Experimental study on the performance of hybrid buoyancy-driven natural ventilation with a mechanical exhaust system in an industrial building

Abstract

Hybrid ventilation is an effective means of minimizing ventilation energy and improving indoor environment. A scale experimental model with a heat source was created for hybrid buoyancy-driven natural ventilation with a mechanical exhaust system. The aim of this study is to examine the performance of hybrid ventilation in an industrial building. The temperature distributions and hybrid ventilation efficiencies with different mechanical exhaust velocities were analyzed. Results showed that the hybrid ventilation efficiency first increased and then decreased with the mechanical exhaust velocity. A critical mechanical exhaust velocity was identified and the hybrid ventilation efficiency reached maximum at the critical mechanical exhaust velocity. The critical mechanical exhaust velocity was 1.4 m/s at the heat flux of the heat source q = 200 W and 1.0 m/s at q = 500 W, and the corresponding ventilation efficiencies were 24.4 and 6.69, respectively. Four modes of hybrid ventilation were investigated, and ventilation strategies of different modes of hybrid ventilation were given. An excessive mechanical ventilation rate will cause consumption of ventilation energy to increase and may lead to short circuiting of airflow and a bad thermal environment. These results should prove helpful in designing of hybrid ventilation systems for industrial buildings.