Simulation Of Heat Exchange Characteristics And Study Of Application Of Earth-to-Air Heat Exchanger

According to current trends,global energy consumption will be more than twice the current level by 2020.This increasing demand for energy will exacerbate environmental pollution and energy shortages.Because the soil temperature is almost constant throughout the year,earth to air heat exchanger systems use underground soil as a heat source or cold source.When air flows into buried pipes,heat exchange between soil and air.The air outlet of the buried pipes can be directly used for space heating or cooling,or combined with air treatment unit.Due to the different climatic conditions and soil temperatures in different regions,the heat transfer performance and energy saving potential of earth to air heat exchangers are also different.In order to explore the feasibility of this system applied in cold area and application effect,this paper,by using ANSYS FLUENT software to establish threedimensional unsteady earth to air heat exchanger model,explore Beijing area earth to air heat exchanger heat exchange effect and energy saving benefits.The temperature distribution of shallow soil in Beijing area was calculated and analyzed,and the effect of comprehensive environmental conditions on the temperature distribution of shallow soil was studied.the results show that in the depth of the 4 m,heat transfer temperature difference during November to February range of 5.92~5.92?,June to August summer heat transfer temperature difference range of 4.34~4.34?,so earth to air heat exchanger is feasible in Beijing area,and it can obtain good effect of building energy conservation.Based on the analysis of the heat transfer principle of earth to air heat exchanger,a three-dimensional unsteady numerical model of earth to air heat exchanger was established.The factors affecting the heat transfer performance of the system and the soil temperature near the pipe were analyzed.Longer,buried deeper,with lower air flow rates and smaller diameters,can promote the improvement of the performance of the system.When the system is operated intermittently,the air temperature difference at the inlet and outlet of the heat exchanger is larger than that during continuous operation.Simulation of one cycle of earth to air heat exchanger operation showed that the soil had good seasonal heat recovery.Based on the above research results,earth-to-air heat exchanger system with a practical application scale was designed for preheating/precooling fresh air.The calculation and analysis results show that the efficiency of the heat exchanger reaches more than 90%,and the system has good energy-saving and economical efficiency.The above work has certain reference value for the practical application of soil-air heat exchangers in Beijing.