Performance analysis of a solar-assisted ground-source heat pump system for greenhouse heating: an experimental study

This study investigates the performance characteristics of a solar-assisted ground-source (geothermal) heat pump system (SAGSHPS) for greenhouse heating with a 50 m vertical 32 mm nominal diameter U-bend ground heat-exchanger. This system was designed and installed in the Solar Energy Institute, Ege University, Izmir (568 degree days cooling, base: 22 °C, 1226 degree days heating, base: 18 °C), Turkey. Based upon the measurements made in the heating mode from the 20th of January till 31st of March 2004, the heat extraction rate from the soil is found to be, on average, 57.78 W/m of bore depth, while the required borehole length in metre per kW of capacity is obtained as 11.92. Design practices in Turkey normally call for U-bend depths between 11 and 13 m/kW of heating. The entering water temperature to the unit ranges from 8.2 to 16.2 °C, with an average value of 14 °C. The greenhouse air has a maximum day temperature of 31.05 °C and night temperature of 14.54 °C with a relative humidity of 40.35%. The heating coefficient of performance of the heat pump (COP_HP) is about 2.00 at the end of a cloudy day, while it is about 3.13 at the end of sunny day and fluctuates between these values in other times. The COP values for the whole system are also obtained to be 5–20% lower than COP_HP. The clearness index during experimental period is computed as average 0.56. At the same period, Cucumus sativus cv. pandora F₁ was raised, and product quality was improved with the climatic conditions in the designed SAGSHPS. However, experimental results show that monovalent central heating operation (independent of any other heating system) cannot meet the overall heat loss of the greenhouse if the ambient temperature is very low. The bivalent operation (combined with other heating system) can be suggested as the best solution in Mediterranean and Aegean regions of Turkey.     

R744热泵系统研究动态

R744作为一种天然工质，是热泵系统中最有潜力的替代工质之一。近10年来，美国、欧洲和日本等发达国家和地区对R744热泵系统进行了大量研究，并取得了一些突破性研究成果，介绍了R744热泵样机及其压缩机、换热器、膨胀阀等各重要部件的研究状况。     

R410A与R22在家用空调中的应用比较(1)

R410A不破坏臭氧层,是一种可以长期替代R22的绿色环保制冷剂,现已在家用空调中得到日益广泛的应用。本文分别对R410A与R22的热力性能,对4台具有可比性的R410A与R22空调的系统性能即制冷量和能效比进行比较考察,结果表明R410A具有良好的热传递与流动特性,有利于减少空调换热器尺寸、提高系统运行效率。     

Theoretical study of R32 to replace R410A in variable refrigerant flow systems

In recent years, global warming has reached critical levels and this has caused a gradual decrease in the use of refrigerants. In the 1997 Kyoto Conference, it was announced that after 2011, use of refrigerants which have higher global warming potential (GWP) of 150 will be restricted. Hence, it was foreseen that R410A, with a GWP of 2088, which has been used in residential heating, ventilating and air conditioning systems, will be prohibited in the near future. This study investigates the thermodynamic performance using R32, which is a potential alternative because of its low GWP, and R410A in variable refrigerant flow (VRF) systems. As a result of theoretical analysis, it was observed that the coefficient of performance of R32 is 5% higher in heating mode and 6% higher in cooling mode than that of R410A. Considering all of this, it was confirmed that R32 can be used in VRF systems as a replacement for R410A in terms of performance.     

A theoretical study of an innovative ejector enhanced vapor compression heat pump cycle for water heating application

This study presents a novel vapor compression heat pump cycle in which an ejector associated with a subcooler is applied to enhance the heating performance for air-source heat pump water heater application. The heating coefficient of performance (COP_h) and heating capacity of the novel cycle using the non-azeotropic mixture refrigerant R417A are theoretically investigated, for the ranges of evaporating temperature (−15 to 10 °C) and condensing temperature (55-60 °C). The theoretical results show that the COP_h and volumetric heating capacity of the novel cycle are better than that of the conventional heat pump cycle. It is found that for the operating conditions considered, the maximum COP_h and volumetric heating capacity can be improved by up to 1.62-6.92% and 15.20-37.32% over the conventional heat pump cycle, respectively. The performance characteristics of the novel cycle show its promise in air-source heat pump water heater applications.     

Experimental study of a solar-assisted ground-coupled heat pump system with solar seasonal thermal storage in severe cold areas

This paper presents the experimental study of a solar-assisted ground-coupled heat pump system (SAGCHPS) with solar seasonal thermal storage installed in a detached house in Harbin. The solar seasonal thermal storage was conducted throughout the non-heating seasons. In summer, the soil was used as the heat sink to cool the building directly. In winter, the solar energy was used as a priority, and the building was heated by a ground-coupled heat pump (GCHP) and solar collectors alternately. The results show that the system can meet the heating-cooling energy needs of the building. In the heating mode, the heat directly supplied by solar collectors accounted for 49.7% of the total heating output, and the average coefficient of performance (COP) of the heat pump and the system were 4.29 and 6.55, respectively. In the cooling mode, the COP of the system reached 21.35, as the heat pump was not necessary to be started. After a year of operation, the heat extracted from the soil by the heat pump accounted for 75.5% of the heat stored by solar seasonal thermal storage. The excess heat raised the soil temperature to a higher level, which was favorable for increasing the COP of the heat pump.     

A parametrical study on the energetic and exergetic assessment of a solar-assisted vertical ground-source heat pump system used for heating a greenhouse

An energetic and exergetic modeling of a solar-assisted vertical ground-source heat pump (GSHP) greenhouse heating system (SAGSHPGHS) for system analysis and performance assessment is presented in this study. Energy (heating coefficient of performance ‘COP’) and exergy efficiencies at various reference and entering water temperatures are also determined. The actual thermal data collected are utilized for the model calculations at different reference temperature values in the range of −0.69 to 25 °C. Furthermore, the performance of a SAGSHPGHS, installed in Solar Energy Institute of Ege University, Izmir, Turkey, is evaluated to show, how energy and exergy efficiencies values change with system. The exergy destructions in the overall SAGSHPGHS are quantified, particularly for a reference temperature of −0.69 °C on 7 January 2004 for comparison purposes. Based upon the measurements made in the heating mode from the 16th of December 2003 till 31st of March 2004, average heating COPs of the GSHP unit and the overall system are obtained to be 2.84 and 2.27, respectively. The best (peak) COP of the GSHP and system were found to be 3.14 and 2.79 on 7 January 2004, respectively. Average exergy efficiency of the system is determined to be 68.11%, while the best exergy efficiency peak values for the GSHP unit and the whole system on a product/fuel basis are obtained to be 76.2% and 75.6%, respectively.     

R404A压缩冷凝机组变环境温度实验研究

本文在蒸发温度不变,而环境温度变化的情况下对压缩冷凝机组进行了性能测试,分析了外界环境温度变化对压缩冷凝机组系统COP、输入功率、压比等性能参数的影响。由实验结果可知:蒸发温度保持不变,环境温度每上升1℃,COP平均下降2.6%,即环境温度对机组运行效率的影响比较大,对压缩冷凝机组进行优化可有效提高机组的性能。该实验为进一步提高压缩冷凝机组的性能提供了实验参考依据。     

Performance of a new refrigeration cycle using refrigerant mixture R32/R134a for residential air-conditioner applications

In this paper, a new refrigeration cycle (NRC) using the binary non-azeotropic refrigerant mixture R32/R134a is presented, which can be an alternative refrigeration cycle applied in residential air-conditioner. In the NRC, refrigerant circuit of the evaporator is separated into two branches. Because the non-azeotropic mixture has the characteristic of temperature glide, an important benefit of such configuration is that the Lorentz cycle can be realized. Compared with that of conventional cycle configuration, the new cycle efficiency can be improved. The calculating results show that, in the conventional refrigeration cycle (CRC), the mixture R32/R134a has a close performance to that is obtainable with pure refrigerant R22. However, the mixture R32/R134a in the NRC will result in a better performance. The maximal COP can be improved in a range of 8–9% over that of the CRC, and the volumetric refrigerating capacity can be approximately increased by 9.5%.     

直燃型氨——水GAX吸收式热泵的计算机仿真及研制

介绍了利用计算机仿真，设计及优化技术研制直燃型氨－水ＧＡＸ（发生器－吸收器热交换）吸收式热泵的过程，并阐述了氨－水单效及ＧＡＸ吸收系统的原理，结构及运行工况。     

R410A与R22在家用空调中的应用比较(2)

本文部分（2）利用Bin参数分析法对R410A与R22空调的全年运行耗电进行计算,采用寿命期气候性能（LCCP）指标对R410A与R22的温室效应总体影响进行考查,同时对R410A与R22空调的生产成本进行比较。结果表明R410A空调由于运行效率高,在使用过程中可以显著节约耗电和运行费用,而且随着原材料价格的上涨和R410A压缩机生产能力的扩大,R410A与R22空调具有相近的生产成本;同时,通过减小温室间接效应以及空调的制冷剂充灌量或泄露量,与R22相比,R410A反而还会有利于降低对气候变暖的影响。     

ANN-GA approach for predictive modelling and optimization of NOx emissions in a cement precalcining kiln

China’s cement production is increasing, but the sustainable development of the cement industry is hindered by pollutants, especially nitrogen oxide, with serious health impacts. This study reports the use of an artificial neural network and a genetic algorithm to control the operation parameters of a new dry-process cement kiln technology to predict and optimise the nitrogen oxide emissions. Comparing the predicted value and actual value, the error of the model is less than 2%. The GA is used to search the optimal operation parameters to achieve the lowest concentration of nitrogen oxide emission, which is 165.9 mg/m³ under optimal conditions. The results of sensitivity analysis show that the furnace temperature, raw material quantity and third air temperature have the greatest influence on the nitrogen oxide emission. This model prediction and optimisation can provide a reference for enterprises in controlling operation parameters to reduce nitrogen oxide emission.     

地源热泵机组冬季运行性能预测

探讨了人工神经网络应用于地源热泵机组性能预测的可行性,建立了地源热泵机组性能预测模型并对机组的冬季运行特性进行了模拟与预测,模拟值与实测值的偏差系数在2.63%以内。     

A thermodynamic analysis of a transcritical cycle with refrigerant mixture R32/R290 for a small heat pump water heater

In this study, a thermodynamic analysis on the performance of a transcritical cycle using azeotropic refrigerant mixtures of R32/R290 with mass fraction of 70/30 has been performed. The main purpose of this study is to theoretically verify the possibility of applying the chosen refrigerant mixture in small heat pumps for high temperature water heating applications. Performance evaluation has been carried out for a simple azeotropic mixture R32/R290 transcritical cycle by varying evaporator temperature, outlet temperature of gas cooler and compressor discharge pressure. Furthermore, the effects of an internal heat exchanger on the transcritical R32/R290 cycle have been presented at different operating conditions. The results show that high heating coefficient of performance (COP_h) and volumetric heating capacity can be achieved by using this transcritical cycle. It is desirable to apply the chosen refrigerant mixture R32/R290 in small heat pump water heater for high temperature water heating applications, which may produce hot water with temperature up to 90 °C.     

地源热泵夏季性能测试及传热模型

对50m深埋地下换热器地源热泵系统夏季间歇运行时的制冷性能进行了测试,分析了系统运行对地温的影响,提出采用混合系统来解决重庆地区冬夏季土壤中吸热、放热不平衡的问题,引入圆柱源理论建立了垂直U型管传热模型,模拟结果与实验结果吻合较好。     

厦门地区应用海水源热泵的探讨

介绍了海水源热泵的概念和工作原理,分析了厦门地区资源现状及其利用海水源热泵的自然条件优势,分析了应用中的问题和对策,并对厦门应用海水源热泵技术的问题进行了探讨,以推动海水源热泵技术的发展。     

Performance study of underground thermal storage in a solar-ground coupled heat pump system for residential buildings

This paper is performed to analyze the performance of underground thermal storage in a solar-ground coupled heat pump system (SGCHPS) for residential building. Based on the experimental results, the system performance during a longer period is simulated by the unit modeling, and its parametric effects are discussed. The results show that the performance of underground thermal storage of SGCHPS depends strongly on the intensity of solar radiation and the matching between the water tank volume and the area of solar collectors. Compared with the solar radiation, the variations of the water tank temperature and the ground temperature rise lag behind and keep several peaks during the day time. For the case of Tianjin, the efficiency of underground thermal storage based on the total solar radiation and absorbed solar energy by the collectors can reach over 40% and 70%, respectively. It is suggested that the reasonable ratio between the tank volume and the area of solar collectors should be in the range of 20–40 L/m².     

R406a应用于中高温热泵热水器的性能研究

为了研究非共沸混合制冷剂R406a应用于中高温热泵热水器的性能,对R406a和R22两种工质的基本物性进行对比分析,并将R406a热泵热水机组放在房间热平衡室内进行试验。在环境温度20℃,机组最终出水温度75℃条件下,对机组进行测试,研究机组的循环性能、排气压力和排气温度。实验结果表明,R406a相比于R22热泵热水器在制取高温热水时,具有相对较低的排气温度和排气压力。在系统出水温度为75℃时,系统的排气温度和排气压力均在安全运行范围以内,且系统COP为2.26。     

土壤蓄冷与土壤耦合热泵集成系统中土壤蓄冷与释冷过程的特性研究

通过建立土壤蓄冷、释冷的数学模型，对土壤蓄冷与土壤耦合热泵集成系统进行了数值模拟。分析了盘管管材、土壤类型、蓄冷温度、流体的流量、盘管间距以及土壤含水率等因素对管束内层盘管运行特性的影响。     

火灾风险评估工程法在高校宿舍中的应用

介绍火灾风险评估工程法,并应用此方法对某高校大学生公寓和普通宿舍进行现场调研和计算评估,通过比较和分析这类场所的火灾危险性,找出影响火灾危险性的主要原因,并提出相应的改进措施,同时也指出火灾风险评估工程法在应用过程中的不足。