Subjective Thermal Comfort in the Environment with Spot Cooling System

Size: px

Start display at page:

Download "Subjective Thermal Comfort in the Environment with Spot Cooling System"

Marvin Summers
5 years ago
Views:

1 Subjective Thermal Comfort in the Environment with Spot ing System Hayato Ohashi 1, Hitomi Tsutsumi 1, Shin-ichi Tanabe 1, Ken-ichi Kimura 1, Hideaki Murakami 2, Koji Kiyohara 3 1 Department of Architecture, Waseda University, Japan 2 Kyushu Electric Power Co.,Inc., Japan 3 Kyudenko Co.,Inc., Japan Corresponding ohashi@tanabe.arch.waseda.ac.jp SUMMARY Subjective experiments were conducted in a climate chamber to evaluate subjective thermal comfort in the environment with spot cooling system, simulating a big factory. Five conditions combined supply air temperature and air volume were set for the first test. The condition without spot cooling system was also examined. Two types of s were developed in the second test. Seven males were exposed for 90 minute under the conditions with and without spot cooling. Subjective metabolic rate were assumed to be 1.8 met. Subjects voted their thermal sensation, air velocity sensation, comfort sensation in the experiments every 30 minute. Thermogram showed that spot cooling system without s cooled down only upper body of subjects, where they felt the draght. On the other hand, it was possible to cool down their whole body using the. Subjects preferred the condition with the, where they felt thermally neutral. INTRODUCTION In large space such as a factory, it is not feasible to control the air in the entire space with HVAC system without huge energy consumption. The air-conditioning in large space usually targets only the occupied zone. It is important that the occupied zone air-conditioning satisfies a comfortable feeling of the human body, and decrease the air-conditioning load as much as possible. Spot cooling system used at the factory is one of the occupied zone air-conditioning, and have potential for energy conservation. The workers' physiological and subjective responses to such environments are different from those to typical uniform thermal environments, and are far less understood for Japanese. In this research, subjective experiments were conducted to evaluate thermal comfort of Japanese subjects in the environment with spot cooling system, simulating a big factory. Different combinations of the jet air temperature and volume, and the shape of s were examined. METHODS Experimental Design Two kinds of subjective experiments were conducted in a climate chamber to evaluate subjective comfort in the environment with spot cooling system in Supply air temperature, air volume and shape of were set for the purpose of evaluating the human comfort under the spot cooling. In the first test, supply air temperature and volume

2 from spot cooling system were controlled. The shape of s was varied in the second test. Seven college-aged males who were in good health were exposed to the experiments. All subjects were volunteers who were paid for participating in the experiment. Considering their circadian rhythms, all subjects took part in the experiments at the same time of day. Experimental Conditions Table 1 lists experimental conditions. In the first experiment, three supply air temperature, 19 C, 25 C and 31 C, with 400m 3 /h of supply air volume were set. The condition with small supply air of 200m 3 /h at 19 o C were also examined. Additionally, the condition without spot cooling system was also analyzed. In the second experiment, two types of s, type I and II, were developed. The condition without was compared with the condition with 2 types of. Supply air temperature and air volume was set at 19 o C and 400m 3 /h for all condition. Table 2 shows 3 kinds of s. For all conditions in both the first and second test, outlet of spot cooling system equipped 3.0 m above the floor. The spot cooling system had a nozzle with an outlet diameter of 0.2m. The temperature where is not influenced by spot cooling system (ambient temperature) were kept at 31 o C simulating a factory [1]. In the experiments, subjects wore hat, work wear (long sleeve), shirt, shoes, socks. Table 1. Experimental condition First experiment Condition Second experiment without I Supply air temperature [ C] Supply air volume [m 3 /h] Ambient temperature [ C] 31.0 Outlet altitude[m] 3m above floor Outlet diameter[mm] 200φ Diffuser Nozzle I Clothing hat, work wear (long sleeve), shirt, shoes, socks Table 2. Three kinds of s I Experimental Procedure Figure 1 illustrates the experimental procedure. Subjects were exposed for 90 minutes under the conditions with and without spot cooling. One test consisted of 3 sessions. During the 30-minute session, subjects performed walking up and down the steps [2] in the ambient area, light work which is putting machine screws in holes and clamping them with nuts in a standing position[3] with spot cooling for 20 minutes. Subjective metabolic rate was assumed to be 1.8 met [4]. Subjects rated at the beginning of

3 the exposure time and after each task during the session. In the second experiment, the different type of s was installed for each session. -30 Figure 1. Experimental procedure Session1 Session2 Session3 (1) (2) (3) (2) (3) (2) (3) Exposure time [90 min.] Measurement The effect of supply air condition and air flow pattern on human comfort was evaluated by the result of environmental measurements (the vertical air temperature distribution, the velocity distribution, vector diagram of the supply air velocity analyzed by PIV), physiological response (the skin temperature, relative humidity and air temperature in clothing, the thermogram), and the subjective psychological measurements. The thermogram is a image visualized the surface temperature of the object. In this experiment, the surface temperature distribution of the subject working under the spot cooling system was analyzed with thermogram. PIV (Particle Image Velocimetry) is a kind of the speed measurement method of the fluid such as water and air. In second experiment, the vector analysis on the air flow with was done by using PIV analysis software (DIPP-Flow) from the image taken with high speed camera. Subjects rated their thermal sensation, air velocity sensation, comfort sensation every 30 minute on the questionnaire as shown in Figure 2. The scales were given as visual analogue scales. Subjects were allowed to rate their sensation either just on the number or between the numbers on the scales. In the second experiment, subjects also evaluated effect of total comfort by difference of. [min.] (1) Change clothes, Questionnaires, Body temperature (2) Walking up and down the steps (3) Light work psychological amount vote Thermal sensation How do you judge the thermal environment? Thermal comfort sensation How do you feel the thermal environment? Cold Neutral Hot Very Air velocity sensation How do you judge the air velocity from the outlet? Comfort sensation to air velocity How do you feel the air velocity from the outlet? Not feel feel Feel Strongly feel Very Figure 2. A part of rating scales Statistical Analysis Data obtained in the experiments were analysed with Non-parametric statistical analysis method [5]. The Wilcoxon Matched-Pairs Signed Ranks test was administered between each condition. In the first experiment, supply air temperature effect was discussed in the pair-wise comparison between and. According to the comparison between,, and, supply air volume effect was reported. P-values presented in the figures indicate the level of significance.

RESULTS AND DISCUSSION The First Experiment Result Thermal Environment Vertical air temperature distribution: Vertical air temperature distribution in occupied zone was less than 3 C under the all

It was found that spot cooling system without s cooled down upper body of subjects such as the head, necks, and the backs.

Subjective vote: The general thermal sensation vote and general comfort sensation vote were displayed in Figure 4.

Among three conditions of 400m 3 /h of supply air volume, people rated significantly cooler at 19 o C and 25 o C than at 31 o C ().

Thermal sensation vote was highest () and most uncomfortable (4) under the condition without. Subjective comfort sensation was the greatest at.

4 RESULTS AND DISCUSSION The First Experiment Result Thermal Environment Vertical air temperature distribution: Vertical air temperature distribution in occupied zone was less than 3 C under the all conditions. Surface temperature: The surface temperature distribution recorded with thermogram is presented in Figure3. It was found that spot cooling system without s cooled down upper body of subjects such as the head, necks, and the backs. This tendency was remarkably observed under the condition at low supply air temperature or with large air volume. Subjective vote: The general thermal sensation vote and general comfort sensation vote were displayed in Figure 4. In two conditions of 19 o C in blow temperature, subjects reported significantly cooler at than at (), and more comfortable at (). Among three conditions of 400m 3 /h of supply air volume, people rated significantly cooler at 19 o C and 25 o C than at 31 o C (). Comfort sensation vote under the condition with 19 o C of jet air was significantly greater than with 31 o C (4). Thermal sensation vote was highest () and most uncomfortable (4) under the condition without. Subjective comfort sensation was the greatest at. It is found that subjective thermal sensation vote was scattered near slightly cool and subjects felt comfortable under the condition of low air temperature and large air volume. Figure3. Surface temperature of subject s body (First experiment) Cold Neutral Hot Very a) General thermal sensation vote b) Thermal comfort sensation vote Figure 4. Subjective thermal comfort Air Flow Subjective vote: The general air velocity sensation vote and comfort sensation vote to air velocity were shown in Figure 5. Pair-wise comparison between 2 conditions with 19 o C of supply air temperature, significantly greater air velocity sensation was observed in air (). Among three conditions of 400m 3 /h of supply air volume, subjects reported significantly higher general air velocity sensation at than at (2). There was no significant difference in the comfort sensation to air velocity between any pair of conditions with spot cooling system by the Wilcoxon Matched-Pairs Signed Ranks test. Subjects rated significantly more uncomfortable under the condition without spot cooling system than at, and (4), and tend to feel more uncomfortable

than at (6). It is found that the comfort sensation to air velocity was improved by setting up the spot cooling system.

Subjective comfort sensation vote to air velocity The Second Experiment Result Thermal environment Surface temperature: The surface temperature distribution recorded by thermogram is shown in Figure6.

Subjective vote: The general thermal sensation vote and thermal comfort sensation vote were presented in Figure 7.

5 than at (6). It is found that the comfort sensation to air velocity was improved by setting up the spot cooling system Strongly feel Feel feel Not feel a) General air velocity sensation vote b) comfort sensation vote to air velocity Figure 5. Subjective comfort sensation vote to air velocity The Second Experiment Result Thermal environment Surface temperature: The surface temperature distribution recorded by thermogram is shown in Figure6. It showed that spot cooling system without s cooled down upper body of subjects, while it was possible to cool down their whole body using the s. It was remarkable in the condition using the type II. Subjective vote: The general thermal sensation vote and thermal comfort sensation vote were presented in Figure 7. Thermal sensation votes were scattered near slightly cool and comfort sensation vote comfort for all conditions in the second test. Especially, subjects tended to feel thermally neutral and more comfortable under the condition using the type II compared with the condition without. It is found that subject felt comfortable when they perceived the thermal environment to be neutral. It is concluded that the thermal comfort sensation improved by cooling down their whole body using s. I Very Figure 6. Surface Temperature(second experiment) 8 8 I I Cold Neutral Hot Very a) General thermal sensation vote b) Thermal comfort sensation vote Figure 7. Subjective thermal comfort

Air Flow Supply air velocity: The vector diagram of the supply air velocity measured with PIV from the is displays in Figure8.

Supply air was diffused due to the, while the air velocity which reached directly subject got smaller and air flow to the subject was weakened.

As the result of the velocity distribution measurements, air velocity 1.7m above the floor indicated up to 1.5m/s under the condition without and with type I.

6 Air Flow Supply air velocity: The vector diagram of the supply air velocity measured with PIV from the is displays in Figure8. Under the condition without, little air flow diffusion was seen, and flowed toward the subjective position. Air velocity right after nozzle was about 4.1m/s. Supply air was diffused due to the, while the air velocity which reached directly subject got smaller and air flow to the subject was weakened. Especially, it was remarkable in the condition with typeii. Air velocity of the diffusion was about 3.5m/s, and that to the direction of the subject was 0.5m/s when the typeii was installed. As the result of the velocity distribution measurements, air velocity 1.7m above the floor indicated up to 1.5m/s under the condition without and with type I. In case of using the type II, air velocity on the same point was measures to be 0.24m/s. Subjective vote: Figure9 shows the general air velocity sensation vote and comfort sensation vote to air velocity. Subjects reported significantly lower air velocity sensation under the condition with typeii than any other conditions (3). In the first experiment, there was no significant difference in the vote of comfort sensation to air velocity between any pair of conditions with spot cooling system. However, subjects reported significantly more comfortable in case of using the typei and typeii than without (5) on the second experiment. Subject reported the air velocity from the outlet was comfortable in case that the velocity sensation was small. It was found that people could feel great comfort due to cooling down their whole body even with very small velocity. typei typeii Figure 8. vector diagram of the supply air velocity 500 I I Strongly feel Feel feel Not feel Very a) General air velocity sensation vote b) comfort sensation vote to air velocity Figure 9. Subjective comfort sensation vote to air velocity Evaluation of Diffuser Subjects ranked three type of in the terms of air supply temperature and velocity. The evaluation of the typei and typeii was higher than that of no as shown in Figure10. Especially, the majority people voted the typeii as 1st place. Though, there

7 were people who rated the typeii as 3rd place, too. This is demonstrated that there was an individual variation in subjects' preference of. 1st place about temperature 1st place about air velocity 3rd place about air velocity 0% 43% 0% 43% I 0% I 57% Figure 10. Evaluation of CONCLUSIONS I 57% 43% 57% In order to evaluate subjective comfort in the environment with spot cooling system, simulating a big factory, two subjective experiments were conducted in the climate chamber. The first experiments were carried out to evaluate the air supply conditions. Subjects were exposed to 5 conditions,,,,, none. Spot cooling system without s cooled down upper body of subjects. It was remarkable in the condition such as low supply air temperature and large air volume. It is found that subjective thermal sensation vote was scattered near slightly cool and subjects felt comfortable under the condition of low air temperature and large air volume. In this experimental condition, when supply air temperature rose and the volume increased, subjects rated feel on air velocity sensation vote. But there was no significant difference in the vote of comfort sensation to air velocity between any pair of conditions with spot cooling system In the second experiment, subjects evaluate the air supply conditions using the s. three experimental conditions were set, typei, typeii and without. It was possible to cool down their whole body using the s. It was contemplated that the thermal comfort sensation improved by cooling down their whole body. Subject reported the air velocity from the outlet was comfortable in case that the velocity sensation was small. It was found that people could feel great comfort due to cooling down their whole body even with very small velocity. The majority people rated the type II as 1st place, though there was an individual variation in subjects' preference of. ACKNOWLEDGEMENT Authors appreciate Mr. J Harigaya Mr. Y Nakagawa and Mr. S Nagareda of Waseda University for their assisting us plan and conduct this research. REFERENCES 1. Song Sung Ki Field Measurements and Simulation on the Heat Load of a Large Factory Space with Occupied Zone Air-Conditioning. Proceedings of International Conference CLIMA Tanabe, S. et al Effects of humidity on thermal comfort in office space (part 3). Annual Meeting of SHASE. pp Melikov, A.K. et al Spot cooling -Part 1: Human responses to cooling with air jets. ASHRAE Transactions, Vol. 100(2). pp Fanger, P O Thermal Comfort. Danish Technical Press.

RELATIONSHIPS BETWEEN OVERALL THERMAL SENSATION, ACCEPTABILITY AND COMFORT

RELATIONSHIPS BETWEEN OVERALL THERMAL SENSATION, ACCEPTABILITY AND COMFORT Yufeng Zhang 1, and Rongyi Zhao 2 1 State Key Laboratory of Subtropical Building Science, South China University of Technology,