Condensation and Evaporation Characteristics of Flows Inside Three Dimensional Vipertex Enhanced Heat Transfer Tubes
AbstractResults are presented here from an experimental investigation of condensation and evaporation heat transfer that compares the performance of three dimensional (3-D) enhanced heat transfer tubes to the performance of a smooth surface tube. The equivalent outer diameter of all the tubes was 12.7 mm with an inner diameter of 11.5 mm. Both the inner and outer surfaces of the 3-D tubes are enhanced by a primary enhancement and a background pattern made up by an array of dimples. Experimental runs were performed using R410A as the working ﬂuid, over the quality range of 0.2 – 0.9. The test apparatus included a horizontal, straight test section with an active length heated by water circulated in a surrounding annulus. Constant heat flux was maintained and refrigerant quality varied. For evaporation, the heat transfer coefﬁcient ratio of the 3-D tubes (comparing the heat transfer coefﬁcient of the enhanced tube to that of a smooth tube) is in the range of 1.1 – 1.80 for a mass ﬂux rate that ranges from 80 to 180 kg/m2s. For condensation, the heat transfer coefﬁcient ratio range is 1.1 - 1.75 for mass ﬂux that ranges from 80 to 260 kg/m2 s. Frictional pressure drop values for the enhanced tubes show some variation. Heat transfer enhancement on the inner surface of the 3-D tubes increases the surface area and interfacial turbulence; producing ﬂow separation, secondary ﬂows and a higher heat ﬂux from the wall to the working ﬂuid. Enhanced heat transfer tubes are important options to be considered in the design of high efficiency systems. A wide variety of industrial processes involve the transfer of heat energy during phase change and many of those processes employ old designs. These processes are ideal candidates for a redesign that could achieve improved process performance. These three dimensional enhanced tubes recover more energy and provide an opportunity to advance the design of many heat transfer products.
How to Cite
Kukulka D., Yan H., Smith R., Li W., 2017, Condensation and Evaporation Characteristics of Flows Inside Three Dimensional Vipertex Enhanced Heat Transfer Tubes , Chemical Engineering Transactions, 61, 1777-1782.