Experimental Study And Numerical Simulation Of The Thermal Performance Of An Earth-air Heat Exchange Fresh Air System

Under the Severe situation of energy shortages and the increasing prominence ofenvironmental issues, the low-carbon and sustainable concept is popularized increasingly.The renewable energy sources has attracted much attention due to its obvious advantages inenvironmental protection and energy-saving. Fresh air system in building with earth-to-airheat exchanger is an independent fresh air system which refers to pipes are laidunderground and coupled to building ventilation system. In this system,the use of earth as aheat source in winter for preheating outdoor fresh air and as a cold source in summer forprecooling outdoor air. In this way we can both save Energy consumption of airconditioning and improve indoor air quality.Fresh air system in building with earth-to-air heat exchanger is mainly include thefresh air inlet part and indoor air terminals and the underground earth-to-air heat exchangerwhich is the key to achieve energy saving target. An one-dimensional numerical model ofthe heat exchanger was developed after further discussion at the theoretical of thermalperformance of this system. The model was showed in Visual Basic（VB）environment asan earth-air heat exchanger design and optimization tool. Analysis of the effect factors ofearth-air heat exchanger depending on the previous model provides the reliable theorybasis subsequent for the experiment system design.After the discussion and analysis of external conditions such as climate,earth and siteand internal conditions of the system, a fresh air system in building with earth-to-air heatexchanger was designed.In addition the experimental system and the monitoring system arecarried out. Thermal performance of the system and the indoor air quality are monitoredand analyzed during the operating condition of winter,summer, transition season andlong-term operating conditions. Under the winter and the summer typical workingcondition of the unit heat transfer area of the underground heat transfer respectively90.9W/m2and44.2W/m2.In the way of discussing and analysis of the earth-air ventilation system and thebuilding thermal performance,a simulation system was established in TRNSYSenvironment. With the TRNSYS program room temperature,fresh air temperature at theoutlet of the tunnel and energy consumption of the building in different modes has carried out to predict,evaluate,and analysis the system effectiveness hour by hour. With the heatrecovery device for the heating season, air preheating effect is obviously enhanced andenergy-saving benefit is more outstanding.In this paper, the research of earth-to-air heat exchange for building fresh air systemprovides great theoretical basis and technical support for the promotion and application ofthe system a in cold region.