Condensation and Evaporation Characteristics of Vipertex 1EHT Enhanced Heat Transfer Tubes

Abstract

Heat transfer enhancement has been an important factor in obtaining energy ef?ciency improvements in refrigeration and air-conditioning applications. Utilization of enhanced heat transfer tubes is an effective method to be utilized in the development of high performance thermal systems. Vipertex™ enhanced surfaces, have been designed and produced through material surface modifications which result in flow optimized heat transfer tubes that increase heat transfer. Heat transfer enhancement plays an important role in improving energy efficiency and developing high performance thermal systems. Heat transfer processes that involve phase-change processes are typically efficient modes of heat transfer; however current energy demands and the desire to increase efficiencies of systems have prompted the development of enhanced heat transfer surfaces that are used in processes involving evaporation and condensation. Vipertex™ was able to develop a series of optimized, three dimensional tubes that enhance heat transfer. This study details the heat transfer and fluid flow results of the Vipertex 1EHT, enhanced heat transfer tube over a range of conditions that involved in-tube evaporation and condensation.
Results are presented here from an experimental investigation of two phase heat transfer that took place in a 12.7 mm (0.5 in) O.D. horizontal copper tube. 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. In-tube evaporation measurements of R22 and R410A are reported forevaporation at 10 °C with mass flow rates in the range of 15 to 40 kg/h. Single phase measurements are reported for mass flow rates from 15 kg/h to 80 kg/h. Condensation tests were conducted at a 47 °C saturation temperature, with an inlet quality of 0.8 and an outlet quality of 0.1. In a comparison to smooth tubes, the localand average heat transfer coefficients for the Vipertex 1EHT tube exceeded those of a smooth tube. Average evaporation and condensation heat transfer coefficients for R22 and R410A in the Vipertex 1EHT tube are approximately two times greater than those of a smooth tube.
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 technology. These processes are ideal candidates for a redesign that could achieve improved process performance. Vipertex 1EHT enhanced tubes recover more energy and provide an opportunity to advance the design of many heat transfer products.