Date of Award
Doctor of Philosophy
Heat transfer from an inclined rectangular cavity with differing boundary conditions at the top plate was investigated using a Mach-Zehnder interferometer integrated with a low speed wind tunnel. Natural convection inside the cavity coupled with external natural convection at the top plate was studied for (theta) = 15(DEGREES), 45(DEGREES), and 60(DEGREES) to the horizontal. At (theta) = 60(DEGREES), coupling with external forced convection was also studied. Also, for (theta) = 60(DEGREES), the case of non-coupled heat transfer from a cavity with an isothermal top plate was studied. In all experiments the bottom hot plate was isothermal. The Rayleigh number, Ra, was varied from subcritical to 6 x 10('5) and the cavity aspect ratio, AR(,x), (length/spacing between plates) from 6.68 to 33.4. The Reynolds number of the external forced flow was constant and approximately equal to 5.8 x 10('4).;The temperature of the cold plate resulting from the coupled convective flows was found to depend strongly on AR(,x), and (theta) and weakly on Ra. Temperature reversal was found to occur inside the cavity and first appeared in the corner regions. The local heat trans- fer rates, Nu(,x), were found to depend strongly on AR(,x), Ra, (theta), and distance from the end walls of the cavity. The dependence of the average heat transfer rates, Nu, on Ra and (theta) was found to be a complex one.;When compared to the non-coupled case coupling of internal and external convective flows at the top plate of the cavity resulted not only in a reduction of the variation of the local heat transfer rates at the cold plate, Nu(,xc) but also in a reduction in the average heat transfer rates from the hot and cold plates of the cavity, Nu(,h) and Nu(,c) for the range Ra > 3 x 10('4). For Ra < 3 x 10('4) the thermal boundary conditions at the top plate did not affect the local or average heat transfer rates from the cavity. The ratio Nu(,h)('-) (coupled)/Nu(,h) (non-coupled) was found to increase from zero at Ra (TURNEQ) 3 x 10('4) to 0.75 at Ra = 6 x 10('5). The effect of coupling with external forced convection compared to coupling with external natural convection at the same Ra-number is limited to small changes in Nu(,xc) and Nu(,c).
Karayiannis, Tassos George, "An Interferometric Study Of Coupled And Non-coupled Convective Heat Transfer From An Inclined Rectangular Cavity" (1986). Digitized Theses. 1500.