寒冷地区土壤冷源直接供冷空调系统的实验研究

提出了用土壤作冷源直接供冷的新构想,并在哈尔滨地区建立了相应的实验系统。经过一个供冷季的实验,该系统的季节供冷系数为9.85,平均供冷率为0.93kW,取冷井的热作用半径小于3m;本文所提出的土壤冷源直接供冷空调系统在一定的地域范围内具有较大的节能潜力。     

Exergetic performance assessment of solar photovoltaic cell (PV) assisted earth to air heat exchanger (EAHE) system for solar greenhouse cooling

An experimental system was developed and tested in order to investigate the exergetic performance of a solar photovoltaic system (PV) assisted earth-to-air heat exchanger (under ground air tunnel) that is used for greenhouse cooling at the Solar Energy Institute, Ege University, Izmir, Turkey. This system was under operational conditions successfully during the 2010 summer cooling season. This paper provides the experimental results obtained between 18th of August and 26th of August of in 2010. Exergy destruction in the system was calculated and presented in this paper using a reference temperature of 15 °C. Results are discussed and interpreted in the paper for various performance metrics, such as the effect of climatic conditions and operating conditions on the system performance. Results show that the system may be satisfactorily used for greenhouse cooling in the Mediterranean and Aegean regions of Turkey.     

Analysis of the energy performance of a ground source heat pump system after five years of operation

GeoCool plant was the result of a EU project whose main purpose was to adapt ground coupled heat pump technology to cooling dominated areas. The execution of this experimental plant was completed at the end of year 2004, starting on February 2005 the regular operation of the air conditioning system. Since then, GeoCool facility has been monitored by a network of sensors characterizing its most relevant parameters. Several aspects of the performance and behaviour of the system during its first operational year were presented on a previous paper. This paper presents the energy performance measurements of GeoCool ground coupled heat pump system acquired during five years of operation as well as the evolution of the return water temperature from the ground as a representative of the ground temperature. The analysis of the experimental results shows that the system energy performance is maintained through the years with no appreciable impact on ground thermal response.     

The impact of auxiliary energy on the efficiency of the heating and cooling system: Monitoring of low-energy buildings

This paper presents a detailed meta-analysis of end and primary energy use for heating, cooling and ventilation of 11 low-energy non-residential buildings and one residential building in Germany that belong to the EnOB research program launched by the German Federal Ministry for Economy. In particular, the analysis emphasizes the substantial impact of auxiliary energy use on the efficiency of heating and cooling performance. The investigated buildings employ environmental energy sources and sinks - such as the ground, ground water, rainwater and the ambient air - in combination with thermo-active building systems. These concepts are promising approaches for slashing the primary energy use of buildings without violating occupant thermal comfort. A limited primary energy use of about 100 kWh_prim/(m²_neta) as a target for the complete building service technology (HVAC and lighting) was postulated for all buildings presented. With respect to this premise, a comprehensive long-term monitoring in high time resolution was carried out over the course of two to five years, with an accompanying commissioning of the building performance. Measurements include the energy use for heating, cooling, and ventilation, as well as the auxiliary equipment, the performance of the environmental heat source and sink, and local climatic site conditions.     

Numerical and experimental analysis of a horizontal ground-coupled heat pump system

The main objective of this work is to evaluate a heat pump system using the ground as a source of heat. A ground-coupled heat pump (GCHP) system has been installed and tested at the test room, University of Firat, Elazig, Turkey. Results obtained during experimental testing are presented and discussed here. The coefficient of performance (COP_sys) of the GCHP system is determined from the measured data. A numerical model of heat transfer in the ground was developed for determining the temperature distribution in the vicinity of the pipe. The finite difference approximation is used for numerical analysis. It is observed that the numerical results agree with the experimental results.     

土壤源热泵单元埋管换热器热响应曲线热电比拟分析

从整体用热电比拟法,由土壤源热泵单元埋管换热器的热响应特性曲线推导出了单元埋管换热器性能的工程计算方法.虽然简单、物理概念清晰,但如果和土壤源热泵系统地下换热器在地下取热或放热量累计测量装置相结合,又不失为一种准确的工程计算方法.     

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.     

水平埋管换热器地热源热泵实验研究及传热模型

介绍了于1998年所建成的埋深分别为0.9m和1.8m的双层水平埋管地热源热泵系统，内容包括实验装置、换热器几何尺寸、测试仪表及测试数据的处理方法等，并用典型日分析了该系统的制冷和制热性能。同时，又对影响地热源热泵系统性能的诸多因素中的埋管尺寸及热泵运行方案等因素作了分析。另外，本文参考VC.Mei传热模型并根据热传导方程建立了水平埋管换热器传热模型。     

氨水蓄能土壤源热泵集成系统工作过程的模拟研究

提出了以浅层土壤为热源/汇的氨水蓄能热泵集成系统,建立了系统工作过程动态数学模型。以长江流域某一办公建筑为例,对该系统夏季空调工况和冬季供暖工况进行了数值模拟。与以空气为热源/汇的氨水蓄能热泵集成系统进行了比较,结果显示以土壤为热源/汇的系统工作性能优于以空气为热源/汇的系统。     

Exergy efficiency analysis in buildings climatized with LiCl–H2O solar cooling systems that use swimming pools as heat sinks

Solar cooling is emerging as one of the most interesting applications in the harnessing of solar energy for alternative uses. Current devices can effectively control the climates of small buildings while addressing the issues associated with the excessive thermal energy captured during the summer months. This article presents an exergy analysis of buildings with solar thermal systems used for Domestic Hot Water (DHW) production and heating and cooling support. The cooling system analyzed is a LiCl–H₂O thermally driven heat pump with integral energy storage that uses outdoor swimming pools as heat sink. All subsystems were integrated into the model and considered as a single energy system, and data from installations in three different locations were used. The influences of the heating and cooling demand ratios and the dead state and house temperatures were analyzed. Further, the use of dissipated energy was analyzed, demonstrating that the proposed method facilitates the realistic study of these systems and provides useful analytical tools for improving the overall exergy performance. The energy delivered for heating, cooling and DHW production strongly influences global performance, suggesting that the appropriate sizing of each system is a priority.     

冬季工况下地埋管地源热泵系统中大地的自调节能力分析

以夏热冬冷地区某实际地埋管地源热泵系统为分析对象,对夏季采用冷却塔供冷而仅冬季采用地埋管和消防水池联合供热的系统运行参数进行了6 a测试。建立了地埋管三维管群模型,通过数值计算方法对地埋管周围岩土的温度分布进行了热平衡分析和计算。通过测试数据与理论计算结果进行对比分析,得到了影响大地自调节能力的影响因素。     

Comparison between design and actual energy performance of a HVAC-ground coupled heat pump system in cooling and heating operation

This work compares the experimental results obtained for the energy performance study of a ground coupled heat pump system with the design values predicted by means of standard methodology. The system energy performance of a monitored ground coupled heat pump system is calculated using the instantaneous measurements of temperature, flow and power consumption and these values are compared with the numerical predictions. These predictions are performed with the TRNSYS software tool following standard procedures taking the experimental thermal loads as input values. The main result of this work is that simulation results solely based on nominal heat pump capacities and performances overestimate the measured overall energy performance by a percentage between 15% and 20%. A sensitivity analysis of the simulation results to changes in percentage of its input parameters showed that the heat pump nominal coefficient of performance is the parameter that mostly affects the energy performance predictions. This analysis supports the idea that the discrepancies between experimental results and simulation outputs for this ground coupled system are mainly due to heat pump performance degradation for being used at partial load. An estimation of the impact of this effect in energy performance predictions reduces the discrepancies to values around 5%.     

焦作市某服务区地源热泵系统地下温度场模拟研究

利用GLD软件对河南省焦作市某高速公路服务区地源热泵系统长期运行工况下的地下温度场进行模拟分析,得出当土壤中长期积累的热量无法排出时,将导致土壤温度上升,进而影响地源热泵系统的换热性能。根据模拟结果,分析了地源热泵系统长期运行过程中不同的建筑冷热不平衡率及钻孔间距对地下温度场的影响。针对地源热泵系统运行所引起的地下温度场的失衡问题提出了部分有效解决措施。     

Swimming pools as heat sinks for air conditioners: Model design and experimental validation for natural thermal behavior of the pool

Swimming pools as thermal sinks for air conditioners could save approximately 40% on peak cooling power and 30% of overall cooling energy, compared to standard residential air conditioning. Heat dissipation from pools in semi-arid climates with large diurnal temperature shifts is such that pool heating and space cooling may occur concurrently; in which case heat rejected from cooling equipment could directly displace pool heating energy, while also improving space cooling efficiency. The performance of such a system relies on the natural temperature regulation of swimming pools governed by evaporative and convective heat exchange with the air, radiative heat exchange with the sky, and conductive heat exchange with the ground. This paper describes and validates a model that uses meteorological data to accurately predict the hourly temperature of a swimming pool to within 1.1 °C maximum error over the period of observation. A thorough review of literature guided our choice of the most appropriate set of equations to describe the natural mass and energy exchange between a swimming pool and the environment. Monitoring of a pool in Davis, CA, was used to confirm the resulting simulations. Comparison of predicted and observed pool temperature for all hours over a 56 day experimental period shows an R-squared relatedness of 0.967.     

Transient characteristics and performance analysis of a vapor compression air conditioning system with condensing heat recovery

The objective of this study is to evaluate the influence of condensing heat recovery on the dynamic behavior and performance of air conditioners. The article includes a test procedure utilized to evaluate the condensing heat recovery system, relevant experimental results, a detail analysis of the mechanisms, and improvement measure on such a system. The experimental results indicate that although the condensing heat recovery has a negative effect on the cooling capacity at the start of the heat recovery process, the average cooling coefficient of performance (COP) of the system can be improved. The study also incorporates a control scheme of the electronic expansion valve (EEV) of the condensing heat recovery system. The experimental comparison between the EEV and the thermostatic expansion valve (TEV) demonstrates that the EEV has better performance in both stability and efficiency in the condensing heat recovery system.     

Computational model for a ground coupled space cooling system with an underground energy storage tank

A computational model for determining annual periodic performance of a cooling system utilizing a ground coupled chiller and a spherical underground thermal energy storage tank is developed. An analytical solution for the transient heat transfer problem outside the storage tank is obtained by the application of complex finite Fourier transform (CFFT) technique. Analytical expressions for heat gain to the space and energy consumption of the chiller are acquired, and these expressions are coupled with the transient temperature field problem to obtain computational model. Variation of water temperature in the storage tank is calculated using the transient solution of the problem over an entire year for different soil, chiller, and storage tank characteristics. Temperature profile of earth surrounding the storage tank and the COP of the cooling unit are also investigated under various assumptions and varying system design and operating conditions. The results show that water temperature in the storage tank remains under ambient air temperature during summer months, and thus the proposed ground coupled cooling system should yield higher COP values compared to a corresponding air source system.     

A raw water source heat pump air-conditioning system

Raw water source is one of the promising new heat sources that researchers are looking into along with various others water-based sources such as ground, lake, river and sewage water. Generally, the water that is taken from the environment and supplied to a water treatment facility is called raw water. In this study, the heating and cooling performance of a heat pump utilizing the heat energy of raw water supplied to a water treatment facility is investigated. The two heat pumps being investigated have a heating capacity of 65.2 kW and were installed at the site for the heating and cooling of the central control room. A brazed plate heat exchanger was used for obtaining heat energy from the raw water. The raw water source provides a favorable heat source compared to the ambient air source except in spring. In the seasons of spring and autumn, the heating and cooling load are extremely low, this is the main reason for the poor performance of the raw-water heat pump system for those seasons. The average unit COP during the heating season is 3.3, and the average unit COP for the cooling season is 7.2.     

天津市某绿色建筑暖通设计方案分析

以天津市某绿色建筑的计算负荷为基础,通过分析不同冷热源方案全寿命周期成本,确定采用地源热泵为系统的冷热源。对地源热泵系统地源侧的年吸、释热量进行计算和分析,确保系统长期运行的稳定性。结合建筑部分负荷运行时间和地源热泵机组部分负荷性能参数,对热泵机组的选型进行分析。此外,对水系统的运行策略和室内空气品质的调控性加以分析。     

基于冷却塔辅助换热的地源热泵空调设计探讨

本文结合工程实例,探讨了采用冷却塔作为辅助换热设备的地源热泵空调系统设计方法,并从空调负荷计算、地源热泵主机选型,土壤换热系统设计,冷却塔选型以及冷却塔的运行策略等方面介绍了该地源热泵空调系统的设计思路,以期为以后的地源热泵空调系统设计提供参考。     

A quasi-steady state mathematical model of an integrated ground source heat pump for building space control

This paper is concerned with the development of a mathematical model, capable of describing the quasi-steady state performance of an integrated ground source heat pump, which is used for heating and cooling of an institutional building located in a Mediterranean climate. The model is structured on functional basis according to the heat pump vapour compression or primary circuit, a secondary ground loop circuit and a secondary building loop circuit. Heat pump heating and cooling capacities, as well as COP, are considered to be dependent variables and are estimated in the model using performance fitted maps. Independent variables include: compressor speed, circulation pump speeds, ground loop return temperature and building circuit return temperature. The model is validated using data from a full-scale ground source heat pump installation. The validated model is used to examine system capacity and performance sensitivity to different control optimisation strategies, including set-point control of room air temperature, room air bandwidth temperature, building loop return water temperature and building loop return bandwidth temperature.