Analysis of Thermal Comfort Near Cold Vertical Surfaces by Means of Computational Fluid Dynamics

Cold surfaces may cause thermal discomfort due to down draught and/or infrared radiation exchange. In this paper a cold vertical surface of 3m height in a room (3 × 3 × 5m3) was investigated using computational fluid dynamics (CFD). Also calculated were a parameter that expresses thermal discomfort for the whole human body – the predicted percentage of (those people) dissatisfied – and parameters of local discomfort such as air speed and draft risk. Five cases with different heat loads (0–80Wm−2) and with/without furniture were simulated, each case with three different temperatures of the cold surface (17.5, 15, and 10°C). The mean operative temperature was approximately 20°C in all cases. It was found that with respect to thermal discomfort, draught was more critical than reduced operative temperatures or radiation asymmetry. An increase of the heat load in the room leads to higher down draught air speeds. Therefore, experiments performed in empty rooms tend to underestimate the maximum air speed that occurs in real, furnished rooms with heat loads. A set of correlations for maximum air speed within the occupied zone is proposed. Additionally, this study shows that CFD is a valuable technique to complement and broaden knowledge gained in laboratory experiments in the field of thermal comfort.

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