Heat Transfer during Downflow Condensation of R21 in Plate-Fin Heat Exchanger with Inclined Texture

The paper presents an experimental study of the heat transfer during condensation of modeling freon R21 in downward flow conditions in an element of a plate-fin heat exchanger with inclined-texture perforated fins. The experiments were carried out for mass velocity of 20 to 50 kg/m²s and wall subcooling of 0.8 to 1.1 K with a heat exchanger with fin density of 850 fins per meter. The texture on the surface of the perforated fins of the heat exchanger was at angle of 45 degrees to the flow direction and made it possible to significantly enhance the heat transfer in comparison with plain fins. It has been found that the heat transfer coefficient depends on the vapor quality, and at a mass velocity of 20 kg/m²s, it exceeds the corresponding value at a velocity of 50 kg/m²s because of a thinner condensate film at the top of the texture.