a study on thermal comfort of the change room of...
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A Study on Thermal Comfort of the Change Room of
Public Bathhouse
Seonghoon Yoon1, Yekyeong Shin1
1Department of Architectural Engineering, Namseoul University,
Seonghwan-eup, Seobuk-gu, Cheonan-city, 31020, KOREA
{aquila, shinyk77}@nsu.ac.kr
Abstract. For the interior thermal environment of a public bathhouses, we
investigated the kind of thermal sensation that the user feels after a bath, as well
as the optimum floor surface temperature which can provide thermal comfort for
the user, before or after the bath. The results showed that the users felt a thermal
sensation corresponding to the PMV index of an average of 0.67, and the
metabolic rate was about 2.35[met] after a bath.
Keywords: Thermal comfort, PMV, Change room, Floor heating
1 Introduction
Public bathhouses, one of the representative multiuse facilities in Korea, are a facility
which has a user morphological feature of which the user will enter a sauna room or
bath with a high temperature, to take a bath for about 30 minutes to an hour. In addition,
in Korea, the floor heating (Ondol) system is universally used as the interior heating
method in the indoor areas including the public bathhouses. Therefore, in the winter
season, the users who have finished their baths in the public bathhouses, have a
relatively higher metabolic rate compared to their physical activity when they enter the
changing rooms which are being heated through floor heating, and the type of thermal
environment that is needed in the aspect of comfort has not been specifically
investigated under these special conditions.
This study investigated the conditions of the thermal environment for the changing
rooms in public bathhouses, and suggests the conditions of the physical thermal factor
in order to provide a pleasant thermal environment for the user.
2 Methods
In order to investigate the thermal environment conditions of the changing rooms while
the floor is being heated, we measured the physical factors of a male changing room in
a public bathhouse located in Cheonan-city for the calculation of PMV. However,
because there is no clear standard for the metabolic rate (MET) of a body after a bath
Advanced Science and Technology Letters Vol.140 (GST 2016), pp.236-239
http://dx.doi.org/10.14257/astl.2016.140.45
ISSN: 2287-1233 ASTL Copyright © 2016 SERSC
(sauna), we estimated the PMV value and used a method to inversely estimate the MET
which satisfies the PMV value. In other words, we analogized the PMV value through
the results of a survey done on 12 subjects about thermal sensation, and by putting in
the physical factors and CLO (index of the clothing insulation) through measurements,
we deducted the MET value, which would result in the estimated PMV value. Table 1
shows the measurement categories and Fig.1 shows the floor plan of the place used for
the study.
Table 1. Measurement Categories and the Measuring Instruments
Category Measurable Range Accuracy Model Name (Manufacturer)
Dry bulb temp. 0~50℃ ±0.6℃ SK-150GT
(SATO) Relative humidity 10~95% ±3%
Black bulb globe temp. 0~80℃ ±2℃
Air velocity 0~10m/s ±0.03m/s testo 480 (TESTO)
Surface temp. -30~300℃ ±2℃ testo 810 (TESTO)
Fig. 1. Floor plan of the place used for investigation
1) Measuring the Thermal Environment
In order to evaluate the thermal environment during the period of heating we took the
measurements on November 19, 2015, where every 10 minutes for an hour at a point
1.2 meters above the floor in the middle of the bathhouse changing room, the dry bulb
temperature, black bulb globe temperature, relative humidity, and air velocity was
measured and the average value was obtained. In addition, the CLO needed to calculate
the PMV was applied as 0, and using the following function, the black bulb globe
temperature was converted to the MRT(Mean Radiant Temperature).
MRT = 𝑇𝑔 + 2.35√𝑣(𝑇𝑔 − 𝑇𝑑) [℃] (1)
Where, 𝑇𝑔 : black bulb globe temperature [℃] , 𝑇𝑑 : dry bulb temperature [℃], 𝑣 : air
velocity [m/s]
Advanced Science and Technology Letters Vol.140 (GST 2016)
Copyright © 2016 SERSC 237
2) Questionnaire
We conducted a survey as seen in Fig. 2, on twelve male users who entered the changing
room after a bath, asking them to tell us their current thermal sensations by choosing
one scale from the 7 steps scale.
Fig. 2. Survey Questions about Thermal Sensation
3 Results
1) Estimating the MET for those who have just took a bath.
The results of the measurements for the physical factors of the changing room were as
follows: the average of the dry bulb temperature was 26.1℃, the black bulb globe
temperature 27.3℃, the relative humidity 25.8%, the air velocity 0.4 m/s, and through
the conversion formula the MRT was calculated to be 29.1℃. Also, the average floor
surface temperature was 36.4℃.
Table 2 shows the results of the questionnaire, and by calculating the arithmetical
mean, the PMV of the changing room was estimated at 0.65.
Therefore, with the measured physical factors and CLO=0, we calculated the MET
that would be needed, in order to draw out PMV=0.67, and the value obtained was
2.35[met].
Table 2. Questionnaire Results
Subject no. 1 2 3 4 5 6 7 8 9 10 11 12
Thermal Scale -1 0 0 0 0 1 1 1 1 1 2 2
2) Examination of the Optimum Thermal Environment of the Changing Room
A changing room is an area where those who come to take a bath and those who have
just finished their bath coexist. For the CLO and MET according to the user's condition,
the following two conditions were estimated to examine the MRT and floor surface
temperature needed in order to develop a pleasant PMV condition.
Advanced Science and Technology Letters Vol.140 (GST 2016)
238 Copyright © 2016 SERSC
Table 3. CLO and MET Conditions
Case No. User's Condition CLO MET
Case 1 Before the Bath 0 1.6 (standing, light work)
Case 2 After the Bath 0 2.35 (after bath, sauna)
In order for the measured physical factors and the results by applying CLO and MET
in table 3, to be within the thermal comfort PMV range -0.5~+0.5 by the ISO 7730, the
MRT was calculated, and in Case 1 it was 29.6℃ (PMV= -0.484) and in Case 2 it was
27.8℃ (PMV=+0.500). Here, the wall and ceiling surface temperature was estimated
to be the same as the air temperature of the middle of the room, and by using the
following formula, the floor surface temperature (𝑇𝑓𝑙𝑜𝑜𝑟) which could satisfy the MRT
value in Cases 1 and 2 was calculated.
𝑀𝑅𝑇 =𝑇𝑤𝑎𝑙𝑙×𝐴𝑤𝑎𝑙𝑙+ 𝑇𝑐𝑒𝑖𝑙𝑖𝑛𝑔×𝐴𝑐𝑒𝑖𝑙𝑖𝑛𝑔+ 𝑇𝑓𝑙𝑜𝑜𝑟×𝐴𝑓𝑙𝑜𝑜𝑟
𝐴𝑤𝑎𝑙𝑙+ 𝐴𝑐𝑒𝑖𝑙𝑖𝑛𝑔+ 𝐴𝑓𝑙𝑜𝑜𝑟 [℃] (2)
Where, 𝑇𝑤𝑎𝑙𝑙, 𝑇𝑐𝑒𝑖𝑙𝑖𝑛𝑔, 𝑇𝑓𝑙𝑜𝑜𝑟 : wall, ceiling, floor surface temperature, respectively
[℃] ,
𝐴𝑤𝑎𝑙𝑙 , 𝐴𝑐𝑒𝑖𝑙𝑖𝑛𝑔, 𝐴𝑓𝑙𝑜𝑜𝑟 : wall, ceiling, floor area, respectively [㎡]
Calculations showed that in Case 1, the floor surface temperature was 35.7℃ and in
Case 2 it was 30.8℃. Though it is hard to satisfy users both before and after a bath, we
determined that maintaining the floor surface temperature within the range of about
31~35℃, would generally enhance thermal comfort.
Acknowledgments. Funding for this paper was provided by Namseoul university.
References
1. ISO 7730-2005, Ergonomics of the thermal environment - Analytical determination and
interpretation of thermal comfort using calculation of the PMV and PPD indices and local
thermal comfort criteria (2005)
2. ANSI/ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy,
(1992)
3. Calucation of Predicted mean Vote and Predicted Percentage Dissatisfied,
4. http://www.eat.lth.se/fileadmin/eat/Termisk_miljoe/PMV-PPD.html
Advanced Science and Technology Letters Vol.140 (GST 2016)
Copyright © 2016 SERSC 239