Heat exchanger, has walls provided with hydrophilic coating formed chemically from aqueous solution

摘要

The walls of the heat exchanger are provided with a hydrophilic coating with a specific range of properties, applied by activating the heat exchange surface and then forming the coating by a chemical reaction from an aqueous solution. A heat exchanger comprises a thermally conducting wall optionally provided with a means for increasing its surface area, e.g. fins. Two media can flow along both sides of the wall in order for a reciprocal heat exchange to take place. The wall and/or the means for increasing its surface area are provided with a hydrophilic coating having at least one of the following properties : (a) a strong adhesion to the wall surface ; (b) providing cover for essentially the entire heat exchange surface area ; (c) a maximum thickness of 50 microns ; (d) a thermal resistance which is small in relation to the total thermal resistance in the heat exchange path between the heat exchange surface and the medium flowing along it ; (e) a hydrophilicity sufficient for a film of water to be spread over the coating surface when it comes into contact with moisture, optionally in combination with the formation of a buffer supply of water stored in capillaries in the coating ; (f) a low surface roughness so that the medium flowing over it is subjected only to a negligible flow resistance ; (g) a low susceptibility to thermal or (bio)chemical degradation, erosion, microorganism growth and fouling ; and (h) morphological, chemical and physical homogeneity. The coating is applied via a chemical method in which each heat exchange surface is initially activated using a chemical and/or mechanical treatment and then the coating is formed by a chemical reaction from an aqueous solution.