Refrigerant two-phase flow behaviour and pressure drop up- and downstream of a sharp return bend

by Kathleen De Kerpel

Institution: Ghent University
Year: 2015
Keywords: Technology and Engineering; Two-phase flow pressure drop; Two-phase flow behaviour; Heat exchanger
Record ID: 1075105
Full text PDF: http://hdl.handle.net/1854/LU-5965826


The European Union’s goals for climate and energy aim for a reduction of Europe's greenhouse gas emissions by 80-95% compared to 1990 levels by the year 2050. One of the technologies that can help to attain such a low-carbon society is a heat pump. It is estimated that the use of heat pumps could reduce the CO2 emissions of the building sector by 50%. An important component of the heat pump system is the heat exchanger, which typically consists of tubes and fins. This type of heat exchanger is also common in other applications such as air-conditioning. For domestic applications it is important that this heat exchanger is constructed in a compact way. To attain a heat exchanger with a limited size, the tubes are folded up into a sequence of short straight channels interconnected by 180° bends. The fluid flowing through these tubes extracts heat from the ambient air and the addition of this heat causes the fluid to evaporate. Research confirms that the presence of the bends do affect the evaporating flow in these channels. However, the underlying mechanisms are still largely unknown. In this work, the effect of the return bend on the flow is investigated and linked to the occurring pressure drop in the channel. The results yield more insight in how the bend geometry affect the flow and what the consequences are for the occurring pressure drop.