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A Study on the Thermal Comfort in Sleeping Environments In ARTICLE IN PRESS Building and Environment 43 (2008) 905–916 www.elsevier.com/locate/buildenv A study on the thermal comfort in sleeping environments in the subtropics—Measuring the total insulation values for the bedding systems commonly used in the subtropics Zhongping Lina, Shiming Dengb,Ã aInstitute of Heating, Ventilation, Air conditioning and Gas engineering, Tongji University, 1239 Siping Road, Shangai 200092, China bDepartment of Building Services Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China Received 9 March 2006; received in revised form 28 November 2006; accepted 10 January 2007 Abstract The total thermal insulation value of a bedding system significantly affects the thermal neutral temperature for sleeping environments and is therefore an important variable in the Comfort Equation developed for sleeping environments reported in a related paper. This paper reports on the measurement of the total insulation values for a wide range of bedding systems (through different combinations of bed, bedding and its percentage coverage over a human body, and sleepwear) commonly used in the subtropical regions using a thermal manikin. The total insulation values of the measured bedding systems varied greatly from 0.90 to 4.89 clo, depending upon bedding, bed and mattress, the type of sleepwear, and percentage coverage of body surface area by bedding and bed. The use of a Chinese traditional style bed—Zongbang bed can provide less insulation than the use of the conventional mattress commonly used in Hong Kong. The use of so-called air conditioning quilt (summer quilt) cannot help lower the total insulation significantly. On the other hand, some factors such as people sweating and moisture permeability of the quilts, etc., were not considered in the current study but may be further studied in future work. r 2007 Elsevier Ltd. All rights reserved. Keywords: Total insulation value; Bedding system; Manikin; Thermal comfort; Sleeping environment 1. Introduction some documents such as ASHRAE Standard 55 [2] and ISO Standard 9920 [3] giving insulation values for clothing. It has been shown in a related paper [1] that the total Therefore, the thermal insulation provided by various thermal insulation value of a bedding system significantly bedding systems commonly used in the subtropics must be affects the thermal neutral temperature for sleeping obtained through extensive laboratory experimental work. environments and is, therefore, an important variable in A large number of previous studies on the thermal the Comfort Equation for sleeping environments. In order insulation of clothing have been reported [4–11]. Based on to evaluate various combinations of the environmental these studies, a complete full-scale database of the thermal variables, which will achieve optimal thermal comfort for insulation and evaporative resistance of clothing ensembles sleeping persons under steady state conditions (i.e., to solve necessary for the use in various thermal comfort models for Comfort Equation for sleeping environments), the total daytime was developed, and adopted by relevant standards resistance, Rt, of bedding systems must be available. (ISO Standard 9920 and ASHRAE Standard 55). There However, no database is currently available on the thermal were also a limited number of previous studies on the insulation for bedding systems used for air conditioned thermal insulation provided by bedding systems, which sleeping environments in the subtropical regions except were carried out using a manikin [12–14]. These studies resulted in a small-scale database of thermal insulation ÃCorresponding author. Tel.: +852 27665859; fax: +852 27657198. values for a variety of bedding systems. However, most of E-mail address: [email protected] (S. Deng). the reported studies were related to heated environments 0360-1323/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.buildenv.2007.01.027 ARTICLE IN PRESS 906 Z. Lin, S. Deng / Building and Environment 43 (2008) 905–916 Nomenclature j number of surface, ND K unit constant (6.45 clo W/(m2 1C)), ND ai area fraction of segment (i) related to whole Rt total resistance of a bedding system including 2 body area Ask, ai ¼ ask,i/Ask,ND the air layer around a covered body, m 1C/W AC percentage coverage of body surface area by ta ambient air temperature, 1C bedding and bed, % tj surface temperature of surface j, 1C FP-j angel factor between manikin and surface j,ND to operative temperature, 1C 2 Hi local heat flux of segment (i), W/m t¯r mean radiant temperature, 1C 2 Hsk whole body heat flux, W/m t¯sk mean skin temperature, 1C IT total insulation of a bedding system including tsk,i local skin temperature of a segment (i), 1C the air layer around the covered body, clo where the objective was to increase thermal insulation value by a bedding system so as to lower indoor air temperature. Furthermore, the types of beddings studied were in generally based on those primarily used in the USA and Europe, and, therefore, not applicable to air-condi- tioned sleeping environments in the subtropics. This paper reports on an experimental study on measuring the total insulation values for a wide range of bedding systems (through different combinations of bed, bedding and its percentage coverage over a human body, and sleepwear) commonly used in the subtropical regions using a thermal manikin. The experimental method is first introduced. This is followed by reporting selection of the components of a bedding system such as bedding, sleep- wear, bed and mattress, etc. and measurement of the physical properties of the selected textiles. Thirdly, the results of measurement, which resulting in a small-scale database of the total insulation values provided by bedding systems commonly used in the subtropics, is reported. Finally, a number of issues related to the factors influencing the total resistance/insulation of a bedding system and the use of summer quilts are discussed. 2. Experimental method The experimental work was based on a thermal manikin with geometry of a real human body in an environmental chamber. The purpose of the experimental work was to develop a database of the total insulation values (I )of T Fig. 1. The manikin (divided into 20 independent segments, each with its bedding systems commonly used in the subtropics. The own heating and computer control system). database obtained was used as an input to solve the Comfort Equation for sleeping environments, and may further be adopted by various standards such an ISO Standard or an ASHRAE Standard. The measurements distribution of a human being. In order to correctly and calculations of the total insulation values were carried simulate the thermal receptors all over the body of a out in accordance with the corresponding ISO [3] and human being, temperature sensing elements are distributed ASTM [15] Standards. all over the manikin surface. The manikin is heated by the The manikin shown in Fig. 1, Alex, is divided into 20 same wiring used for measuring. An individual propor- independent segments (Left/Right: foot, low leg, front tional integrate (PI) controller is used to produce the thigh, back thigh, hand, forearm, upper arm, and pelvis, required mean skin temperature in each body segment of backside, face, crown, chest and back), each with its own the manikin. The mean skin temperature settings were temperature sensors, and heating and computer control 31 1C for hands and feet, and 35 1C for other body system to approximately simulate the skin temperature segments, respectively. Thus a mean skin temperature of ARTICLE IN PRESS Z. Lin, S. Deng / Building and Environment 43 (2008) 905–916 907 34.6 1C for the whole body (thermal neutral in a sleeping The operative temperature was calculated as the mean of air environment) was produced. and mean radiant temperature based on that the difference The manikin was placed with a supine position on a between mean radiant and air temperature is small (o4 1C): single bed with a dimension of 1900 (L) Â 920 (W) mm in ta þ t¯r an environmental chamber. Besides a conventional air to ¼ , (3) conditioning system to control the indoor air temperature 2 and relative humidity, a wall panel cooling/heating system, X6 which can be used to control the wall temperature, is also t¯r ¼ tjF PÀj. (4) available in the environmental chamber. There are 10 wall j¼1 temperature sensors distributed evenly in the wall panels. For each experimental condition, both the indoor air A test was also carried out with the nude manikin temperature and the temperatures of internal surfaces of suspended horizontally in air to determine the air layer wall, ceiling and floor were all maintained constant at insulation, Ia, (fixed at 0.73 clo, exactly the same value as 22 1C, while the relative humidity inside the chamber at that obtained by McCullough et al. [12]). 50%. The air velocity was controlled at not greater than 0.15 m/s. During each test, the power input, the mean skin 3. Selection of bedding, sleepwear, bed and mattress temperature of each segment, indoor air and panel wall temperature, and indoor relatively humidity were continu- The components of a bedding system include bedding, bed ously monitored and recorded at an interval of 1 min. The and mattress, and the sleepwear used by occupants during mean value of each parameter was calculated based on at sleep. The results of a previous study [16] showed that 92% of least 30 steady-state data. Fig. 2 shows an example of one the respondents would wear sleepwear (47% used full-slip measuring condition. The total thermal resistance (Rt) and while the other 45% used half-slip sleepwear) and 90% would insulation (IT) of a bedding system, including the resistance cover themselves with quilts (50%) or blankets (40%) during or insulation from the air layer around the tested manikin, sleep.
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