Occupant’s thermal responses to asymmetric radiant thermal environment with warm wall and cool ceiling, Part A: Overall thermal responses

Abstract

A radiant ceiling cooling (CC) system integrated with a mechanical ventilation system, which can improve human thermal comfort and reduce HVAC system energy consumption simultaneously, has been extensively applied in the modern office building with glass curtain walls. In a ceiling cooling room with a glass curtain wall, the horizontal and vertical asymmetric radiation caused by the warm wall and cool ceiling may result in different thermal responses of human body. Therefore in this paper, occupant’s thermal responses in a simulated ceiling cooling office room with mixing ventilation (MV) or underfloor air distribution (UFAD) were investigated by a combination of subjective and objective experiments. Indoor operative temperature was increased from 23.0 °C to 30.0 °C as the surface temperatures of warm wall and cool ceiling were from 30.0 °C to 40.0 °C and from 14.0 °C to 27.0 °C. The results showed that the indoor thermal environment with CC + MV or CC + UFAD was comfortable and acceptable as the indoor operative temperature was from 25.0 °C to 27.0 °C. The thermal neutral operative temperature in the room was 25.6 °C with CC + MV and 26.4 °C with CC + UFAD, and the corresponding thermal neutral skin temperatures was 33.4 °C and 33.7 °C, respectively. Moreover, the thermal comfort stability of indoor operative temperature was close to 0.30 °C−1 with CC + MV or CC + UFAD, and the corresponding thermal comfort stability of mean skin temperature was 0.90 °C−1–0.94 °C−1. There were clearly linear relationships between thermal sensation or thermal preference and indoor operative temperature or mean skin temperature, and these relationships may be beneficial for the intelligent control of a radiant ceiling cooling system combined with a mechanical ventilation system.