Coupling of earth-to-air heat exchangers and buoyancy for energy-efficient ventilation of buildings considering dynamic thermal behavior and cooling/heating capacity

Abstract

Energy-efficient technologies such as earth-to-air heat exchangers (EAHEs) and buoyancy-driven natural ventilation (BV) are employed for space conditioning. However, a fan is required in conventional EAHEs for air circulation, and BV normally serves as a passive cooling measure in temperate transitional seasons. This paper proposes the coupling of EAHEs and the buoyancy generated inside a building to achieve passive and autonomous ventilation without requiring any mechanical system. A model is developed to investigate the effects of the coupled system, with a primary focus on the dynamics of the airflow temperature, flow rate, and cooling/heating capacity provision. The model results are in good agreement with those of the computational fluid dynamics simulation. The model is applied in a hypothetical building located in a hot-summer/cold-winter region (Chongqing, China). The proposed coupled scheme is superior to the BV in hot and cold seasons. The indoor air temperature, ventilation flow rate, and cooling/heating capacity are found to fluctuate asynchronously. The cooling capacity is 56.3 kWh for the hottest day, and the heating capacity is 111.1 kWh for the coldest day. The maximum cooling or heating capacity is nearly achieved at the hottest or coldest times with the help of ventilation flow rate fluctuation.