Computer modelling and thermodynamic assessment of an aqua-ammonia absorption cycle solar heat pump

An assessment based on steady state thermodynamic analysis of an aqua-ammonia absorption cycle solar heat pump for space heating is presented. The system consists of a solar heated generator, rectifier, condenser, evaporator, absorber liquid heat exchanger and a subcooler. During heat pump operation, the evaporator absorbs heat at low temperature from the outside atmospheric air, while the heat rejected by the absorber, condenser and rectifier is used to warm the interior air of the space to be heated. A numerical computer modelling based on the solution of simultaneous heat and mass balance equations for various components of the system has been carried out. The influences of component temperatures and heat exchanger effectiveness on the heating coefficients of performance and heat transfer rates have been investigated to obtain optimum operating conditions for the proposed heat pump system. Further, the absorption cycles are compared with an ideal reversible cycle operating over the same range of temperatures. It has been found that the performance of the absorption cycle does not continue to improve as the input temperature increases and that additional components will be required to allow the machine to take advantage of the higher temperatures available from modern collectors.     

Development and experimental validation of a novel indirect-expansion solar-assisted multifunctional heat pump

This paper proposes a novel indirect-expansion solar-assisted multifunctional heat pump (IX-SAMHP) which integrates a domestic heat pump with a solar water heater. The IX-SAMHP can not only work in operation modes included in the two household appliances, but also operate in four new energy-saving operation modes for the space cooling, space heating and water heating. All operation modes have functioned successfully and can be switched to each other smoothly on a purpose-built experimental setup. Experiments of the heat pump water heating mode at outdoor air temperatures of 8 °C and 15 °C and the solar-assisted space heating mode at indoor air temperatures of 20 °C have been investigated in detail. Electric heaters were used to simulate solar radiation intensity in different weather conditions. The experimental results show that the IX-SAMHP can produce hot water with much less electric consumption in cloudy days compared with a solar water heater and can operate in much higher coefficient of performance than a domestic heat pump in cold winter. The IX-SAMHP is especially suitable for the regions abundant in solar radiation where the space heating, space cooling and water heating are required all the year round.     

夏热冬冷地区办公建筑降低供暖空调能耗的技术路径

以上海地区某办公建筑为例,基于EnergyPlus能耗模拟,探讨了围护结构性能提升和暖通空调系统优化这2条节能技术路径对夏热冬冷地区办公建筑降低供暖空调全年能耗的有效性.结果 表明:围护结构性能提升的节能潜力较小,经济性较差;单纯提高围护结构保温隔热性能并不能保证降低建筑年耗冷量,应综合分析全年供热供冷能耗确定围护结构...     

Modeling and economic analysis of gas engine heat pumps for residential and commercial buildings in various climate regions of Iran

There is an increasing trend in using heat pumps in air conditioning (heating/cooling) systems of residential and commercial buildings. The required power to drive the compressor of vapor compression heat pump cycles may be provided by either an electrical motor or an internal combustion engine. In this paper thermal modeling and economic analysis of gas engine heat pumps (GEHPs) are presented based on energy and mass balance equations as well as the gas engine operating parameters (such as thermal efficiency, fuel consumption and fuel mass flow rate) and heat pump operating parameters (such as evaporator and condenser capacity and compressor input power). Based on the modeling results and with estimating GEHP fuel consumption, the economic analysis of using gas engine heat pumps (in comparison with the electrical heat pumps) at various climate regions of Iran, for both residential and commercial (office) buildings, and for both cooling and heating modes, was performed. Appropriate cost functions for predicting GEHP capital investment were proposed. Three approaches including equivalent uniform annual cost (EUAC), the annual cost of energy consumption, and payback period were applied in the economic analysis.     

Monitoring the energy consumption in a district heated apartment building in Copenhagen,with specific interest in the thermodynamic performance

The energy consumption in an apartment building in Copenhagen supplied by district heating has been monitored from November 2000 to June 2002. During the period heat cost allocators were installed on the radiators and the set point for domestic hot water was raised in order to prevent the Legionella Disease. Results from the space heating system and the loading circuit for production of domestic hot water are discussed with respect to heat loads, cooling of the district heating water and the efficiency of the pump and the heat exchangers. The Public Service Obligation for utility companies in Denmark to help their customers to save energy calls for tools to analyse the energy consumption and the efficiency of the system. The possibility to use three-dimensional plots to analyse the thermodynamic performance is discussed as one option.     

Analysis of a combined photovoltaic–geothermal gas-fired absorption heat pump system in a Canadian climate

This study examines the technical feasibility of using a geothermal gas-fired absorption heat pump (A-GSHP) for space conditioning and domestic hot water heating in a Canadian climate. The A-GSHP is coupled to a photovoltaic (PV) system with battery storage intended to ensure the full autonomy of the heating, ventilating and air conditioning (HVAC) system from the electric grid. The system is modelled using TRNSYS with standard models and a new performance-based A-GSHP model, which accounts for part-load operation. Results indicate that the coefficient of performance (COP) is equal to 1.12, 0.55 and 1.79 for heating only, cooling only and simultaneous cooling and domestic hot water (DHW) heating, respectively. A 13.5 kWp PV array and a 400 kWh battery storage are necessary to provide the electrical power required to operate the A-GSHP and the associated HVAC system at all times without importing electrical energy from the grid.     

集体宿舍热泵辅助太阳能热水器热性能分析

我国既有建筑面积为560亿m~2,绝大部分为高能耗建筑,生活热水能耗占建筑能耗的20%~30%。建筑节能势在必行。通过对上海地区某高校学生宿舍空气源热泵辅助太阳能热水系统的实际运行工况下的热性能测试和分析计算,得到该系统年运行耗能为807 445.6 MJ,热泵的平均COP为3.2,系统太阳能保证率为47%,系统年运行费用仅为37 147.4元,具有极大的节能经济性,为生活热水能耗研究提供了一定的理论指导。     

封闭式水系统全年空调的构思与分析

提出了一种可使用水冷冷水机组同时实现夏季制冷和冬季供暖的集中空调系统冷热源方案，该机组夏季可利用水冷冷水机组制冷系数高的特点而冬季又能以热泵方式工作。初步分析表明在中南部地区其全年能耗低于空气源热泵机组。     

Modelling of a water-to-air variable capacity ground-source heat pump

The present work aims at presenting the development of a performance-based model of a water-to-air variable capacity ground-source heat pump. The main challenge is to apply the recommended control strategy to vary the speed of the compressor for each mode of operation and to be able to switch from one mode to the other. A series of verification tests tend to confirm that the speed control strategy has been correctly implemented. The proposed model is used in annual simulations of a residential system equipped with a variable capacity ground-source heat pump. In this case, the seasonal performance factor (SPF?=?ratio of the annual energy requirement for heating, cooling and domestic hot water (DHW) over the annual total energy consumption) is 3.64. The corresponding value for a conventional system composed of a fixed capacity heat pump operating in on–off mode and a separate electric DHW tank is 2.60.     

宾馆热泵热水系统的试验研究

探讨了适用于宾馆的热泵热水系统的加热方式及水箱布置形式。结合工程实例,对不同卫生热水温度下的热泵制热性能系数及不同水箱布置形式的热泵热水系统耗电量进行了试验研究。在宾馆使用热泵制备卫生热水可行。在选择合适的冷凝器卫生热水进出口温差以提高热泵制热性能系数时,应优化水箱布置形式,减少循环泵数量及其能耗,以提高热泵热水系统的制热性能系数。     

A simulation appraisal of performance of different HVAC systems in an office building

The article reports on a simulation appraisal of energy consumption, energy costs and environment impact of three systems used for space heating, and space cooling of an office building in Kragujevac, Serbia. Three investigated systems are (1) a system with a natural gas boiler and convective baseboard heaters for water space heating and window air conditioners for air space cooling; (2) a system with a natural gas boiler and individual air reheaters for air space heating and a chiller plant for air space cooling; and (3) an air-to-air heat pump for air space heating, and cooling. The systems are modeled and simulated by using EnergyPlus software. After simulations, it is found that the first investigated system has the highest energy efficiency, the best economy, and the lowest environmental impact. That is because of the fact that the first system has water as a heating medium and uses predominantly natural gas as fuel. However, in future, when for generation the grid electrical energy requires less primary energy, and becomes decarbonized, the third system would be best to conserve energy resources and environment.     

An aquifer thermal storage system in a Belgian hospital: Long-term experimental evaluation of energy and cost savings

Over a three years period, an aquifer thermal energy storage system was monitored in combination with a heat pump for heating and cooling of the ventilation air in a Belgian hospital. The installation was one of the first and largest ground source heat pump systems in Belgium. Groundwater flows and temperatures were monitored as well as the energy flows of the heat pumps and the energy demand of the building. The resulting energy balance of the building showed that the primary energy consumption of the heat pump system is 71% lower in comparison with a reference installation based on common gas-fired boilers and water cooling machines. This corresponds to a CO₂-reduction of 1280 ton over the whole measuring period. The overall seasonal performance factor (SPF) for heating was 5.9 while the ATES system delivered cooling at an efficiency factor of 26.1. Furthermore, the economic analysis showed an annual cost reduction of k€ 54 as compared to the reference installation, resulting in a simple payback time of 8.4 years, excluding subsidies.     

Simulation and analysis on thermodynamic performance of surface water source heat pump system

This work established a thermodynamic performance model of a heat pump system containing a heat pump unit model, an air conditioning cooling and heating load calculation model, a heat exchanger model and a water pump performance model based on mass and energy balances. The thermodynamic performance of a surface water source heat pump air conditioning system was simulated and verified by comparing the simulation results to an actual engineering project. In addition, the effects of the surface water temperature, heat exchanger structure and surface water pipeline transportation system on the thermodynamic performance of the heat pump air conditioning system were analyzed. Under the simulated conditions in this paper with a cooling load of 3400 kW, the results showed that a 1 °C decrease in the surface water temperature leads to a 2.3 percent increase in the coefficient of performance; furthermore, an additional 100 m of length for the closed-loop surface water heat exchanger tube leads to a 0.08 percent increase in the coefficient of performance. To decrease the system energy consumption, the optimal working point should be specified according to the surface water transportation length.     

燃气机热泵在夏热冬冷地区应用的经济性分析

以上海地区某独立的两层结构别墅为对象,考虑了燃气机热泵、电驱动空气源热泵与电热水器及燃气热水器组合3种方案,比较了三者在夏季制冷、冬季供暖、制备生活热水时的全年能耗及运行费用。在生活热水产量相同的情况下,燃气机热泵的能耗和运行费用均低于电驱动空气源热泵与电热水器及燃气热水器组合方案,经济性显著。     

基于的热泵与水泵联合优化运行仿真及操作软件

研究热泵空调系统在全年变负荷运行下,为了减少热泵系统运行的有效能损失,提高能量利用的完善度,在满足系统供冷、供热的可靠运行条件下,以系统总损失(热泵机组和水泵损失)最小为目标函数,即minE=Epc+Epe+Ecom+Ec+Ee+Elip(E表示水源系统总的损失;Epc表示冷凝器侧水泵的损失;Epe表示蒸发器侧水泵的损失;Ecom表示压缩机的损失;Ec表示冷凝器的损失;Ee表示蒸发器的损失;Elip表示节流结构的损失),并从系统结构设计及主要功能、仿真模型的建立、建立开放型数据库、系统优化运行仿真可视化等方面,介绍在微机上基于可视化的热泵系统优化运行仿真系统的研究成果。通过一个实例详细地介绍了整个优化过程,并将优化结果以图文并茂的形式显示出来,可为空调系统优化设计、运行提供参考,为热泵系统在微机上实现在线优化控制策略奠定了基础。     

Energy savings potential of a desiccant assisted hybrid air source heat pump system for residential building in hot summer and cold winter zone in China

In hot summer and cold winter zone in China, air conditioning system has four running modes yearly including cooling with dehumidification, cooling, dehumidification and heating in residential buildings. The conventional air source heat pump (ASHP) system is not designed to independently control temperature and humidity, and is not very suitable for the dehumidification mode in the view of building energy consumption. A novel ASHP system combining radiant cooling/heating for residential buildings was presented. The main feature of this hybrid ASHP system is that desiccant wheel and cooling coil accomplish dehumidification process together, and the regenerative heat needed by the desiccant wheel is supplied by the condenser dissipated heat. Based on simulation studies and performance analysis, this paper predicts the primary energy consumption of the hybrid ASHP system in comparison with the conventional ASHP system during the cooling and heating seasons. It was found that primary energy requirement can be reduced by more than 8% in cooling with dehumidification mode, by 50% in dehumidification mode, and by more than 14% in heating mode. The study results prove that the hybrid ASHP system can keep great energy saving and running cost saving yearly, especially in the dehumidification process.     

蓄热型空气式太阳能集热-空气源热泵复合供暖系统在寒冷地区的应用研究

设计了一种蓄热型空气式太阳能集热-空气源热泵复合供暖系统。该系统具有太阳能供热、太阳能辅助热泵供热和热泵供热3种运行模式,可根据环境工况及供暖负荷的变化自动切换运行模式,保证室内供暖的稳定性。在通辽市的实验研究结果表明:在整个供暖季内,该系统可持续提供42.6℃的热水,维持室内温度在21.3~24.1℃之间;平均COP为3.6,实现了太阳能的高效利用,减少了常规能源的消耗,可节约标准煤21 t;与电供暖、燃煤锅炉供暖及燃气锅炉供暖系统相比,年运行费用可分别降低62.2%、49.1%、46.2%,回收期分别为4.7、9.8、10.3 a。     

多种生活热水供热系统技术及经济对比分析

以小区中央热水系统改造为背景,对太阳能集热器+电加热器热水系统、空气源热泵+电加热器热水系统、空气源热泵+板式换热器+电加热器热水系统、水源热泵、地源热泵热水系统等几种热源供热系统进行了对比分析,结果表明利用空气源热泵+板式换热器+电加热器热水系统最节能,与小区原电加热系统相比可以使热水工作费用降低76.8％.     

空气源热泵全年能耗分析应用软件的开发

介绍了空气源热泵奏年能耗分析应用软件的开发,该软件根据空调冷负菏、室外干球温度、热泵出水温度求解热泵供冷全年能耗;在求热泵共热能耗时,除考虑上述3个参数以外,还将室外空气相对湿度这一重要因素考虑到热泵供热性能中,使热泵供热能耗计算更准确。     

Development and experimental validation of a high-temperature heat pump for heat recovery and building heating

The performance of a high-temperature heat pump unit using geothermal water for heat recovery in buildings is experimentally evaluated. The unit consists of a twin-screw refrigeration compressor, a condenser, an evaporator and an oil cooling system. The effect of the cooled oil temperature on the performance of the heat pump unit is experimentally investigated. Results show that the unit stably produces outlet hot water at a constant temperature of 85 °C and performs well in a wide range of high-temperature conditions with a high energy efficiency ratio. The results also indicate that the key to improving the performance of a high-temperature heat pump unit often depend on the selection of proper cooled oil temperature. The optimum cooled oil temperature is 50-65 °C when the condensing temperature is above 70 °C. At these temperatures, the oil cooling system can increase the energy efficiency ratio of the heat pump by 6.3%.