Quantitative flow visualization in the distributor of a plate-fin heat exchanger

The flow distribution and head loss in the distributor of a plate-fin heat exchanger were experimentally investigated using quantitative and qualitative flow visualization methods. The flow distribution and head loss are important parameters related to the thermal performance and economic design of the heat exchangers. The effect of the different distributor angles (30°, 45°, and 60°) and the alignment configuration at the junction in the distributor were studied. The Reynolds number based on the hydraulic diameter was varied from 100 to 1200. Flow visualization using the dye injection and hydrogen bubble methods was applied to capture the qualitative flow structure inside and around the distributor. Digital particle image velocimetry was used to measure the instantaneous velocity fields, and the flow maldistribution was quantified by using the averaged velocity information. The qualitative flow visualization showed the variation of streamwise velocity in the end of the distributor and the existence of the secondary flow at the junction. From the velocity and pressure measurement, we found that the 30° model has the worst flow distribution and the smallest head loss among other models and the 60° model with misaligned configuration has the best flow distribution and the largest head loss.