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Edward Arens – One of the best experts on this subject based on the ideXlab platform.

  • Preferred temperatures with and without Air Movement during moderate exercise
    Energy and Buildings, 2020
    Co-Authors: Yongchao Zhai, Hui Zhang, Shengkai Zhao, Yunfei Gao, Wenxin Song, Liu Yang, Edward Arens

    Abstract:

    Abstract During exercise, comfort requirements are different because of the elevated metabolic heat production. It is essential to know the preferable thermal environment to give environmental design suggestions to sports facilities. Experimental studies on preferred temperature were conducted on 20 healthy human subjects walking on a treadmill at 4, 5, and 6 km/h, with and without self-controlled Air Movement. Physiological responses (metabolic rate, skin temperature, skin wettedness, and heart rate) were monitored, while their subjective responses were collected by questionnAires. Metabolic rates were 3.0, 3.5, and 4.5 met for 4, 5, and 6 km/h walking. Preferred temperatures were significantly lower without fan (23.3, 22.8, and 22.1 °C without fan vs. 24.9, 24.1, and 23.6 °C with fan), and all subjects were satisfied with their preferred thermal environment. PMV model was found to overestimate the cooling requirements for exercising people. Our results indicate that human in exercise does not necessarily want neutral temperature but want somewhat warm sensations, with lower temperature, higher skin wettedness, and higher core temperature. Overall, the results suggest that design temperature shall be 22–24 °C without Air Movement, and 24–26 °C with personally controlled Air Movement.

  • Using Air Movement for comfort during moderate exercise
    Building and Environment, 2015
    Co-Authors: Yongchao Zhai, Edward Arens, Hui Zhang, Christopher Elsworth, Yufeng Zhang, Lihua Zhao

    Abstract:

    Fitness centers are energy-intensive in warm climates, cooling the interior to low temperatures that are comfortable for exercise. There is little existing guidance on how to do this efficiently. However it is well-known that significant energy can be saved by cooling sedentary occupants with Air Movement at elevated setpoint temperatures. This experiment investigated thermal comfort and Air Movement at elevated activity levels. Comfort votes were obtained from 20 subjects pedaling a bicycle ergometer at 2, 4, and 6 MET exercise intensities in four temperatures (20, 22, 24, 26 °C, RH 50%) under personal controlled ceiling fan Airflow, as well as in a 20 °C still-Air reference condition. An additional test of frontal Airflow was conducted at 26 °C. The hypothesis, that Air Movement together with higher temperatures would produce equal or better comfort and perceived Air quality below the reference condition, Center for the Built Environment (CBE) University of California, Berkeley was confirmed for every temperature up to 26 °C. Subjects preferred Air speeds up to 2.3 m/s to maintain acceptable thermal environment at 6 MET. The small frontal fan affecting the facial area was effective but the ceiling fan affecting the whole body provided greater comfort. Fitness centers should operate with elevated Air Movement to improve both comfort and efficiency.

  • applicability of whole body heat balance models for evaluating thermal sensation under non uniform Air Movement in warm environments
    Building and Environment, 2014
    Co-Authors: Li Huang, Edward Arens, Hui Zhang, Yingxin Zhu

    Abstract:

    Abstract In ASHRAE Standard 55-2010, the comfort effects of elevated Air Movement are evaluated using the SET index as computed by the Gagge 2-Node model of whole-body heat balance. Air Movement in reality has many forms, which might create heat flows and thermal sensations that cannot be accurately predicted by a simple whole-body model. This paper addresses two of such potential inaccuracies: 1) indoor Airflows may affect only a portion of the body surface (e.g., above desktop), and the affected body surface might be variably nude (e.g., face) or clothed, 2) the turbulence intensity (TI) in some typical Airstreams (e.g., those created by fans) might have a different impact on heat transfer than the TI implicit in 2-Node’s single convective heat transfer coefficient. For both these issues, can a whole-body index like SET represent such a wide range of possible exposures to Airflow? Measurements of thermal sensation were obtained from human subjects using face-level fans in warm environments. Previous laboratory studies of a range of Airstream sources were also analyzed. The effects of turbulence intensity were examined with manikin tests. The results show that indices derived from the 2-Node model of whole-body heat balance are effective at predicting thermal sensation under most non-uniform Air Movement. In contrast, the PMV index underestimates cooling in warm conditions. Turbulence increases the cooling effect of Air Movement, but by amounts that might be neglected for most design purposes.

M. Olenets – One of the best experts on this subject based on the ideXlab platform.

  • heat transfer and Air Movement in the ventilated Air gap of passive solar heating systems with regulation of the heat supply
    Energy and Buildings, 2015
    Co-Authors: M. Olenets, J.z. Piotrowski, A Stroy

    Abstract:

    Abstract The article describes the heat transfer and Air Movement that occur in the ventilated Air gap of a building’s passive solar heating system under winter and summer conditions. The physical and mathematical models of these processes are presented for the Trombe wall with and without venetian blinds arranged in the Air gap. The mathematical models allow for the determination of the heat and Air stream distribution and the surface temperature change of the constructive elements in both cases. The transfer of heat by radiation and convection are considered separately, making it possible to estimate in an analytical way the influence of constructive materials and covering properties on the heat flow distribution and regulate it. The mathematical models were developed on the basis of the analysis of the heat transfer and Air Movement and therefore they can be complemented and improved depending on the constructive and climatic conditions. Examples of comparative calculations of the heat transfer and Air Movement in the Air gap of the conventional Trombe wall and the Trombe wall equipped with a venetian blind for regulation of heat supply are presented. For the winter period the comparative calculations were carried out with a different intensity of solar radiation.

  • Mathematical Description of Heat Transfer and Air Movement Processes in Convectional Elements of a Building’s Passive Solar Heating Systems
    Energy Procedia, 2014
    Co-Authors: M. Olenets, J.z. Piotrowski, A. Stroj

    Abstract:

    Abstract The article discusses convectional elements of a building’s passive solar heating systems. Mathematical description of heat transfer and Air Movement processes in the convection elements is presented as an equation set in differential form. The set of equations allows the determination of the temperature distribution in the convectional element as well as the heat flow being supplied into the room. At the same time, it is possible to analyze structural factors influencing the heat flow. The mathematical description of the heat transfer and Air Movement processes is illustrated by examples of calculations and diagrams of Air Movement in the convectional elements.

Hui Zhang – One of the best experts on this subject based on the ideXlab platform.

  • Preferred temperatures with and without Air Movement during moderate exercise
    Energy and Buildings, 2020
    Co-Authors: Yongchao Zhai, Hui Zhang, Shengkai Zhao, Yunfei Gao, Wenxin Song, Liu Yang, Edward Arens

    Abstract:

    Abstract During exercise, comfort requirements are different because of the elevated metabolic heat production. It is essential to know the preferable thermal environment to give environmental design suggestions to sports facilities. Experimental studies on preferred temperature were conducted on 20 healthy human subjects walking on a treadmill at 4, 5, and 6 km/h, with and without self-controlled Air Movement. Physiological responses (metabolic rate, skin temperature, skin wettedness, and heart rate) were monitored, while their subjective responses were collected by questionnAires. Metabolic rates were 3.0, 3.5, and 4.5 met for 4, 5, and 6 km/h walking. Preferred temperatures were significantly lower without fan (23.3, 22.8, and 22.1 °C without fan vs. 24.9, 24.1, and 23.6 °C with fan), and all subjects were satisfied with their preferred thermal environment. PMV model was found to overestimate the cooling requirements for exercising people. Our results indicate that human in exercise does not necessarily want neutral temperature but want somewhat warm sensations, with lower temperature, higher skin wettedness, and higher core temperature. Overall, the results suggest that design temperature shall be 22–24 °C without Air Movement, and 24–26 °C with personally controlled Air Movement.

  • Using Air Movement for comfort during moderate exercise
    Building and Environment, 2015
    Co-Authors: Yongchao Zhai, Edward Arens, Hui Zhang, Christopher Elsworth, Yufeng Zhang, Lihua Zhao

    Abstract:

    Fitness centers are energy-intensive in warm climates, cooling the interior to low temperatures that are comfortable for exercise. There is little existing guidance on how to do this efficiently. However it is well-known that significant energy can be saved by cooling sedentary occupants with Air Movement at elevated setpoint temperatures. This experiment investigated thermal comfort and Air Movement at elevated activity levels. Comfort votes were obtained from 20 subjects pedaling a bicycle ergometer at 2, 4, and 6 MET exercise intensities in four temperatures (20, 22, 24, 26 °C, RH 50%) under personal controlled ceiling fan Airflow, as well as in a 20 °C still-Air reference condition. An additional test of frontal Airflow was conducted at 26 °C. The hypothesis, that Air Movement together with higher temperatures would produce equal or better comfort and perceived Air quality below the reference condition, Center for the Built Environment (CBE) University of California, Berkeley was confirmed for every temperature up to 26 °C. Subjects preferred Air speeds up to 2.3 m/s to maintain acceptable thermal environment at 6 MET. The small frontal fan affecting the facial area was effective but the ceiling fan affecting the whole body provided greater comfort. Fitness centers should operate with elevated Air Movement to improve both comfort and efficiency.

  • applicability of whole body heat balance models for evaluating thermal sensation under non uniform Air Movement in warm environments
    Building and Environment, 2014
    Co-Authors: Li Huang, Edward Arens, Hui Zhang, Yingxin Zhu

    Abstract:

    Abstract In ASHRAE Standard 55-2010, the comfort effects of elevated Air Movement are evaluated using the SET index as computed by the Gagge 2-Node model of whole-body heat balance. Air Movement in reality has many forms, which might create heat flows and thermal sensations that cannot be accurately predicted by a simple whole-body model. This paper addresses two of such potential inaccuracies: 1) indoor Airflows may affect only a portion of the body surface (e.g., above desktop), and the affected body surface might be variably nude (e.g., face) or clothed, 2) the turbulence intensity (TI) in some typical Airstreams (e.g., those created by fans) might have a different impact on heat transfer than the TI implicit in 2-Node’s single convective heat transfer coefficient. For both these issues, can a whole-body index like SET represent such a wide range of possible exposures to Airflow? Measurements of thermal sensation were obtained from human subjects using face-level fans in warm environments. Previous laboratory studies of a range of Airstream sources were also analyzed. The effects of turbulence intensity were examined with manikin tests. The results show that indices derived from the 2-Node model of whole-body heat balance are effective at predicting thermal sensation under most non-uniform Air Movement. In contrast, the PMV index underestimates cooling in warm conditions. Turbulence increases the cooling effect of Air Movement, but by amounts that might be neglected for most design purposes.