Experimental study of the two-phase flow distribution in helical-structured vertical headers

Abstract

A vertical header is a crucial component of a microchannel heat exchanger that facilitates the distribution of the two phases of the refrigerant into horizontally aligned channels. Ensuring an even distribution of the refrigerant into the channels is imperative for achieving the designed optimal performance. Previous studies have indicated that the distribution characteristics of the vertical header are contingent upon the mass flow rate and geometric properties of the header. This study aims to investigate the distribution characteristics of two-phase flow resulting from structural modifications in the header, specifically by implementing a vertical header with a helical structure. Hence, an experimental device simulating a microchannel heat exchanger found in a commercial air conditioning system was employed. The distribution characteristics of the vertically oriented header with a helical structure were measured by varying the inlet conditions (mass flow rate: 50–100 kg h−1; vapor quality: 0.1–0.2). The measured distribution characteristics were compared with those obtained from a conventional straight vertical header possessing the same cross-sectional properties. The experimental findings demonstrated that the helical structure induced a distinctive flow pattern and facilitated the mixing of the two phases. Furthermore, this helical structure exhibited reduced inertial forces compared to the simple vertical header, leading to improved distribution performance.

Keywords

• Microchannel heat exchanger
• Flow distribution
• Helical header structure
• Vertical header
• Maldistribution