Analysis About The Operating Characteristies Of Heat Pump Based On Underground Tunnel Air In Winter In Shenyang

The heat pump based on underground tunnel air uses the air which is heated(cooled)by the tunnel for heating or cooling.The ordinary air source heat pump has some problems,for example,the temperature of the air outdoor is low in winter,the coefficient of performance of heat pump is also low.And it's easy to frost to use the air source heat pump in winter.So using the air which is heated by the tunnel can not only take advantage of the rich resources of air-raid shelter in our country,but also make full use of the heat in the soil.In this paper,the characteristic of the heat transfer between tunnel and air is studied,the effect made by different factors is analyzed,so as to improve the utilization efficiency of energy in the soil,to reduce the heat pump frosting at the same time.This subject research is about the tunnel air project in Shangyang area.Software is used to simulate and calculate the temperature field of the heat transfer between tunnel and air,analyze the variable rule of temperature,and theoretically study the problem of the air source pump frosting in the coolest month.Firstly,the effect that the thermal physical parameters have on the soil temperature variation is analyzed by a lot of knowledge such as the heat transfer theory,fluid mechanics and mass transfer theory,and the variation regularity of the soil temperature wave underground is pointed out.A mathematical model of the heat transfer between tunnel and air is established.Software is used to calculate and analyze the effect that the length,air velocity,buried depth and structure size of the tunnel have on the the heat transfer between tunnel and air.We can find that air temperature of the tunnel exit increase as the growth of the tunnel length,when the tunnel is longer than 500m,the temperature of the tunnel exit is basically unvariable;the heat exchange effect of the tunnel and air enhances with the increase of the air velocity in tunnel,suggesting the air speed is lower than 5 meter per second;air temperature of the tunnel exit increase with the burid depth increasing,he heat transfer effect is not various when the burid depth reaches 6 meter;air temperature of the tunnel exit decreases as the tunnel diameter increasing,so the tunnel capacity of heating the air decrease,the tunnel equivalent diameter should not be less than 2 meter.Secondly,ventilation process of the square tunnel which have the same equivalent diameter and double-round tunnel which have the same cross-sectional area as the single-round tunnel is simulated and analyzed.Conclusion can be obtained by analysis and comparison:the heating capacity of square tunnel is slightly better than the single-round tunnel;air temperature of the double-round tunnel exit is higher that of the single-round tunnel,the heat exchange effect enhances with the space of the two tubes increasing.According to the characteristics of the heat transfer between tunnel and air,the design of the tunel air engineering in Shenyang can choose accurate value within the optimum scope,so as to improve the efficiency of tunnel air system.Finally,the frosting problem of air source heat pump system based on the tunnel air is theoretically studied.Compared to the ordinary air source heat pump,the frosting of the air source heat pump system based on tunnel air in shenyang area in the coolest months reduces largely,which has important significance to improve the heat capacity,coefficient of performance of air source heat pump system.