Heat Transfer in Circular Channel with Spiral Intensifiers during Circulation of Non-Azeotropic Alcohol-Water Mixture

The use of mixtures as refrigerants and heat carriers in various power systems has become widespread. The thermophysical properties of mixtures differ from the properties of their components. This paper presents the results of a study of the intensity of heat transfer to a non-azeotropic alcohol-water mixture with weight concentration of the volatile component of 20% during forced circulation in a heated smooth circular channel, as well as in a channel with spiral intensifiers with a hydrophobic coating. The experiments were carried out on a closed circulation circuit at a pressure in the storage vessel of 0.04–0.055 MPa. The test section was a stainless steel tube with inner diameter of 7.6 mm and wall thickness of 0.2 mm. The heating was provided due to the electric current passed in the tube wall. The spiral intensifiers had winding pitch of 4 mm; the thickness of the PTFE sleeve was 0.9 mm. The experiments were carried out at mass flux rates of 44–46 kg/m² and 316 kg/m². The heat flux density varied in the range \(1200<q<15200\) W/m². The use of the spiral intensifiers with the hydrophobic coating during circulation of the non-azeotropic alcohol-water mixture (20%) in the circular channel led to the formation of a significant amount of the vapor-gas phase in the flow at channel wall temperatures below the saturation point of this mixture. The heat transfer coefficient in the channel with the intensifiers grew 2–5 times compared with those in a smooth channel.