Scholarly article on topic 'Thermal Comfort during Summer in a High-speed Railway Station in Cold Region of China'

Thermal Comfort during Summer in a High-speed Railway Station in Cold Region of China Academic research paper on "Earth and related environmental sciences"

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Procedia Engineering
Keywords
{"Thermal comfort" / "railway station" / PMV / "Thermal Sensation Vote ;"}

Abstract of research paper on Earth and related environmental sciences, author of scientific article — Gang Liu, Chenyi Lin, Yanbin Zhuo, Deheng Guo, Rui Dang

Abstract This study explores the interaction between perceived and calculated thermal comfort in high-speed railway station in Cold Region of China. To achieve this, a questionnaire survey in two typical high-speed railway stations in Cold Region of China was conducted in conjunction with physical measurements. The study results reveal that there is a relatively large difference between perceived thermal sensations and calculated predicted mean vote (PMV) from the measurements for the majority of the waiting hall of high-speed railway station. This finding implies that the calculation of PMV is not suitable for the situation in air conditioned waiting hall of high-speed railway stations. The results also show that the length of time a respondent staying in the waiting hall also have effect on the rule of the thermal comfort.

Academic research paper on topic "Thermal Comfort during Summer in a High-speed Railway Station in Cold Region of China"

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Procedía Engineering 121 (2015) 838 - 844

Procedía Engineering

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9th International Symposium on Heating, Ventilation and Air Conditioning (ISHVAC) and the 3rd International Conference on Building Energy and Environment (COBEE)

Thermal Comfort during Summer in a High-speed Railway Station

in Cold Region of China

Gang Liu1, Chenyi Lin1, Yanbin Zhuo1, Deheng Guo1, Rui Dang1*

1TianjinUniversity, No.72 Weijin RoadNankai Tianjin, China

Abstract

This study explores the interaction between perceived and calculated thermal comfort in high-speed railway station in Cold Region of China. To achieve this, a questionnaire survey in two typical high-speed railway stations in Cold Region of China was conducted in conjunction with physical measurements. The study results reveal that there is a relatively large difference between perceived thermal sensations and calculated predicted mean vote (PMV) from the measurements for the majority of the waiting hall of highspeed railway station. This finding implies that the calculation of PMV is not suitable for the situation in air conditioned waiting hall of high-speed railway stations. The results also show that the length of time a respondent staying in the waiting hall also have effect on the rule of the thermal comfort.

© 2015 TheAuthors.PublishedbyElsevierLtd.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of ISHVAC-COBEE 2015 Keywords:Thermal comfort; railway station; PMV; Thermal Sensation Vote;

1. Introduction

In China, studies about building thermal and humid environment as well as human thermal comfort have been carried out widely. However, most of them are about residential building and office building. The research about large public building especially about train station is limited.

Usually, the high-speed railway stations in China have large space and open halls. Compared with other type of traditional buildings, high-speed railway stations have massive human traffic, and also people stay in the buildings for

* Corresponding author. Tel.: +8613682009163; E-mail address:dr_tju@ 163.com

1877-7058 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of ISHVAC-COBEE 2015 doi: 10. 1016/j .proeng .2015.09.038

shorter time. Thus, thermal comfort studies about simple civil buildings are no longer applicable for high-speed railway stations.

Thermal design regions for civil buildings in China are composed by five regions, namely, Cold Region, Very Cold Region, Hot Summer & Cold Winter Region, Hot Summer & Warm Winter Region and Mild Region (As Fig. 1). This article is based on research in the Cold Region, where the design outdoor dry bulb temperature in summer is 34.2°C, and the design outdoor relative humidity in summer is 63%.

Fig. 1. Thermal design regions for civil buildings in China (The picture drawn by author).

Thermal comfort aspects during summer time in cold Region of China are often overlooked; few researches have been done in this field. But in fact, the outdoor temperatures in summer in Cold Region are often more than 35°C, creating a comfortable indoor thermal environment in Cold Region is necessary as well as other regions.

This paper focuses on the 2 typical high-speed railway stations in Cold Region of China. Data collected about the passengers' thermal preferences was supplemented by measurements of the railway stations' internal conditions and the external climate to explore the thermal adaptive strategies employed by the passengers.

2. Methods

2.1. Data collection

• Background information questionnaire

In order to conducting the thermal comfort survey, back ground information about the respondents was obtained through interviews using a standardized survey form. Information was collected about the passengers' age, gender, highest education level and occupation. During this interview, the respondents were also asked about when they arrived at the waiting hall and how long have they been in the waiting hall.

• Evaluation of the thermal environment

During the monitoring period, the adult passengers were asked to respond to a comfort survey on a regular basis. The survey questions asked their thermal sensation, preference, and clothing in the"right here and right now" mode. The main questions were: (1) How long have you been in the railway station? (2) How do you feel right here and right now (from hot to cold, ASHRAE 7-point scale), (3) would you prefer to be warmer, cooler or no change (3-point preference scale), (4) Describe your activities within 20min and (5) Describe your clothing (choose the cloths exactly what they were wearing).

2.2. Correlating thermal environmental data with thermal comfort survey

Correlating thermal environmental data was collected during the survey, including the mean radiation temperature, air temperature, humidity and air velocity. There were 8 measuring points set in the waiting hall .The indoor temperature and humidity were recorded by HOBO automatic observer, the mean radiation temperature was recorded by black-bulb thermometer, and the air velocity was measured by hot-wire anemometer.

2.3. Data analysis

• PMV and PPD

By Fanger's (1970) PMV heat-balance index, PMV is calculated from six variables-- indoor dry-bulb temperature, black globe temperature, air velocity, clothing insulation, metabolic rate—using the ASHRAE Thermal Comfort Tool software (Fountain and Huizenga 1996).

PPD is predicted percentage of dissatisfied, which is related to the PMV as defined in Formula (1).

• Thermal sensation votes

Thermal sensation votes (TSV) range from hot (+3) to cold (-3), as ASHRAE 7-point scale.

• Operative temperature

According to ASHRAE Standard 55-2010, in most practical cases where the relative air speed is small (<0.2 m/s, 40 fpm) or where the difference between mean radiant and air temperature is small (<4°C, 7°F), the operative temperature can be calculated with sufficient approximation as the mean value of air temperature and mean radiant temperature.

• Thermal neutrality

According to de Dear, Richard's article, statistical analysis of subjective thermal sensation votes within each building were used to define thermal neutrality—the operative temperature found to correspond most closely with the scale's central vote of neutral. Neutrality was calculated for each building in the meta-analysis by the following steps:

1. Bin the building's indoor operative temperature observations into half-degree (°C) increments, and analyze the bins' mean thermal sensation responses.

2. Fit a weighted linear regression model between sensations and operative temperature (to): mean thermal sensation = a + b * (to)

3. Neutrality was derived by solving each building's regression model for a mean sensation of zero.

PPD = 100 - 95 x exp (-0.03353 x PMV4 - 0.2179 x PMV2)

3. Results and discussion

A total of 803 responses to the thermal comfort survey were collected during this period, 534 of these were male people with the rest are female. The results are as following.

3.1. Thermal sensation vote

The responses to the thermal comfort survey were given when the indoor temperature was between 23.1 and 26.8°C. The thermal sensations votes (TSV) during this period varied from 'Cold' (-3) to 'hot' (+3). The number of the TSV is presented in Fig. 2. The highest number of the responses was the 'neutral' votes (almost 600) followed by votes of 'slightly cool' (106).

700 600 500 400 300 200 100 0

_ ■ ■ - _

Cold (-3) Cool (-2) Slightly cool (-1) Neutral (0) Slightly warm (1) Warm (2) Hot (3)

TSV 8 24 106 599 40 19 7

Fig. 2. The number of the TSV.

3.2. Staying time

Most of the passengers arrived at the waiting hall more than 15minutes before departure time. The number of the TSV is presented in Fig.3. The highest number of the responses was 'less than 30 and more than 15min' (280) followed by votes of 'less than 60 and more than 45min' (121). The average staying time of the passengers is 37.8 minutes.

300 250 200 150 100 50 0

less than 15 min 15~30 30~45 45~60 60~120 more than 120 min

■ Sojourn time 208 280 41 121 86 48

Fig. 3. The number of staying time.

3.3. Mean thermal sensation vote and PMV

Fig. 4 shows the mean thermal sensation votes (mTSV) and mean PMV (mPMV) in waiting hall of high-speed railway station against operative temperatures. The results show a high correlation between operative temperatures and mTSV (R2=0.78).Ideal neutral temperature is calculated to be 27.314°C, while the real neutral temperature is 25.884°C.

Fig. 4. Liner Regression of mPMV and mTSV.

3.4. Thermal comfort and staying time

Separate the respondents in to two groups: stayed in the waiting room less than 30 minutes and more than 30 minutes (including equal to 30 minutes). Calculate the neutral temperature of the two groups of data, and compare with PMV model. The result of statistics and analysis are as Table 1.

Fig.5 and Fig.6 show the liner regression of mTSV and mPMV in waiting hall of high-speed railway station against operative temperatures of the two groups of people mentioned above.

Table 1. Analysis of different staying time.

Percentage Mean TSV Ideal Neutral Temperature, °C Real Neutral Temperature, °C

<30min 40% -0.109 27.42 25.91

^30min 60% -0.244 26.10 27.36

y = 0.2523x -6.5847 R2 = 0.7473 • ...... y = 0.415x -11.354

> R2 = 0.9246 £2 23.00 23.50 24.00 24.50 25.00 25.50 26.00 26.50 27.00

E -0.50

mTSV mPMV

Mean Operative Temperature, °C

Fig. 5. Liner Regression of mPMV and mTSV for passengers who stay less than 30min.

0.50 y = 0.1489x -3.858 R2 = 0.6464

0.00 23.00 y = 0.3951x -10.835

> CO 23.50 25.00 25.50 26.00 26.50 R2 = 0.8161 27.00

H E o3 --> -0.50 • .............. ......... • mTSV

Q_ E -1.00 -1.50 -2.00 •......... *................... • • mPMV

Mean Operative Temperature, °C

Fig. 6. Liner Regression of mPMV and mTSV for passengers who stay more than or equal to 30min.

4. Conclusion

According to the research, the ideal neutral temperature in the high-way railway station is 27.3°C, while the vote neutral temperature is 25.9°C. Passengers in the waiting hall prefer lower temperature than it is predicted by the thermal comfort model of PMV.

The thermal comfort model for those who have being stayed in the waiting hall larger than or equals to 30 minutes more close to Fanger's PMV thermal comfort model, which proves that PMV is relatively suitable to predict human body thermal comfort under stable environment. However, it still is not appropriate for the waiting hall of high-speed railway stations.

The study shows the people who stay in waiting hall less than 30 minutes have better capacity to withstand the different environment. This provides good evidence for finding out the potential ability to reduce the energy consumption of high-speed railway station.

5. ACKNOWLEDGEMENTS

The research presented in this paper was financially supported by (1) the National Natural Science Foundation of China (the Key Program) through grant No. 51338006; (2) the Programme of Introducing Talents of Discipline to Universities through grant No. B13011. The authors would like to thank Prof. Lihui Cao at Tianjin Chengjian University and all the railway stuffs and passengers for supporting this investigation.

6. Reference

[1] ASHRAE, Standard 55-2010, Thermal Environmental Conditions for Human Occupancy. Atlanta: American Society of Heating, Refrigerating, and Air-Conditioning Engineers, 2010.

[2] National Standard of the People's Republic of China, Thermal Design Code for Civil Building, GB50173-93, China Plan Press, 1993.

[3] National Standard of the People's Republic of China, Design Code For Heating Ventilation And Air Conditioning Of Civil Buildings, GB50736-2012, China Plan Press, 2012.

[4] De.D. Richard, G.S. Brager, Developing an adaptive model of thermal comfort and preference, Center for the Built Environment, 1998.