建筑環(huán)境與設(shè)備工程 - 專英 論文(3)

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1、 Investigation of the Influence of the Indoor Air Temperature and Mean Radiant Temperature to the Thermal Comfort Index of the Public Buildings in the Typical Subtropical Climatic Region Zhangyuan Wanga, * a School of Civil and Transportation Engineering, Guangdong University of Technology, Gua

2、ngzhou, Guangdong 510006, China *Corresponding author: zwang@ mailto:xzhao@dmu.ac.uk(Dr. Z. Wang) Tel.: +86 20 3932 2515; fax: +86 20 3932 2511. Abstract Aim of the paper is to investigate the effect of the envelopes’ inner air temperature and mean radiant temperature to indoor thermal comf

3、ort of the buildings. This work was undertaken by the combination of the literature review, theoretical analyses and index identification, as well as experimental measurement and analyses, on basis of the selected 12 public buildings in Dongguan City (Guangdong Province, China), located at the typic

4、al sub-tropic climatic region. An extensive review into indoor thermal comfort research was conducted indicating that the effect of indoor air temperature and mean radiant temperature toward indoor thermal comfort has not yet been systematically studied. The theoretical analyses presented the existi

5、ng standards of thermal comfort, index for evaluating the thermal comfort, as well as its dependency with a number of factors affecting the thermal comfort, with particular focus on the relationship between the comfort index and the indoor air temperature and mean radiant temperature. Measurement to

6、wards the selected 12 buildings in Dongguan City was carried out that depicted the regulatory correlation between the comfort index and the building’s indoor air temperature and mean radiant temperature. It indicated that when the indoor air temperature and mean radiant temperature reached to a leve

7、l of 30oC or above, an uncomfortable thermal environment would occur for the natural ventilated buildings. Therefore, 30oC was taken as the upper temperature limit of the thermal comfort zone. For the buildings with air-conditioning operation, the envelope surface temperature could be reduced to bel

8、ow 30oC, which was the recommended method for meeting the summer thermal comfort standard. The building type, e.g., office, hotel, etc, could influence the indoor air temperature that the office buildings performed the best with the most comfortable environment, and hotels were always overcooling du

9、ring the testing period. However, building type was not the obvious reason for the change of the PMV-PPD index. In order to improve the quality of thermal environment, some recommendations were put forward, e.g., the turn-on of the air-conditioning, relatively small construction area, appropriate bu

10、ilding space arrangement, and utilization of climate data. This research can help determine the favorite operational and control strategies of the HVAC systems in the public buildings located at the sub-tropical climatic regions and improve the indoor thermal comfort and living standards within the

11、buildings. The research will therefore contribute to development of the smart building design in terms of providing the enhanced thermal comfort and indoor air quality. Keywords: subtropical climatic region; public building; indoor environment; thermal comfort; measurement Nomenclature A – a

12、rea, m2; fcl – ratio of the surface area of clothed body to that of nude body; hc – convective heat transfer coefficient, W/(m2·oC); Icl – thermal resistance of clothing, (m2·oC)/W; M – metabolic rate, W/m2; pa – water vapor pressure, Pa; PMV – predicted mean vote; PPD – predicted percentage

13、 of dissatisfied; va – relative air velocity, m/s; W – external work, W/m2; t – temperature, oC; ta – air temperature, oC; tcl – surface temperature of clothing, oC; tr – mean radiant temperature, oC; Subscripts 1, 2, …, n – number of envelops’ inner surface; 1. Introduction Thermal co

14、mfort is an important index of residents’ satisfaction on the indoor thermal environment. In industrialized countries,?people?spend more than 90% of their?time?indoors on average [1], which makes people to the indoor environment has become interested in research on the effects of thermal comfort of

15、human body. In addition, indoor thermal comfort is one of the most heretic topics in the area of the smart and energy efficient buildings. The influence factors of thermal comfort can be divided into two parts, i.e., environmental and human factors [2]. The environmental factors are involved in

16、indoor air temperature, air speed, relative humidity, occupancy density, mean radiant temperature of the building envelope. The factors related to the people are metabolism and clothing. Windows and HVAC systems are often the major means by which building occupants control the indoor environment.

17、 At present, most of the research work in the thermal comfort has been carried out by some western countries such as America and Europe. Early thermal comfort index statistics was carried out by the laboratory or field investigations. Temperature and sensory indicates of human response to the ther

18、mal environment were often expressed in terms of the known response in a controlled laboratory environment as a standard [3]. Experiments using the Kata-Thermometer [4] in the 1930s integrated the average radiation temperature, air temperature and speed to the thermal comfort. ASHRAE [5] with Effect

19、ive Temperature defined a human body comfort zone. In order to find a more widely use of comprehensive thermal comfort index, Fanger [6] put forward the famous idea of thermal comfort equation of the Predicted Mean Vote and Predicted Percentage of Dissatisfied (PMV-PPD) model defined in terms of the

20、 heat load. Winslow’s Skin Wettedness Index of ‘Thermal Discomfort’ defined in terms of the fraction of the body surface, wet with perspiration, required to regulate body temperature by evaporative cooling [3]. Nowadays, some researchers believed that the architectural form, climate, ethnic diff

21、erences and some other construction factors may also cause people around the world in the same thermal environment different to the thermal sensation and thermal comfort. Yao et al. [7] presented in detail a theoretical adaptive model of thermal comfort based on the ‘Black Box’ theory, taking into a

22、ccount factors such as culture, climate, social, psychological and behavioral adaptations, which had an impact on the senses used to detect thermal comfort.? Nikolopoulou et al. [8] presented the results of the microclimatic and human monitoring in relation to the thermal environment and comfort con

23、ditions in open spaces. The findings confirmed a strong relationship between microclimatic and comfort conditions, with air temperature and solar radiation being important determinants of comfort, although one parameter alone was not sufficient for the assessment of thermal comfort conditions. Atmac

24、a et al. [9] analyzed the interior surface temperatures for different wall and ceiling constructions with their effect on thermal comfort. Cena and Dear [10] studied the thermal comfort and behaviour strategies in office buildings located in a hot-arid climate. Deng et al. [11] investigated the indo

25、or comfort characteristics under the control of a direct expansion air conditioning unit having a variable-speed compressor and a supply air fan. Kang et al. [12] developed a correlation in thermal comfort and natural wind. Newsham [13] constructed a computer model to predict the effect of the cloth

26、ing to be a thermal comfort moderator of human and its related energy consumption of the building. Rowe [14] estimated the average activity rates to the thermal comfort of office occupants in Sydney. Although the current domestic and foreign researches on thermal comfort have become widely, the

27、conventional theories of thermal comfort were primarily setup based on steady state laboratory experiments, rarely representing the real situation in buildings. Besides, the affect of the indoor air temperature and inner wall radiant temperature to indoor thermal comfort has not yet well studied.

28、 In sub-tropic climatic area where the hot and humid air conditions are commonly in existence, the indoor overheating, a phenomena frequently appeared in summer, is resulted from the long-wave radiations from the high-temperature surface and the solar incidences through the glazing, as well as the

29、higher external air temperature. While in cold area, the cold radiation may occur owing to the lower internal wall surface temperature, leading to reduced indoor thermal comfort quality. Both the indoor air temperature and radiant temperature of the envelopes’ inner surface are needed to quantitativ

30、ely assess the indoor thermal comfort of the public buildings. In this paper, the effect of the envelopes’ inner surface temperature and air temperature to indoor thermal comfort of the buildings will be experimentally investigated based on the 12 selected public buildings in Dongguan City, Guang

31、dong Province, China, located at the typical sub-tropic climatic region. This research will fill up the deficiency in this research area and make valued contribution to thermal comfort studies. 2. Theoretical analyses of the thermal comfort index and setup of the computer model 2.1 Principle of

32、human body energy balance 2.2 Thermal comfort index Existing international thermal comfort standards, e.g., the Fanger’s PMV-PPD model, ASHRAE Standard 55 ‘Thermal environmental conditions for human occupancy’, and ISO Standard 7730 ‘Moderate thermal environments - calculation of the PMV and PPD

33、 thermal comfort indices’, specified combinations of environmental and human factors that will be deemed acceptable to 80% or more of the occupants [5, 15]. Fanger’s PMV-PPD index showed the quantitative values of the degree of discomfort and the effectiveness of not only environment factors but

34、 also human factors [6, 16]. PMV predicted the mean value of the votes of a large group of people exposed to the same environment in a 7-grade thermal sensation as in Table 1, i.e. from -3 (cold) to +3 (hot). According to Fanger [6], the PMV values from -1 to +1 were evaluated as ‘Comfortable’, and

35、the values higher than +1 or lower than -1 were considered as ‘Uncomfortable’. PPD predicted the percentage of thermally dissatisfied people, which was more reliable than PMV because individual votes showed scatter due to human factors. Table 1 Relationship between PMV and thermal sensation PMV

36、 -3 -2 -1 0 +1 +2 +3 Thermal sensation Cold Cool Slightly cool Neutral Slightly warm Warm Hot 2.1.1 PMV The most widely used thermal comfort index was the PMV. Depending on human activity, clothing, air temperature, relative humidity, relative air velocity, and mean radiant tempe

37、rature, PMV could be defined as [16, 17]: (1) Where, tcl was the surface temperature of clothing, which can be obtained from Eq. (2): (2) hc was the convective heat transfer coefficient, which can be determined as:

38、for for (3) fcl was the ratio of a person's surface area while clothed to the surface area while naked. for

39、 for (4) tr was the mean radiant temperature that in practical applications, tr was considered to be the weighted average of th

40、e summed products of the surface areas and their equivalent surface temperatures, which can be presented as [18, 19]: (5) 2.1.2 PPD To predict the number of people likely to feel uncomfortable

41、 as a cooling or warming feeling, the feeling was sited under the category of the PPD. The output of PPD was classified into two categories, comfortable and uncomfortable, based on human sensation. PPD was determined from PMV that the relationship between PPD and PMV was summarized in Eq. (6) and Fi

42、g. 1 [16, 17]. (6) Fig. 1 Relationship between PMV and PPD 2.2 Setup of the computational model The relationship between the PMV-PPD index and the depending factors, e.g., human activity, clothing, ai

43、r temperature, relative humidity, relative air velocity, and mean radiant temperature, could be analyzed through the setup of a computer model. The algorithm used for modeling setup was presented in a flow diagram as shown in Fig. 2, which can also be interpreted as follows: Fig. 2 Flowchart of

44、 computer model setup 1. Given the description of the target building, the parameters related, e.g., surface temperature and area of each envelope of the building, could be obtained; 2. Then the mean radiant temperature (tr) could be obtained using Eq. (5); 3. Assuming the thermal resistance of

45、 the human clothing (Icl), the ratio of the surface area of clothed body to that of nude body of the human (fcl) could be determined by using Eq. (4); 4. Assuming the air velocity (va), air temperature (ta), relative humidity and metabolic rate (M); 5. Carrying out thermal balance to determine the

46、 surface temperature of clothing (tcl) by using Eq. (2); (1) Assuming that the initial clothing temperature (tcl) equals to the air temperature (ta); (2) The convective heat transfer coefficient (hc) could be determined by using Eq. (3); (3) The left and right sides of Eq. (2) could be separately

47、 calculated; (4) If the difference between the left and right sides of Eq. (2) is higher than 0.1oC, increasing tcl by 0.05oC, and return to step 5 for recalculation; (5) If the difference between the left and right sides of Eq. (2) is less than -0.1oC, decreasing tcl by 0.05oC, and return to step

48、 5 for recalculation; (6) If the difference between the left and right sides of Eq. (2) is in the range of 0.1oC and -0.1oC, the Eq. (2) was considered to reach a balance, and tcl was obtained. 6. PMV could be calculated using Eq. (1); 7. PPD could be calculated using Eq. (6); 8. Program stops.

49、 3. Experimental processes, results and analyses 3.1 Experimental processes Located south of the Tropic of Cancer, Dongguan City, Guangdong Province, China [20] has a subtropical oceanic climate. The average annual temperature is 22.8°C and the average rainfall is 1,756.8 millimeters. Dongguan

50、 is a characteristic Pearl River Delta wetland, warm and rich in resources, and is well-known in the area for its rice, banana, lichee, longan, and aquatic product. Facing the South Sea, Dongguan has 150 square kilometers of sea area and 116 kilometers of coastline as well as 4 rivers, 5 lakes and 6

51、 mountains. Dongguan had an estimated 6,949,800 inhabitants at the end of 2008, among which 1,748,700 were local residents and 5,201,100 permanent migrants from other parts of the country. Dongguan is also a famous hometown for many?overseas Chinese, the family origin of over 700,000 people in Hong

52、Kong,?Taiwan?and Macau and over 200,000 nationals living abroad. In the period of September 2006 to November 2006, a total of 12 typical public buildings in Dongguan City were selected for carrying out indoor thermal comfort experiment. The building types selected include those for sports fitnes

53、s, offices, hotels, and commercial purpose, representing the majority kinds of public buildings at the subtropical area as in Table 2. G-01 (recreation) and G-02 (sports centre) were tested in natural ventilation condition, and the other buildings were air-conditioned for testing. The experiment for

54、 each building was conducted around 11 days with 8 operational hours every day. 21 Table 2 Summary of the selected 12 public buildings for carrying out experiment in Dongguan City Building no. Floor area (m2) Building function Description of the building Floor External wall Roof Inte

55、rnal wall Air-conditioning system Story Thickness (mm) Finishing Roof tile Thermal insulation Height (m) Number G-01 - Recreation 600mm *600mm lime-color tile 250 Mosaic ceramic tile (tint) - - - - 2.8 8 G-02 195.0 (small) 588.0 (large) Sports Wooden floor 230 - Wave-sha

56、pe iron-sheet tile Blue cloth - - 6.8 1 G-03 23.4 Office - 260 White ceramic tile Hollow prefabricated roof slab - White-paint-coated internal wall Split air conditioning systems (KF-26W-039) - - G-04 - Hotel - 260 White ceramic tile Hollow prefabricated roof slab - White

57、-paint-coated internal wall Split air conditioning systems (KF-26W-039) - - G-05 8035.2 Retail - - Glass curtain and clay brick - - - Central air-conditioning - - G-06 189.2 Sports Wooden floor - - - No insulation, replaced by 100mm thick soil, planted roof without plant soil

58、 - - 4.0 - G-07 363.5 Office Gray ceramic tile 250 Faint-yellow wall paint - With insulation - - 2.6 - G-08 - Hotel Gray ceramic tile 240 - - - - - 3.0 Located on 3rd floor G-09 50.5 Office Gray ceramic tile 210 - - - - With air-conditioning 2.8 Located on

59、3rd floor G-10 24.0 Hotel White ceramic tile 220 - - - - With air-conditioning 2.4 - G-11 39.8 Hotel Deep color carpet 290 Mosaic - - - With air-conditioning 2.4 - G-12 22.8 Office Gray carpet floor 210 Mosaic - - - With air-conditioning 3.0 - The most imp

60、ortant parameters to be measured in determining the thermal comfort condition included (1) indoor air temperature and relative humidity; (2) environmental air temperature and velocity, relative humidity and solar radiation; (3) surface temperatures of the inner wall, windows, doors, floor and ceilin

61、g; (4) outer surface temperatures of the outside wall, windows and ceiling; and (5) indoor air quality. The indoor and outdoor air temperature and relative humidity were tested by using a JTDW-2 data logger that the temperature and humidity probes were located at the height of 1-1.5m of the buil

62、ding wall. For the indoor operation, the probes were evenly arranged to cover all the interior space and avoided the air vent and other overheating or overcooling local devices for the measurement accuracy. For the outdoor, the probes were positioned to avoid the direct sunlight and raining, and the

63、 number of the probes in the north and south directions was no less than 2. The outdoor maximum air velocity was measured by using an anemometer, and the data were recorded in every 30 minutes. The testing probe for the anemometer was also positioned at the height of 1-1.5m and to avoid the body

64、blocks. A pyranometer was applied for the measurement of the solar radiation in every 30 minutes. For the rainy day without sunlight, the start and end times of the rain were recorded as well as the size of the rain. For the surface temperatures of the wall or window constructions measured,

65、a heat flux and temperature automatic testing device was used that the patches of the device were attached to the inner surface of the constructions using the insulation tape. The temperature data was automatically recorded to a computer for subsequent analysis. As to the surface temperatures of the

66、 ceiling and floor, the infrared surface temperature testing equipment was needed that the testing points was evenly arranged to cover all the areas of the ceiling and floor. The indoor air quality, including the indoor temperature, relative humidity, CO concentration and CO2 concentration, was tested by using an indoor air quality detector in every 30 minutes. It should be mentioned that during the testing period, the test should not be stopped arbitrarily, and the weather da