Practical Investigation of Cool Chair in Warm Offices

Transcription

1 Proceedings of Clima 7 WellBeing Indoors Practical Investigation of Cool Chair in Warm Offices Yu KOGAWA 1, Tatsuo NOBE and Ayako ONGA 3 1 DAI-DAN Co., Ltd., Japan,3 Kogakuin University, Japan Corresponding oldriver.nov@gmail.com SUMMARY This study investigated on a subject s thermal sensation and use of a Cool Chair in two actual warm offices. We developed a chair-mounted isothermal airflow generator called the Cool Chair that adjusts the local thermal environment by changing airflow velocity against the body surface. It was designed as a personal air-conditioning system. The Cool Chairs were used by workers in technical occupations in actual offices. The Cool Chair use rate, occupancy rate, and evaluations were recorded. The user s thermal sensation and comfort sensation were improved by utilization of the Cool Chair. Despite a uniform room temperature, the workers could select an airflow that provided individual comfort, which may result in a decrease in the worker complaints. Thus, the usefulness of the Cool Chair s thermal adjustability was confirmed. INTRODUCTION Individuals have different perceptions of thermal comfort. A comfortable temperature is dependent on factors such as a person s physical condition, clothes, and activity level. However, in a typical office environment, there are many workers in the same space, which maintains a uniform room temperature through air-conditioning. Therefore, allowing workers to adjust their local thermal environment is important. The chair-mounted isothermal airflow generator called the Cool Chair [1] is a personal air-conditioning system, which allows an individual to control the local thermal environment by adjusting the airflow (Figure 1). The conventional personal air-conditioning system uses a non-isothermal airflow. In contrast, the mechanism of the Cool Chair is simple, allowing the user to feel cool by using the isothermal airflow. An adaptive model that requires a voluntary, passive action was proposed by R. J. de Dear et al. []. The adaptive model defines a person as a subject that transfers heat to the outside if uncomfortable. The adaptive model is different from a heat balance model. The adaptive model consists of three elements: behavioral adjustment, physiological adjustment, and psychological adjustment. Although a psychological adjustment is the most effective, it is difficult to evaluate quantitatively. A standard chair does not allow thermal adjustability that provides psychological adjustment. In contrast, the Cool Chair allows thermal adjustability. This simple device between the office environment and the worker contributes to thermal comfort, a feeling of control, and energy conservation [3].

2 Proceedings of Clima 7 WellBeing Indoors METHODS Cool Chair The Cool Chair functions by drawing air into the seat and the backrest and blowing it out through the armrests (Figure ) [,5]. The amount and direction of airflow are easily adjusted. The maximum amount of airflow is 7 m 3 /h. Airflow adjustment is accomplished using a controller on the right armrest. Power was supplied by a battery. The battery required several hours to charge, which is done by having the user plug the Cool Chair cord into an electrical outlet when out of the office. to blow out to inhale Figure 1. External view of the Cool Chair. Summary of Practical Investigation Figure. Function of the Cool Chair. A summary of the study is shown in Table 1. Investigation was conducted at office K and office H in Japan (Figures 3 and ). It was conducted in office K for weeks from 31 st August 5 through 15 th September. Eight subjects were divided into two groups (the A group was composed of males and females; the B group was composed of 1 male and 3 females). The workers in the A group used the Cool Chair during the first week and used a standard chair for the second week. The workers in the B group used the Cool Chair during the second week. All of the workers were employed in a technical field inside an office. From 7 th September 5, the investigation was conducted in the office H for one week. A male and a female, employed as a sales representative and an office worker, used the Cool Chair. Every morning and afternoon the workers supplied responses to a questionnaire regarding the type of clothing, thermal sensation, and comfort sensation. Table 1. Summary of investigation. Investigated Office Place Office K Minato Ward, Tokyo Measurement Schedule 3, Aug, - 7th, Sep th, Sep - 15th, Sep Cool Chair User A,B,C,D E,F,G,H Standard Chair User E,F,G,H A,B,C,D Survey Item Seat occupancy rate Thermal sensation vote, Comfort sensation vote Questionnaire Room temperature Office H Osaka city, Osaka 7th, Sep - th, Oct I,J

3 Proceedings of Clima 7 WellBeing Indoors Figure 3. Office K involved in the study. Figure. Office H involved in the study. To determine airflow, the terminal voltage of the blower was recorded with a small voltage logger. In addition, the temperature of the weight-bearing surface was recorded with a small temperature logger to determine the times when the person was seated. Mean room temperature fluctuation during the investigation period is shown in Figure 5 (temperature was measured at a height of 11 mm). Room temperature during working time was nearly 7 o C. Room Temperature[ o C] Office K Office H : 3: : 9: 1: 15: 1: 1: Time Figure 5. Ambient temperature.

4 Proceedings of Clima 7 WellBeing Indoors RESULTS Usage condition of Cool Chair The airflow rate was not constant, because a worker repeatedly sits down and stands up during the day (Figure ). Room temperature during the day was approximately 7 o C and the amount of airflow selected by the user was m 3 /h. When the air-conditioning system stopped outside of office hours, the room temperature increased and the amount of airflow selected was m 3 /h. Amount of airflow [m 3 /h] 1 Amount of airflow Room temperature : : : 1: 1: : : Figure. Usage of Cool Chair (an example). Time Figure 7 shows the relation between Cool Chair use and amount of airflow. The respective Cool Chair users are shown on day 1. Females used a greater airflow for a longer time compared to the males. Figure shows where the airflow was directed. Most of the time the workers directed the airflow toward the arms, followed by the side of the body, neck, and chest. The circumstances under which the workers used the Cool Chair are shown in Figure 9. The Cool Chair was used mainly when the activity level increased. In addition, the subject used the Cool Chair when he or she felt that the air-conditioning system was not effective Room temperature [ o C] Airflow [m 3 /h] Male Female Blowing fraction usage rate [%] Face Neck Chest Arm Thigh Below knee Side of body Abdomen Figure 7. Usage/Airflow. Figure. Applied airflow.

5 1 1 Proceedings of Clima 7 WellBeing Indoors 1 When returning from outside Thermal Sensation Vote and Comfort Sensation Vote The workers impression of the Cool Chair is shown in Figure 1. Most workers reported that the Cool Chair was Comfortable. The mean values for males and females for TSV and CSV in office K are shown in Figures 11 and 1. The TSV shifted from warm to neutral, and the CSV shifted from uncomfortable to comfortable through the use of the Cool Chair. The cooling effect of the isothermal airflow despite a relatively warm indoor temperature was confirmed by these results. 3 After moving When airconditioning is not effective After the food Figure 9. Circumstances when the Cool Chair was used. etc Uncomfortable 3 Neutral Slightly comfortable Comfortable Very comfortable Figure 1. Impressions of Cool Chair. 1 1 TSV - Thu nd 5th th 7th TSV - th 9th 1th 13th ThuCool Chair Standard Chair 1th 15th Figure 11. Comparison of TSV values. CSV CSV - Thu nd 5th th 7th - th 9th 1th 13th ThuCool Chair Standard Chair 1th 15th Figure 1. Comparison of CSV values.

6 Proceedings of Clima 7 WellBeing Indoors 1 Inadequate Slightly inadequate Evaluation of airflow Adequate Slightly too much Too much Figure 13. Impressions of airflow rate. Cool Slightly cool Neutral Slightly warm Warm Figure 1. Impressions of airflow temperature. Figure 13 shows the users impressions of the Cool Chair's maximum airflow rate. Results indicated most users were satisfied with the airflow of the Cool Chair. Figure 1 shows user's impressions of the airflow temperature. Results indicated that the user was cooled sufficiently by the isothermal airflow. DISCUSSION The performance of the Cool Chairs was tested under actual office conditions. Airflow rate and temperature were sufficient in actual practice. The amount and direction of airflow were controlled by the user based on thermal comfort. Results indicated that the thermal adjustability of the Cool Chair increases user comfort. This thermal adjustable device contributes to worker thermal comfort and feeling of control, and energy conservation. ACKNOWLEGEMENT This research is supported by Academic Frontier Project for Private Universities from Ministry of Education, Culture, Sports, Science and Technology. REFERENCES 1. Nobe, T. et al.. Chair-mounted Isothermal Airflow Generator, Proceedings of Roomvent, CD-R.. Richard J.de Dear., et al Developing an Adaptive Model of Thermal Comfort and Preference, ASHRAE Transaction, Vol. 1(1a) pp Nobe, T.. Practical Evaluation of COOL CHAIR in Warm Office, Summaries of Technical Paper of Annual Meeting Architectural Institute of Japan D- pp Kogawa, Y. et al.. Development of Chair Mounted Iso-thermal Airflow Generator Part7:Specificaiton of Cool Chair 5 Model and Outline of Subjective Experiment, Summaries of Technical Paper of Annual Meeting Architectural Institute of Japan D- pp Onga, A. et al. 7. Time Series Analysis of Cool Chair Operating Conditions, Proceedings of CLIMA7, (in press)