Free convection across air gap between corrugated and flat plates

Natural convection heat transfer across air gap between a lower hot semicircular corrugated plate and an upper cold flat plate has been studied experimentally for a range of corrugation aspect ratio (air gap to the amplitude of corrugation), 3.5 < A < 9.5, inclination angle, 0^0 < 0 < 45^0, and Rayleigh number, 3.4 x 10^4 Ra < 2.0 x 10^6. A corrugation plate has been formed with the multi-semicircular bars. The heat transfer coefficients are found to be a strong function of corrugation aspect ratio, inclination angle and Rayleigh number. The results are compared with the available information in the literature on natural convection and found to be about 10% and 20% higher than those for a gap between vee corrugated and flat plate and between two flat plates, respectively. Finally, a correlation has been developed for this configuration for a range of parameters studied herein.