-
Abstract This paper predicts some trends foreseen in the new century as regards the indoor environment and thermal comfort. One trend discussed is the search for excellence, upgrading present standards that aim merely at an “acceptable” condition with a substantial number of dissatisfied. An important element in this connection is inpidual thermal control. A second trend is to acknowledge that elevated air temperature and humidity have a strong negative impact on perceived air quality and ventilation requirements. Future thermal comfort and IAQ standards should include these relationships as a basis for design. The PMV model has been validated in the field in buildings with HVAC systems that were situated in cold, temperate and warm climates and were studied during both summer and winter. In non-air-conditioned buildings in warm climates occupants may sense the warmth as being less severe than the PMV predicts, due to low expectations. An extension of the PMV model that includes an expectancy factor is proposed for use in non-air-conditioned buildings in warm climates. The extended PMV model agrees well with field studies in non-air-conditioned buildings of three continents.21608
- 上一篇：雷达成像技术对钢筋混凝土桥梁的无损检测英文文献和中文翻译
- 下一篇：公路桥梁英文文献和中文翻译
Keywords: PMV, Thermal sensation, Inpidual control, Air quality, Adaptation
A Search for Excellence
Present thermal comfort standards (CEN ISO 7730, ASHRAE 55) acknowledge that there are considerable inpidual differences between people’s thermal sensation and their discomfort caused by local effects, i.e. by air movement. In a collective indoor climate, the standards prescribe a compromise that allows for a significant number of people feeling too warm or too cool. They also allow for air velocities that will be felt as a draught by a substantial percentage of the occupants.
In the future this will in many cases be considered as insufficient. There will be a demand for systems that allow all persons in a space to feel comfortable. The obvious way to achieve this is to move from the collective climate to the inpidually controlled local climate. In offices, inpidual thermal control of each workplace will be common. The system should allow for inpidual control of the general thermal sensation without causing any draught or other local discomfort. A search for excellence involves providing all persons in a space with the means to feel thermally comfortable without compromise.
Thermal Comfort and IAQ
Present standards treat thermal comfort and indoor air quality separately, indicating that they are independent of each other. Recent research documents that this is not true . The air temperature and humidity combined in the enthalpy have a strong impact on perceived air quality, and perceived air quality determines the required ventilation in ventilation standards. Research has shown that dry and cool air is perceived as being fresh and pleasant while the same composition of air at an elevated temperature and humidity is perceived as stale and stuffy. During inhalation it is the convective and evaporative cooling of the mucous membrane in the nose that is essential for the fresh and pleasant sensation. Warm and humid air is perceived as being stale and stuffy due to the lack of nasal cooling. This may be interpreted as a local warm discomfort in the nasal cavity. The PMV model is the basis for existing thermal comfort standards. It is quite flexible and allows for the determination of a wide range of air temperatures and humidifies that result in thermal neutrality for the body as a whole. But the inhaled air would be perceived as being very different within this wide range of air temperatures and humilities. An example: light clothing and an elevated air velocity or cooled ceiling, an air temperature of 28ºC and a relative humidity of 60% may give PMV=0, but the air quality would be perceived as stale and stuffy. A simultaneous request for high-perceived air quality would require an air temperature of 20-22ºC and modest air humidity. Moderate air temperature and humidity decrease also SBS symptoms and the ventilation requirement, thus saving energy during the heating season. And even with air-conditioning it may be beneficial and save energy during the cooling season.