Online & Oslo, Norway
21-23 June 2021
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Session 8: Thermal comfort
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10:30am - 10:42am
Provision of thermal comfort via user-centric radiant cooling elements: An experimental investigation
TU Wien, Austria
This contribution explores the performance of a user-centric radiant cooling approach. In comparison to conventional radiant cooling solutions, this approach i) positions radiant panels in close proximity to occupants, and ii) allows for panel surfaces temperatures below dew point and thus for potential surface condensation, which is dealt with via integrated water collection devices. The user-centric radiant panels were tested in a laboratory setting. Prototypical panels were installed in two mock-up office rooms. Twenty-eight participants evaluated thermal comfort (including radiant asymmetry and local thermal discomfort) for eight scenarios, including multiple panel surface temperatures as well as different ambient air temperatures. The results provide insights into the potential and limits of the proposed approach. Specifically, the findings pertain to panel surface temperatures, which are necessary to provide thermally comfortable conditions, as well as to surface condensation and radiant asymmetry.
10:42am - 10:54am
Verification of Thermal Comfort of Combined Convection-Radiation Air Conditioning System using Building Structure
1Shimizu Corporation, Japan; 2Shibaura Institute of Technology, Japan
Air conditioning systems have been required to achieve both energy-saving performance and occupants’ comfort. To satisfy this requirement, we have developed an air conditioning system that uses both TABS (Thermal Activated Building System) and airflow to promote heat transfer. The system is called ‘Combined Convection-Radiation Air Conditioning System’. Experiments were carried out for the purpose of verifying the thermal comfort of this system, and are reported in the following.
This air conditioning system is being introduced in buildings whose structure is formed by concrete slabs and beams. The ceiling surface is a concrete slab, and water pipes and radiation fins are in contact with the ceiling surface. Additionally, fans which generate airflow on the ceiling surface are installed beneath the slabs. The jet from the fans blows toward the ceiling. Then the air flows along the fins and the bottom surface of the slabs, reaches the sides of the beams, and subsequently descends to the living area. The system aims to create a thermal environment suitable for human’ metabolism by using the air-flow in the living area. By not burying the piping, the system reduces building frame weight and improves response to heat load fluctuation.
The purpose of the experiments is to verify whether comfort can be maintained in a 27°C temperature environment with a view to energy-saving. Subjects were exposed to thermal environments with different fan operating conditions while imposing tasks with different metabolic rates. The subjects were then asked to give their votes as regards thermal comfort and thermal sensation, and were also measured of their physiological data. Thermal comfort was evaluated from these votes, and the relation of physiological data.
Despite the hot conditions indicated by the comfort index such as PMV, more than 60% reported "comfort" that includes three stages (large to slight) of comfort, and less than 5% reported "discomfort" side. On the thermal sensation vote, there were many replies on the cool side. It was conjectured that the airflow and radiant environment generated in the living area caused cool feeling.
It was thus confirmed that this air conditioning system can form a good thermal environment by combining a TABS with a low velocity air-flow generated in the living area, and that comfort can also be maintained. It is considered that this paper can provide useful data for a control method adjusted to change of metabolic rate.
10:54am - 11:06am
Evaluation of Personalized Thermal Conditioning Chair in Net Zero Energy Building Office
1Kogakuin university, Tokyo, Japan; 2Dai-dan co.,ltd, Osaka, Japan; 3Sinko industries ltd., Osaka, Japan
The net Zero Energy Building (ZEB) aims at promoting productive activities with highly occupant’s satisfaction and minimum energy input. Personal air-conditioning is the technology that contributes to ZEB.
In this paper, we show the effects of improving occupant’s satisfaction by personalized thermal conditioning chair (TCC). We describe as follows.
(i) We show some features of the TCC. It has 2-modes which are blowing mode and heating mode. Users can control their own thermal environment according to themselves senses. Users can carry it everywhere in their office because its power source is Li battery. It can send the data by Bluetooth. Thermal environment of whole of room and air-conditioning power can be optimized by feedbacking the TCC’s data.
(ii) The TCC is able to change equivalent temperature -0.7~1.2 °C. It is examined by thermal manikin’s test. This effect was measured only sensible heat transfer. Adding latent heat transfer, the cooling effect would be 2~3 times (-1.4~-2.1 °C). Because the TCC can promote evaporating user’s sweat due to improving convection around user’s body.
(iii) Users controlled the TCC according to their thermal senses. It has been installed at the office which is achieved net Zero Energy Building in design phase and operational phase. Users chose the blowing mode mainly in summer and heating mode in winter according to seasons. Exceptionally, the TCC was used under blowing mode in winter according to increasing metabolic rate of users. This shows that users control the TCC autonomously.
(iv) The TCC was controlled to keep user’s preference thermal environment. Each user’s around temperature under operating the TCC is different from each other. Because their preference thermal environment is different from each other. Users are able to keep their own thermal environment comfortable by operating the TCC.
(v) The thermal sensation votes of users converged to “neutral”. It shows that the user has felt comfortable due to their ability of controlling own thermal environment has improved.
11:06am - 11:18am
Electroencephalography associated with thermal discomfort induced by temperature upward ramping
Yonsei University, Korea, Republic of (South Korea)
This experiment examines the EEG patterns according to the thermal discomfort of the occupants with gradual temperature increasing from comfortable to uncomfortable thermal environment by identifying the moment of participants perceiving “hot” or “uncomfortable” and measuring the changes in EEG at that moment.
Total 72 men and women in their 20s and 30s participated in a chamber experiment. For comparing the EEG in a comfortable environment with that of the moment of changing to an uncomfortable environment, the indoor environment was maintained at the air temperature of 25°C and the relative humidity of 50% for 10 minutes after the start of the experiment. After that, the temperature and humidity were gradually changed so that participants could experience from a comfortable environment to a very uncomfortable environment. At the end of the experiment, the set value of the air temperature was 32°C and the relative humidity was 65%.
We asked subject’s thermal sensation and thermal comfort to measure participants’ psychological response with regard to the gradual upward ramping. Participants, while staying in the climate chamber, pressed the voting button when they perceived hot or cold, and responded to the questionnaire about thermal comfort at that time. And then, they should respond to the questionnaire at any time when the thermal sensation or thermal comfort changed, so the gradual change in psychological responses was examined.
As a result of the temperature increasing, the participants felt uncomfortable and the relative power value of all frequency bands gradually increased. As a result of correlation analysis of individual thermal comfort change and relative power change, the alpha power at Cz, C3, the beta power at Fz, Cz, and C4 and the gamma power at C4 increased. This indicates that unlike the clear change in the specific points and frequency of EEG in case of thermal displeasure experience (Son 2019), EEG increased at all frequency bands.
11:18am - 11:30am
Thermal comfort and skin temperature of adolescents compared to young adults
Yonsei University, Korea, Republic of (South Korea)
This study examined thermal comfort and skin temperature of adolescents and young adults to analyze the individual difference in their thermal responses. In a climate chamber with increasing temperature, skin temperature was measured at seven body parts with survey responses. As a result, the indoor environment, thermal comfort, and skin temperature have significant correlations, and there were differences between adolescents and adults in their responses. The neutral temperature of adolescents was slightly lower than that of adults. Generally, adolescents have a higher mean skin temperature than adults, and the hand skin temperature of the adult male group changed much sensitively than others. The difference in thermal comfort and related skin temperature implies the need for investigating adolescents as a separate group from adults for accurate thermal comfort prediction. The results are expected to be used for optimal environmental setting for adolescents.
11:30am - 11:42am
Association between physiological signal from wearable device and alertness of office workers
Yonsei University, Korea, Republic of (South Korea)
Through physiological signals, detecting the changes of occupants' physical and psychological aspects is possible, and wearable devices have enabled measurement in daily life. In this study, to see whether the wearable device could be used for interpreting the state of the office workers, a field experiment was conducted. A wearable device was applied for monitoring the occupant, and productivity responses were collected inside a real office. As a result, when the productivity and alertness decreased, the room temperature was high, and the skin temperature and electrodermal activity were increased. A comparison between the group of alert and drowsy states was also made. The average and the gradient of skin temperature had a significant difference between the states. The result of skin temperature could be interpreted as suppressing the sympathetic nervous systems in the drowsy state, increasing blood flow, and increasing temperature at the terminal skin. Significant relation with the electrodermal activity can be explained through sweat secretion. The results showed the insight of understanding the occupants' alert state through wearable device measured data.
11:42am - 11:54am
Thermal Insulation of Clothing: Assessment of Cleanroom Clothing Ensembles
Czech Technical University in Prague, Faculty of Civil Engineering, Department of Indoor Environmental and Building Services Engineering
Besides the known environmental conditions and the level of activity, the occupants’ clothing and its properties are important for the assessment of thermal comfort and determination of optimal temperatures of the analysed environment. The thermal properties of clothing significantly affect the heat balance of the organism, thus also the level of thermal satisfaction of occupants. Without the known and correctly determined values of thermal insulation, the effect of the clothing on the heat balance is skewed.
In the case of the cleanroom clothing, unfortunately, the values of the thermal insulation for these specific ensembles can not be found in the international standards ISO 7730 and ISO 9920. Only, the values can be estimated based on the selected casual ensembles or as a combination of individual garments available in the standards which clearly make the thermal comfort assessment unreliable.
This study is focused on the assessment of cleanroom clothing to determine the thermal insulation properties. For the purpose of this study, four frequently used cleanroom clothing ensembles were selected. These sets represent the most prescribed ensembles in cleanrooms operated as the ISO Class 7 cleanroom known as the most common classes of cleanliness. The measurement of the thermal insulation was carried out following the standard ISO 15831 for the testing by means of a thermal manikin. In this study, the stationary Newton thermal manikin with 36 zones placed inside the climatic chamber was used. The manikin was operated in the temperature mode ensuring the uniform surface temperature in all zones. The testing of each ensemble was repeated two times as the tolerances of the results were below the requirements (2.3 %, 1.8 %, 0.2 % and 1.2 %). The thermal insulation was calculated using the parallel method (ISO 15831) suitable for this type of measurement.
The results showed the variations in the thermal insulations of ensembles that reflect the layers of garments and their materials. The importance of finding the thermal insulation of cleanroom clothing is not only in the more accurate calculation of PMV and PPD indexes but also in the setting of more suitable indoor temperatures in relation to the used ensembles. The casual ensembles available in standards can not represent the specific cleanroom clothing. Thus, the more precise method of determining the thermal insulation with the use of a thermal manikin is needed. Despite the high accuracy, the high investment and operating costs are responsible for the limited applicability of this method.
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