Thermal Comfort In Non-uniform Environments Research Articles

The correlation between the overall thermal comfort, the overall thermal sensation and the local thermal comfort in non-uniform environments with local cooling

The evaluation of overall thermal comfort in non-uniform thermal environments has not been fully clarified; it was therefore studied in this paper. For this aim, a series of experiments were conducted under non-uniform thermal environments with local cooling, where subjects’ thermal responses were surveyed by questionnaires. The correlations between the overall thermal comfort, the overall thermal sensation and the local thermal comfort were explored under both steady and unsteady states. As well, the relationship between the overall thermal comfort and the local thermal comfort was examined under steady-state conditions. The results indicated that the overall thermal comfort was dependent on the overall thermal sensation and also on the local thermal comfort at the body parts exposed to local cooling, whether in steady or transient states. Considering the two factors, the overall thermal comfort models were proposed for steady and unsteady states. Also, the overall thermal comfort was approximated by the average of the maximum and minimum local thermal comfort under steady states. Another overall thermal comfort model was therefore proposed. The two overall thermal comfort models for the steady state were verified by experimental results.

Investigation on temperature range for thermal comfort in nonuniform environment

This study uses the previously adopted local ventilation air-conditioning mode to study the effect of temperature on thermal comfort for subjects. Three room temperatures (26, 28, 30°C (78.8, 82.4, 86°F)) and three local ventilation temperatures (20, 26, 28°C (68, 78.8, 82.4°F)) were used for the study. The air velocity was purposely set low for the local ventilation tests, in order to focus on the temperature combinations between the ambient and local air temperature from the local ventilation device. Eighteen subjects participated in the experiment, using the within-subjects design method. During exposure in the room, the subjects reported thermal sensation and thermal comfort accompanied by the skin temperature measurement of the subjects. The room temperature of 28°C (82.4°F) combined with the local ventilation temperature of 26°C (78.8°F) (28°Crt and 26°Clv (82.4°Frt and 78.8°Flv)) was assessed to be the most comfortable environment. Through the experiments, the neutral room temperature of 26°C (78.8°F) combined with the local ventilation temperature of 20°C (68°F) as well as the warm room temperature of 30°C (86°F) combined with 26°C (78.8°F) was found to be within the comfortable range. The results imply that compared with the traditional air conditioning mode, which creates a uniform comfortable environment by setting the air temperature to be 26°C (78.8°F), the adoption of local ventilation could improve the thermal comfort while consuming less energy.

Thermal comfort, skin temperature distribution, and sensible heat loss distribution in the sitting posture in various asymmetric radiant fields

This study aimed at investigating the thermal comfort for the whole body as well as for certain local areas, skin temperatures, and sensible heat losses in various asymmetric radiant fields. Human subject experiments were conducted to assess the overall comfort sensation and local discomfort, and local skin temperatures were measured. Through thermal manikin experiments, we discovered a new method for the precise measurement of the local sensible heat loss in nonuniform thermal environments. The local sensible heat losses were measured by the use of a thermal manikin that had the same local skin temperatures as the human subjects. The experimental conditions consisted of the anterior–posterior, right–left, and up–down asymmetric thermal environments created by radiation panels. A total of 35 thermal environmental conditions were created ranging from 25.5 to 30.5 °C for air temperature, from 11.5 to 44.5 °C for surface temperature of radiation panels, from 40% RH to 50% RH for humidity, and less than 0.05 m/s for inlet air velocity to the climatic chamber. The local skin temperature changed depending on the environmental thermal nonuniformity, even if the mean skin temperature remained almost the same. It is essential to use the skin temperature distribution as well as mean skin temperature for expressing thermal comfort in nonuniform environments. The local sensible heat loss changed depending on the environmental thermal nonuniformity, even if the mean sensible heat loss remained almost the same. The relationship between the local skin temperature and local sensible heat loss cannot be depicted by a simple line; instead, it varies depending on the environmental thermal nonuniformity. The local heat discomfort in the head area was dependent on both the local skin temperature and local sensible heat loss. However, the local cold discomfort in the foot area was related only to the local skin temperature.