Two-phase flow in air-cooled heat exchangers

Brandon White, Test Engineer

Air-cooled heat exchangers are one of the most widely used types of heat exchangers. At times, they can experience two-phase flow separation and flow maldistribution inside their header boxes, potentially reducing process heat transfer.At HTRI’s Research & Technology Center, we are currently working on a project to enhance the prediction capabilities of Xace®. This involves testing an adiabatic mock-up of an air-cooled heat exchanger, as shown in Figure 1. The mock-up is a scaled-down version of a full-sized air-cooled heat exchanger and is used to verify the concept of construction and measurement techniques.

Schematic for the mock-up of the air-cooled heat exchanger
Figure 1. Schematic for the mock-up of the air-cooled heat exchanger

Both the front header and the tube bundle are transparent, allowing us to visualize the flow. A mixture of air and water is used to simulate a two-phase flow regime. By varying the amounts of air and water at the inlet to the heat exchanger, different qualities and void fractions can be achieved.

The data collected from this test will be used to quantify the maldistribution of two-phase flow in an air-cooler front header. This will allow us to improve HTRI’s software and design recommendations.

In the video below, the mock-up of the air-cooled heat exchanger is seen from various angles and frame rates.

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