The Study On The Performance Of Hybrid Heat Exchanger GSHP System

In recent years, as an efficient renewable technology, people pay more attention on ground source heat pumps. At present, researches focus on the performance of ground source heat pump system with separate heat exchanger, such as horizontal pipe heat exchanger and verticle pipe heat exchanger. Research results on that verticle pipe heat exchanger and horizontal pipe heat exchanger operated simultaneously are still defective. In this paper, the heat pump system using verticle pipe heat exchanger and horizontal pipe heat exchanger for heat exchange will be called hybrid heat exchanger GSHP(Ground Source Heat Pump) system.Paper based on an office building in Tian Jin city. To start with output load of heat pump, primarily confirmed the load ratio of two types of heat exchanger according to building reality and economy. Then developing operation-control strategy of hybrid heat exchanger GSHP conformed to the office building load characteristics. Numerically simulating the coupled heat transfer for verticle pipe heat exchanger and horizontal pipe heat exchanger respectively, and determining the design programme of the hybrid heat exchanger GSHP system. Confirming advantages of the hybrid heat exchanger GSHP system through analyzing the energy efficiency and economy of the ground pipe side system. Optimizing operation hydraulic regime of the system. At last, experimentally verifying the correctness of the numerical calculation of three-dimension heat transfer model of ground pipe heat exchanger.Firstly, building the load calculation model based on an office building in Tian Jin and calculating the annual cooling and heating load hourly. Converting the cooling and heating load to output load of the heat pump, then primarily confirming the load ratio of two types of heat exchanger according to building reality and economy. Developing operation-control strategy of hybrid heat exchanger GSHP conformed to the office building load characteristics. According to the design programme of hybrid heat exchanger GSHP system, numerically simulating the coupled heat transfer for verticle pipe heat exchanger and horizontal pipe heat exchanger respectively and analysing the performance of the heat exchanger. Based on above steps, the number of heat units of horizontal pipe heat exchanger and verticle pipe heat exchanger will be confirmed. But when the function of the building change to hospital, the load characteristic have great impact on the performance of heat exchanger and numerical results show that it is not appropriate using hybrid heat exchanger GSHP system for the hospital load characteristic.Building the energy consumption model of hybrid heat exchanger GSHP system and calculating energy consumption of the system in cooling and heating period. Getting the linear regression between COP of heat pump and inlet water temperature of condenser in summer and the linear regression between COP of heat pump and inlet water temperature of evaporator in summer, then subsequently the hourly COP of the heat pump and the hybrid heat exchanger GSHP system.As the load ratio of horizontal pipe heat exchanger and verticle pipe heat exchanger changed, the economy would also be changed using annual cost to analyse. When the load ratio changes from 1:1 to 1:8, the annual cost of the system increased gradually, but their annual costs are all higher than the GSHP with verticle pipe independently. Defining the heat economy, and it was used for preliminary judging if the economy of horizontal pipe heat exchanger would be better than verticle pipe heat exchanger. Combining the performance of hybrid heat exchanger with exonomy of the system, the paper summarized the method to choose the best load ratio of the hybrid heat exchanger.For decreasing the time for heat transfer calculation, the paper used independently numerical results of heat exchanger to evaluate performance of heat exchanger. And it was necessary to analyse the difference between independently heat exchange numerical results and combined heat exchange numerical results. Results showed that independently heat exchange calculation method have little influence on heat transfer results.Proposing two setting modes of the cooling pump in the hybrid heat exchanger GSHP system. Getting the actual flow of two projects by hydraulic calculation and annular pipe network hydraulic calculation and hydraulic analysis software under the condition of actual selection pump parameters, and confirming the better project design for the hybrid heat exchanger GSHP system of the office building. It provided new ideas to optimize the hydraulic regime of hybrid heat exchanger GSHP system.Verifying the correctness of the numerical calculation of three-dimension heat transfer model of ground pipe heat exchanger by tests. Then measuring the hybrid heat exchanger GSHP system and contrast independently heat exchange numerical results and combined heat exchange numerical results. The results showed that independently heat exchange numerical results have great difference with combined heat exchange numerical results under the experimental conditions, and combined heat exchange numerical results are more close to measured results. Instead of combined heat exchange calculation method, using independently heat exchange numerical results must be under the condition that load characteristic match the load ratio of horizontal pipe heat exchanger and verticle pipe heat exchanger.