Enhanced Condensation Outside Horizontal Heat Transfer Tubes

摘要

Experimental investigation of heat transfer and friction characteristics was conducted on the out side of horizontal carbon steel heat transfer tubes under the pressure of saturated vapour 0.04MP (gauge pressure). The test tubes included spiral-grooved tubes, corrugated tube and smooth tube. The use of water as test fluids has allowed to cover a wide range of turbulent fluid flow conditions: Reynolds number from 1 x 104 to 5×104. The heat transfer coefficients and amount of vapour condensation of spiral-grooved tube with different structure parameters are measured. The spiral-grooved tube has the best heat transfer performance compared with corrugated tube and smooth tube. The maximum heat transfer coefficients and amount of vapour condensation of spiral -groove tube is respectively 2.32 and 1.72 times as smooth tube. The maximum ηof spiral groove tube as comprehensive performance evaluation is 1.86. The corrugated tube increase heat transfer coefficients only in the Reynolds numbers lower than 1.5×104, but lower than spiral groove tube, and transfer performance is worse than smooth tube with the Reynolds numbers grow. The structure parameters influence on spiral-grooved tube performance results show that the deeper of the groove, the better heat-exchange performance with the drag coefficient increased in the same Reynolds numbers. And the greater the fin pitch and trough radius, the poorer the heat exchange effectiveness with the drag coefficient decreased.