Numerical investigation of the working mechanisms of solar chimney coupled with earth-to-air heat exchanger (SCEAHE)

Abstract

Solar chimney coupled with earth-to-air heat exchanger (SCEAHE) can provides fresh air and cooling capacity simultaneously without any electricity consumption. To understand the complex working mechanism of the coupled system, a numerical model has been established and verified to investigate various geometric and climatic parameters related to system performance. It is found that the system has the optimum performance when the pipe length is 60 m and pipe diameter is 0.6 m. Increasing the solar collector length or the chimney height can both increase the system performance. However, the effect of chimney height is not as significant as that of solar collector length. For the same increase in chimney height and solar collector length, the cooling capacity is increased by 51.6% and 77.8%, respectively. The higher the solar intensity, the higher the buoyancy force, airflow rate, outlet air temperature, and cooling capacity. The cooling capacity is increased by 101.4% by increasing solar intensity from 100 W/m2 to 600 W/m2. The higher the outdoor air temperature, the lower the buoyancy force and airflow rate, but the higher the outlet air temperature and cooling capacity. Moreover, the effect of outdoor air temperature on outlet air temperature is more significant than that on airflow rate. When the outdoor air temperature increases from 36 °C to 46 °C, the temperature reduction is increased by 75.8%, while the airflow rate is only decreased by 15.6%. The model developed in this study can be used for design and performance prediction of SCEAHE system.