Temperature difference at the inlets of the cold and hot fluids in the heat exchanger

1. The temperature difference is a requirement of the process, and in most cases it cannot be determined based on experience. 2. If you have to decide on your own, it depends on what the purpose of heat exchange is. For example, if you want to recover thermal energy, the greater the temperature difference, the better. However: 1) The temperatures on both sides must not intersect ； 2) Effective temperature difference on both sides: for plate-type heat exchangers, it should be above 2°C; for shell-and-tube heat exchangers, it should be above 5°C. 3) The temperature difference correction factor should not be lower than 0.8, otherwise the heat exchanger will be too large and the investment in the equipment will be high. This is a general principle.

This post was last edited by bfdlwolf on 2018-11-13 at 14:28. Selection and design of heat exchangers 8. Selection of temperature in process conditions 8.1 The outlet temperature of the cooling water should not exceed 60°C to avoid severe scaling. The temperature difference at the high-temperature end should not be less than 20°C, and the temperature difference at the low-temperature end should not be less than 5°C. When heat exchange occurs between the two process streams, the temperature difference at the lower temperature end should not be less than 20°C. 8.2 When a shell-and-tube heat exchanger with multiple tubes and a single shell is used, and water is employed as the coolant, the outlet temperature of the cooling water shall not be higher than the outlet temperature of the process stream. 8.3 When cooling or condensing a process stream, the inlet temperature of the coolant should be higher than the freezing point of the components in the process stream that are prone to freezing, typically by 5°C. 8.4 When cooling the reactants, in order to control the reaction, the temperature difference between the reaction stream and the coolant should be maintained at no less than 10°C. 8.5 When condensing process materials containing inert gases, the outlet temperature of the coolant should be lower than the dew point of the process materials, typically by 5°C. 8.6 To prevent hydrates from forming in natural gas and condensate gas, which could block the heat exchange tubes, the outlet temperature of the material being heated must be higher than its hydrate dew point (or freezing point), typically by 5  10°C.

This post was last edited by iwjtueabk on 2018-11-14 at 10:52. Basically, the temperature difference between the inlet and outlet of hot and cold fluids represents the conditions you currently have compared to those you desire; empirical values have no further relation to factors such as the size of your equipment, the size of the tube bundles, or the way the tubes are installed... It is recommended to read relevant articles first; understanding more about these topics will enable you to ask more professional questions. -------------------------------------------------- -------------------------------------- Making an effort on your own will also yield better results

:handshake Thank you so much