Subjective evaluation of thermal comfort of tropically acclimatized subjects in air conditioned,naturally ventilated and radiant cooling environments

Abstract

The thermal sensation of people is subjective. It depends on the external climatic condition and thermal history of a person. Thermal comfort standards suggest a narrow temperature range to assert an environment as comfortable or otherwise.

It is important to evaluate people’s thermal perception in different climatic regions and set comfort limits based on their thermal perception. This study evaluates the thermal perception of subjects in hot and humid climatic regions at higher indoor temperatures and air velocities. Three different thermal environments chosen for the study are air conditioned (AC), naturally ventilated (NV), and radiant cooling (RC) thermal environments. The study shows that more than 80% of subjects voted as comfortable in AC and RC thermal environments for the measured T_op and v_a range of 25.3 – 28.4℃/0.1 – 0.3m/s and 25.9 – 29.1℃/0.1 – 0.9m/s respectively.

The findings gathered from the study in NV environment indicate that 68% of subjects opt for the use of table fans over ceiling fans. The subjects' free control of air movement improves their thermal sensation over no control of air movement, indicating that they prefer table fans and free control of air movement. In AC, NV, and RC thermal environments, humidity and air quality remain uncontrolled. In AC and RC thermal environments, less than 20% of subjects voted unacceptable for the humidity sensation and Perceived air quality (PAQ) scales in nearly all the studied experimental conditions. In NV thermal environment, the percentage of subjects voting dissatisfied on the humidity sensation scale and PAQ scale is 30-52% and 26-37%, respectively. This outcome shows that a thermally comfortable environment with air movement improves subjects' humidity sensation and PAQ even when humidity and air quality are unaltered. The study points out that air velocity played a vital role in influencing the thermal sensation, humidity sensation and perceived air quality of subjects in the three studied thermal environments. Further the study shows that with free control of air movement will significantly aid in rising the comfort temperature band of tropically acclimatized subjects.

Practical application

The study shows the variation in limits of thermal comfort indices such as operative temperature and air velocity for tropically acclimatized subjects in three thermal environments. The same group of subjects participated in the subject study conducted in air conditioned, naturally ventilated and radiant cooling thermal environments. The outcomes indicate that subjects are comfortable at higher indoor temperature and air velocity. Further the outcomes showed that the humidity and air quality sensation of subjects is influenced by the subjects’ thermal sensation and air velocity.

Keywords

Air conditioned naturally ventilated radiant cooling thermal comfort subject study ceiling fan table fan hot and humid climatic condition

Get full access to this article

View all access options for this article.

References

Frontczak

Wargocki

. Literature survey on how different factors influence human comfort in indoor environments. Build Environ 2011; 46(4): 922–937.

Roelofsen

. The impact of office environments on employee performance: the design of the workplace as a strategy for productivity enhancement. J Facil Manag 2002; 1(3): 247–264.

Humphreys

Fergus Nicol

. The validity of ISO PMV for predicting comfort votes in every day thermal environments. Energy Build 2002; 34: 667–684.

de Dear

Brager

. Developing an adaptive model of thermal comfort and preference. Build Eng 1998; 104(1): 1–18.

Hwang

Cheng

Lin

, et al. Thermal perceptions, general adaptation methods and occupant’s idea about the trade-off between thermal comfort and energy saving in hot-humid regions. Build Environ 2009; 44(6): 1128–1134.

Gagge

Fobelets

Berglund

. A standard predictive Index of human response to thermal environment. Build Eng 1986; 92(2B): 709–731.

Indraganti

Ooka

Rijal

. Field investigation of comfort temperature in Indian office buildings: a case of Chennai and Hyderabad. Build Environ 2013; 65: 195–214.

Hoyt

Arens

Zhang

. Extending air temperature set points: Simulated energy savings and design considerations for new and retrofit buildings. Build Environ 2015; 88: 89–96.

Rupp

Kim

de Dear

, et al. Associations of occupant demographics, thermal history and obesity variables with their thermal comfort in air-conditioned and mixed-mode ventilation office buildings. Build Environ 2018; 135: 1–9.

10.

Singh

Mahapatra

Atreya

. Adaptive thermal comfort model for different climatic zones of North-East India. Appl Energy 2011; 88(7): 2420–2428.

11.

Golja

Tipton

Mekjavic

. Cutaneous thermal thresholds - the reproducibility of their measurements and the effect of gender. J Therm Biol 2003; 28(4): 341–346.

12.

Nakano

Tanabe

Kimura

. Differences in perception of indoor environment between Japanese and non-Japanese workers. Energy Build 2002; 34(6): 615–621.

13.

Rijal

Humphreys

Nicol

. Adaptive thermal comfort in Japanese houses during the summer season: behavioral adaptation and the effect of humidity. Buildings 2015; 5(3): 1037–1054.

14.

Pang

, et al. Field study of thermal comfort in non-air-conditioned buildings in a tropical island climate. Appl Ergon 2018; 66: 89–97.

15.

Nicol

Raja

Allaudin

, et al. Climatic variations in comfortable temperatures: the Pakistan projects. Energy Build 1999; 30: 261–279.

16.

Mishra

Ramgopal

. Thermal comfort in undergraduate laboratories - a field study in Kharagpur, India. Build Environ 2014; 71: 223–232.

17.

Mishra

Ramgopal

. Thermal comfort field study in undergraduate laboratories - an analysis of occupant perceptions. Build Environ 2014; 76: 62–72.

18.

Singh

Kumar

Ooka

, et al. Status of thermal comfort in naturally ventilated classrooms during the summer season in the composite climate of India. Build Environ 2018; 128: 287–304.

19.

Kumar

Singh

Loftness

, et al. Thermal comfort assessment and characteristics of occupant’s behaviour in naturally ventilated buildings in composite climate of India. Energy for Sustainable Development 2016; 33: 108–121.

20.

Candido

de Dear

Lamberts

. Combined thermal acceptability and air movement assessments in a hot humid climate. Build Environ 2011; 46(2): 379–385.

21.

Zhai

Zhang

, et al. Human comfort and perceived air quality in warm and humid environments with ceiling fans. Build Environ 2015; 90: 178–185.

22.

Pang

, et al. Field study of thermal comfort in non-air-conditioned buildings in a tropical island climate. Appl Ergon 2018; 66: 89–97.

23.

Zhai

Zhang

, et al. Comfort under personally controlled air movement in warm and humid environments. Build Environ 2013; 65: 109–117.

24.

Indraganti

Rao

. Effect of age, gender, economic group and tenure on thermal comfort: a field study in residential buildings in hot and dry climate with seasonal variations. Energy Build 2010; 42(3): 273–281.

25.

Kumar

Mathur

, et al. An adaptive approach to define thermal comfort zones on psychrometric chart for naturally ventilated buildings in composite climate of India. Build Environ 2016; 109: 135–153.

26.

Indraganti

. Behavioural adaptation and the use of environmental controls in summer for thermal comfort in apartments in India. Energy Build 2010; 42(7): 1019–1025.

27.

Schiavon

Melikov

. Energy saving and improved comfort by increased air movement. Energy Build 2008; 40: 1954–1960.

28.

Alterman

Page

Moghtaderi

. The significance of the adaptive thermal comfort limits on the air-conditioning loads in a temperate climate. Sustainability 2019; 11: 6–16.

29.

Yau

Chang

. Performance analysis on an air-conditioning system installed with and without a fuzzy logic thermostat in an office building. Proc Inst Mech Eng A J Power Energy 2018; 232(8): 1079–1092.

30.

Mapsofindia . Custom mapping/GIS services, 2022. https://www.mapsofindia.com/geography/koppen-climate-classification.html

31.

Fang

Liu

, et al. Experimental investigation on thermal comfort model between local thermal sensation and overall thermal sensation. Energy Build 2018; 158: 1286–1295.

32.

Vellei

Herrera

Fosas

, et al. The influence of relative humidity on adaptive thermal comfort. Build Environ 2017; 124: 171–185.

33.

Mishra

Ramgopal

. A thermal comfort field study of naturally ventilated classrooms in Kharagpur, India. Build Environ 2015; 92: 396–406.

34.

, et al. The influence of personally controlled desk fan on comfort and energy consumption in hot and humid environments. Build Environ 2017; 123: 378–389.