Effect of flow rate on the performance and fouling of a spiral plate heat exchanger in the phosphoric acid cooling process

Abstract

The E-2502B cooler in the phosphoric acid concentration unit is used to reduce the temperature of H3PO4 product after concentration before storage. Fluctuations in mass flow rate and outlet temperature indicate the need to evaluate equipment performance to maintain safe and optimal cooling. This study evaluates the performance of the E-2502B Spiral Plate Heat Exchanger (SPHE) based on heat transfer, Log Mean Temperature Difference (LMTD), clean overall coefficient (Uc), design overall coefficient (Ud), fouling factor (Rd), and efficiency. The analysis used actual operating data from 18-27 July 2025, including inlet-outlet temperatures and mass flow rates on the hot and cold sides. The analysis was conducted under the lowest data conditions through heat balance, overall heat-transfer coefficient calculations, and comparison between the actual fouling factor and theoretical limits. The results show an actual cooler efficiency of 50%, with Uc of 853.319 kJ/m²h°C, Ud of 422.689 kJ/m².h.°C, and Rd of 0.001194 m².h.°C/kJ. The actual Rd value exceeds the theoretical range of 0.00018-0.00072 m².h.°C/kJ, indicating fouling that reduces heat-transfer performance. Stable mass flow, periodic cleaning of the acid and cooling-water plates, and flow-rate sensor verification are required to maintain cooler performance.