Overall and local thermal sensation & comfort in air-conditioned dormitory with hot-humid climate
Introduction
Thermal environment of dormitories in university is important for students' health and study. Nowadays, most dormitories of universities in south of China are naturally ventilated in both winter and summer. While in north of China, most dormitory rooms are naturally ventilated in summer and heat-supplied in winter. This condition usually causes discomfort for students in dormitory rooms, especially in southern regions of China [1], [2], [3]. With the development of economics and increasing number of university students, better indoor environment of dormitories in universities are quite in need. In recent years, air-conditioned dormitories are gaining popularity in some universities located in big cities in south of China, but they are not so wide-spread. Meanwhile, thermal environment and comfort in school buildings have been concerned by many researchers and related organizations [4], [5], [6], [7], [8], [9], [10], [11], but attention for dormitories was insufficient.
Xia et al. [1] carried out a survey in three naturally-ventilated dormitory buildings located in Xi'an in summer. They reported high percentage of unsatisfied and attributed this to the terrible natural ventilation condition, which resulted in high indoor temperature even though the outside temperature remained comparatively low. Similarly, Tan et al. [2] declared that indoor environment of naturally-ventilated dormitories in summer didn't meet 80% acceptability criteria prescribed by ASHRAE Standard [12]. Wang and Xiao [13] conducted a field measurement in naturally-ventilated dormitories of universities located in Chongqing, China. The obtained results showed that the average air temperature reached 32.4 °C during daytime which far deviated from the comfort zone suggested by ASHRAE Standard [12] due to hot climate in summer. In their another survey [14], they found that few effective methods were available for students to control indoor environment of dormitory rooms, but students still exerted endurance ability to hot-humid condition. Wan et al. [15] found that students took various adaptive behaviors to reduce the stimulation caused by cold environment in naturally-ventilated dormitories. Similar phenomenon was observed in the survey of Lu et al. [3]. They confirmed that adaptive behaviors were taken by occupants in dormitory rooms located in Shanghai, China in summer. However, the proportion of occupants who complained about high temperature and bad ventilation condition was pretty high. Cheng et al. [16] investigated thermal comfort requirements of students in both naturally-ventilated and air-conditioned dormitories, while the differences of neutral temperature and prefer temperature were quite small between two conditions. After a wide survey with 3712 students participated in, Sun et al. [17] pointed out that more than 30% of students in heat-supplied dorm rooms had sick building syndrome (SBS) symptoms in winter. They also found that girls suffered more SBS symptoms than boys. He et al. [18] conducted a field survey in 25 air-conditioned dormitory rooms of Chongqing University in winter in Chongqing, China. The results indicated that more than 30% of students voted on cool side even though the mean indoor temperature reached 23 °C, and this probably resulted from the humid climate in winter.
However, some problems remains unclear. For instance, previous researches mainly focused on naturally-ventilated dormitories which were common for most universities in summer in China, while few researches on students' comfort in air-conditioned dormitories were found, especially in summer. It's insufficient for the popularization of air-conditioned dormitories. Further, current studies focused on occupants' overall thermal sensation and comfort, while local thermal sensation and comfort for individual body parts were often ignored. It's indicated by Zhang et al. [19], [20], [21] that special attention must be paid on local thermal sensation and comfort before higher level of comfort of occupants' is achieved in air-conditioned environment.
This paper aims to investigate students' overall and local thermal sensation & comfort in air-conditioned dormitories of university in summer. A field survey was conducted in dormitory rooms with split-type air conditioners during July to September in 2015 in Changsha, which is located in south of China with hot-humid climate in summer. This survey combined indoor environmental parameters and questionnaires to occupants. Based on obtained data, occupants' local thermal sensation and comfort were analyzed. Then, the influencing factors were discussed. Also, the obtained results were compared with those of previous literature. This paper also provided references for improving students' comfort in dormitories with air conditioners.
Section snippets
Location and climate
This field investigation was conducted in dormitory rooms with split-type air conditioners in Hunan University which is located in Changsha, China. The survey was carried out in sunny or cloudy days.
Changsha, a big city located in central-south region of China, belongs to Hot Summer & Cold Winter zone which covers most regions of south China. As for Changsha, the air temperature during day time is often higher than 30 °C while it did not decrease much at night in summer [22]. Changsha is also
Thermal environment
The environmental parameters of one certain dormitory room showed very little fluctuation during our measurement due to the air-conditioner, thus the average value of environmental parameters when the occupants replied to the question was used for analysis. The data of thermal environment parameters were listed in Table 3. Compared with occupants in naturally-ventilated dormitories [1], [2], [3], those in this survey experienced indoor environments which were within or close to comfort zone [12]
Analysis on local thermal sensation
According to the results in section 3.3.1 Overall and local thermal sensation, 3.3.2 Air temperature and local thermal sensation, it's clear that there were differences of sensation proportion and influences of body parts. This result can be explained by following factors:
- (1)
Physiological factor: As shown in Table 5, there were significant differences of sensitivity and neutral temperature for individual body parts. As mentioned in section 3.3.2, sensitivity decided how easy body parts would feel
Conclusions
This paper showed the results of a field study on local thermal sensation and comfort in air-conditioned dormitories with hot-humid climate. Main conclusions of this study were summarized as below:
- (1)
In air-conditioned dormitory rooms with hot-humid climate in summer, head exerted the highest influence on OTS, followed by calf and foot, then the influences of chest and back were comparatively lower, while for the rest body parts, their effects were negligible.
- (2)
LTS and its effect on OTS in
Acknowledgements
This study was financially supported by the National Natural Science Foundation of China (Project No. 51578220). Meanwhile, the authors would also like to express the heartfelt thanks to all students participated in the survey.
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