Thermal Environment Parameters Research Articles

An investigation of outdoor thermal environments with different ground surfaces in the hot summer-cold winter climate region

This study aims to find the impact of different ground surfaces on thermal environments in outdoor activity space. Field measurements were conducted in a university campus located in the hot summer-cold winter climate zone. Five typical outdoor ground surfaces were selected: light-colored marble brick, plastic track, bluestone slate under the shade, lawn under the shade, and unobstructed lawn. Thermal environment parameters, including air temperature, relative humidity, solar radiation, surface temperature, mean radiant temperature (Tmrt) and the physiological equivalent temperature (PET) were measured and calculated for summer and winter, respectively. It is confirmed that the property of the ground surface had a significant effect on surface temperature and Tmrt in winter and had a significant effect on relative humidity and PET in summer. The use of ground surfaces with low reflectivity which could increase the surface temperature by 4.5 °C in winter while reduce the heat stress (PET) by 3.7 °C in summer, should be encouraged in outdoor activity space.

On the temporal dimension of adaptive thermal comfort mechanisms in residential buildings

In response to the change of indoor thermal environment, building occupants constantly interact with the surrounding environment through various adaptive behaviours. The purpose of this study is to better understand the adaptive thermal comfort mechanisms by investigating the interrelationship between the expectation of the occupants (the psychological adaption), their behavioural adjustment (the physical adaption), and the indoor thermal environment in the context of residential buildings. Eleven households in South Korea participated in this longitudinal field study carried out between 2015 and 2017. The indoor thermal environmental parameters, the occupant subjective evaluations of thermal comfort, and their adaptive behaviour pattern were monitored. On average, 1,512 datasets from each household and a total of 16,632 datasets were collected and analyzed. Our analysis focused on understanding both the temporal dimension (i.e. duration of thermal discomfort episodes) and the intensity of stimuli (i.e. deviation from the comfort zone) both before- and after the participants’ decision on the use of air-conditioners. The study proposes the constructs of ‘discomfort capacity’ and ‘comfort restoration’ as multi-dimensional indices to better understand the triggering mechanisms for household air-conditioner usage. Using these indices, the study quantified householders’ tolerance of thermal discomfort events before they resort to air-conditioning.

Investigations on the Winter Thermal Environment of Bedrooms in Zhongxiang: A Case Study in Rural Areas in Hot Summer and Cold Winter Region of China

In this paper, onsite measurements and a subjective questionnaire were conducted to study the thermal environment and heating condition of bedrooms during the winter in rural areas in China’s hot summer and cold winter (HSCW) region. Indoor and outdoor thermal environmental parameters were measured to evaluate the thermal conditions of bedrooms. Thermal sensation/tendency/acceptance, heating, and health condition were investigated to complete the analysis of attitudes of local residents on the thermal environment of bedrooms, heating and health issues, as well as the analysis of buildings. The observed results demonstrate that occupants in this region have a strong tolerance to low-temperature environments with the 80% acceptable lower temperature of 4.7 °C and a neutral temperature of 10.7 °C, with an average clothing insulation over 2.2 clo. Oversized volume and acreage of buildings and windows induce a lower temperature in the bedroom. Infants have a significant effect on heating requirements, including heating duration and temperature setpoint. Local residents are highly concerned about the costs, safety, and health related to heating and thermal environments. All evidence obtained through this investigation shows that it is beneficial to formulate regulations for the shape, envelope, and centralized heating policy for rural residential buildings in the HSCW region.

Research on Free Jet Test Technology

Aerodynamic thermal ground test can not completely simulate flight conditions, and there is no simple and clear similarity criterion as aerodynamic test. In practical application, it is often to grasp the local flow characteristics of materials or structures and use ground test equipment to simulate their main thermal environment parameters. Therefore, according to the thermal environment characteristics of different parts of the aircraft, a variety of arc heating test techniques have been developed. For example, free jet test technology has been developed for material test of simplified model and assessment test of small-scale components. It effectively solves some problems of thermal protection test examination.

Annual thermal performance analysis of underground cave dwellings based on climate responsive design

The underground cave dwelling located in loess plateau of China is known for its use of natural and passive environment control systems for a comfortable indoor environment. However, it has not been proved by a detailed and quantitative analysis so far. This paper conducts qualitative and quantitative evaluations on the thermal performance of ancient cave dwellings.Firstly, the authors conducted a qualitative analysis on the passive strategies of vernacular underground cave dwellings by field investigations. The orientation of building, the presence of underground courtyard, use of biomass massive building envelope, etc. Formed the indoor environment. Secondly, a quantitative analysis was also carried out based on long-term remote monitoring experiments by recording thermal environment parameters in a selected building. The analysis results were very much in agreement with the inferences drawn from the qualitative analysis. Finally, in order to evaluate the whole annual thermal performance, numerical simulations on the Yaodong models was also conducted using the software Energyplus. The study provided positive results confirming that climate responsive strategies employed in underground cave dwellings were highly effective in providing methods and implications to create more comfortable indoor environments for rural residences.

Study on Coil Optimization on the Basis of Heating Effect and Effective Energy Evaluation during Oil Storage Process

With the rapid development of crude oil reserves, energy consumption in heating increases gradually, so it is necessary to study heating effect and energy utilization. In this paper, a theoretical model of coil heating process for large floating roof crude oil tank is established, with dynamic thermal environment and variable physical parameters of oil products taken into consideration comprehensively. The influence mechanism of coil structure on the coupling characteristics of heat transfer and flow of crude oil during heating process is revealed. On this basis, the heating effect of crude oil in storage tank is evaluated from the point of view of time and space respectively. Simultaneously, the properties of energy and its quality are both considered, the effective energy utilization efficiency of crude oil in storage tank during heating process is analyzed, and an optimization method for heating coil of tank oil is proposed. The results show that the temperature of oil products in the center and bottom of the tank increases linearly with the influence of heat sources, and the temperature of oil products at the roof and wall of the tank is greatly affected by the dynamic thermal environment, which is showing a change regulation of fluctuating pattern. The heating effect is greatly affected by coil length. The increase of coil length can obviously improve the flow structure of crude oil in the tank. A larger eddy structure can be formed in a shorter period of time, which can increase the heating rate of crude oil and further reduce the non-uniformity of temperature field. However, effective energy efficiency is greatly affected by coil diameter. The increase of coil diameter increases the convective heat transfer coefficient between coil and crude oil, which promotes crude oil to absorb heat more easily from heat sources and improves the effective utilization of energy and exergy. Therefore, the heating effect and effective energy utilization of oil coil can be further optimized by changing the length and diameter of coil. Relevant research results can provide theoretical and technical support for improving the utilization efficiency of reserve energy and reducing the cost of reserve energy consumption.

Nonlinear Thermo-Mechanical Stability Analysis of Eccentrically Spiral Stiffened Sandwich Functionally Graded Cylindrical Shells Subjected to External Pressure

A new analytical approach to investigate the nonlinear buckling and postbuckling of the sandwich functionally graded circular cylindrical shells reinforced by ring and stringer or spiral stiffeners subjected to external pressure is presented in this paper. By employing the Donnell shell theory, the geometrical nonlinearity in Von Kármán sense and developed Lekhnitskii’s smeared stiffener technique, the governing equations of sandwich functionally graded circular cylindrical shells are derived. Resulting equations are solved by applying the Galerkin method to obtain the explicit expression of critical buckling external pressure load and postbuckling load–deflection curve. Effects of spiral stiffeners, thermal environment, external pressure, and geometrical parameters on nonlinear buckling behavior of sandwich functionally graded circular cylindrical shells are shown in numerical results.

Seed responses to temperature indicate different germination strategies among Festuca pallescens populations from semi-arid environments in North Patagonia

Seed germination is one of the earliest phenotypes expressed by plants, and the accuracy to germinate in the correct time and place is essential for plant population fitness. Cues that regulate germination have been exhaustively characterized in laboratory experiments. However, the way in which seed populations respond to these cues and the ecological meanings of this phenomenon are scarcely known. To help filling this gap, we studied the thermic regulation of seed germination and its link with local climatic characteristics in Festuca pallescens populations, an iconic perennial grass species of Patagonia. By coupling thermal time models with field and environmental data, we evaluated seed responsiveness to temperature during germination of nine Festuca pallescens populations distributed across their complete longitudinal range in North Patagonia. The idea behind this experimental design was to search for inter-population differences in early life traits relevant for recruitment of the species, and associate seed traits with local environmental characteristics. F. pallescens populations showed strong differences in seed sensitivity to temperature for the thermal regulation of the germination rate, described by the population mean thermal time for germination (θ(50)) and its standard deviation (σθ). The greatest values of θ(50) and σθ corresponded to populations inhabiting harsh environments. Moreover, θ(50) of the different populations showed strong correlations with their local thermal environmental parameters, indicating a relation between seed physiological traits and climate across the longitudinal gradient. We did not observe inter-population differences in the minimum temperature that allows germination (Tb = -0.47 ± 0.19 °C). Higher θ(50) and σθ in populations from harsh climates may constitute a strategy of the species to increase fitness in hostile habitats, preventing anticipated germination and promoting a slower seed bank depletion in regions where establishment is highly limited.

Experimental study on natural ventilation of cotton tent in summer

Cotton tents are frequently used in the army and disaster relief. Because of the special structure of the cotton tent, its heat preservation and heat insulation performance is poor in the summer. In order to improve the rest environment of soldiers, experimental studies on improving the internal thermal environment of tents by natural ventilation were done at Tianjin in the summer. The thermal environment parameters of tents with different natural ventilation schemes were recorded and analyzed. The experimental results show that the natural ventilation plays a certain role in adjusting thermal environment of tents.

Study on indoor thermal environment of rural dwellings in Northwest China in winter

In order to study the status of the indoor thermal environment of the northwest rural dwellings in winter, the thermal performance and the residents’ adaptability are investigated and the indoor and outdoor thermal environment parameters are measured in Zhongwei region of Ningxia, the indoor thermal environment is analyzed and evaluated by the operating temperature. The results show that the northwest rural residents have strong adaptability to the cold indoor thermal environment in winter. In this area, the cold and daily temperature difference in winter is large, but the solar energy is rich, and it has the geographical advantage of developing passive solar building. The thermal performance of existing rural dwellings is poor and the indoor thermal environment is not ideal. It is necessary to enhance the thermal performance of building’s heat collection, thermal storage and enclosure structure.

Evaluation of changes in tonic immobility, vigilance, malondialdehyde, and superoxide dismutase in broiler chickens administered fisetin and probiotic (Saccharomyces cerevisiae) and exposed to heat stress

The study evaluated changes in tonic immobility (TI), vigilance behavior, malondialdehyde (MDA), and superoxide dismutase (SOD) in broiler chickens administered fisetin and probiotic. Sixty Arbor Acre breed of broiler chickens at day old, allotted into 4 groups of 15 birds each, were used. Group I (control) was given only sterile water; group II, fisetin (5 mg/kg); group III, probiotic (4.125 × 106 cfu/100 mL); and group IV, fisetin + probiotic. At weeks 3, 4, and 5, thermal environment parameters, TI and vigilance behavior, were recorded each day at 07:00 h, 13:00 h, and 18:00 h. The vigilance at self-righting during each TI test was observed in broiler chickens and ranked as (1) fearlessness, (2) slightly fearful, and (3) fearfulness. MDA concentration and SOD activity in breast muscle were determined using a spectrophotometer. Temperature-humidity index (25.55-35.30) was outside the thermoneutral zone (20.8) for broiler chickens above 3 weeks of age. Week 3 had the longest (P < 0.05) duration of TI in the controls, but the shortest (P < 0.05) duration was recorded in the fisetin + probiotic group. At week 4, the shortest (P < 0.05) TI duration was recorded in the probiotic-supplemented group, while the longest (P < 0.05) TI was obtained in the control group. The shortest (P < 0.05) TI duration was recorded at week 5 in the probiotic and fisetin + probiotic groups, compared with that of the controls. The highest (P < 0.05) TI duration was recorded at 13:00 h in the controls, but the shortest (P < 0.05) was obtained at 18:00 h in the probiotic and fisetin + probiotic groups. At week 3, the vigilance behavior ranking recorded in the probiotic, fisetin + probiotic, and fisetin broiler chickens were lower (P < 0.05) than that obtained in the control group, which was the highest. At week 4, the highest (P < 0.05) vigilance behavior ranking was obtained in the control group. At week 5, the lowest (P < 0.05) vigilance behavior ranking was recorded in the probiotic-supplemented group, but the highest (P < 0.05) value was obtained in the control group. At 7:00, 13:00, and 18:00 h, there was no significant difference (P > 0.05) in the vigilance behavior ranking in the control, fisetin, probiotic, and fisetin + probiotic groups of broiler chickens. The MDA concentration in broiler chickens administered probiotic, either alone or in combination with fisetin, was lower (P < 0.05) compared with that of the controls. The activity of SOD was higher (P < 0.05) in fisetin + probiotic broiler chickens than in the control group. Probiotic and/or fisetin ameliorated the behavioral stress response in the broiler chickens via oxidative stress mechanism, as evidenced by increase in SOD activity and decrease in MDA concentration in the breast muscle of the chickens. In conclusion, administration of probiotic, either alone or in combination with fisetin, decreased duration of TI and vigilance behavior ranking, increased SOD activity, and lowered MDA concentration in broiler chickens exposed to heat stress.

Correction: Assessment of heat stress in 7-week old dairy calves with non-invasive physiological parameters in different thermal environments.

[This corrects the article DOI: 10.1371/journal.pone.0200622.].

Daily rhythms of rectal and body surface temperatures in donkeys during the cold-dry (harmattan) and hot-dry seasons in a tropical savannah.

The aim of the study was to evaluate daily rhythms of rectal temperature (RT) and body surface temperature (BST) of adult, yearling and foal donkeys during the cold-dry (harmattan) and hot-dry seasons in a tropical savanna. The RTs and BSTs of 30 clinically healthy, free-ranging donkeys were recorded using digital and infrared thermometers. The RT and BST of each donkey and thermal environmental parameters inside the pen were measured bi-hourly from 0600 to 0600hours (GM + 1) on each experimental day. Application of single cosinor procedure showed that RT and BST exhibited varying levels of daily rhythmicity in both seasons, with values usually higher during the afternoon periods of the photophase of the light/dark cycle. The oscillatory pattern differed with season, with greater amplitude recorded during the cold-dry season than the hot-dry season. The acrophases of the RT and BST were mostly restricted to the photophase of the light/dark cycle in both seasons. The mean values of RT in the adult (37.10 ± 0.10°C), yearling (37.19 ± 0.10°C) and foal (37.45 ± 0.11°C) donkeys were higher (F = 93.41, P < 0.0001) during the hot-dry season than the cold-dry season (35.40 ± 0.05°C, 35.50 ± 0.04°C and 36.20 ± 0.05°C, respectively). In conclusion, seasonal changes influenced significantly the daily rhythmicity of RT and BST in donkeys, kept under natural light/dark cycle.

Perception of thermal comfort and prediction of heat stress (PHS) due to heat gain in tropical university classrooms

Comfortable indoor climate is anticipated in hot-humid tropical condition. University classrooms are such kind of space which quality can improve the occupant’s performance directly. Due to lack of their adaptation ability, like the fixed schedule of activities and clothing causes extra heat gain from the environment and make hazardous situation. In this research, we focused to find out the comfortable condition of university classrooms in Bangladesh. The field monitoring was conducted at Chittagong University of Engineering and Technology (CUET) during the hottest months in the country (April-July). The measurements included the basic thermal environmental parameters like air temperature (AT), relative humidity (RH), indoor air velocity (V), and indoor Light (L) during regular class time 9:00 to 17:00. Predicted Heat Strain (PHS) has been calculated using obtained data with a known metabolic rate and clothing. It is found that the skin temperature crosses 34°C frequently in PHS scale and creates health risk.

Thermal environment sensor array: Part 2 applying the data to assess grow-finish pig housing

Current thermal environment (TE) assessment techniques for controlling livestock and poultry facilities often solely use dry-bulb temperature (Tdb) and occasionally relative humidity (RH) as assessment parameters. The TE sensor array (TESA; Part 1) provides the opportunity to simultaneously quantify Tdb, RH, airspeed, and black globe temperature, but there are no existing methods incorporating these additional TE parameters to accurately assess the TE based on the thermal demands of the animal. Hence, the goal of Part 2 of this series was to develop a technique for evaluating the TE as a function of mean body temperature difference from thermally comfortable (ΔTb) using body mass, Tdb, RH, and airspeed inputs. Multiple regression analysis of the simulated data from the mechanistic thermal balance model for group-housed growing pigs was used to develop the Housed Swine Heat Stress Index (HS2I), which scales impact of the TE from 0 (thermally comfortable) to 10 (severe heat stress). Further, a wetted skin adjustment parameter was included to enable analysing TE with sprinklers. Simulated and predicted ΔTb agreed well without wetted skin (R2 = 0.98; RMSE = 0.061 °C) and with wetted skin (R2 = 0.97; RMSE = 0.054 °C). The HS2I was applied to assess the spatiotemporal TE data collected by TESA in the commercial grow-finish facility presented in Part 1. HS2I can be used to evaluate the potential impact of the TE in existing facilities and as a design tool to explore different ventilation and cooling strategies.

Assessment of heat stress in 7-week old dairy calves with non-invasive physiological parameters in different thermal environments.

We estimated thermal stress in 7-week old Holstein bull calves during a warm episode in summer to study acute physiological responses of calves to heat stress. Data were collected over a 5-day period: day 1 (control), day 2 (heat stress), and a 3-day post-stress period in shaded (n = 8) and unshaded (n = 8) thermal environments. On the control day, both groups were shaded. Thermal environment was characterized by relative humidity, ambient temperature, and the temperature–humidity index (THI). Physiological variables included respiratory rate, rectal temperature, ear skin temperature and heart rate. Correlations between animal-based and meteorological indices were calculated, and ambient temperature correlated slightly better with physiological measures than THI. Rectal temperature was the only animal-based parameter that showed stronger correlations with the thermal indices when calculated for the shaded than for the unshaded environment [r = 0.42 vs. r = 0.47, P = 0.032 (ambient temperature), r = –0.39 vs. r = –0.45, P = 0.012 P = 0.015 (relative humidity), r = 0.41 vs. r = 0.46, P = 0.022 (THI)]. No differences were found between groups during the control day for any of the physiological parameters. During days 2 and 3, average and maximal values of respiratory and heart rates were higher in unshaded calves than in shaded ones. Maximal respiratory rates were in average by 25.9, 17.8 and 10.1 breaths/min lower in shaded calves than in unshaded calves for days 2, 3 and 4, respectively (P < 0.001, P < 0.001 and P = 0.024). Maximal heart rate was 127.4 ± 8.5 vs. 99.2 ± 6.3 beats/min on the heat stress day (P < 0.001), and 121.0 ± 6.9 vs. 103.4 ± 7.7 beats/min on day 3 (P = 0.006) in unshaded and shaded calves, respectively. Maximal body temperatures were higher measured either in the rectum or on the ear skin in unshaded calves than in shaded ones (with 0.5 and 1.6°C, P = 0.040 and P = 0.018, respectively), but only on the heat stress day. Based on our results, shading of young calves may be adequate for alleviating acute heat stress in continental regions. Ambient temperature is appropriate to estimate acute heat stress in dairy calves.

Experimental comparison of thermal comfort during cooling with a fan coil system and radiant floor system at varying space heights

With the development of the economy, architectural space forms and air conditioning systems have become more and more diverse. This paper presents a comparative study on thermal comfort in spaces of varying heights using a fan coil system and a radiant floor system for cooling in the “Comprehensive Experiment Platform of Variable Building Space” located in Tianjin, China. A total of 30 subjects participated the questionnaire survey under 8 different experimental conditions, and the indoor thermal environmental parameters were collected for these two systems at varying space height by instrument monitoring. Results indicated that space height had a significant effect on thermal comfort for both the fan coil system and the radiant floor system. The neutral temperature at space height of 3, 5, 7, and 9 m were 24.8 °C, 24.2 °C, 23.8 °C, and 23.5 °C, respectively. The neutral temperature gradually decreased with height of the ceiling when using a fan coil system, which means that participants had greater requirements for cooling at greater heights. In contrast, the neutral temperature at heights of 3, 5, 7, and 9 m were 23.5 °C, 23.8 °C, 24.1 °C, and 24.5 °C, respectively. The neutral temperature gradually increased when using the floor radiant system with increasing height, indicating that participants had lower requirements for cooling at greater heights. Furthermore, the results of this study demonstrate that the floor radiant system had an advantage over the fan coil system for thermal comfort in a space of greater height.

Investigation on thermal environment improvement by waste heat recovery in the underground station in Qingdao metro

The thermal environment parameters, like the temperature and air velocity, are measured to investigate the heat comfort status of metro staff working area in winter in Qingdao. The temperature is affected obviously by the piston wind from the train and waiting hall in the lower Hall, and the temperature is not satisfied with the least heat comfort temperature of 16 °C. At the same time, the heat produced by the electrical and control equipments is brought by the cooling air to atmosphere for the equipment safety. Utilizing the water-circulating heat pump, it is feasible to transfer the emission heat to the staff working area to improve the thermal environment. Analyzed the feasibility from the technique and economy when using the heat pump, the water-circulating heat pump could be the best way to realize the waste heat recovery and to help the heat comfort of staff working area in winter in the underground metro station in north China.

Experimental study on the characteristics of secondary airflow device in a large enclosed space building

Large space building using side wall nozzle air-conditioning system may result in poor ventilation effectiveness for positions out of the reach of primary supply air. A secondary airflow device is proposed to be applied in such system to improve the uniformity of temperature and velocity distribution in the occupied zone under cooling condition. The characteristics of the secondary airflow device, including central-line velocity decay and jet trajectory model were investigated through experiments to provide fundamental data for the system design. The indoor thermal environment parameters were measured and compared between with and without the secondary airflow device system in a large space factory workshop conditioned by side wall air supply nozzles. Experimental results with the secondary airflow device showed that the vertical thermal stratification height slightly changed, with lower air temperature in unoccupied zone and higher temperature in occupied zone comparing to the cases without secondary airflow device. At occupied level, air diffusion performance index (ADPI) significantly improved, while the percentage dissatisfied (PD) due to draught decreased in the occupied zone. Air velocity uniformity at occupied level also significantly increased. The results of this study provide an exemplary reference for the design of the air distribution system in large-space buildings.

Field study on adaptive thermal comfort in typical air conditioned classrooms

This study investigates adaptive thermal comfort in air conditioned classrooms in Hong Kong. A field survey was conducted in several typical classrooms at the City University of Hong Kong. This survey covered objective measurement of thermal environment parameters and subjective human thermal responses. A total of 982 student volunteers participated in the investigation. The results indicate that students in light clothing (0.42 clo) have adapted to the cooler classroom environments. The neutral temperature is very close to the preferred temperature of approximately 24 °C. Based on the MTSV ranging between −0.5 and + 0.5, the comfort range is between 21.56 °C and 26.75 °C. The lower limit is below that of the ASHRAE standard. Of the predicted mean vote (PMV) and the University of California, Berkeley (UCB) model, the UCB model predictions agree better with the mean thermal sensation vote (MTSV). Also, the respective fit regression models of the MTSV versus each of the following: operative temperature (Top), PMV, and UCB were obtained. This study provides a better understanding of acceptable classroom temperatures.