Effects of Multi-Stage Sudden Expanded Channel on Heat Transfer and Flow in Earth-Air Heat Exchanger

Abstract

The thermal-hydraulic performance of a multi-stage sudden expanded channel design for Earth-Air Heat Exchanger (EAHE) application is explored in this study. The computational analysis is based on a horizontal cross-section model composed of a series of large (diameter 0.1 m) and small (diameter 0.05 m) cylindrical sections of length 0.5 m each. The study compares the heat transfer and pressure drop characteristics of the different Reynolds number for inlet air temperature at 50°C and surface temperature at 30°C at a velocity of 2.98 m/s. The results show that the multi-stage sudden expansion configuration can improve heat transfer performance considerably while introducing some pressure loss, which is more than that of the basic sudden expansion configuration. Optimum design configurations are analyzed by considering the thermal performance enhancement ratio and hydraulic performance penalty ratio.