Comparison of Application Effects of Capillary Radiation Heat Pump and Electric Heating Wire in Greenhouse Seedling Cultivation

Heat pumps with water as heat exchange medium applied in greenhouse heating have not been used for vegetable seedling cultivation. In this work, a multi-connected direct expansion capillary radiation pump (MDCRHP) was designed cultivation, and closed local temperature control (CLTC) method proposed to accurately air substrate temperatures beds, enhance the effect reduce equipment cost. The results show that CLTC can achieve good quickly raise air/substrate at speed of 1 °C/min from 8 °C about 20 within 12 min. fields beds were evenly distributed. differences different horizontal positions heights less than °C, relative humidity 100%, which is conducive grafting seedling. It be concluded test MDCRHP had strong adaptability obviously superior electric wire (EWH). output capacity compressor controlled by adjusting operation frequency meet requirements stages Under conditions similar external ambient energy saving rate 47–50.7% compared EWH. cost 7.2% lower conventional pump. takes 3–3.5 years recover investment.