Structural effect on the flow distribution in a vertical header of Microchannel Heat Exchanger

Abstract

Microchannel heat exchanger (MCHX) as a cutting edge technology, offers compactness while providing higher heat transfer capability and thermal energy savings for applications like aeronautics, automotive, manufacturing industries and residences. However, due to many microchannels within the MCHX, the fluid flow distribution becomes worst. This leads to 20 to 30% heat transfer degradation. In this paper, the behavior of two-phase flow distribution is presented when the microchannel tube protrusion depth (0% and 50%) and inlet flow orientation towards the header (top, middle and bottom) are varied. Mass flux is at 125 kg·m_-2·s_-1 or 100 kg·h_-1 (m_in) and vapor quality (x_in) at 0.2. 20 microchannel flat tubes are connected to the header, where every 4 is grouped into one measurement tube. Both experiment and visualization are conducted, which have yielded the best distribution for the bottom inlet port and 50% tube protrusion explained by the governing physical phenomena occurring within the header.