| Building heating energy consumption is extremely high in the cold regions,and building energy conservation is one of the important ways to reduce energy waste.Shallow geothermal energy reserves in China’s severe cold regions are rich and can be exploited.The use of heat pump technology for shallow geothermal energy mining is an energy-saving and environmentally friendly technology,and underground heat extraction is the core of the entire system.The soil source heat pump system in the severe cold area has problems such as low heat exchange rate of the buried pipe heat exchanger,and serious cold accumulation of the soil.This project relies on the actual project of greenhouse heating in Harbin Academy of Agricultural Sciences to study the above problems in the cold source soil source heat pump.Firstly,through the on-site drilling exploration,The lithology analysis,aquifer analysis and original temperature measurement are carried out in the heat source wells;secondly,the existing casing type underground tube heat exchanger is improved;Thirdly,the calculation method of drilling depth of casing type heat source well in severe cold area is summarized;Fourthly,the monitoring system is established to study the operation of the soil source heat pump and the recovery of soil temperature in the cold region through experiments.Finally,the soil source heat pump and electric boiler are Three types of greenhouse heating systems,such as gas boilers,conduct energy conservation analysis,environmental analysis and economic analysis.The research results show that the heat treatment of the outer wall tube of the casing heat exchanger 0-50m and the core tube can greatly increase the heat extraction.The experiment proves that the average unit length of the external in-and-out circulation method is higher than the internal heat and the outflow temperature,and the external in-and-out circulation mode is more suitable for the operation of the soil source heat pump in the cold area.For the casing type buried-tube heat exchanger studied in this subject,the 4m3/h circulating flow rate takes the largest amount of heat,which is reasonable.Through the full-period intermittent operation experiment,it can be seen that the soil temperature after the recovery period of 6 months basically achieved natural recovery,the average unit COP was 3.5,and the average system COP was 2.6.Analysis of long-cycle intermittent operation experiments shows that the aquifer has obvious effect on soil temperature recovery.The continuous operation time of the unit should be controlled within 6 hours to maintain high energy efficiency operation.The recovery time of the unit shutdown can be restored to a higher temperature around 6h.For experiments with intermittent start-stop ratios,the smaller the start-stop ratio is,the larger the COP is.Comparing the intermittent operation experiments according to demand,it can be seen that the COP of the average unit COP of the working condition 1,working condition 2 and working condition is increased by 5.2%,8.1%,10.7%,respectively,compared with the COP of the continuous operation 8h,and the average unit length is taken.Compared with continuous operation for 8 hours,the conditions were increased by 5.2%,9.2%,and 12.2%,respectively.For the automatic control intermittent operation experiment,the average unit COP of the automatic control intermittent operation increased by 11.9%compared with the continuous operation average unit COP,and the average system COP increased by 14.3%.For the feasibility analysis of the soil source heat pump,the soil source heat pump has the best energy saving performance and achieves zero emission during the operation.Although the initial investment of soil source heat pump is the highest,but the lowest annual cost,the long-term use of soil source heat pump has the best comprehensive effect on greenhouse heating.The research work of this subject provides basic experimental data for the operation of soil source heat pumps in severe cold regions,and provides guidance for practical projects. |
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