【2026 Heat Exchangers】Excessively small temperature difference between the inlet and outlet of the heat exchanger tubes

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What is the reason for the excessively small temperature difference between the inlet and outlet of the heat exchanger’s tube side (decreasing from the design value of 15°C to 5°C)? Will it affect the manufacturing process? An insufficient temperature difference is a direct indication of inadequate heat transfer capacity; if this issue is not resolved, it will result in the process medium not reaching the required temperature, and may even lead to the shutdown of subsequent equipment. The main causes should be investigated in terms of flow rate, scaling, and leaks. Key contributing factors: ① Insufficient flow rate of the fluid in the pipeline (the valve at the pump outlet is not opened enough, resulting in a flow rate of only 60% of the design value; the low flow velocity leads to a decrease in the heat transfer coefficient) ； ②Fouling of tubes (for example, 0.5 mm of fouling on the walls of cooling water pipes increases the heat transfer resistance by 40%, preventing effective heat transfer) ； ③Internal leakage in the tube or shell side (mixing of cold and hot fluids, resulting in an offsetting temperature difference; for example, cross-flow between cold water and high-temperature materials in chemical plants, leading to a sharp drop in temperature difference). Impact on production: ① If it is a heat exchanger for cooling, it will cause the outlet temperature of the process medium to exceed the specified limits (e.g., insufficient cooling of the reaction vessel, loss of control over the reaction temperature, and a 10%-15% decrease in product yield) ； ②If it is a heat exchange unit for heating, it will result in insufficient preheating temperature of the raw materials, thereby reducing the conversion rate in subsequent reactions (for example, if the feed to the catalytic unit is not properly preheated, the catalyst’s activity cannot be fully utilized). Solution: ① Check the operating status of the pump; open the outlet valve fully to ensure that the flow rate reaches the design value ； ②In the case of scaling, high-pressure water cleaning or chemical cleaning (such as immersion in citric acid solution) is carried out ； ③In the case of internal leakage, the leaking pipe is located through a hydrostatic test, and then the pipe is sealed for repair. In a chemical plant, the temperature difference in the cooling heat exchanger of a reaction vessel was too low; after cleaning the scale buildup in the tube side, the temperature difference returned to 14°C, the reaction temperature stabilized, and the yield of the product increased by 8%.