ENHANCEMENT OF HEAT-TRANSFER IN ROTARY HEAT-EXCHANGERS BY STREAMWISE-CORRUGATED FLOW CHANNELS

Experimental design data (St vs Re, Nu vs x*, and f vs Re) are presented for four trapezoidal ducts with corrugated walls and one with smooth (noncorrugated) walls with constant wall temperature boundary conditions. The trapezoidal channel has top and bottom walls corrugated in the flow direction, while the two side walls are smooth. A smooth (noncorrugated) channel is used as a reference. For rotary regenerators used in air-conditioning systems, such trapezoidal channels with all four walls smooth are common. The corrugated walls then yield heat transfer enhancement. A test rig has been built, and measurements have been taken for one smooth and four corrugated channels using a steady-state oil-to-air heat transfer. The corrugation height and wavelength of the top and bottom walls were varied. The investigation covered a Reynolds number range of 500 < Re < 5000. The corrugated channel with the largest corrugation height and smallest wavelength provides the best enhancement of the heat transfer (about 100%), but the pressure drop penalty is very large (about 270% increase). Flow area goodness factor and volume goodness factor comparisons of the heat transfer surfaces are made for the assessment of investigated channels.