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 coef ficients are estimated using novel and existing time series methods, a nd are compared with those obtained from the standard ratio of means a pproach, and those given in the CIBSE Guide. The time series methods a re used to estimate an impulse response function of the heat flux at t he surface to the temperature difference through the air boundary laye r 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 p rocess. The area under the estimated response function yields the 'gai n' between the surface heat flux and the air-surface temperature diffe rence, or the convective heat transfer coefficient. This methodology i s employed to estimate the convective heat transfer coefficient of the ceiling within an experimental building, in a convective heating envi ronment. The variation of the convective heat transfer coefficient acr oss the boundary layer is shown,from which the thickness of the bounda ry layer is estimated. A methodology for the estimation of the hourly variation of the convective heat transfer coefficient is also presente d, and is employed to investigate the lime varying nature of the conve ctive heat transfer coefficient.