Showing papers on "Thermal comfort published in 1991"

Thermal comfort in the humid tropics: Field experiments in air conditioned and naturally ventilated buildings in Singapore

Abstract: Thermal comfort field experiments were conducted in Singapore in both naturally ventilated highrise residential buildings and air conditioned office buildings. Each of the 818 questionnaire responses was made simultaneously with a detailed set of indoor climatic measurements, and estimates of clothing insulation and metabolic rate. Results for the air conditioned sample indicated that office buildings were overcooled, causing up to one-third of their occupants to experience cool thermal comfort sensations. These observations in air conditioned buildings were broadly consistent with the ISO, ASHRAE and Singapore indoor climatic standards. Indoor climates of the naturally ventilated apartments during the day and early evening were on average three degrees warmer than the ISO comfort standard prescriptions, but caused much less thermal discomfort than expected. Discrepancies between thermal comfort responses in apartment blocks and office buildings are discussed in terms of contemporary perceptual theory.

Air temperature and humidity and human comfort index of some city parks of Mexico City.

Abstract: A series of air temperature (Ta) and relative humidity (HR) measurements were carried out in five urban parks and their surroundings in Mexico City. It was found thatTa is lower andRH is higher inside the parks. There were differences (P<0.05) between the parks and surroundings in air temperature, relative humidity, vapour pressure (e), vapour pressure deficit (VPD) and the thermohygrometric human comfort index (THI).Ta differences were more marked during the early afternoon. Maximum differences ofTa, e, andDPV were 5.6°C, 0.6 and 1.2 mbar. There is strong evidence that the magnitude of differences inTa are directly proportional to the surface of urban parks.

Testing of localized ventilation systems in a new controlled environment chamber.

Abstract: This paper describes tests of thermal comfort and air distribution performance of two relatively new occupant-controlled localized ventilation (also called task ventilation) systems. The first is a raisd-floor distribution system providing air through grilles in the floor panels, and the second is a desk-mounted unit supplying conditioned air at desktop level. The tests were performed in a new controlled environment chamber (CEC) having unique capabilities for detailed studies of space conditioning and thermal comfort in office environments. Measurements were made in a mockup of a typical partitioned open-plan office, and the resulting temperature and air velocity distributions are reported for a variety of system- and locally controlled conditions. Comfort model predictions are presented to describe the degree of environmental control and range of occupant comfort levels produced in the workstations. The results are also compared to those produced by a conventional ceiling supply system. The tests investigated the effects of supply volume, supply location, supply vent orientation, supply/return temperature difference, heat load density, and workstation size and layout. Temperature differences in the range of 1–2.5°C were observed between adjacent workstations, and local air velocities in the vicinity of outlets could exceed 3 m/s. Such wide-ranging values could violate existing comfort standards (ASHRAE, 1981; ISO, 1984), if strictly interpreted. However since these systems put the local thermal conditions within the workstations under the direct control of their occupants, it is recommended that the standards grant exceptions to such systems.

Laboratory studies of the effect of air movement on thermal comfort: a comparison and discussion of methods - eScholarship

Abstract: This paper compares and contrasts methods used in laboratory studies of thermal comfort that focus on the effect of air movement. In laboratory studies, subjects typically wear standardized or similar clothing, are prescreened for healthy body temperature, are restricted in activity, and are exposed to a set of environmental variables that remain constant for a specific period of time. Three broad methodological categories are compared: experiments in which subjects have control of (1) air velocity or (2)air temperature or (3) neither. Specific experimental practices that may confound results are discussed.

Laboratory studies of the effect of air movement on thermal comfort: a comparison and discussion of methods

Abstract: This paper compares and contrasts methods used in laboratory studies of thermal comfort that focus on the effect of air movement. In laboratory studies, subjects typically wear standardized or similar clothing, are prescreened for healthy body temperature, are restricted in activity, and are exposed to a set of environmental variables that remain constant for a specific period of time. Three broad methodological categories are compared: experiments in which subjects have control of (1) air velocity or (2)air temperature or (3) neither. Specific experimental practices that may confound results are discussed.

Aspects of thermal preferences in housing in a hot humid climate, with particular reference to Darwin, Australia

Abstract: This paper presents findings of a study of thermal discomfort and preferences in housing in the humid tropics The study was conducted in Darwin, Australia Thirty-one households, approximately half with fully airconditioned houses and half without airconditioning, were involved in the study Data were collected by interviews, which covered topics such as use patterns of airconditioners and attitudes to airconditioning; and by comfort vote loggers, electronic devices which record temperature and humidity, and house-occupants' clothing and activity levels, experience of air movement, and ‘vote’ on a thermal discomfort scale

Draught, Radiant Temperature Asymmetry and Air Temperature – a Comparison between Measured and Estimated Thermal Parameters

Abstract: Thermal comfort measurements were taken in 17 enterprises at 129 work sites in shops, stores and offices. The measurements included air temperature, air velocity, relative humidity and radiant temperature asymmetry according to ISO 7726 and ISO 7730 standards. The workers also answered a questionnaire dealing with thermal comfort. Predicted mean vote (PMV) and the percentages of workers complaining of draught (“percentage dissatisfied”, PD) were determined and compared with the workers' assessments of thermal conditions. The estimations of air temperature were always too low, and the estimated PMV indicated that the thermal environment was too warm. The calculated PMVs were usually lower than the estimated ones. Most of the workers complained of draught, even though, according to the PD index, fewer than 17% of the workers should have felt discomfort due to draught. The radiant temperature asymmetry was always small and did not explain complaints of draught on the basis of the reference value. Judged by the present reference values, and the measurement of the thermal environment, the workers overestimated the sensation of thermal discomfort.

Effect of solar absorptivity and emissivity of exterior surfaces on the thermal performance of a building

Abstract: The effects of the solar absorptivity and the thermal emissivity of exterior building surfaces on the indoor air temperature of a one room building are evaluated in terms of the discomfort index. The thermal performance of the building has been investigated for four different climates prevalent in India, namely, composite (New Delhi), hot and dry (Jodhpur), cold and humid (Srinagar), and cold and dry (Leh). The results confirm the common-sense view that the building surface should have low solar absorptivity and high thermal emissivity in hot climates and high solar absorptivity and low thermal emissivity in cold climates for indoor thermal comfort conditions.

Thermal comfort in starter homes in the uk

Abstract: This paper reports on ratings, on the ASHRAE scale of thermal sensation, made by people in their own homes and compares the results to those of previous studies of climate chambers. It is based on BRE's sUIVey of "starter" homes: owner-occupied homes with one or two habitable rooms, constructed 1980-85. The mean living room temperature (19.2°C) and the preferred room temperature (19.4°C) were similar and corresponded to a rating of "slightly warm" on the ASHRAE scale. Thus the "neutral" point on the ASHRAE scale was not the preferred condition and occupants of starter homes preferred living-room temperatures slightly lower than those previously assumed comfortable (21°C) and those established by climate chamber studies (25°C). Mean thermal sensation was proportional to room temperature (r=O. 95) but thermal sensation was uniformly "slightly warm" between 18 and 23°C. This plateau was predominantly due to higher income groups who appeared to be more able to achieve thermal comfort at a wider range of temperatures than the lower income groups. However the older respondents, although on a lower income, lived in homes with higher room temperatures. As expected, respondents adjust their level of clothing to compensate for the room temperature.

Effects of Air Temperature and Clothing on Thermophysiological Responses and Thermal Comfort Vote during Rest and Physical Exercise

Abstract: This study was experimentally investigated in order to clarify effects of air temperature and clothing on thermophysiological responses and thermal comfort vote during rest and physical exercise. The experiments were carried out in a climate chamber at Nara Women's University at different air temperatures from 15 to 30•Ž and in 3 types of clothing conditions. Nude: half naked (bathing bra and panties), Half: a half-sleeved cotton T-shirts, cotton shorts, bathing bra, panties and cotton socks, Long: a long-sleeved cotton sweater, cotton trousers on the Half type ensemble. The relative humidity was 50%. The mean radiant temperature was equal to the ambient air temperature, and air velocity was less than 0.2 misec. The subjects were three healthy untrained young women. They rested for 30 min and then took physical exercise on a bicycle ergometer for 40 min. The results were as follows:

Thermal comfort in the space with personal radiant panel heating system

Abstract: OA化に伴う熱負荷の偏在化, オフィスワーカーの個人差のため, 均一温熱環境をつくりだすのみで快適環境を実現することは難しくなっている. 本研究では, オフィスや居住空間において温風暖房によって発生した上下温度分布による不快を減少させることを目的として, パーソナルふく射暖房パネルの体感効果に関して報告する. 体感実験の結果, パーソナルふく射パネルは下肢の冷えを解消する効果があるが, パネル表面温度が高くなると気流速が増加し, 局部温冷感による不快感を生じる可能性があることが明らかになった. また, パネル表面温度が高温にならないように注意し, 他の暖房方式との併用によって, より快適な居住空間を形成することが必要であることがわかった.

The optimum selection of the window shading levels and of the indoor ventilation rates as a design strategy for bioclimatic commercial buildings

Abstract: Ventilation rates, shading level of windows and indoor air temperature are analyzed together in order to single out the optimum mix referred to the thermal comfort situations of thermally moderate commercial buildings. Thermal comfort is here taken into account by means of the Predicted Mean Vote ( Fanger, 1970 ). A short selection of graphs is proposed, able to provide the simultaneous view of the effects produced, on the PMV, by modifications of the above cited parameters. Graphs can be usefully adopted for the proper design of the glazed surfaces, especially for passive solar buildings.

New simulator for measuring temperature of clothing surface next to skin

Abstract: A new type of simulator for clothing microclimate was constructed. It was designed to simulate the humidity fluctuation in clothing microclimate as observed under the light working conditions and to measure the surface temperature of a fabric specimen faced to skin by means of a radiation thermometer. Knitted fabrics of cotton and polyester, and a polyethylene film were used as specimens with different hygroscopicities. The quick rises and drops in the surface temperature of cotton fabrics were observed under the rapid fluctuation of the microclimate humidity. Under the same humidity fluctuation, the temperature of polyester fabrics rose and dropped more moderately than that of cotton fabrics, and the temperature of the polyethylene film did not change. Generally, the higher is the rate of change in stimulus temperature, the closer approaches the threshold temperature of warm sensation on the skin to a given adapting temperature. Therefore, the quick and large changes in the fabric temperature faced to skin, which were observed especially for hygroscopic cotton fabrics, must affect the thermal comfort of clothing.

Cooling of commercial buildings by means of large cold radiant ceilings

Abstract: The possibility of using different cooling tools working with lower radiant temperatures and higher air velocity is explored. Lower energy consumptions may be achieved in specific climates with reasonable levels of thermal comfort.