Preliminary Study On Summer Cooling Effect Of Different Shallow Geothermal Heat Exchange Systems In Plastic Greenhouses

This experiment has proposed two new geothermal heat exchange systems of different forms against the climate characteristics of high temperature and high humidity in areas of southern Jiangsu,and named them as S-type systems and I-type systems respectively.We hope we can reduce the temperature and humidity in the local summer greenhouse,provide a more favorable cultivation environment for the greenhouse crops and improve the production efficiency of the use of local summer greenhouses after use the two new geothermal heat exchange systems.By measuring the temperature,humidity,ground temperature and other environmental parameters in two plastic greenhouse,the enthalpy difference,average heat flux,average density of heat flow,heat storage,and energy consumption of heat exchange pipes are calculated.Based on the above data,analyzing the cooling effect of the two geothermal heat exchange systems and choose out the better,more suitable one for local use.Finally,analyzing the problems to be optimized found in the test and proposing the improvement plan.The main test results are the following:(1)On sunny days,the geothermal heat exchange system has a significant cooling effect when the shading net is turned on.Compared with the control shed,the maximum cooling temperature of the S-type shed is 3.7?,and the average cooling temperature is3.0?.The maximum reduction of the I-type shed is 1.9?,and the average reduction is0.9?.On cloudy days,when the shade net was turned on,compared with the control shed,the temperature in the S-type shed fell by an average of 2.1°C.The temperature conditions in the I-type shed were basically the same as those in the control shed and there was no significant difference.On rainy days,the average temperature of the S-type shed decreased by1.3?,and there was no significant difference between the I-type shed and the control shed.(2)The two geothermal heat exchange systems have been in a state of heat storage during the continuous opening of the fan for 10 hours.Due to the long-term continuous heat storage in the S-type heat exchange system,the soil temperature around the underground pipeline is increased,and the heat storage efficiency is reduced.But The heat exchange system in the I-type shed does not reduce the heat exchange efficiency due to the extension of the heat exchange time,because the heat exchange piping is long enough.The average daily heat storage capacity of the heat exchange system between the S-type shed and the I-type shed was 1.95*10~3 MJ and 1.74*10~3 MJ,respectively,and the average daily power consumption was 31.2 kw·h and 37 kw·h respectively.Compared with the I-type shed,the heat storage capacity of the S-type shed has increased by 12.3%,and electricity consumption has decreased by 15.7%.Considering the cooling effect and heat storage performance of the two systems,the S-type geothermal heat exchange system is more suitable for cooling applications in local plastic greenhouses.