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ASHP system is extensively applied to maintain indoor thermal environment but contributes to high building energy consumption. Better energy efficiency is possible through cooling performance improvements. This study investigates, using full-scale experiments, the cooling performance of ASHP. In the series of experiments, we vary the major influencing factors—evaporator inlet air temperature, air velocity, and compressor frequency and measured their impacts on response variables that include cooling capacity, compressor power, and the COP. The design of experiment (DOE) approach is used to plan and analyze the experiments. The results show that cooling capacity of ASHP system significantly increases with the rising evaporator inlet air temperature, air velocity, and compressor frequency. However, because of increasing fan and compressor power with rising air velocity and compressor frequency, COP dramatically decrease. Finally, the study of develop a simple predictive model for assessing the COP of ASHP. Comparing with the predicted and experimental results shows an agreement within 10% deviation, which indicates the suitability of the prediction model. Therefore, a predictive model can help system operators to set the optimal design parameters for achieving optimal COP performance of ASHP system. [ABSTRACT FROM AUTHOR]

Abstract Heat stress negatively influences human health and performance, leading to lower efficiency in daily activities. In particular, strenuous training in outdoor hot environment conditions increases the potential for developing heat illness, such as heat cramps, heat exhaustion, and heat stroke. Few investigations have been conducted on heat stress during high-intensity outdoor training. The present study aims to summarize the evidence on the relations between high-intensity outdoor training and heat illness and between heat indices, including Wet Bulb Globe Temperature (WBGT), Physiological Equivalent Temperature (PET) and Universal Thermal Climate Temperature (UTCI), and environmental parameters. In this investigation, fresh students were invited as volunteers to answer the questionnaire about their heat perception with microclimate measurements when they had a rest in a session of outdoor training. The results showed that some students had heat syncope and more than 30% suffered from "profuse sweating." The effect of air temperature on thermal comfort was most significant. The stress categories of WBGT, PET, and UTCI need to be modified for freshmen outdoor training to avoid overexposure in a hot outdoor environment. Highlights • Field survey and microclimate measurements were conducted in freshmen outdoor training. • Regression lines were obtained between MTSV and WBGT, PET and UTCI. • The effect of the air temperature on the MTSV was more significant than other parameters. • The stress categories of WBGT, PET, and UTCI were modified for freshmen outdoor training. [ABSTRACT FROM AUTHOR]

In order to understand passengers' demand for thermal comfort in aircraft cabins, we carried out a measurement of thermal environment parameters and thermal comfort field survey in an aircraft cabin under cruising at altitude in both summer and winter. The results showed that the air temperature studied was always kept within the range of 25℃ to 28℃ and the relative humidity was maintained within the range of 20% to 35%. The Mean Thermal Sensation Vote (MTSV) of passengers' back and feet was higher than other local body parts, with lower air movement sensation. The MTSV of passengers in winter was higher than that in summer. Due to the muggy thermal environment, more than 60% of passengers advocated that it was necessary to utilize the personal ventilation system. In their usage of the personal ventilation nozzle, more than half of these passengers chose to cool upper body parts, only a minimum number of passengers opened the nozzle to direct airflow to their head. Therefore, we concluded that the position of the personal ventilation nozzle should be as close to the upper body part of a passenger's body as possible, making it more convenient and effective to regulate passengers' thermal comfort. [ABSTRACT FROM AUTHOR]

Stratum ventilation can energy-efficiently provide quality indoor air and thermal comfort. The room air temperature in the occupied zone is a dominant parameter for thermal comfort. The non-uniform thermal environment of stratum ventilation challenges the dynamic control of the room air temperature. This study proposes a dynamic control method of the room air temperature for stratum ventilation based on heat removal efficiency. The proposed method requires inputs of only supply air temperature, supply airflow rate and exit air temperature, and can be readily employed by the building management system in practice. Dynamic experiments, with a wide variation range (i.e., from 24.5 °C to 30 °C), different variation rates (i.e., from 0 °C/min to 0.088 °C/min) and different variation trends (i.e., increase, decrease and steady) of the room air temperature, are conducted to validate the proposed method. The time interval of the dynamic experiments is 1 min. Furthermore, the effects of the cooling load and room occupancy are also analyzed to demonstrate the robustness of the proposed method. The differences between the predicted room air temperatures by the proposed method and measurements are no more than 0.33 °C, and the root mean square errors are no more than 0.18 °C. Compared with the conventional method, which assumes that the room air temperature equals to the exit air temperature at the air terminals, the proposed method improves the accuracy in the room air temperature prediction by 79.3%–93.3%. The proposed method can be applied to dynamically control the room air temperature to meet the requirement of thermal comfort. [ABSTRACT FROM AUTHOR]

With the development of the urban city, increasing attention has been paid to outdoor thermal comfort. In this paper, an analysis of the sensitivities of different factors, including the personal factors and physical parameters of the thermal environment was conducted. The results showed that there was a strong linear relationship between the Physiological Equivalent Temperature (PET) and operation temperature. When the operation temperature was lower than 32 °C, the effect of air velocity on the PET was positive. However, the effects of other factors, including relative humidity, clothing insulation, and metabolic rate, on the PET were insignificant. An exponential relationship was found between the UTCI and the operation temperature. The effect of air velocity change on the UTCI became weaker and weaker with the increase of operation temperature. Compared with the PET, the linear relationship between the UTCI and relative humidity was clearer. A field survey of thermal comfort carried out in Guangzhou University was used for the validation of the thermal comfort models. It was observed that the clothing insulation requirement increased with the decrease of air temperature in autumn. The variations in metabolic rate were also obvious, from 1met to 3.8 met. More than 70% of the people had been walking before they arrived at the survey locations. In addition, there were some differences in the neutral PET and UTCI temperature between the metabolic rates of 1.0–2.0 met and of 2.6 met. Meanwhile, models of MTSV against the PET and UTCI under different metabolic rates were established. [ABSTRACT FROM AUTHOR]

Extreme thermal environment harms the health of outdoor workers and poses a potential threat to workplace safety. A field survey, including thermal parameter measurements, was conducted at construction sites in South China during the summer of 2019. The relationship between health risk and thermal parameters was obtained. The thermal sensation and satisfaction rate of the workers at different outdoor environmental conditions were analyzed, and recommendations were made based on the comparison of thermal indices. The thermal stress categories of the thermal indices were also investigated. The results suggest that the intensity of working conditions should be reduced when the air temperature is higher than 34 °C; the satisfaction rate of workers was found to be relatively high when the outdoor temperature is lower than 34 °C and the wind speed is greater than 1.3 m/s. Thermal indicators used to evaluate the comfort level of outdoor workers need to be modified according to the local climate and working environment to avoid excessive exposure to high-temperature work environments. • Extreme thermal environment harms the health of outdoor workers. • Thermal parameter measurements were conducted at construction sites in summer. • Labor intensity should be reduced when temperature is higher than 34 °C. • At air temperature <34 °C and wind speed >1.3 m/s, satisfaction rate of workers is high. [ABSTRACT FROM AUTHOR]

A suitable outdoor thermal environment can encourage people to partake in outdoor activities, which, in turn, reduces building energy consumption. This can be achieved by accurately predicting the outdoor thermal environment. Most existing prediction models of the outdoor thermal environment focus on the relationship between environmental parameters and human perception, while ignoring the effects of personal factors (e.g., clothing level and metabolic rate). This study explores the relationships between the microclimate environment, personal factors, and human perception of the thermal environment during each season. A field survey was conducted between July 2016 and June 2017, across all four seasons. Thermal environment parameters, including air temperature, relative humidity, wind speed, and globe temperature were recorded and analyzed together with questionnaire survey responses. The results indicated that air temperature has the most significant effect on thermal sensation. In colder or warmer conditions, the mean thermal sensation vote increases with the increase in clothing insulation. Notably, when people kept low metabolic rate activities, including seated and quiet, standing, and walking at 3.2 km/h, the effect of metabolic rate on thermal sensation are negligible. Considering the effect of seasonal differences on the thermal environment parameters, prediction models for each season were obtained using multiple linear regression (the R-squared are 0.560(annual), 0.255 (spring), 0.207 (summer), 0.176 (autumn), 0.145 (winter)). Except for wind speed, all other factors were found to have a positive effect on the prediction models, especially air temperature and mean radiation temperature. • All factors on thermal sensation in different seasons are reported. • Air temperature has the most significant effect on thermal sensation. • Effects of metabolic rate lower than 2.0 met on thermal sensation can be ignored. • Each season predicted model is obtained using multiple linear regression. [ABSTRACT FROM AUTHOR]

Sudden changes in outdoor air temperature within the time scale of several days can affect human thermal comfort demand. Although the influence of short-term thermal experience on the thermal sensation (STEI) in one season (e.g., in summer) has been focused on, the differences of this effect in different seasons have rarely been studied. In this study, to investigate the regularity of the difference, a follow-up field survey was conducted from July 2019 to January 2020 in Chongqing, China. The results show that when outdoor air temperature suddenly rises, the STEI is higher in summer than that in autumn (approximately 0.14 scales) when the indoor air temperature is 28–30 °C. When the indoor air temperature is 24–27 °C, no significant difference was observed. In addition, the STEI is higher in autumn than that in summer (approximately 0.09 scales) when the outdoor air temperature suddenly decreases, and when the STD is −1 °C, the impact of short-term thermal experience on the body in autumn is less than that in winter, by approximately 0.04 scales. The effect can cause a variation of approximately 0.28–0.84 °C in the body's neutral temperature, with a maximum of 1.3 °C based on Griffiths method (G = 0.356/K). • The impact of short-term thermal experience on thermal sensation is quantified. • The seasonal difference of effect of short-term thermal experience is compared. • The impact of short-term thermal experience is asymmetry as △T > 0 or △T < 0. • The dynamics of thermal adaptation in summer and autumn show asymmetry trajectories. [ABSTRACT FROM AUTHOR]

• Stratum-air-distributed radiant-convective room air conditioner is proposed. • First time for stratum ventilation to be applied to room air conditioner. • First time for radiant-convective heater to be integrated with advanced air distribution like stratum ventilation. • Enlarged heat output and advanced air distribution result in improved thermal comfort and energy efficiency. The radiant-convective room air conditioner has been demonstrated to improve the coefficient of performance and the heating capacity effectively. However, the applicability of the radiant-convective room air conditioner in modulating the indoor thermal environment is unclear. This study proposes a stratum-air-distributed radiant-convective room air conditioner and evaluates its effectiveness for providing thermal comfort under heating mode with experimentally validated CFD simulations. Results show that the heat output of the radiant panel of the room air conditioner accounts for 20.7 %- 34.5 % of the total heat output. The supply airflow rate should be properly determined to balance the highly coupled heat output and air distribution. Compared with the conventional room air conditioner, the proposed room air conditioner under proper operation more effectively warms the occupied zone because of the enlarged heat output and improved air distribution, thereby increasing the predicted mean vote from −0.15 to −0.02, reducing the vertical air temperature difference from 6.7℃ to 0.8℃, and enhancing the thermal utilization effectiveness from −0.09 to 0.25. In addition, the draft rating and radiant temperature asymmetry of the proposed room air conditioner are thermally acceptable. Therefore, the proposed room air conditioner can modulate the indoor thermal environment energy-efficiently from the aspects of both overall and local thermal comfort. [ABSTRACT FROM AUTHOR]