Thermal Comfort in Environments with Different Vertical Air Temperature Gradients.
Authors of this article are:
Möhlenkamp M, Schmidt M, Wesseling M, Wick A, Gores I, Müller D.
A summary of the article is shown below:
The use of displacement ventilation for cooling environments is limited by the vertical temperature gradient. Current standards recommend a temperature difference of up to 3 K/m between the head and the feet. This paper reviews the scientific literature on the effect of vertical temperature gradients on thermal comfort and compares this to the results of our own experiments. Early experiments have demonstrated a high sensitivity of dissatisfied test subjects to changes in the temperature gradient between head and foot level. Recent studies have indicated that temperature gradients of 4 K/m to 5 K/m are likely to be acceptable, and the mean room temperature may have a greater sensitivity on the percentage of dissatisfied (PD). In new experiments, test subjects have evaluated the thermal comfort of different vertical air temperature gradients in a modular test chamber, the Aachen Comfort Cube (ACCu), where they have assessed vertical temperature gradients of ΔT/Δy = 1, 4.5, 6, 8 and 12 K/m at a constant mean room temperature of 23 °C. The results of the different temperature gradients are in contrast to ANSI/ASHRAE Standard 55,1 as the PD increases almost constantly with higher vertical air temperature gradients. The PD for the overall sensation increases by approximately 7 % between gradients of 1 K/m and 8 K/m. The evaluation of our own tests has revealed that vertical temperature gradients of up to 8 K/m or higher are likely to be acceptable for test subjects. This article is protected by copyright. All rights reserved.
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This article is a good source of information and a good way to become familiar with topics such as:
displacement ventilation;local thermal comfort;thermal comfort;thermal sensation;thermal stratification;vertical temperature gradient
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