Heating Test Of Air Source Heat Pump In Multi Span Film Greenhouse And Thermal Environment Analysis

With the rapid development of modern agriculture in China,energy saving and high efficiency is an important theme of sustainable development in the future.The traditional heating method of greenhouse is combustion heating,which consumes a lot of energy and emits a large amount of harmful gases such as CO2、CO、SO2 and NOx in the exhaust gas,causing serious environmental pollution.As a new energy-saving technology with energy saving,high efficiency and environmental protection,heat pump system is favored by the public and has a good application prospect in the sustainable development of agriculture.In this paper,the greenhouse was heated by the application of air source heat pump and pipeline air supply in the circular arc-shaped thin-film greenhouse of Changyinsha farm in Zhangjiagang city,Suzhou city,Jiangsu province.The main research contents are as follows:First of all,the middle part of the test greenhouse,2 spans and 4 partitions,was selected as the test greenhouse in the greenhouse.The same size was selected as the control greenhouse in the west side of the test greenhouse,adopt thin polyethylene(PE)closed.The roof ridge of the test greenhouse runs from north to south,with a single span of 8.0m from east to west,2 spans in total,and a single space of 4.0m from north to south,with a total of 4 Spaces,with shoulder height of 3.0m and ridge height of 5.0m.Then,the measuring point arrangement and debugging of the air source heat pump system were carried out for the selected greenhouse.After everything was normal,the test began and data was collected.Data was collected every other week,and the stability of the system was adjusted to ensure the normal operation of each instrument.The COP(coefficient of performance)value of the air source heat pump system in this test was 1.76,compared with the electric boiler under the same conditions,the energy saving is 46%,and compared with the gas boiler,the energy saving is51.04%.and compared with the coal-fired boiler,the energy saving is 60%.According to the chart analysis,it can be concluded that during the test period,compared with the control greenhouse,the air source heat pump heating effect on continuous sunny days was 5.9 ～ 9.5℃,and the humidity was 13.4 ～ 30.8% lower.The night heating effect was 3.8 ～ 4.3℃,and the humidity was 17 ～ 20.2% lower.In continuous rainy weather,the heating effect of air source heat pump in daytime is 10.6 ～ 12.2℃,andthe humidity is 34.69% lower.The night heating effect was 3.1 ～ 3.8℃,and the humidity was 19.3% lower.It indicates that the air source heat pump with pipeline air supply heating system has good greenhouse heat supply capacity and dehumidification.The CFD temperature field calculation model was established and compared with the actual measured value,and the average error between simulation and measurement was obtained to be 7.6%.It was verified that the model could be used to study the temperature field and air flow field distribution of the greenhouse with air source heat pump and heat transfer duct.Then set the temperature field and air flow field distribution in the greenhouse under different opening diameters and different opening angles of the inlet and outlet.It is concluded that the temperature distribution in the greenhouse is the most uniform and the temperature supply effect is the best under the condition that the inlet opening is vertically facing down,the outlet opening is vertically facing up and the opening diameter is 100 mm.