EVALATION OF BOREHOLE GSHP PERFORMANCE FOR GREENHOUSE IN JAPAN AND ITS NUMERICAL MODEL
A ground source heat pump (GSHP) system was installed to maintain an appropriate temperature for the growth of orchid in Akabira city,Japan.The borehole field consists of 78 vertical boreholes with a depth of 85m each.It provides a maximum heating and cooling load of 640 and 648 kW respectively.As one of the biggest borehole system in the country,it is valuable to evaluate the variation of the soil temperature in the deep ground caused by the huge heat extraction and injection during a long term operation.The performance of the system during the period of October 2010 to May 2011 was monitored and analyzed.The results indicate that the COP ranges from 2.5 to 3.5 while SCOP varies between 2.27 to 3.0,respectively.The average heat extraction rate of the system was found approximately 27.2W/m.162 tons of CO2 can be reduced assume an SCOP of 2.0.On the other hand,the ground temperature at a depth of 40m decreased from around 7.8℃ to 0℃ during 7 months operation.Through the measurement data,it is found that the system could guarantee the desired greenhouse indoor temperature even in the coldest month.As the heating demand of Akabira region surpass its cooling demand,a numerical model was developed by FEFLOW to predict its behavior and examine the balance between the extracted and injected heat.The model was examined by the experimental data first,and then the matched model was used for the long-term operation prediction.It is concluded from the simulation results that the system could maintain the heat exchange rate after several years without degradation on its performance.What is more,the variations of the average heat extraction against the groundwater velocities and the thermal conductivity of the grout were discussed to estimate their influence to the borehole performance.
LI HUAI NAGANO KATSUNORI LAI YUANXIANG SHIBATA KAZUO FUJII HIKAI
Graduate School of Engineering,Hokkaido University,N13-W8,Kita-ku,Sapporo 060-8628,Japan Nissin Techno Co.Ltd,Sapporo,Japan Kyushu University,Kyushu,Japan
国际会议
西安
英文
1-12
2012-08-26（万方平台首次上网日期，不代表论文的发表时间）