Lecture-4a-Radiative-Convective_Heating_Compatibility_Mode_

Lecture-4a-Radiative-Convective_Heating_Compatibility_Mode_...

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1/7/2009 1 Transient Thermal Comfort Performance of Radiant and Convective Heating System Radiant and Convective Heating System During Startup Period 1 Introduction y Radiant system is known to be superior to convective system at steady state. It provides thermal comfort at low energy cost [Buckley, 1989]. y The transient performance of the radiative system is not well studied and it is not known whether it is superior to the convective system during transient conditions. 2 •Buckley, N. 1989. Application of radiant heating saves energy. ASHRAE Journal 31:17-26.
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1/7/2009 2 Motivation This study is important for: y The intermittent operation of the heating system conserves energy on the expense of lack of therma conserves energy on the expense of lack of thermal comfort during the transient period from the time the heating system is turned until human comfort conditions are reached. y Selecting the proper heating system for such applications. 3 Introduction y The main trouble with the strategy of turning off the heating system during unoccupied periods is whether the heating system is capable of providing comfort to occupants and on the ability of the occupants to operate effectively during the period that extends from turning on the heating system till space reaches the steady state thermal comfort conditions. y To maximize energy savings without sacrificing comfort, it is necessary to use energy efficient heating systems characterized by 4 rapid heating after turning it on.
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1/7/2009 3 Introduction (cont’d) y Studying transient thermal comfort is not as straight forward as the case of steady thermal comfort that could be assessed by ISO 7730 or ASHRAE standard 55. It requires direct information on rate of change of human skin temperatures. y In this case a bioheat model that is capable of simulating the transient physiological response and skin temperature changes of the human body is a must. 5 Objectives y To investigate the transient thermal comfort performance of convective and radiative heating systems for a person who has been walking in the outdoors and entering the cold space and turning on the heating system. y To asses the energy cost of the two systems if both systems would have the same level of comfort during the 6 transient period from the time of entrance till the time the person achieves thermal comfort conditions.
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1/7/2009 4 Integrated Thermal space, Bioheat, and Transient Thermal Comfort Models y The elements of the integrated model consists of: y View Factors Model between the different space surfaces and between the human body elements and the space surfaces. y Transient SpaceThermal Model y Transient Clothed Segmental Human Bioheat Model Sensitive to Radiant Asymmetry. y Transient Sensation and Comfort Model [Zhang’s Model, 2003] 7 •Zhang, H., 2003, “Human Thermal Sensation and Comfort in Transient and Non-Uniform Thermal Environments.” PhD thesis. University of California, Berkeley.
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Lecture-4a-Radiative-Convective_Heating_Compatibility_Mode_...

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