TIME-SERIES ESTIMATION OF CONVECTIVE HEAT-TRANSFER COEFFICIENTS

In this work a novel methodology for the estimation of convective heat transfer coefficients is presented. The convective heat transfer coefficients are estimated using novel and existing time series methods, and are compared with those obtained from the standard ratio of means approach, and those given in the CIBSE Guide. The time series methods are used to estimate an impulse response function of the heat flux at the surface to the temperature difference through the air boundary layer to the bulk air within the enclosure. The impulse response function displays the time-delayed response of the surface heat flux to the air-surface temperature difference, and thus indicates the speed of the process. The area under the estimated response function yields the 'gain' between the surface heat flux and the air-surface temperature difference, or the convective heat transfer coefficient. This methodology is employed to estimate the convective heat transfer coefficient of the ceiling within an experimental building, in a convective heating environment. The variation of the convective heat transfer coefficient across the boundary layer is shown,from which the thickness of the boundary layer is estimated. A methodology for the estimation of the hourly variation of the convective heat transfer coefficient is also presented, and is employed to investigate the lime varying nature of the convective heat transfer coefficient.