Evaporation and Boiling Heat Transfer at Film Irrigation of Horizontal Roughened Tubes

Industrial shell and tube heat exchangers require often pipes of considerable length. The surface treatment of such tubes to enhance heat transfer parameters of the equipment must be cheap and simple in manufacturing. Two kinds of tube surface treatment are compared: sandblasting and machining. The tubes with OD = 10 mm, ID = 6 mm, and 625 mm long were tested within a bundle of horizontal tubes installed in a rectangular evaporator shell. Hot water pumped through bundle tubes used as a heat carrier. Refrigerant R21 at the pressure of \(\sim\)3 bara is used as working liquid. Tests have been performed at \(Re\) numbers from 500 to 1500. The micro-rough tubes (machined duralumin tube, sandblasted copper tube) provide considerable heat transfer enhancement at transition to bubble boiling. At low heat fluxes (evaporation regime) heat transfer on these tubes are close to plain tubes.