Effects of temperature and supply airflow rate on thermal comfort in a stratum-ventilated room

Abstract

Providing an appropriate thermal comfort level is crucial for the technical feasibility of stratum ventilation at elevated room temperatures. This paper presents a subjective study of thermal comfort in a stratum-ventilated environmental chamber. Overall thermal sensation (OTS), local thermal sensation (LTS) of body segments, overall thermal comfort (OTC) and draft were investigated. The objectives of this study were twofold: to evaluate the effect of room temperature on thermal comfort (Test Series 1) and to assess the effect of supply airflow rate and supply air temperature on thermal comfort (Test Series 2). Test Series 1 revealed that the room temperature had a great impact on the OTS, LTS, OTC and draft. Under 10 air change per hour (ACH), a room temperature of 27 °C provided neutral OTS, satisfactory OTC and low draft risk. However, at room temperatures of 24 and 29 °C, the percentages of subjects feeling comfortable were obviously less than 80%. Test Series 2 showed that at the room temperature of 27 °C, increasing the supply airflow rate from 7 ACH to 17 ACH only exhibited a small influence on the thermal sensation and draft, indicating a preference for air movement. More than 80% subjects felt comfortable at 27 °C. However, to minimize draft complaints, the supply air temperature should not be below 20 °C. These results show that stratum ventilation provides a thermally comfortable environment, so that people can have the feeling of “cool head and warm feet”, with low draft risk at a room temperature up to 27 °C.