Bv. Antohe et Jl. Lage, EXPERIMENTAL INVESTIGATION ON PULSATING HORIZONTAL HEATING OF A WATER-FILLED ENCLOSURE, Journal of heat transfer, 118(4), 1996, pp. 889-896
Experimental results of the natural convection generated by the time p
eriodic horizontal heating of a square cross-section enclosure filled
with water are reported. A pulsating (on/off) heat flux is delivered t
o the heating wall of the enclosure, with the opposite wall cooled by
a high thermal capacitance system. All other surfaces are insulated He
ating periods from 32 to 1600 seconds and cycle-averaged heat-flux bas
ed Rayleigh numbers from 2.5 x 10(8) to 1.0 x 10(9) are considered. Re
sults presented in terms of time series, phase-plane portraits, and cy
clic evolution of surface-averaged cooling and heating wall temperatur
es illustrate the main characteristics of the evolution to periodic re
gime. Also presented are the cycle-averaged heat transfer coefficient
versus heating period, and the corresponding average Nusselt number ve
rsus Rayleigh number for various heating frequencies. These results, w
hich support published theoretical and numerical analysis, indicate th
at by tuning the heating period properly, the heat transfer across an
enclosure can be enhanced The results also reveal that short heating p
eriods hinder the convection within the enclosure, in general (e.g., f
or Ra = 7.5 X 10(8) and a period of 32 s the heat transfer coefficient
is 13 percent smaller than the steady heating value). The sensitivity
of the transport phenomenon to pulsating heat is shown to depend stro
ngly on Ra. Finally, a correlation for estimating the maximum heat tra
nsfer coefficient derived from the experimental results, is presented.