Thermal Neutral Temperatures Research Articles

Adaptive thermal comfort in university dormitories in the severe cold area of China

A field survey was conducted on students' thermal comfort in typical university dormitories from the late autumn to the early spring covering the whole space heating period in Harbin, China. It aims to research the influence of climatic adaptation and indoor thermal history on university students in the severe cold area of China. The indoor physical parameters were measured, while the participants answered the online questionnaires about their thermal sensation and thermal comfort, adaptive methods, etc. The results show that the mean thermal sensation votes (MTS) were always greater than PMV predictions. And the deviations between MTS and PMV were evidently discrepant in different seasons. Meanwhile, the thermal neutral temperatures varied in different seasons. As a long-lasting thermal exposure to the artificial heating environment, the participants' thermal adaptability to cold climate had been gradually undermined. Moreover, the participants were sensitive to the indoor temperature fluctuations, especially to the indoor temperature reduction after they had adapted to the indoor heating condition. The implications for energy use and human health during space heating were suggested.

Evaluation of outdoor thermal comfort in sunlight, building shade, and pergola shade during summer in a humid subtropical region

This study evaluated outdoor thermal comfort during summer in a humid subtropical region. Meteorological inspections were conducted in sunlight, building shade, and pergola shade. The participants included 42 collegiate male subjects who completed questionnaires on thermal sensation and thermal comfort. To evaluate the thermal environments, we used three thermal indices: the universal effective temperature (ETU), the universal thermal climate index (UTCI), and the outdoor standard effective temperature (OUT_SET*). We confirmed that the ETU model is a suitable index for evaluating outdoor thermal comfort in the range of this study. Thermal neutral temperatures, as measured by ETU, UTCI, and OUT_SET*, were 33.1 °C, 34.0 °C, and 28.9 °C, respectively. Under sunlight, intense solar radiation raised the ETU value considerably; however, humidity and air velocity lowered it due to increased skin wettedness from the hot environment. The ETU model can provide a more detailed understanding of the various parameters affecting thermal comfort in the outdoor environment. At 800 W/m2 of total solar radiation in sunlight, the building shade and pergola shade with plants provided cooler thermal environments with ETU reductions of 18.4 °C and 16.2 °C, respectively, compared with sunlight. In cloudy conditions with total solar radiation of 300 W/m2, the building and pergola shades had ETU reductions of 9.3 °C and 6.8 °C, respectively.

Thermal comfort in naturally ventilated buildings in hot-humid area of China

Human responses to thermal environments in naturally ventilated (NV) buildings in hot-humid area of China were systematically investigated in the present study. Thirty local inhabitants long-time living in NV buildings participated in the study and reported their thermal sensations and perceptions and adaptive behaviors while all physical and personal variables were collected. Based on a year-long survey, a close match of indoor physical variables and occupants’ clothing insulation with outdoor climate was found as an important feature of NV buildings. Integrated indices can capture more thermal contexts in the NV buildings in hot-humid area of China than simple indices. Thermal sensation was found to be a good linear function of SET* with the thermal neutrality of 25.4 °C and the 90% (80%) acceptable range of 23.5–27.4 °C (22.1–28.7 °C) in SET*. The adaptive evidences were obtained for clothing adjustment, window opening and using fan respectively and the modified PMV model was validated to be applicable in NV buildings in hot-humid area of China with an expectancy factor of 0.822. Comparisons with other field studies indicate that people can develop various human-environment relationships through thermal adaptation to local climate, resulting in different thermal neutral temperatures in various climates. The subjects in hot-humid area of China are more acclimated and tolerable with hot and humid environments and more uncomfortable and intolerable with cold environments while compared with those in temperate climates.

Neutral temperature in subtropical climates—A field survey in air-conditioned offices

The thermal environment for air-conditioned offices in subtropical climates is examined from the prospect of maintaining an optimum operative temperature for the occupants. In this study, the optimum neutral temperature is evaluated from 422 occupants’ responses towards the perceiving thermal environment in 61 air-conditioned offices and 186 complaints of thermal discomfort in an air-conditioned office building on an electronic questionnaire, using a semantic differential evaluation scale and a dichotomous assessment scale. In particular, physical parameters for the thermal comfort study were measured by an indoor environmental quality (IEQ) logger, and the operative temperature was correlated with the occupants’ thermal responses. The probability of accepting an operative temperature for the thermal comfort of the occupants was correlated with logistic regression curves; the optimum operative temperature was derived in order to maximize the probability of thermal comfort expressed by the occupants. The results showed that the thermal neutral temperatures for air-conditioned offices in subtropical climates were 23.6 and 21.4 °C in summer and winter, respectively. The preferred thermal environment in Hong Kong should be slightly cool, corresponding to about 1 °C below the neutral temperature, in order to satisfy most of the occupants in the office space.

Infant Weight and Gestational Age Effects on Thermoneutrality in the Home Environment

To describe infant temperature in the home environment and explore factors, particularly weight and gestational age at birth, associated with maintenance of thermal neutral temperatures in the home. Continuous abdominal skin temperature was recorded at 1-minute intervals for a 24-hour period in both full-term and preterm infants, using a two-group exploratory design. Infants were studied in the home environment. Twenty-four preterm and 16 full-term infants were studied at approximately 44 weeks postconceptional age. Abdominal skin temperature was coded as within, over, or under the thermal neutral zone, and the percentage of time in these thermal conditions was calculated. Regression analysis was conducted, and weight, gestational age, and weight by gestational age interaction were found to be statistically significant predictors of percent of time over and under the thermal neutral zone. Smaller preterm infants were overheated, whereas heavier preterm infants were underheated. Smaller full-term infants were underheated, and heavier full-term infants were overheated. Thermal care of infants in the home may be influenced by parental perception of thermal vulnerability relative to weight and gestational age at birth.

The Effect of Wind and Air Temperature on Metabolism and Evaporative Water Loss Rates of Dark-Eyed Juncos,Junco hyemalis:A Standard Operative Temperature Scale

Because wind significantly increases heat loss from birds, its effects must be incorporated in studies of behavior, habitat selection, and ecological energetics. We studied dark-eyed juncos (Junco hyemalis) exposed to air temperatures (Ta) from −10 ° C to 40° C and wind speeds of 0.1, 0.64, 1.96, and 3 m/s. We measured O₂ consumption, CO₂ production, and evaporative water loss (EWL). Metabolic rate M increased with decreasing temperature and increasing wind speed for Ta < 22.5° C. As Ta dropped from 22.5° C to 15° C, M increased rapidly. The rate of increase slowed as Ta dropped below 15° C. Metabolic rate was independent of Ta and wind from 22.5° C to 37.5° C and appeared to increase at 40° C. The ratio of EWL to M increased with temperature, but the increase was less marked than that of the standard avian curve. Overall thermal conductance decreased as Ta decreased from 37° to 0° C. We divided the data set and used one part to define and the other to test an operative temperature scale (Tes) for juncos. The Tes scale eliminated wind effects on M, and data for all wind speeds fell on a common curve. A generalized passerine Ts scale was somewhat less effective. The variation of M among individuals had a standard deviation of about 0.065 W. This is equal to the difference between metabolic rates in sheltered versus unsheltered roosts. We found evidence that 15%–20% of the individuals may have increased metabolic rate in response to fan noise or wind force at thermal neutral temperatures.

Heat Production and Thermal Resistance in the Little Penguin Eudyptula minor in Relation to Wind Speed

Wind is an important factor in avian energy budgets. The effect of wind speed on metabolic rate and partitional resistance in little penguins was examined at thermal neutral and cold ambient temperatures. Metabolic rate remained constant at thermal neutrality at wind speeds up to 4.7 m/s and correlated equally well with wind speed or the square root of wind speed during cold exposure. The primary effect of wind on partitional resistance at thermal neutral and cold temperatures was a decrease in environmental resistance provided by the thermal boundary layer. Wind speeds up to 4.7 m/s had little effect on plumage thermal resistance. At thermal neutrality, increased convective heat loss with wind was compensated by an increase in body resistance, so that total thermal resistance remained relatively constant. During cold exposure at zero wind speed, body and plumage resistance had attained maximum values, whereupon increased wind speed resulted in a decrease in total resistance. Boundary layer resistance with increased wind speed was equivalent to flow around a circular cylinder at its critical Reynolds number.

Bioenergetic benefits of huddling by deer mice ( Peromyscus maniculatus)

1. 1. Both short photoperiod and communal social living conserve metabolic energy by deer mice held in thermal neutral ambient temperatures. 2. 2. Initial socialization was energetically more costly than solitary living, but huddling behaviors reduced thermal conductance and mass specific metabolic rate by 30% within 5 days. 3. 3. While short photoperiod reduced metabolic energy expenditure by decreasing thermoregulatory demand, huddling mediated behavioral conservation was achieved with hyperthermic core temperatures.

Photoperiodic adjustment of thermal conductance in deer mice

1. 1. Seasonal changes in metabolic rate can be induced in mice held in thermal neutral (26–29°C) ambient temperatures. 2. 2. The metabolic effect of winter photoperiod is a lower metabolic rate without compromise to metabolic reserve. 3. 3. Manipulations of photoperiod or melatonin backgrounds adjust the thermoregulatory setting for core temperature level and affect thermal conductance.

Energetics of the red squirrel: A laboratory study of the effects of temperature, seasonal acclimatization, use of the nest and exercise

1. 1. Minimum resting oxygen consumption at thermal neutral temperatures of the red squirrel ( Tamiasciurus hudsonicus) did not change seasonally and was 1.12 cm 3O 2g −1h −1. 2. 2. Minimum thermal conductance ( C) was 0.062 cm 3O 2g −1h −1oC −1 in summer and 0.052 cm 3O 2g −1h −1oC −1 in winter-aclimatized animals. 3. 3. Combined C of an animal and its nest was 0.021 cm 3O 2g −1h −1oC −1. 4. 4. At low air temperatures, heat generated by exercise did not replace thermoregulatory heat production, apparently due to increased C during exercise. 5. 5. Thermal conductance increased with increased running speed.