High Neutral Temperature Research Articles

Identifying sensitive population associated with summer extreme heat in Beijing

Severe high-temperature leads significant risks of human health under the highly population concentration and climate change. The thermal sensitivity to high temperature is needed to be quantified associated with different population characteristics. Thermal condition was quantified by universal thermal climate index (UTCI) and thermal sensitivity was identified by thermal sensation votes (TSV), thermal comfort votes, and thermal unacceptability votes based on 667 questionnaires in Beijing, China. This study designated four indicators, i.e., neutral temperature, neutral temperature range, tolerance temperature, and tolerance temperature range to analyze the effects of individual characteristics on thermal sensitivity. A one-way ANOVA was used to identify the effects of long-term adaptation and psychological factors. Results showed that: (1) Older residents had a higher neutral temperature, narrow tolerance temperature range, and lower tolerance temperature of 1.2 °C UTCI than younger residents. (2) People with chronic disease had a narrow tolerance temperature range and lower tolerance temperature of 1.3 °C UTCI than healthy ones; (3) The proportion of people who voted strong thermal sensation (TSV≥2) rated the highest in building areas, while the proportion decreased 31.6% in spaces with dense trees; (4) Residential history and city attractiveness had significant impacts on mean thermal sensation votes and mean thermal comfort votes, excluding the effect of thermal stress level. This study provided useful implications of specific adaption for summer extreme heat according to different population characteristics.

Adaptive Thermal Comfort for Occupants of Low-Cost Dwellings in a Hot Dry Climate

Adaptive models are based on the observation that there are some actions that people can and actually do take to achieve thermal comfort. Studies regarding thermal comfort conditions in economical dwellings were carried out simultaneously in seven Mexican cities, corresponding to warm dry and warm humid climates. In this article, case studies of low-cost dwellings in the city of Hermosillo (in northwest Mexico), are presented and analyzed. Field surveys were carried out to obtain information about the physical characteristics of the dwellings and their occupants, as well as the indoor thermal environment. Neutral temperature was obtained from the applied survey. The high neutral temperature reveals the effect of inhabitants' adaptation mechanism to extreme climates. Occupant comfort votes as a function of indoor air temperatures were analyzed, and different characteristics such as age, size and gender were evaluated separately. The results show the variability of the neutral temperature and the tolerance to temperature changes, depending on the population's specific characteristics. In many cases where the population does not have access to artificial acclimatization devices, the neutral temperature values for specific climates and people can inform architects when choosing the most suitable thermal strategies for building design.

Using the adaptive model of thermal comfort for obtaining indoor neutral temperature: Findings from a field study in Hyderabad, India

There is a dearth of thermal comfort studies in India. It is aimed to investigate into the aspects of thermal comfort in Hyderabad and to identify the neutral temperature in residential environments. This was achieved through a thermal comfort field study in naturally ventilated apartment buildings conducted during summer and monsoon involving over 100 subjects. A total of 3962 datasets were collected covering their thermal responses and the measurement of the thermal environment. The comfort band (voting within –1 and +1), based on the field study, was found to be 26–32.45°C, with the neutral temperature at 29.23°C. This is way above the indoor temperature standards specified in Indian Codes. It was found that the regression neutral temperature and the globe temperature recorded when voting neutral converged when mean thermal sensation of the subjects was close to 0. This happened during the period of moderate temperature when the adaptive measures were adequate. The indoor temperatures recorded in roof-exposed (top floor) flats were higher than the lower floors. The thermal sensation and preference votes of subjects living in top floors were always higher. Consequently, their acceptance vote was also lower. It was found that the subjects living in top floor flats had a higher neutral temperature when the available adaptive opportunities were sufficient. This was due to their continuous exposure to a higher thermal regime due to much higher solar exposure. This study calls for special adaptive measures for roof-exposed flats to achieve neutrality at higher temperature.

Energizing and depletion of neutrals by a collisional plasma

Neutral depletion can significantly affect the steady state of low temperature plasmas. Recent theoretical analyses predicted previously unexpected effects of neutral depletion in both collisional and collisionless regimes. In this paper we address the effect of the energy deposited in the neutral gas by a collisional plasma. The fraction of power deposited in the neutrals is shown to be independent of the amount of power. The first case we address is of a thermalized neutral gas. It is shown that a low heat conductivity of the neutral gas is followed by a high neutral temperature that results in a high neutral depletion even if the plasma pressure is small. In the second case neutrals are accelerated through charge exchange with ions leading to what we call neutral pumping, which is equivalent to ion pumping in a collisionless plasma. Neutral depletion is found in the second case for both a closed system (no net mass flow) and an open system (a finite mass flow). A thruster that employs a collisional plasma and pumped neutrals is compared with the thruster analyzed before that employs collisionless plasma.

Measurements and modeling of ion and neutral distribution functions in a partially ionized magnetically confined argon plasma

The influence of ion-neutral collisions on the ion and neutral distribution functions is studied in low field (<0.15 T) rf heated argon discharges of the H-1 Heliac [S. M. Hamberger, B. D. Blackwell, L. E. Sharp, and D. B. Shenton, Fusion Technol. 17, 123 (1990)], both experimentally and theoretically. The distribution function measurements are based on the Doppler broadening of plasma ion and neutral spectral lines using a novel coherence imaging camera. Measurements show that neutrals are abundant throughout the plasma. The neutral temperature is found to be in the range 1–2 eV, which, when compared with ion temperatures of the order of 10 eV, suggests that neutrals are being heated substantially through ion-neutral collisions. Measurements of the ion distribution function reveal a substantially elevated fraction of low energy particles (whose energy is similar to the neutral temperature), associated with charge exchange and ionization. In order to understand the origin of the high neutral temperature and distorted ion distribution function, the ion and neutral distribution functions are modeled using the Boltzmann equation including collision operators for ion-ion and ion-neutral collisions, ionization, heating, and particle loss. The simulation results compare well with the experimental results.