Performance Degradation Due to Micro Fouling Layers in Large-Scale Industrial Heat Exchangers

The 16T Propulsion Wind Tunnel, located at Arnold Engineering Development Complex (AEDC), Arnold Air Force Base, Tennessee, is a closed-circuit wind tunnel consisting of a 16-foot by 40-foot long test section. The test section temperature is controlled by a 50-foot diameter cross flow air to water heat exchanger, the K1 Cooler. Over the last several years, the performance of the K1 Cooler has deteriorated and the thermal capacity of the cooler has come into question. A study was initiated to quantify the deterioration and determine how critical bundle replacement was to future operations. To aid this investigation, multiple tubes were removed from the cooler and analyzed. It was found that the tubes had an internal layer of particulate fouling that could be causing a degradation in cooler performance. Since the original design did not account for an accumulating internal fouling layer, a Matlab model was created to simulate cooler exit air and water temperatures for varying values of the fouling layer thermal conductivity and fouling layer thickness. Results were compared to empirical data at multiple test conditions.