Study On The Performance Of EAHE For Fresh Air Preheating And Pre-cooling

The soil has a good heat storage capacity.The heat of the shallow soil is mainly absorbed by the solar radiation,and the temperature is attenuated and delayed in the depth direction,so that the soil temperature at a certain depth can be maintained all the year round.Compared with the ambient temperature,it can keep the winter and summer cool.Extracting heat from the soil through the soil air heat exchanger can make full use of the geothermal energy.In combination with the building room,it needs to meet the fresh air demand,and the preheating/pre-cooling of the fresh air to reduce the total energy consumption of the building is a way of utilizing renewable energy.Based on the soil heat transfer process and the soil temperature wave equation,the CFD numerical model of solid-gas coupled heat transfer in soil-air heat transfer and the Earth-Tube analytical model in Energyplus are established respectively,which fully utilizes CFD in heat and mass transfer.The advantages and advantages of Energyplus in building energy calcula-tions.The evaluation of the heat transfer performance of the soil air heat exchange system model can be carried out efficiently,which is reflected in the heat exchange efficiency,the soil temperature field change,the cumulative heat exchange amount and the energy efficiency ratio.In general,in order to obtain a higher heat transfer rate,the principle of higher flow rate,small pipe diameter and long pipe should be adopted.The simulation study shows that the pipe-line should not be too long in the design process of the soil air heat exchanger.When the length reaches a certain length,the heat transfer efficiency does not change much.When the heat transfer efficiency is 70%,the suitable flow rate and diameter can be selected.The length of the pipe.The heat transfer process between the soil and the pipeline causes the temperature of the surrounding soil to change,and the long-term operation causes the heat exchange efficiency to be greatly reduced.Therefore,it should be operated in a batch mode to repair the soil,thereby improving the heat exchange efficiency,with a length of 20 m.In the case of 6h per run,the heat transfer efficiency is always above 80%by stopping for 2h.Through the analysis of the energy efficiency ratio,it is considered that the flow velocity value in the pipeline should not exceed 8 m/s.For determining the flow rate and the length of the pipe,there is a pipe diameter value that maximizes the COP value at that pipe diameter.When selecting a thinner pipe diameter,the flow rate/flow rate should not be too high and the pipe length should not be too long.When the pipe diameter is 0.1m,the flow rate should not exceed 200m3/h,and the length should not exceed 50m,otherwise the COP value is too low.The energy consumption analysis of a hypothetical room was carried out by establishing the Earth-Tube model.The results show that the use of soil air heat exchanger can effectively reduce the fresh air load of the room and reduce the total load.Compared with the conventional fresh air mode,the building uses the green energy-saving standard.The hot fresh air method can save 44.8%of heat supply and 40%of cooling capacity.Through optimization of the build-ing energy consumption model,it is found that if the cost is considered,the large pipe diameter is too high,and it is difficult to recover the pipe with a diameter of 0.45 m and a length of 15 m in a short time.Therefore,it is more suitable to replace the pipeline by excavating the tunnel.