Heat transfer efficiency of the heat exchanger
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What are the methods to address poor heat transfer performance in heat exchangers?
In the heat transfer process, reducing the thermal resistance in shell-and-tube heat exchangers to improve the heat transfer coefficient is an important issue. The thermal resistance mainly stems from the thin layers of fluid adhering to the heat transfer surfaces on both sides of the partition (known as boundary layers), as well as the fouling layers that form on both sides of the walls during the operation of the heat exchanger; the thermal resistance of metal walls is relatively low. Increasing the flow velocity and turbulence of the fluid can thin the boundary layer, reduce thermal resistance, and improve the heat transfer coefficient. However, increasing the fluid flow rate raises energy consumption; therefore, a proper balance must be struck between reducing thermal resistance and minimizing energy use during design. To reduce the thermal resistance of fouling, efforts can be made to delay its formation and to clean the heat transfer surfaces regularly.
Poor heat transfer performance in heat exchangers is usually due to the following three reasons: 1. The system has just been put into use, and it wasn’t thoroughly cleaned before operation; debris such as sand, slag, wood chips, and plastic bags remains inside the system, blocking the heat exchanger tubes and affecting heat transfer. 2. In systems that are already in use, it’s possible that the packing material in the recirculating water filter, such as quartz sand, has leaked out, blocking the heat exchanger tubes and impairing heat transfer. 3. The chemicals used for treating recirculating water are ineffective, allowing algae to grow in the water; these algae eventually turn into sludge that adheres to the inner walls of the heat exchanger tubes, reducing their thermal conductivity and thus affecting heat transfer. Therefore, the following measures should be taken to address these issues: 1. Clean the system to remove all debris from it. 2. Fix any leaks in the filter; it’s likely that the water cap of the filter is damaged, and it should be replaced immediately. 3. Clean the heat exchangers affected by sludge; in severe cases, chemical cleaning may be necessary. If the damage is severe, the entire recirculating water system may need to be cleaned as well.
What was said on the 4th floor is more in line with actual production practices and is also more comprehensive