| Today,building accounts for about 30 % of the world ' s total energy consumption.As an efficient energy saving technology,heat pump became a hot spot for scholars at home and abroad.Because the summer cooling load is larger than the winter heat load,it is easy to cause the problem of soil heat accumulation when uses the ground-source heat pump in Shanghai.In this reason,the operational efficiency of the system will decrease.One practical solution is to use auxiliary cooling equipment.This experimental platform is a “ground source heat pump aided by closed cooling tower air conditioning system” located at Songjiang District in Shanghai.Closed cooling tower and buried pipe heat exchangers used the parallel connection method.The experimental platform used the SIEMENS S7-200 series PLC to complete the control of electric valve and circulating pump and complete the acquisition of temperature value,used multi-function meter equipped RS485 interface to complete the collection of all power data based on the Modbus communication protocol and used configuration software-SIMATIC Win CC in the host computer to communicate with PLC and multi-function meter using OPC communication technology.Then the functions of system configuration,state monitoring,data archiving and so on are realized in SIMATIC Win CC.Based on this experimental platform,the following five experimental strategies are designed,namely: separate ground source heat pump continuous operation,separate ground source heat pump intermittent operation,separate closed cooling tower in manual control,separate closed cooling tower in automatic control,closed cooling tower-ground source heat pump combined operation.And according to the flow ratio closed coolingtower-ground source heat pump combined operation mode is divided into three kinds of operation strategy,namely closed cooling tower and ground source heat pump 1:2 coupling,2:1 coupling and 1:1 coupling.And the following conclusions are drawn:(1)For the closed cooling tower-ground source heat pump operation strategy,when closed cooling tower and ground source heat pump is coupled with 2:1 flow ratio,the heat released by the system to the soil decreased by 5.1% and 18.5% compared with the 1:1coupling and 1:2 coupling scheme,the temperature increased most slowly and became stable after 12 hours' startup.This is the best coupling strategy of cooling tower and ground source heat pump.(2)Compared with all summer experiments,the heat pump unit EER of closed cooling tower and ground source heat pump 1:2 coupling strategy was 7.58,which was significantly higher than other experimental strategies.And through the comparison of the soil temperature curve,it is found that if the cooling load is shared by closed cooling tower and buried pipe heat exchanger the increase rate and range of soil temperature will be obviously smaller than using buried pipe heat exchanger to bear cold load only.It can be seen that the closed using cooling tower as the auxiliary cooling equipment of the soil source heat pump system can effectively solve the problem of soil heat accumulation,thereby improving the refrigerating energy efficiency ratio of the system and increasing the stability of long-term operation.(3)Compared with the ground source heat pump continuous operation,intermittent operation exploited the soil natural recovery ability and effectively slowed down the increase of soil temperature,reduced the temperature of the circulating water in the buried pipeline and enhanced the heat pump unit EER.(4)Compared with manual control,using automatic control strategy could reduce the power consumption of the wind turbine and improve the system EER.After calculation,the power consumption of the closed cooling tower of the optimal automatic control strategy in the first experiment stage is reduced by 33.3% compared with the manual control,and the power consumption of the closed cooling tower in the second experiment stage is reduced by 54.2% compared with the manual control. |
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