CH-12-033 (RP-1345) -- Effect of Condensation Temperature and Water Quality on Fouling of Brazed-Plate Heat Exchangers PDF

This paper is based on findings resulting from ASHRAE Research Project RP-1345.

Brazed-plate heat exchangers (BPHEs) have been recently introduced in the air-conditioning industry because they could provide higher heat-transfer rate per unit volume and are more compact than conventional tube-and-shell exchangers. This paper presents experimental data of waterside fouling performance of BPHEs used in direct refrigerant-to-water condensers for cooling tower applications. The effects of refrigerant condensation temperature and water quality were experimentally investigated and asymptotic values of the fouling resistance were determined. Two saturation temperatures of 105.5°F and 120°F (c.41°C and c.49°C) and two water qualities for high- and medium-fouling potentials were applied in controlled laboratory fouling experiments and BPHEs with soft chevron corrugation angles were significantly affected by these operating parameters. For hard chevron corrugation angles, the fouling resistance was still dependent on the refrigerant saturation temperature, but the degradation of the heat flux in fouled condition was only of few percents. The fouling of the plates affected the waterside pressure drop significantly, which was from 10% higher up to 11 times higher than the corresponding waterside pressure drop across the BPHE in clean conditions. The effect of the cooling tower water quality was also quantified in the present work and asymptotic values of the fouling resistance were derived for water with moderate to severe mineral scaling conditions.