Heat exchangers are widely used equipment in waste heat recovery and thermal systems. In order to obtain the best economic benefits, it is necessary to involve the optimal design of heat exchangers. Although the use of heat exchangers can recover heat energy, it increases investment and operating costs. There is currently no unified and recognized best method for the optimal design of heat exchangers. More methods are to use the aforementioned efficiency-heat transfer unit. Number (E-NTU) method.

The temperature of the heat exchanger medium depends on the process conditions. Although we hope that the heat transfer temperature and pressure will be larger to increase the heat transfer intensity, the medium temperature may be too high or too low, and the phenomenon of fouling, precipitation, crystallization, etc. may occur, which will cause heat transfer. deterioration. At the same time, the choice of medium temperature has an impact on the selection of wall materials and the requirements of thermal compensation. It is not economically cost-effective to blindly pursue high efficiency. For this reason, you can refer to the following data.

The temperature difference at the hot end is not less than 20℃; the temperature difference at the cold end is not less than 5℃; the initial temperature of the coolant in the cooler or condenser should be higher than the freezing point of the fluid to be cooled; for the condensation of non-condensable gases, the final temperature of the coolant It is required to be 5°C lower than the dew point temperature of the condensed gas; the temperature difference between the hot fluid outlet of the air-cooled heat exchanger and the air population should not be less than 20°C, etc. Some of the above indicators can be obtained through technical and economic calculations. Of course, these indicators should be considered comprehensively in practice according to different occasions and purposes.

The evaluation of heat exchangers should be comprehensively considered based on technical and economic analysis, such as economy, safety, manufacturing, installation, operation and maintenance process technology and material requirements, etc., especially the improvement of heat exchangers in energy-saving projects It should be noted that under the same pressure drop conditions, its heat transfer coefficient K, heat exchanger efficiency E. On the basis of comparability, with many technical and economic indicators such as equipment investment and operating costs, energy-saving evaluation has universal guiding significance.