Keeping the sheets clean is one of the important conditions for maintaining a high heat transfer coefficient. Between the plates, the medium moves along the narrow and meandering flow path. Even if a relatively thick scale layer is generated, it will cause changes in the flow path, affecting the movement of the fluid, increasing the pressure drop, and reducing the heat transfer coefficient. For example, a sugar mill uses a plate heat exchanger in heating. Because the secondary water is not well treated, the flow channel is blocked for only two months during use and cannot continue to operate.
1. chemical cleaning method
This method is to cyclically pass a chemical solution through the heat exchanger to dissolve and discharge the dirt on the surface of the sheet. This method does not require disassembling the heat exchanger, which simplifies the cleaning process and reduces the labor level of cleaning. Since the corrugation of the sheet can promote the turbulent flow of the cleaning liquid and facilitate the dissolution of the scale layer, the chemical cleaning method is a better method.
2. mechanical (physical) cleaning method This method is to manually clean the plate after the brush, in order to achieve the purpose of removing dirt on the surface of the plate. Although this method is relatively straightforward, it is not easy to clean the harder and thicker scale layer.
3. the comprehensive cleaning method for the dirt layer is relatively hard and thick, simply using the above method is difficult to clean. The comprehensive method is to first soften the scale layer by chemical cleaning, and then remove the scale layer by mechanical (physical) cleaning method to keep the sheet clean.
4. precautions when cleaning
1 The solution should maintain a certain flow rate during chemical cleaning, generally 0.8 ~ 1.2m / s. Its purpose is to increase the degree of turbulence in the solution.
2 Different chemical cleaning solutions should be used for different soils. In addition to the frequently used diluted soda ash solution, a 5% nitric acid solution can be used for the scale. For the scale generated in the production of soda ash, a 5% hydrochloric acid solution can be used. However, chemical lotions that corrode the plates should not be used.
3 Mechanical (physical) cleaning does not allow the use of carbon steel brush to scrub stainless steel, so as not to accelerate the corrosion of the plate. At the same time, the surface of the plate cannot be scratched or deformed.
4 After cleaning, the plate should be rinsed with water and dried, and the plate should be prevented from being deformed.