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Thermal comfort in environments with different vertical air temperature gradients
Author(s) -
Möhlenkamp Martin,
Schmidt Martin,
Wesseling Mark,
Wick Andreas,
Gores Ingo,
Müller Dirk
Publication year - 2019
Publication title -
indoor air
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.387
H-Index - 99
eISSN - 1600-0668
pISSN - 0905-6947
DOI - 10.1111/ina.12512
Subject(s) - ashrae 90.1 , temperature gradient , thermal comfort , displacement ventilation , environmental science , ventilation (architecture) , sensitivity (control systems) , operative temperature , air temperature , vertical displacement , thermal , thermal sensation , air conditioning , environmental chamber , materials science , atmospheric sciences , meteorology , chemistry , thermodynamics , geology , engineering , physics , structural engineering , electronic engineering
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 4‐5 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 Δ T /Δ y = 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 ( Thermal Environmental Conditions for Human Occupancy , Atlanta GA, American Society of Heating, Refrigerating and Air Conditioning Engineers, 2013) 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 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.