Scholarly article on topic 'Influence of Natural Ventilation on Thermal Comfort in Semi-open Building under Early Summer Climate in the Area of Tropical Island'

Influence of Natural Ventilation on Thermal Comfort in Semi-open Building under Early Summer Climate in the Area of Tropical Island Academic research paper on "Earth and related environmental sciences"

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Procedia Engineering
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{"Thermal comfort" / "Natural ventilation" / "Field studies" / "Tropical Island"}

Abstract of research paper on Earth and related environmental sciences, author of scientific article — Shilei Lu, Kun Fang, Yunfang Qi, Shasha Wei

Abstract In this paper, The research was based on the thermal comfort questionnaires of people and the thermal comfort parameters test of the environment in semi-open lobby of ten starred hotels in Sanya. Through analyzing the thermal comfort questionnaire, the highest acceptable thermal comfort temperature in summer was 30.6°C in the semi-open space with natural ventilation. It is not scientific to just use thermal sensation to judge the thermal comfort of human body, so thermal satisfaction, thermal preference and thermal comfort all should be considered in the human body thermal comfort evaluation.

Academic research paper on topic "Influence of Natural Ventilation on Thermal Comfort in Semi-open Building under Early Summer Climate in the Area of Tropical Island"

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Procedía Engineering 121 (2015) 944 - 951

Procedía Engineering

www.elsevier.com/locate/procedia

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

Influence of Natural Ventilation on Thermal Comfort in Semi-open Building under Early Summer Climate in the Area of Tropical

Island

Shilei Lu a*, Kun Fanga, Yunfang Qia, Shasha Weia

aSchool of Environmental Science and Technology, Tianjin University, Tianjin 300072, China

Abstract

In this paper, The research was based on the thermal comfort questionnaires of people and the thermal comfort parameters test of the environment in semi-open lobby of ten starred hotels in Sanya. Through analyzing the thermal comfort questionnaire, the highest acceptable thermal comfort temperature in summer was 30.6°C in the semi-open space with natural ventilation. It is not scientific to just use thermal sensation to judge the thermal comfort of human body, so thermal satisfaction, thermal preference and thermal comfort all should be considered in the human body thermal comfort evaluation.

© 2015TheAuthors. PublishedbyElsevierLtd.Thisis 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, Natural ventilation, Field studies, Tropical Island

1. Introduction

In recent years, scholars around the world do a lot of research work for thermal comfort of natural ventilation. According to their research the acceptable temperature range in natural ventilation buildings is broader than that in air conditioning buildings [1,2,3] , which has to do with that people is a positive adaptation to environment[4]. China begins the study about human thermal comfort in natural ventilation environment around the year 2000 [4,5,6,7,8,9] Yet, at present, China had no specific research on thermal comfort under natural ventilation conditions in tropical island regions building.

* Corresponding author. Tel.: +86 22 27402177; fax: +86 22 27402177. E-mail address: lvshilei@tju.edu.cn

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 .2015.09.060

2. Methods

2.1. Subjects

In this field investigation, investigators used random sampling method and obtained 402 questionnaires. The background information of subjects is shown in table 1.

Table 1. The background information of subjects

Different gender Different living place Total

male female local resident tourist

Age(years) 32.60 30.30 28.24 32.80 31.50

Height(cm) 171.90 164.49 167.90 168.52 168.34

Weight(kg) 71.01 52.92 62.50 62.25 62.32

Number 209 193 115 287 402

2.2. Objective test data

In this field survey, four indoor thermal environment parameters were mainly tested and recorded. The test instrument is Richter. Technical parameters of Richter are shown in table 2. Besides, three outdoor environment parameters were mainly tested by portable climatic station H21-002. Outdoor meteorological parameters can be monitored continuously for 24 hours and recorded automatically with 1 minute interval.

Table 2. Technical parameters of Richter thermal comfort test system test probe

Sensors Measurement range Accuracy Response time

Black ball temperature sensors -20~60°C ±0.5°C (5~45°C) , ±1°C(<5°C, >45°C) 30s

Dry and wet bulb temperature sensor -20~60°C, 0~100% ±0.5°C (5~45°C) , ±1°C(<5°C, >45°C), (°C): 30s (RH%): 8s

±2% (10-90RH%, 25°C) 0-0.5m/s, ±5cm;

Air speed sensor 0.01-20m/s 0.5-1.5m/s, ±10cm; >1.5m/s, 4%

2.3. Subjects questionnaire

Subjective questionnaire survey is an essential part of the field thermal comfort studies and carried out simultaneously during thermal environment tests. The main contents of this survey are: Background information, Clothing and activity, Thermal comfort field survey

3. Results and discussion

3.1. The characteristic of environment

During the investigation period, the outdoor mean temperature ranges from 24.51 °C to 34.52 °C and mean relative humidity ranges between 59.9% and 94.8% the outdoor wind speed ranges from 0 to 2.52 m/s. Table 3 presents the statistical results of the thermal environment parameters measured in the lobby during the survey and environmental

testing. Fig. 1 present the frequencies of the thermal environment parameters measured in natural ventilation environment.

Table3 Statistical summary of indoor climatic

Minimum

Maximum

Average

standard deviation

Air temperature(°C) 26.07 34.23 29.95 1.23

Relative humidity (%) 61.07 87.20 78.85 4.51

Black ball temperature (°C) 26.91 34.68 30.59 1.14

Wind speed(m/s) 0 3.90 1.38 0.85

Fig. 1. The frequency distribution of each thermal environment parameter

3.2. Thermal sensation, humidity sensation, air movement sensation

From Fig. 2 we can know that most people feel moderate and hot. It can be concluded that there are great individual differences of human thermal sensation on the environment under the condition of high temperature in summer. Fig. 3 shows that during test, the majority of humid sensation is neutral and slightly humid. we can know that due to individual differences in high humidity environment people exist differences on humid feeling.

Fig. 2. Thermal sensation frequency distribution and distribution boxplot

Humidity sensation Fig. 3. Humid sensation frequency distribution and distribution boxplot

Fig. 4. Air movement sensation frequency distribution and distribution boxplot

From Fig.4 We find that the wind speed range concentrates from 1.19 m/s to 2.32m/s when people vote all right (0), illustrating the wind speed is at least 1.19m/s when most people are satisfied with the wind speed.

Through analyzing the voting result in Fig. 5. In this survey, 76% of the subjects were considered to be thermal acceptable. Meanwhile, there are 50.5% of the subjects who vote comfortable (0) that are considered to feel comfortable with the thermal conditions. To our surprise, although most people are satisfied or feel comfortable with the thermal conditions, there are still 76% of the subjects preferring a cooler environment.

-4 -3 -2 -1 o Thermal satisfaction

Thermal preference

-4 -3 -2 -1 0 Thermal comfort

Fig. 5. The satisfaction frequency distribution of thermal satisfaction, thermal preference and thermal comfort

3.3. Subjective thermal reflection cross analysis

From the Fig.6, we can visually see the thermal comfort distribution under different thermal sensation. The analysis results show that some people voting +2 or +3 still feel comfortable. This indicates that thermal sensation fails to evaluate thermal environment under natural ventilation condition.

From the Fig.7 can see that only 41.38% of the subjects are satisfied and 54.19% feel acceptable in the vote of "comfortable"; in the vote of "slightly uncomfortable", there are still 4.14% of the subjects being satisfied and 64.14% feeling acceptable.

v ! .1 Intolerable I I Very uncomfortable [N>N Uncomfortable Y//Á Slightly uncomfortable I I Comfortable

I III Very dissatisfied 1 J Dissatisfied '..'.; Slightly dissatisfied IAcceptable I 1 Satisfied_

Thermal sensation

Thermal comfort

Fig. 6. Cross analysis between thermal sensation and thermal comfort Fig. 7. Cross analysis between thermal comfort and thermal satisfaction

From the Fig. 8, we can see while subjects vote comfortable (0) there are only 41.38% prefer no change; although people vote slightly comfortable (-1) and uncomfortable (-2), there are still some subjects who prefer on change.

rTT~1 Very dissatisfied VZA Dissatisfied

Thermal comfort Thermal P'etoence

Fig. 8. Cross analysis between thermal comfort and thermal preference Fig 9 Cross analysis between thermal preference and thermal satisfaction

In Fig. 9 in the vote of "no change", 49.45% of the subjects are satisfied and 47.25% feel acceptable, while there are still few feel slightly dissatisfied or dissatisfied. Meanwhile, although people prefer a cooler or warm environment, some still feel satisfied or acceptable.

3.4. Acceptable thermal comfort temperature

From subjective thermal reflection cross analysis, we can see that we should synthetically consider the three vote values when we conduct the thermal comfort evaluation. After accumulating the three vote values, we can get a cumulative value in the range between -9 to 1. Table 4 shows the cumulative value result of the comprehensive thermal comfort vote and presents the different conditions of thermal satisfaction, thermal preference and thermal comfort under different cumulative values.

Table 4. Comprehensive thermal comfort vote

Comprehensive thermal comfort voteValue result

Very comfortable 1 0 satisfied-> warmer comfortable satisfied-> no change-> comfortable

Comfortable -1 satisfied-> cooler comfortable & acceptable-> no change-> comfortable

-2 acceptable-> cooler comfortable & acceptable-> no change-> slightly uncomfortable

Acceptable -3 acceptable-> cooler slightly uncomfortable

-4 slightly dissatisfiedcooler slightly uncomfortable

Uncomfortable -5 -6 slightly dissatisfiedcooler uncomfortable & dissatisfied-> cooler slightly uncomfortable dissatisfiedcooler uncomfortable & slightly dissatisfied-> cooler very uncomfortable

-7 very dissatisfiedcooler uncomfortable

Very uncomfortable -8 very dissatisfiedcooler very uncomfortable

-9 very dissatisfiedcooler intolerable

The air temperature considering wind speed compensation (Ta-Tv) is arranged from low to high with 0.5°C as a group, calculating the average comprehensive thermal comfort vote value of each group. The fitting result is shown in fig. 10. The correlation coefficient R is 0.897. The thermal comfort temperature is 25.0°C, the upper limit of acceptable thermal comfort temperature is 30.6°C.

Fig. 10. Linear fit between comprehensive thermal comfort vote and Ta-Tv

4. Conclusions

In this paper, researchers issue questionnaires to 402 persons and test the thermal comfort parameters test of the environment in semi-open lobby of ten starred hotels in Sanya. Through the analysis of the questionnaire, there are great individual differences between people on human thermal sensation and humidity sensation in high thermal and humid natural ventilation environment. For air movement sensation, the wind speed is at least 1.19m/s when most people are satisfied with the wind speed .Through the cross analysis we think thermal satisfaction, thermal preference and thermal comfort should all be used to evaluate thermal comfort of human body, what's more, the upper limit of acceptable thermal comfort temperature is 30.6°C in natural ventilation environment.

Acknowledgements

The authors would like to acknowledge the Department of Housing and Urban-Rural Development of Hainan in contacting sampled buildings and providing valuable comments for this research. This research has received support from the National Twelfth Five-Year Technology Support Program (2011BAJ01B05).

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