Numerical modeling and optimization of thermal comfort in building: Central composite design and CFD simulation

A “hybrid ventilation system that uses both natural and mechanical ventilation has drawn attention with its low operation cost and constant ventilation rate”. This study is to advance the use of hybrid ventilation concepts in building design by assessment of opening air supply with an operation of ceiling fan-assisted ventilation system. Airflow characteristics of ceiling fan and its effect on the thermal comfort was investigated numerically. Thermal comfort criteria namely; predicted mean vote has been used to predict the thermal comfort zone inside the room. After validation of the model, effect of supply air velocity and blade pitch on the flow and thermal field is investigated.  The response surface methodology based on 5 factorial central composite design (CCD) was employed to investigate the optimum parameters of thermal comfort. The response factor PMV was set to be in slightly cool zone to slightly warm zone (−0.5-0.5). A mathematical model of the relationship between the environmental and operational factors considered was then derived from the data. One of the predicted optimal values for the warm-humid climate zones (maximum temperature of 36 °C and humidity of 80%) were as follows: blade pitch = 5.75°, fan speed = 99 rpm, inlet air temperature = 36 °C and inlet air humidity = 73.3%, which led to keep PMV within recommended comfort range (slightly cool) defined by ISO and ASHRAE.