Modeling and assessing earth-air heat exchanger using the parametric performance design method

Abstract

ABSTRACT Earth-air heat exchanger (EAHE) is a passive technique that can reduce the energy consumption for indoor heating and cooling. This paper aims to evaluate the performance of EAHE in Qingdao, China by using a proposed all-in-one simulation model according to the parametric performance design method. This model can predict the performance and feasibility of EAHE and generate various required results with just one click. It was also validified by the actual field experiment to prove its appropriateness. In the simulation, the influence of eight parameters on the outlet air temperature was firstly analyzed to understand their interrelationships. Secondly, thermal capacity and heat transfer efficiency were evaluated to test the performance of EAHE. Finally, this paper provided a feasibility analysis of EAHE. The findings indicate that deeper burial depth, longer tube length, and smaller tube diameter can achieve better heat transfer efficiency and thermal capacity. However, when tube length exceeded 40 m, burial depth exceeded 2 m, or tube conductivity was higher than 1W/m-K, the change in the outlet air temperature was no longer substantial. More importantly, the feasibility analysis suggested a promising application prospect for EAHE in Qingdao. The maximum average daily cooling and heating capacities of the system were 15.56 kW and 18.49 kW, respectively. The maximum heat transfer efficiency of the system in July (86.02%) and January (87.89%) can be obtained, when the tube length was 70 m and the inlet airflow speed was 1 m/s, respectively. The economic feasibility analysis indicated that EAHE could save 507.8 Yuan each year, and the payback period was about 6.2 years.