Two-phase flow distribution in compact heat exchanger manifolds

In this paper an experimental study to investigate two-phase flow distribution in compact heat exchanger manifolds is presented. An experimental test rig to measure the flow distribution in realistic manifold geometries and under relevant operating conditions was built. To elucidate the effect on the flow distribution, the following factors are investigated: vapour fraction at the manifold inlet, heating load on the heat exchanger tubes, diameter of the manifold and manifold inlet tube length. The experimental system simulated an evaporator for an automobile air conditioner with a design cooling capacity of 5 kW. From the horizontal manifold, the two-phase refrigerant flow was distributed in 10 parallel heat exchanger tubes. The orientation of the test rig could be varied to measure both upward and downward flow out of the manifold. To ensure similarity to an actual heat exchanger, counterflowing water was used as heat source in the evaporator section. The experimental setup made it possible to measure the heat added to the evaporating refrigerant in each tube by using separate water flow circuits. Refrigerant R134a was used as refrigerant. (C) 2003 Elsevier Inc. All rights reserved.