Analysis of convective heat transfer during immersion frying

Immersion frying was studied as a high temperature drying process and analo gies drawn between periods found in drying and similar periods in immersion frying. Analysis of external heat transfer during immersion frying showed a highly complex system of free and forced convection augmented by boiling conditions. Oil flow was found to be driven downward by buoyancy forces due to cooling at the sample surface then upward due to entrainment in vapor b ubbles during boiling conditions. Experimental work showed the convective h eat transfer coefficient to be a dynamic property ranging from 300 to 1100 W/m2 degrees C and to be strongly coupled with bulk movement of the oil. He at flux measurements found a peak flux of nearly 30,000 W/m(2). Based on an alysis of bubble dynamics it is hypothesized that heat flux increases with increased oil degradation through a reduction in vapor bubble size and incr ease in bubble frequency due to changes in interfacial properties of the oi l.