W. Turnbull et P. Oosthuizen, Theoretical evaluation of new phase delay methods for measuring local heattransfer coefficients, T CAN SOC M, 23(3-4), 1999, pp. 361-376
Citations number
8
Categorie Soggetti
Mechanical Engineering
Journal title
TRANSACTIONS OF THE CANADIAN SOCIETY FOR MECHANICAL ENGINEERING
A one-dimensional analytical solution has been derived for unsteady heat co
nduction within a semi infinite body, of high thermal resistance, that is s
ubject to a surface heat flux that varies periodically with time. The heat
flux is assumed to be generated within a thin isothermal coating. The model
predicts that a phase delay will develop between the heat flux and the coa
ting thermal response. This phase delay is independent upon the material pr
operties of the substrate and coating, on the heat flux driving frequency,
and on the Focal heat transfer. coefficient. With the exception of this las
t quantity the other parameters are known a priori, hence if the phase dela
y can be measured experimentally it can then be used to determine the local
heat transfer coefficient. Absolute values of the local coating temperatur
e and local heat flux are not required. Hence calibration of the devices fo
r measuring these quantities should not be required. In contrast to the ove
rall surface temperature, it is predicted that the phase delay angle will a
ttain a steady-state value within;a few heat flux cycles, thus reducing the
time required obtaining a measurement. Furthermore, the one-dimensional ma
thematical model that has been developed reduces to those used in previous
experimentally validated techniques, when appropriate constants in the boun
dary condition are used.