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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.

Christhina Candido – One of the best experts on this subject based on the ideXlab platform.

  • effects of artificially induced heat acclimatization on subjects thermal and Air Movement preferences
    Building and Environment, 2012
    Co-Authors: Christhina Candido, Richard De Dear, Masaaki Ohba
    Abstract:

    Abstract There is evidence suggesting that subjects become accustomed to levels of warmth prevailing within buildings on time scales of weeks to months. Such exposure will influence in occupants’ expectation of their thermal environments (i.e. thermal history). This paper investigates the effects of short-term physiological acclimatization on subjects’ perception of thermal and Air Movement preferences. Subjective thermal perception experiments were carried out in a climate chamber to evaluate temperature and Air Movement acceptability across a range of simulated hot-humid conditions. Experiments were carried out during the winter season in Japan so that subjects, from different nationalities, could all be brought to comparable levels of heat acclimatization. This method consists in exposing subjects to hot-humid conditions and increasing their core temperature by means of exercise on a daily basis. The physiological monitoring of subjects in these experiments established that core temperature was increased through exercise in heat. The increment in core temperature by three consecutive days appeared to be an effective short acclimatization procedure, as demonstrated by the diminution in thermal sensation, improved thermal acceptability and thermal preferences during exposure to warm thermal environments (SET∗ varying from 25 to 31 °C). The results showed that it is possible to acclimatize such ‘Air-conditioning addicts’ to warmer indoor environments without, however, compromising their thermal acceptability. In warm and humid climates, such trend for saturation of Air-conditioning exposure needs to be more understood. The results presented reinforce the opportunities to use higher set-points in Air-conditioning buildings, contributing to significant energy consumption cut-offs within the built environment.

  • combined thermal acceptability and Air Movement assessments in a hot humid climate
    Building and Environment, 2011
    Co-Authors: Richard De Dear, Christhina Candido, Roberto Lamberts
    Abstract:

    Abstract In the ASHRAE comfort database [1] , underpinning the North American naturally ventilated adaptive comfort standard [2] , the mean indoor Air velocity associated with 90% thermal acceptability was relatively low, rarely exceeding 0.3 m/s. Post hoc studies of this database showed that the main complaint related to Air Movement was a preference for ‘more Air Movement’ [3] , [4] . These observations suggest the potential to shift thermal acceptability to even higher operative temperature values, if higher Air speeds are available. If that were the case, would it be reasonable to expect temperature and Air Movement acceptability levels at 90%? This paper focuses on this question and combines thermal and Air Movement acceptability percentages in order to assess occupants. Two field experiments took place in naturally ventilated buildings located on Brazil’s North-East. The fundamental feature of this research design is the proximity of the indoor climate observations with corresponding comfort questionnAire responses from the occupants. Almost 90% thermal acceptability was found within the predictions of the ASHRAE adaptive comfort standard and yet occupants required ‘more Air velocity’. Minimum Air velocity values were found in order to achieve 90% of thermal and Air Movement acceptability. From 24 to 27 °C the minimum Air velocity for thermal and Air Movement acceptability is 0.4 m/s; from 27 to 29 °C is 0.41–0.8 m/s, and from 29 to 31 °C is >0.81 m/s. These results highlight the necessity of combining thermal and Air Movement acceptability in order to assess occupants’ perception of their indoor thermal environment in hot humid climates.

  • Air Movement acceptability limits and thermal comfort in brazil s hot humid climate zone
    Building and Environment, 2010
    Co-Authors: Richard De Dear, Christhina Candido, Roberto Lamberts, Lia Bittencourt
    Abstract:

    In hot humid climates, natural ventilation is an essential passive strategy in order to maintain thermal comfort inside buildings and it can be also used as an energy-conserving design strategy to reduce building cooling loads by removing heat stored in the buildings thermal mass. In this context, many previous studies have focused on thermal comfort and Air velocity ranges. However, whether this Air Movement is desirable or not remains an open area. This paper aims to identify Air Movement acceptability levels inside naturally ventilated buildings in Brazil. Minimal Air velocity values corresponding to 80% and 90% (V80 and V90) Air Movement acceptability inside these buildings. Field experiments were performed during hot and cool seasons when 2075 questionnAires were filled for the subjects while simultaneous microclimatic observations were made with laboratory precision. Main results indicated that the minimal Air velocity required were at least 0.4 m/s for 26 °C reaching 0.9 m/s for operative temperatures up to 30 °C. Subjects are not only preferring more Air speed but also demanding Air velocities closer or higher than 0.8 m/s ASHRAE limit. This dispels the notion of draft in hot humid climates and reinforce the broader theory of alliesthesia and the physiological role of pleasure due to Air Movement increment.

Fred Bauman – One of the best experts on this subject based on the ideXlab platform.

  • effect of acoustical clouds coverage and Air Movement on radiant chilled ceiling cooling capacity
    Energy and Buildings, 2018
    Co-Authors: Caroline Karmann, Fred Bauman, Stefano Schiavon, Paul Raftery, Mike Koupriyanov
    Abstract:

    Abstract Thermally activated building systems have the potential to achieve significant energy savings, yet, the exposed concrete may also create acoustical challenges due to the high reflectivity of the hard surface. Free-hanging acoustical clouds reduce the acoustical issues, but also the cooling capacity of a radiant chilled ceiling system. Fan-induced Air Movement can be used to compensate for the cooling capacity reduction. We experimentally assess the combined effect of acoustical clouds and fans on the cooling capacity for an office room. We installed a ceiling fan between the clouds (blowing in the upward or downward direction) and small fans above the clouds (blowing horizontally) at the ceiling level to increase the convective heat transfer along the cooled ceiling. We tested the different fan configurations against a reference case with no elevated Air Movement. The tests conducted without fans showed that cooling capacity decreased, but only by 11%, when acoustical cloud coverage was increased to 47%, representing acceptable sound absorption. The ceiling fan increased cooling capacity by up to 22% when blowing upward and up to 12% when blowing downward compared to the reference case over the different cloud coverage ratios. For the variants with small fans, cooling capacity increases with coverage, up to a maximum increase of 26%. This experiment proves that combining fans with acoustical absorbents close to the radiant surface increases cooling capacity while simultaneously providing improved acoustical quality, and quantifies the impact.

  • A study of occupant cooling by personally controlled Air Movement
    Energy and Buildings, 1998
    Co-Authors: Edward Arens, Marc Fountain, K. Miura, Zhang Hui, Fred Bauman
    Abstract:

    Abstract This study addresses the effectiveness of Air Movement cooling, an alternative to compressor-based cooling of the Air itself. Subjects in an environmental chamber were exposed to a range of warm temperatures and allowed to adjust Air Movement to suit their individual preferences, while answering a series of questions about their comfort. Air Movement was from the subject’s side, in two modes of turbulent flow. The Air speeds chosen by the subjects, and their subjective responses, are evaluated in the context of existing comfort standards and prediction techniques. Choosing Air speeds up to 1.4 m/s, over 80% of subjects at 1.2 met were comfortable up to 29 °C, and at 1.0 met up to 31 °C. The cooling effectiveness was significantly affected by the nature of the turbulence. A zone is proposed within which personally controlled Air Movement provides a likely alternative to mechanical Air conditioning.

  • Comfort and Health Considerations: Air Movement and Humidity Constraints
    Center for the Built Environment, 1995
    Co-Authors: Edward Arens, Fred Bauman, Hui Zhang, Marc Fountain, K. Miura, A. Baughman, Takashi Akimoto
    Abstract:

    This report describes the results of research completed to date during Phases I and II of the project. The report is organized in terms of the major type of work that have taken place. These are: 1) Laboratory studies of Air Movement and comfort. 2) Review of the influences of humidity on health, particularly as they impact evaporative cooling and naturally cooled architecture. 3) Development of a computer model of the human body sensitive to localized effects of Air Movement, localized radiant feilds, and other environmental influences. 4) Assistance with the workshops to create compressor-free house designs.