Conference Year
2016
Keywords
Brazed plate heat exchanger, experimental test rig, high pressure evaporation
Abstract
In this contribution, the experimental heat transfer coefficient  and the pressure drop measured during HFC refrigerants vaporization inside small brazed plate heat exchanger (PHE) at typical evaporation temperature for organic Rankine cycle systems for low thermal energy quality applications are presented. Scientific work focusing on the heat transfer in PHEs has been carried out since the late 19th century. More recent publications have been focusing on vaporization and condensation of refrigerants at heat-pump like operation. Despite PHEs are largely used for small to medium organic Rankine cycle (ORC) systems (5-250 kWel), literature covering the heat exchanger performance at temperatures and pressures suitable for ORCs is scarce. In order to fill the lack of experimental data for heat transfer in ORC-like operation, a dedicated heat transfer test installation has been designed and built at the Technical University of Denmark. The rig features six small brazed PHEs installed in series which allow simulating various heat transfer conditions. The first measured experimental results are presented. The tests include vaporization runs carried out at three different saturation temperatures (70, 80, and 90 °C) and different evaporator outlet conditions (outlet vapor quality around 0.4 and 1.00) and  various inlet sub-cooling around 5 and 10 °C for HFC-134a. The recorded data are compared with available two-phase correlations in the literature. Furthermore a correlation for frictional pressure drop is proposed.