Ratings Of Thermal Sensation Research Articles

The effects of solar radiation on thermal comfort

The aim of this study was to investigate the relationship between simulated solar radiation and thermal comfort. Three studies investigated the effects of (1) the intensity of direct simulated solar radiation, (2) spectral content of simulated solar radiation and (3) glazing type on human thermal sensation responses. Eight male subjects were exposed in each of the three studies. In Study 1, subjects were exposed to four levels of simulated solar radiation: 0, 200, 400 and 600 Wm(-2). In Study 2, subjects were exposed to simulated solar radiation with four different spectral contents, each with a total intensity of 400 Wm(-2) on the subject. In Study 3, subjects were exposed through glass to radiation caused by 1,000 Wm(-2) of simulated solar radiation on the exterior surface of four different glazing types. The environment was otherwise thermally neutral where there was no direct radiation, predicted mean vote (PMV)=0+/-0.5, [International Standards Organisation (ISO) standard 7730]. Ratings of thermal sensation, comfort, stickiness and preference and measures of mean skin temperature (t(sk)) were taken. Increase in the total intensity of simulated solar radiation rather than the specific wavelength of the radiation is the critical factor affecting thermal comfort. Thermal sensation votes showed that there was a sensation scale increase of 1 scale unit for each increase of direct radiation of around 200 Wm(-2). The specific spectral content of the radiation has no direct effect on thermal sensation. The results contribute to models for determining the effects of solar radiation on thermal comfort in vehicles, buildings and outdoors.

Physiological and performance benefits of halftime cooling

This study examined the effect of a 10-min, halftime cooling application on physiological and psychological parameters known to affect performance. Fourteen volunteers (10 male, 4 female) completed two randomised trials 48 hr to 7 days apart. Trials consisted of a 1-hr cycling protocol: 30 min at 75% VO2max followed by 10 min cooling (application of a cooling jacket) or passive recovery (control), and a second 30-min exercise bout consisting of 20 min at 75% VO2max, immediately followed by a 10-min maximal effort, where work was measured as energy expended (kJ). Performance of the 10-min maximal intensity phase tended to improve (171.5 +/- 30.4 kJ vs 165.4 +/- 29.2 kJ, p = 0.087) following the cooling trial. Heart rate during the 5th min of the maximal effort, (183 +/- 9 beats.min(-1) vs 180 +/- 7 beats.min(-1), p = 0.024), blood lactate concentration at 6 min post-exercise (9.3 +/- 3.1 mmolxL(-1) vs 7.9 +/- 3.2 mmolxL(-1), p = 0.007), rating of perceived exertion at the 20th min post-halftime recovery (15 +/- 2 vs 16 +/- 2, p = 0.042), and subjective rating of feelings and emotions differed between the cooling and control conditions. Sweat loss, core and mean skin temperature and rating of thermal sensation failed to differ significantly between conditions. Halftime cooling tended to result in greater aerobic performance. Psychological assessment revealed a dramatic placebo effect from the cooling application confounding these results. Furthermore, the cooling intervention failed to induce any significant thermoregulatory effects.

WEARING A CAP, THERMAL BALANCE, AND THERMAL SENSATION DURING RUNNING IN A WARM ENVIRONMENT

Head cooling during exercise in a warm environment removes 20% of the metabolic heat produced, reducing physiological strain, rectal temperature, sweat rate, and thermal discomfort. Wearing a cap during long distance running races in a warm environment is common. Theoretically, wearing a cap during running in a warm environment may impede body heat loss, increasing body core temperature and thermal discomfort, but this is unclear based upon the scientific literature. PURPOSE: To determine if wearing a cap alters thermal balance and thermal sensation during running in a warm environment. METHODS: Eight (6 males, 2 females) well-trained runners ran for 1 hour at 67% VO2 max in a warm environment (Tdb = 31 °C, relative humidity = 41%) wearing (CAP) or not wearing (NOCAP) a white cotton/polyester cap. During both running trials, subjects consumed 2 ml kg−1 of water every 15 minutes. Thermal balance was assessed using continuous monitoring of rectal (Trec) and skin temperatures (Ts, weighted mean: forehead, chest, lower back, forearm, palm, thigh) as well as measurement of whole-body sweat loss and thermal sensation of the head and overall body (10-point scale). RESULTS: Mean (± SEM) Trec rose steadily from 36.81 (± 0.24) °C to 38.16 (± 0.15) °C during NOCAP and from 36.76 (± 0.19) °C to 38.27 (± 0.29) °C during CAP. There were no significant differences in Trec or Te (p > 0.05) between groups. One hour of running in a warm environment elicited a whole-body sweat loss of 1.23 (± 0.11) liters during NOCAP and 1.30 (± 0.13) liters during CAP with no differences (p > 0.05) between treatments. Ratings of thermal sensation for the head and overall body indicated that subjects felt warm during both NOCAP and CAP, with no differences (p > 0.05) between running trials. Heart rate increased similarly to 164 (± 3.88) and 166 (± 8.38) beats min−1 during the last 5 minutes of NOCAP and CAP. Rating of perceived exertion averaged 12.5 (± 0.73) and 13.38 (± 1.15) during the last few minutes of NOCAP and CAP, respectively, with no differences (p > 0.05) between groups. CONCLUSION: Wearing a cap during prolonged, moderate intensity running in a warm environment does not significantly alter thermal balance, thermal sensation, or physiological stress. Therefore, such a practice should not compromise endurance performance or increase the incidence of thermal injury.

Predicted and reported thermal sensation in climate chambers, offices and homes

Past thermal comfort research has shown differences in the thermal sensation votes given in field and laboratory settings. However, such research tends to compare the votes of different groups of people in different environments rather than comparing the same people in each environment. Therefore, a two-phase study was conducted of the thermal comfort of 30 BRE employees in their home, in their office, and in a climate chamber. In the first phase each subject spent two 3 h sessions in each environment and the temperature was adjusted between sessions within the range 18–26°C. Data loggers were used to record the air and mean radiant temperature, air velocity and relative humidity; subjective ratings of thermal sensation were obtained using questionnaires. The subjects wore the same clothing in each session and were allowed to conduct only sedentary activities. The reported thermal sensation votes were compared with those predicted using ISO 7730. The observed neutral temperatures for each of the three environments differed by up to 2°C and were up to 1°C different to those predicted. This finding has implications for energy use. In the second phase, the subjects were studied in their home and office only. No restrictions were imposed on clothing, previous or current activities, or environmental conditions. The observed thermal sensation votes were very poorly correlated with those predicted and with operative temperature.

User-Adaptable Comfort Control for HVAC Systems

This paper describes a new approach to the control of heating, ventilating, and air-conditioning (HVAC) systems. The fundamental concept of the new approach is that the controller learns to predict the actual thermal sensation of the specific occupant by tuning parameters of a model of the occupant’s thermal sensation. The parameters are adjusted with respect to thermal sensation ratings acquired from the specific occupant and measurements of physical variables that affect thermal sensation so that with time the model accurately reflects the thermal sensation of the specific occupant. From a lumped-parameter model of a singleroom enclosure, it is shown that the stability of the nominal system can be maintained by utilizing a priori information about the parameters of the thermal sensation model. The method is implemented on a ductless, split-system heat pump. Experiments using human subjects verify the feasibility of the method.

Effects of body morphology and mass on thermal responses to cold water: revisited.

Seven male volunteers were divided into two groups based on body morphology and mass. The large body mass (LM) group (n = 4) was 21.2 kg heavier and 0.32 m2.kg-1 smaller in surface area-to-mass ratio (P < 0.05) than the small body mass (SM) group (n = 3). Both groups were similar in total body fat and regional skinfold thicknesses. All subjects were immersed to the first thoracic vertebrae for 120 min in stirred water at 18 degrees C. Overall, tissue insulation was similar (P > 0.05) between the SM and LM groups across time. Perceptual ratings of thermal sensation increased (P < 0.05) across time. Therefore, as cold water immersion progressed, tissue insulation was similar and thermal sensation increased (P < 0.05) in males matched for subcutaneous fat and total fat but differing in body mass and morphology.

Responses of young and older men during prolonged exercise in dry and humid heat

Eight young, sedentary men (aged 34 years, SD 3) and six older moderately active, unacclimated men (aged 57 years, SD 2) walked on a treadmill at 30% of their maximum oxygen consumption up to 3.5 h in a thermoneutral [dry bulb temperature (Td) 21 degrees C, relative humidity (r.h.) 43%)], a warm humid (Tdb 30 degrees C, r.h. 80%) and a hot dry (Tdb 40 degrees C, r.h. 20%) environment while wearing ordinary working clothes (0.7 clo). Their oxygen consumption, heart rate (fc), rectal (Tre) and mean skin temperature (Tsk), sweat rate (SR), and evaporative rate (ER) were measured during the tests. The ratings of thermal sensation (TS) and perceived exertion (RPE) were assessed using standard scales. In the heat stress tests, the number of experiments discontinued did not significantly differ between the two groups. The mean levels and end-exercise values of Tre, Tsk, fc, TS and RPE were not significantly different between the young and older subjects in any of the environments. In the warm humid environment, however, the Tre and RPE of the older subjects increased continuously (P less than 0.05) during the test compared to the young subjects. No significant difference between the groups was observed in SR or in ER. In the hot dry environment, however, the ER of older men increased more slowly compared to the young men. In spite of some time-related differences observed in Tre, RPE, and ER, the older subjects did not exhibit higher fc during exercise in the heat, they were not more hyperthermic and their performance times were similar to the young subjects.(ABSTRACT TRUNCATED AT 250 WORDS)