Field Study on Thermal Environment and Thermal Comfort at Rural ...

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Abstract In order to investigate indoor thermal environment and thermal comfort at rural houses, a field study was carried out at 10 rural houses in 2 villages near.
Chapter 46

Field Study on Thermal Environment and Thermal Comfort at Rural Houses in Severe Cold Areas Zhaojun Wang, Xiaohui Sheng, Jing Ren and Dongdong Xie

Abstract In order to investigate indoor thermal environment and thermal comfort at rural houses, a field study was carried out at 10 rural houses in 2 villages near Harbin from December 2012 to January 2013. The environmental parameters and the subjects’ thermal sensation were collected simultaneously. The results showed that the indoor air temperature ranged from 9.0 to 21.8 °C, with an average of 16.6 °C. The operative temperature varied within the range of 10.5–22.7 °C, averaging 18.1 °C. The average relative humidity was 40.4 %. The mean air velocity was 0.08 m/s. The mean surface temperature of Chinese Kang was 35.1 °C. The mean surface temperature of exterior window was 9.5 °C. The neutral operative temperature was 18.5 °C. The lower limit of the accepted operative temperature by 80 % of the peasants was 10.6 °C, much lower than the specified heating temperature for urban residential buildings, because the peasants wore more clothes than residents in the urban. The mean clothing insulation was 1.47clo. 92.5 % of the subjects felt the thermal environment acceptable, and 92.5 % of the subjects felt the humidity of the environment acceptable. Regulating the Kang and the separated heating equipments were the main measures taken by the occupants to improve the indoor environment.







Keywords Thermal environment Thermal comfort Rural houses Field study

46.1 Introduction In recent years, many field studies have been conducted on indoor thermal environment and thermal comfort. However, most studies focused on urban residential buildings, a few on rural houses. Researches showed [1] that human past Z. Wang (&)  X. Sheng  J. Ren  D. Xie School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China e-mail: [email protected]

A. Li et al. (eds.), Proceedings of the 8th International Symposium on Heating, Ventilation and Air Conditioning, Lecture Notes in Electrical Engineering 261, DOI: 10.1007/978-3-642-39584-0_46, Ó Springer-Verlag Berlin Heidelberg 2014

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living environment, climate conditions, and cultural background had significant influences on their expectations of the indoor thermal environment, which would in turn affect the human adaptability to the thermal environment. Compared with the city residents, both the living habits and economic level of people living in rural areas are different. Therefore, it is necessary to study on indoor thermal environment and thermal comfort at rural houses in China. Zhang et al. conducted a field study on thermal environment and thermal comfort at rural houses in a hot summer and cold winter area [2]. Zhu et al. carried out an investigation on indoor thermal comfort at rural houses around Beijing during heating period [3]. Jin et al. mainly focused on the indoor thermal environment at rural houses in severe cold areas, instead of human thermal comfort [4]. Wang et al. conducted some field studies on thermal comfort in Harbin residential buildings [5–7]. For further study, we launched an investigation on the indoor thermal environment and thermal comfort at 10 rural houses in 2 villages near Harbin during December 2012 to January 2013.

46.2 Method 46.2.1 Subjects Ten rural houses in 2 villages near Harbin were chosen for this study. A total of 40 valid subjective questionnaires were provided by 40 respondents, of whom 17 were females. The subjects were all local peasants who had lived in the suburb of Harbin for a long time, which indicated that they had fully adapted to the cold and dry climate of the severe cold area.

46.2.2 Indoor Environmental Parameters The test instruments include a temperature and humidity data collector (HT-II), a blackball temperature recording instrument (HWZY-1), a hot-wire anemometer (Testo425) and an infrared thermometer (Testo830-T1). The temperature and humidity data collector is used to measure air temperature and relative humidity simultaneously. The accuracy of air temperature measurement is within 0.5 °C and its measurement accuracy of relative humidity is ±3 %. The accuracy of the blackball temperature recording instrument is within ±0.4 °C. The air velocity can be measured by hot-wire anemometer with an accuracy of ±(0.03 m/s ? 5 % measured value) in the measurement range of 0–20.0 m/s. The infrared thermometer is used to measure the surface temperature of the external window and Chinese Kang (built of stone or brick) with an accuracy of ±1.5 °C.

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Bedroom and living room were selected as testing zone. As the residents usually sit or lie down in the room, the air temperature, relative humidity, blackball temperature, and air velocity were measured at a height of 0.6 m above the floor, and then, the mean radiant temperature was derived by calculation. The surface temperatures of the exterior window and the Chinese Kang were measured on the center points. Table 46.1 provides statistical summaries of the indoor for the rural houses in winter. The indoor air temperature fell within the 9.0–21.8 °C interval, with an average of 16.6 °C. The blackball temperature varied within the range of 10.7–23.1 °C, averaging 18.5 °C. The operative temperature varied within the 10.5–22.7 °C range, with a mean of 18.1 °C. The mean surface temperature of exterior window was 9.5 °C. The mean surface temperature of Kang was 35.1 °C. The relative humidity fell within the range of 26.0–57.4 %, with a mean of 40.4 %. And the relative humidity was in the thermal comfort zone. The mean air velocity was 0.08 m/s, which was similar with the air velocity in Harbin residential buildings [5]. The mean clothing insulation was 1.47clo, ranging from 0.93clo to 2.11clo.

46.2.3 Subjective Questionnaires The subjective questionnaires were collected simultaneously with the measurement of the indoor parameters. The questionnaires included: (1) Background survey, such as gender, age, etc. (2) The clothing and activities of the subjects. (3) Thermal sensation, which used the ASHRAE seven-point scale: -3 cold, -2 cool, -1 slightly cool, 0 neutral, +1 slightly warm, +2 warm, +3 hot. (4) Thermal expectation: -1 cooler, 0 no change, +1 warmer. (5) Thermal acceptability, evaluating the environment acceptable or unacceptable directly. (6) The measures of improving the indoor thermal environment, such as regulating the Kang, regulating their own separated heating equipment, opening the windows, changing clothes, changing activity level, etc.

Table 46.1 Indoor environmental parameters and clothing insulations in winter Average Maximum Minimum Standard deviation Air temperature/°C Relative humidity/% Air velocity/m/s Blackball temperature/°C Mean radiant temperature/°C Operative temperature/°C Surface temperature of Kang/°C Surface temperature of exterior window/°C Mean clothing insulation/clo

16.6 40.4 0.08 18.5 19.6 18.1 35.1 9.5

21.8 57.4 0.18 23.1 26.1 22.7 46.0 16.0

9.0 26.0 0.04 10.7 12.0 10.5 16.5 -2.0

3.4 9.4 0.03 3.5 3.8 3.3 7.7 4.7

1.47

2.11

0.93

0.33

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46.3 Results and Analyses 46.3.1 Thermal Neutral Temperature and Ranges of Acceptable Temperature The operative temperature was used to evaluate the indoor thermal environment, and the temperature–frequency method was applied. The linear regression equation between mean thermal sensation vote and indoor operation temperature is as follows: MTS ¼ 0:094to  1:742

ð46:1Þ

where to is the indoor operative temperature, °C; MTS is the mean thermal sensation vote. The correlation coefficient R = 0.581. Let MTS = 0, we get the thermal neutral temperature of 18.5 °C. The slope of the MTS-on-operative temperature was quite small, which indicates the sensitivities of the subjects to temperature changes. If the indoor operative temperature changes 1 °C, the thermal sensation will only change about 0.094. Let MTS = -0.75, we obtain the lower limit of the accepted operative temperature by 80 % of the respondents of 10.6 °C, which was much lower than that specified heating temperature for urban residential building. So it is necessary to further research the thermal environment at rural houses.

46.3.2 Thermal Acceptability and Thermal Expectation The subjects were asked if they accepted the thermal environment they were exposed to. The results show that 95 % of the subjects marked acceptable. Figure 46.1 shows the distribution of thermal expectation votes. The thermal expectation vote used Preference scale: -1 (colder), 0 (no change), +1 (warmer). In this study, 60 % of the subjects wanted ‘‘no change’’, 37.5 % requested ‘‘warmer’’, and only 2.5 % requested ‘‘colder’’.

46.3.3 Improvement Measures of Indoor Thermal Environment Figure 46.2 gives the distribution of measures taken by the occupants to improve the indoor environment. The measures were as the follows: regulating the Kang, regulating their own separated heating equipment, opening or closing the door and window, changing clothes, adjusting activity levels and so on.

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Fig. 46.1 Distribution of thermal expectation votes

Frequency /%

80 60 40 20 0 -1

0

1

Other

Adjust activity levels

Change clothes

Drink hot water

Open the door and window

Close the door and window

Regulate heating equipment Regulat the Kang

60 50 40 30 20 10 0

No regulation

Fig. 46.2 Distribution of measures to improve the indoor environment

Frequency /%

Thermal expectation

Measures to improve the indoor environment

Fifty-five percent of the peasants adjusted indoor temperature by regulating the power of Kang, 42.5 % regulated their own separated heating equipment, and 20 % closed the door and window. 22.5 % of the occupants improved their comforts by putting on more clothes and 27.5 % by more activities. It is found that regulating the Kang and their own separated heating equipment were the main processes used by the occupants to improve the indoor environment.

46.4 Discussions Wang et al. [5, 6] conducted a field study in 66 apartments in Harbin from 2000 to 2001 in winter. They have derived a linear regression equation between mean thermal sensation votes and indoor operative temperature as follows: MTS ¼ 0:302to  6:506

ð46:2Þ

The correlation coefficient R = 0.872. The neutral temperature is 21.5 °C. Compared the two Eqs. (1) and (2), it is found that the neutral operative temperature of their urban samples was 3 °C higher than that of our suburb samples. The peasants were less sensitive to temperature changes.

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The mean clothing insulation was 1.47clo at rural houses, larger than those of the urban residential buildings of 1.37clo [5]. The lower neutral temperature and the lower limit of the accepted operative temperature of 10.6 °C may be explained by the higher metabolic rate and larger clothing insulation of people at rural houses.

46.5 Conclusions Based on the above study at rural houses around Harbin, we got the following conclusions: 1. The mean indoor air temperature was 16.6 °C. The average operative temperature was 18.1 °C. The average RH was 40.4 %. The mean air velocity was 0.08 m/s. 2. The neutral temperature was 18.5 °C. The lower limit of the operative temperature accepted by 80 % of the peasants was 10.6 °C. 3. Ninety-five percent of subjects voted the thermal environment acceptable. The indoor relative humidity fell in the range of thermal comfort. The mean air velocity was similar with the air velocity in Harbin residential buildings. 4. The mean clothing insulation was 1.47clo, more than the occupants in Harbin residential buildings. 5. Regulating the Kang and their own separated heating equipment were the main measures taken by the occupants to improve the indoor environment at rural houses.

Acknowledgments The work presented in this paper is funded by the 12th Five Year National Science and Technology Support Key Project of China (No. 2011BAJ08B07).

References 1. Dear RJ, Brager GS (2004) Developing an adaptive model of thermal comfort and preference. ASHRAE Trans 104(1):145–167 2. Han J, Zhang GQ, Zhou J (2009) Research on the rural residential thermal environment and thermal comfort in hot summer and cold winter climate zone. J Hunan Univ 36(6):13–17 (in Chinese) 3. Huang L, Zhu YX, Ouyang Q et al (2011) Indoor thermal comfort in rural houses around Beijing in heating season. HVAC 41(6):83–85, 115 (in Chinese) 4. Jin H, Zhao H, Wang XP (2006) Research on the indoor thermal comfort environment of rural housing in winter in super-cold region. J Harbin Inst Technol 38(12):2108–2111 (in Chinese) 5. Wang ZJ, Wang G, Lian LM (2003) A field study of the thermal environment in residential buildings in Harbin. ASHRAE Trans 109(2):350–355

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6. Wang ZJ (2006) A field study of the thermal comfort in residential buildings in Harbin. Build Environ 41(8):1034–1039 7. Wang ZJ, Zhang L, Zhao JN et al (2011) Thermal responses to different residential environments in Harbin. Build Environ 46(11):2170–2178