Abstract
The purpose of this study is to improve the liquid-distribution uniformity of refrigerant gas-liquid flows in parallel-flow type heat exchangers that consist of dividing/combining headers and multiple branch tubes connected to them. The test channel had a vertical header with a height of 81.5mm and 8 horizontal branch tubes connected in parallel at a pitch of 10mm. We tested the refrigerant-supplying method using a pipe with multiple outlet holes installed in the dividing header, i.e., multi-hole inner pipe. Gas-liquid distribution ratios in each branch tube were measured changing an inner diameter and outlet-hole diameters of the inner pipe. It was confirmed that the liquid-distribution uniformity was much improved with the multi-hole inner pipe. Based on the design of experiment with the orthogonal table, we evaluated quantitatively the influence of geometrical parameters of the multi-hole inner pipe on the liquid distribution characteristics. We found that the inner diameter of the inner pipe had the large influence on the maximum reaching height of liquid, while the uniformity of the liquid distribution was influenced by the outlet-hole diameter of the inner pipe. The liquid-distribution uniformity was improved by using the inner pipe with a smaller outlet-hole diameter.
