CONDENSATION OF A REFRIGERANT CFC11 IN HORIZONTAL MICROFIN TUBES - (PROPOSAL OF A CORRELATION EQUATION FOR FRICTIONAL PRESSURE-GRADIENT)

Local heat transfer and pressure drop measurements were made during co ndensation of CFC11 in horizontal microfin tubes. A smooth tube and tw o microfin tubes with different fin dimensions were tested. Flow obser vation study with use of an industrial borescope revealed that the con densate flowed along the grooves, and a thick condensate him covered f ins in the lower part of the tube in the low quality region. Static pr essure gradients in the microfin tubes were up to 70% larger than that in the smooth tube. A correlation equation for the local frictional p ressure gradient was derived, in which the effect of refrigerant mass velocity was introduced on the basis of the how regime consideration. The measured frictional pressure gradient data were found by the prese nt method to have a mean absolute deviation of 8.3%. (C) 1998 Elsevier Science Inc. All rights reserved.