Einfluß der Oberflächenporosität und Ölkonzentration auf den Wärmeübergang der Kältemittel R12 und R22 in berieselten Wärmetauschern

Abstract

The effect was studied of heat flux d. pressure, spray-liq. properties, spray d., porous layer structure, etc. on the heat transfer during boiling of R12 and R22 in a spray evaporator. Expts. were carried out in a tube bundle (tube diam. 20 mm) with a porous coating of Cu and stainless steel (thickness 100 - 1000 micro-m) at a heat flux d. of 1 - 25 kW/m². The results are compared with those obtained on a smooth pipe with no coating. For R12 at a satn. temp. of -30°, stable boiling was obsd. in coated tubes at a heat flux d. of 1 kW/m², whereas for smooth tubes similar boiling was obsd. onyl at 15 kW/m². The heat transfer coeff. on the tube surface was 2 - 5 times and 10 - 20 times larger than that for smooth tubes under spray and submerged conditions, resp.