems). This paper provides a detailed review of the solar closed sorption (absorption and adsorption) refrigeration systems, which utilise working pairs (fluids). After an introduction of the basic principles of these systems, the history of development and recent advances in solar sorption refrigeration technologies are reported. The adsorption cooling typically has a lower heat source temperature requirement than the absorption cooling. Based on the coefficient of performance (COP), the absorption systems are preferred over the adsorption systems, and the higher temperature issues can be easily handled with solar adsorption systems. The thermodynamic properties of most common working fluids, as well as the use of ternary mixtures in solar-powered absorption systems, have been reviewed in this study. The paper also refers to new approaches to increase the efficiency and sustainability of the basic adsorption cycles, such as the development of hybrid or thermal energy storage adsorption systems. This research shows that solar-powered closed sorption refrigeration technologies can be attractive alternatives not only to serve the needs for air-conditioning, refrigeration, ice making, thermal energy storage or hybrid heating and cooling purposes but also to meet the demands for energy conservation and environmental protection. [ABSTRACT FROM AUTHOR]

The ground-coupled heat pump (GCHP) system is a type of renewable energy technology providing space heating and cooling as well as domestic hot water. However, experimental studies on GCHP systems are still insufficient. This paper first presents an energy-operational optimisation device for a GCHP system involving insertion of a buffer tank between the heat pump unit and fan coil units and consumer supply using quantitative adjustment with a variable speed circulating pump. Then, the experimental measurements are used to test the performance of the GCHP system in different operating modes. The main performance parameters (energy efficiency and CO 2 emissions) are obtained for one month of operation using both classical and optimised adjustment of the GCHP system, and a comparative analysis of these performances is performed. In addition, using TRNSYS (Transient Systems Simulation) software, two simulation models of thermal energy consumption in heating, cooling and domestic hot-water operation are developed. Finally, the simulations obtained using TRNSYS are analysed and compared to experimental data, resulting in good agreement and thus the simulation models are validated. [ABSTRACT FROM AUTHOR]

This paper provides a comparative study of the energy efficiency of a conventional ventilating and air conditioning (VAC) system with three configurations. This system was used to cool an experimental room in an office building in more control scenarios realised by adopting different cooled water temperatures and chiller cooling systems. In this purpose, an air–water mist cooled system for an air-cooled chiller is proposed. Depending on the components, the analysed VAC system has the following configurations: (1) air handling unit (AHU) and fan-coil units (FCUs); (2) air handling unit (AHU); and (3) heat recovery unit (HRU) and fan-coil units (FCUs). The electricity consumption weight of the equipment of each VAC system, the total energy consumption and the influence of control parameters on this consumption are analysed. The results of the experiments indicate that the optimal efficiency VAC system in office buildings includes an AHU and FCUs with an air–water mist cooled chiller and a cooled water temperature of 8 °C. For this system, a mathematical model is developed to minimise the electricity consumption by optimal control, where the consumption depends only on non-controlled parameters (solar radiation intensity and outdoor air temperature). This model is verified with actual measurements to confirm its accuracy, and a good agreement between the prediction and measurement is achieved. Additionally, the assessment of thermal comfort in the experimental office is performed based on the PMV-PPD model using the ASHRAE Thermal Comfort programme. The obtained results demonstrate that the AHU&FCUs system assures an increase in thermal comfort. Finally, a TRNSYS simulation model of energy consumption and PMV-PPD indices for the AHU&FCUs system is developed and experimentally validated. [ABSTRACT FROM AUTHOR]

The paper presents a review on recent development of possible substitutes for non-ecological refrigerants from HVAC&R equipment based on thermodynamic, physical and environmental properties and TEWI (Total Equivalent Warming Impact) analysis. This review contains a good amount of information regarding the environmental pollution produced by the working fluids of the air-conditioning, heat pump and commercial refrigeration applications and the ecological refrigerant trend. Overall, it is useful for those readers who are interested in current status of alternative refrigerant development related to vapour compression-based refrigeration, air-conditioning and heat pump units. The study describes the selection of refrigerants adapted to each utilisation based on the thermodynamic, physical and environmental properties and explores the studies reported with new refrigerants in domestic refrigerators, commercial refrigeration systems, air-conditioners, heat pumps, chillers and in automobile air-conditioners. Additionally, a comparative analysis of the TEWI for possible substitutes of refrigerant R22 used in various air-conditioning, heat pump and refrigeration systems is performed. [ABSTRACT FROM AUTHOR]

Highlights: [•] It is provided a detailed literature review of GSHP systems and their recent advances. [•] Typical simulation and ground TRT models for vertical GHEs are summarized. [•] A new GWHP with a special heat exchanger tested in laboratory is described. [•] We reviewed various hybrid GCHP systems for cooling or heating-dominated buildings. [•] Energy, economic and environmental performance of a closed-loop HGCHP system is analyzed. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the method of decreasing the size of heat exchanger surfaces by increasing the heat transfer coefficients and the importance of heat transfer enhancement for vaporization. We report an experimental study on surfaces modified by passive methods applied to heat transfer surfaces mechanically processed, covered with sleeves made by metallic tissues or covered with metallic porous layers performed using welding procedures. Experiments are made to investigate the heat transfer coefficient on copper tubes with a 22mm external diameter using heat from inner source to outer vaporizing liquid. There are developed specific heat transfer correlations for each group of enhanced surfaces. The experimental data and new proposed correlations are compared with well known correlations. The results are in best agreement with the Cornwell–Houston correlation. [Copyright &y& Elsevier]

Highlights: [•] We provided a detailed review of different solar refrigeration technologies. [•] Theoretical basis and practical applications for cooling systems were presented. [•] Different working pairs were illustrated by their COPs and maximum temperatures. [•] It was explored solar hybrid cooling systems with heterogeneous composite pairs. [•] A comparison of various solar cooling systems and some use suggestions were given. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]