Influence of heat storage mode of domestic hot water on the performance of ground heat exchanger in ground-source heat pump system

The vertical U-tube ground-coupled heat pump system provides cold and heat for the controlling of indoor environment. Under the air-conditioning condition, the vertical U-tube ground-coupled heat pump system with heat recovery can provide domestic hot water. The influence of supplying domestic hot water on the heat transfer performance of ground heat exchangers is different under different operating modes in summer and winter. Through a project design of ground-source heat pump system, the influence of supplying domestic hot water under heat storage mode on the heat transfer performance of ground heat exchangers in summer and winter is respectively analyzed. The dynamic performance of heat exchangers under different working conditions is analyzed, and through numerical calculation, the heat transfer performance parameters of ground heat exchangers under different operating modes are obtained. From the calculation results, the adjusting methods based on the load characteristics of this project represent.     

Analysis of the Ground Adjustment Ability of the Ground Source Heat Pump Systems in Winter

Based on an actual ground source heat pump system in hot summer and cold winter area, the system operation parameters were tested for 6 years under the state of using cooling tower for cooling in summer but the ground heat exchanger and fire pool for heating in winter. A three dimensional (3D) tube group model was established, and the thermal balance analysis and calculation of the ground temperature distribution around the ground heat exchanger were conducted by the numerical calculation. According to the comparison between the test data and the theoretical results, the influencing factors of the ground adjustment ability were obtained.     

The Key Parameters Method of Calculating Geothermal Heat Exchanger Length

The geothermal heat exchanger is the key component of ground coupled heat pump systems. We discuss the key parameters method of calculating geothermal heat exchanger length based on line source theory. Typical meteorological year data is used to determine the hottest month, the coldest month and annual average surface temperature. The building hourly load can be obtained by introducing the concept of equilibrium temperature. The cooling fraction and the heating fraction then can be calculated using building hourly load and performance parameters curve fit of a water source heat pump unit. The method for selecting the hottest and lowest entering fluid temperature and calculating the borehole and ground thermal resistance is given. A vertical U tube heat exchanger length calculation procedure is proposed.     

制冷工况下水平埋管换热器运行试验研究

通过夏季工况的地源热泵运行试验,对运行过程中水平埋管的换热性能参数、试验场地周围气象因素和换热过程中土体的温湿度变化等因素进行实时监测,探讨了地源热泵运行过程中水平埋管换热器热交换性能及其周围土壤的温、湿度场变化规律。研究结果表明,地源热泵间隙运行有利于土壤温度场的恢复,随着停机时间的增加,水平埋管与周围土壤的热交换能力明显提高;气候变化对水平埋管周围土壤的温度场分布具有显著影响,随着埋深的递减,土壤温度受气候变化的影响越明显;水平埋管周围土壤温度的变化幅度随着与埋管距离的增加呈递减趋势,其影响半径为1.0m左右;热交换对水平埋管周围土壤湿度场的影响不明显,但大气降雨引起的地表水入渗对土壤湿度场的分布具有显著影响。     

Energy Efficiency of Water Transportation System for Surface Water Source Heat Pump

The forms of water transportation, arrangement and operation of pumps contribute to the water transportation energy consumption, which influences the energy-saving effect of surface water source heat pump. The relation between the pumping height and energy consumption of pumps is found by analyzing the model of pump energy consumption. The concept and calculation of critical pumping height is presented considering the limited rate of system energy efficiency. Based on the principle that the pump power changes with water flow rate, the determination of pumps arrangement of one or two stage pumps is described with a concrete example. The influence of water flow rate on heat pumps and water pumps is analyzed, and the energy efficiency of constant and variable water volume are compared. The operation way of this example is concluded for the optimal system energy efficiency. It is found that there is a critical pumping height for the energy-saving effect of surface water source heat pump compared with the traditional system. Moreover, the operation strategies should be determined by the system optimal model since the energy consumptions proportions of heat pumps and water pumps are variable.     

The determination method of limit energy consumption of water supply in open-loop surface water source heatpump systems

For the open-loop surface water source heat pump systems, energy consumption of water supply is the key factor for energy saving of system. On the basis of energy consumption model of heat pump unit and energy consumption model of water supply etc., open-loop surface water source heat pump system energy efficiency ratio coupling model is established. Based on energy efficiency ratio,the coupling limit value of surface water source heat pump system in different temperature of water supply and different energy consumption of water supply is obtained.Through the actual case, energy saving rate of the system is calculated in different temperatures of water supply and different system modes. And the determination method of the limit energy consumption of water supply of open-loop surface water source heatpump systems is established.     

Experimental Study of Ground-source Heat Pump Systems with Horizontal Heat Exchanger

This paper describes the double layer horizontal ground source heat pump systems constructed in 1998 with the buried depth of 0.9 m and 1.8 m. The program of study includes experimental equipments, heat exchanger size, testing meter and methods for data analysis. In addition, the heating and cooling performance at typical days are also illustrated. Among the influencing factors on the performance of the ground source heat pump systems, the parameter of heat exchanger and operation patterns of heat pump systems are analyzed.A heat transfer model has been set up for horizontal heat exchanger.     

武汉与重庆典型地质结构下的地埋管换热性能

地埋管地源热泵换热器的换热性能受到不同地质结构的影响。以武汉和重庆地区的典型地质构成为边界条件,建立了三维地埋管的单孔双U管换热模型,通过模型计算,获得了两种地质条件下的地埋管换热性能,以重庆地区的地源热泵热响应测试结果以及工程运行数据出发,对模型的计算结果进行了验证,结果表明,模型吻合度较好,可以应用于工程分析。以模型为条件,进行地质结构对换热性能的影响度分析,预测了两地地埋管地源热泵的换热性能并计算得到换热器的平均换热系数分别为武汉地区K₁=1.65（W/m·K）,重庆地区K₂=1.51（W/m·K）。     

Analysis of the Temperature Limit of Dynamic Water Intake of Open loop Surface Water Source Heat Pump Systems

Energy consumption of water intake is one of the key factors for energy saving in the application of the open loop surface water heat pump system. An energy efficiency ratio coupling model for open loop surface water source heat pump systems was established on the basis of the energy consumption model for the water intake and the heat pump units. According to energy saving rate and regulation of energy consumption of water intake, dynamic temperature limits of water intake in different water supply temperature of cooling tower and different pump head were proposed so as to find a calculation method of temperature limits of water intake of open loop surface water heat pumps. Moreover, the energy saving rate of surface water source heat pump systems compared with traditional air conditioning systems under various condition was also calculated.     

水源热泵在温室加温中的应用研究

采用多层覆盖、减小直接加热空间的温室节能设计措施,设计建造了试验温室,在水源热泵热风加温条件下,对试验温室的温度、空气相对湿度、水源热泵的实际制热系数进行了测定,对试验温室采用水源热泵加温的节能效果进行了评价,结果表明：夜间水源热泵加温条件下,温室东西方向的水平温度分布均匀,南北相距12m的水平方向上存在着0.9℃的温差,中部距地面2.2m的垂直空间上平均存在1℃的温差,24:00—08:00,空气相对湿度低于80%;试验用水源热泵实际热系数为3.31。与燃煤锅炉热水加温的玻璃温室相比,试验温室采用水源热泵加温相对节能46.5%,直接加温成本较燃煤锅炉加温高82.2%,经计算,当试验温室与对照玻璃温室面积相等时,采用水源热泵加温可相对节能69.1%,直接加温成本仅较燃煤锅炉加温的玻璃温室高5.8%。     

Degital Simulation for the Direct Torque Control of Induction Motors Using the Circle Flux Path

This paper introduces the importance of developing the Ground-Source Heat pump and describes the prospects of it.with the method used abroad to acquire the temperature profiles within surrounding soil of the underground heat exchanger with buried tubes, in this paper the line heat source theory and thermal resistance network analysis method were used to set up the heat transfer model.The original temperature of the ground is determined by calculation and is compared with test results. Experiments of running single tube and running three series connection tubes are carried out on the built underground exchangers of vertical buried tube type.And the data which can provide reference for the Ground-Soure Heat pump technique are acquired.     

Influence of Backfill Air Gap on Soil Temperature Recovery in Ground coupled Heat Pumps

Air gap may easily emerge in the progress of backfill in ground heat exchange due to field operation problems. The single U tube three dimensional numerical heat transfer model is set up and there are 3 kinds of backfill air gap assumptions for computational analysis, which are the most common situations in practical projects. Different air gap situations will have considerable effects on soil heat transfer, especially the factor of soil temperature recovery performance, which is investigated in this research, and there is practical project operating data for the comparison confirmation with the theoretical calculation results in inlet and outlet water temperatures. It can be concluded that the backfill air gap will increase the soil average excess temperature in the period of recovery inside the place where the air gap is, and degrade the heat transfer performance of the ground heat exchange.     

A Three-Dimensional Numerical Model and Experimental Research for U-Tube Ground Heat Exchanger in Heating Operation

In terms of the theory of a transient energy balance on the finite controlled volume, in this paper, a transient three-dimensional heat transfer model for the simulation of a single vertical U-tube ground heat exchanger based on finite-difference methods is systematically proposed. The model is also compared with experimental results during the heating operation in winter. What's more,based on test data and domestic and foreign literature, the equations to determine the undisturbed ground temperature for wet and heavy soil in Chongqing are presented. These formulae are essential conditions to calculate the heat transfer model.     

地源热泵技术在中国温室设施中的应用探讨

当前在中国温室设施中应用和推广地源热泵技术尚存在诸多不利因素,大大限制了该项技术在设施农业领域中的发展。为探寻合理的解决途径,对地源热泵空调系统的关键技术和其在中国的发展概况进行了相关的阐述和分析,并以中国农业大学上庄实验站已经建成使用的地下水式温室地源热泵空调系统为实例,介绍该系统的组成、工作流程、性能参数和使用情况,探讨温室地源热泵空调系统在推广和使用中可能出现的投资较高,长时间运行性能不稳定等问题,分析其原因并提出相应的对策建议。     

地下水渗流作用下地埋管间歇散热特性

为了探求地下水渗流对地埋管换热器间歇运行性能所产生的影响,基于移动的有限长线热源理论模型解析解,利用MATLAB软件编程计算,分析渗流对单钻孔地埋管换热器的影响。同时对比分析了连续和间歇运行情况下其周围土壤的温度响应特征和过余温度场分布特点。研究表明：埋管周围土壤的温度变化是由热流密度、土壤本身的热物性和实际渗流速度耦合作用影响的,而在间歇运行下其因素影响更加明显。     

River Water Quality Comprehensive Evaluation for Water Source Heat Pump

River water quality is one of the important conditions must be considered when river water source heat pump is used. It is also the key factor of efficiency of river water source heat pump. Based on analysis of the water quality factors which influence the river water source heat pump heat exchanger fouling, the main quality indicators and value are conformed. Using fuzzy comprehensive evaluation method and the actual monitoring data, quality classification of river water which is the source of water source heat pump is analyzed. For the difficulty of multiple indicators which need to detect and meet the related national standard in practical engineering application, the definition of scaling potential value is put forward. As the water quality comprehensive evaluation index of water source heat pump, the scaling potential value not only can consider the influence of the main water quality parameters on water source heat pump heat exchanger fouling, but also can conveniently and quickly provide direct basis for water quality judgment and system selection in the engineering application.     

Performonce of Fouling Fluidized-Removing and Heat Transfer Enhancement on Sewage Side of Sewage-Source Heat Pump System

High thermal resistance resulted by fouling in heat exchanger restricts the application of sewage source heat pump (SSHP) system. The fouling forming mechanism was applied with solid-liquid fluidized bed technique for fouling prevention and removing of SSHP system. Shearing stress model of solid-liquid fluidized bed heat-exchanger is analyzed, and collision stress model is modified. Preventing and removing fouling mechanisms of solid-liquid fluidized bed technique by shearing stress and collision stress was explained. An experimental study on how to solve the fouling problem (such as fouling prevention and removing, heat transfer enhancement, etc) is discussed. The results of theory and experiment show that solid-liquid fluidized bed technique can be used not only to increase convection coefficient, but also to restrict fouling growing, it can effectively solve the fouling problem in SSHP system.     

Comparative Analysis of Heat Exchange Performance ofEnergy Piles and Borehole Heat Exchangers in GSHP System

Due to their enhanced cost-effectiveness and efficiency over traditional borehole exchangers, energy piles are increasingly used in Ground Sourced Heat Pump (GSHP) projects. In this paper, the structural characteristics of these two types of heat exchangers and their heat transfer mechanism were discussed firstly. The thermal response tests (TRT) were performed on two testing energy piles in one GSHP project in Nanjing, China. The TRT results were then used to verify the numerical simulations, which suggests that the heat exchange performance of energy piles is superior to that of the traditional borehole exchangers. Meanwhile, the numerical simulation method used in this paper was considered applicable to the optimization design of ground heat exchangers in GSHP system.     

Design and Construction of an Air Conditioning System Employing a Ground Source Heat Pump Combined with a Radiant Floor

The air conditioning system using a ground source heat pump(GSHP) combined with a radiant floor integrates the advantages of both types,giving such a system large potential for popularization.After experimenting with one house's hybrid system,the design processes and construction methods for such a system can be summarized.In the experiment,different terminal devices were used to adopt varying winter and summer climatic conditions.It is suggested that the constructors should make good use of resources and waste water during the construction phase.The experimental results show that this hybrid system runs steadily and it supports a better temperature field to meet the requirement for the human comfort.Finally,a hybrid system managment strategy is suggested.     

Heat Transfer Model and Application of Buried Tube Heat Exchanger for Ground Source Heat Pump

This paper introduces the theoretical basis and application method for heat transfer model of buried tube (pipe in pipe and U- type) heat exchanger for ground source heat pump, and a practical example is calculated. Then, the calculation results are analyzed and discussed. In particular, the correlation coefficient and calculation method of tube group exchanger is discussed; the method for determining known parameter and some basic data for main procedure GSHP.HTM is analyzed. The calculation formula and data sampling for JSW.HTM subroutine is introduced. At last, the problems in application of calculation procedure, to which should pay attention, are discussed.