Numerical investigation of different type earth-air heat exchangers in passive air conditioning system

In this study, analyzes regarding the cooling and heating performance of different type 8 earth–air heat exchanger (EAHE) system (4 horizontal and 4 vertical) with 3D–modeled equal pipe lengths for the summer and winter climatic conditions of Bitlis (Turkey) were investigated in ANSYS FLUENT 19.2 software program. Thermal analyzes of EAHE systems were evaluated using the standard k-ε turbulence model at steady state condition of the Computational Fluid Dynamics (CFD) based software program. H–Model III and V–Model IV EAHE systems provided the best thermal performance as a result of the thermal analyzes performed for the 2x104 value of Re number. As a result of the parametric analyzes, it was determined that the increase in the air inlet velocity and the pipe inner diameter significantly affected the EAHE thermal performance, while the soil thermal conductivity had less effect on the EAHE thermal performance. More comprehensive cooling and heating performance analyses were performed by using the different values of Re = 5x103, 104, 2x104, 4x104, 6x104, 8x104, 105 numbers for EAHE systems (H–model III ve V–model IV) providing the best thermal performance. In cooling condition, V–Model IV EAHE system provided the best thermal performance for Re number 5x103, 104, 2x104, 4x104, 6x104 and 8x104 values, and H–Model III EAHE system provided the best thermal performance for Re number 105 value. In heating condition, V–Model IV EAHE system provided the best thermal performance for Re number 5x103, 104 and 2x104 values, and H–Model III EAHE system provided the best thermal performance for Re number 4x104, 6x104, 8x104 and 105 values. The highest COP values were provided by the V–Model IV EAHE system with 505.735 and 1146.719 for cooling and heating conditions, respectively. The highest exergy loss rates were obtained from D-Model IV EAHE system with 32.586 W and 52.728 W for cooling and heating conditions, respectively. The D-Model IV EAHE system was provided the highest exergy efficiencies with 42.56% and 45.90% for cooling and heating conditions, respectively.