Commonly used heat exchangers - how to choose shell and tube heat exchangers?
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Selection of commonly used heat exchangers - Shell and tube heat exchanger process conditions 1 Temperature The cooling water temperature is higher than 60°C and is prone to scaling. The temperature difference at the high temperature end should not be <20°C, and the temperature difference at the low temperature end should not be <5°C. When the process stream is undergoing heat exchange, the temperature difference at the low temperature end should not be <20°C.
When a multi-tube single-shell heat exchanger is used and water is used as the coolant, the cooling water outlet temperature shall not be higher than the process fluid temperature. The coolant inlet temperature should be higher than the freezing point of the easily frozen components of the process stream. When condensing materials with inert gas, the coolant outlet temperature should be lower than the dew point of the process material.
2. The pressure drop increases the process flow rate, which can increase the heat transfer coefficient and make the heat exchange structure compact. However, the increase in flow rate is related to the pressure drop. 3 Logistics Arrangement☆ In order to save the insulation layer or reduce the thickness of the shell, high-temperature logistics generally go through the tube side. Sometimes, in order to cool the materials, high-temperature logistics can also go through the shell side. ☆ Higher pressure, high viscosity, small flow rate, and small heat transfer film coefficient can easily cause turbulence in the process flow and increase the heat transfer coefficient. ☆ For pipe runs that are highly corrosive and have specific requirements for pressure drop, the heat transfer coefficient and pressure drop calculation errors are small. ☆ The dirtier and easier-to-scale material flows through the pipe, making it easier to control and clean dirt. ； If the shell side is used, a square arrangement should be used, and the heat exchanger can be disassembled.
☆ Pipe diameter: The smaller the pipe diameter, the more compact the structure, the cheaper the heat exchanger, and the greater the pressure drop. Commonly used pipe diameters are 19mm, 25mm, and 32mm. ☆ manager: When there is no phase change heat, the tube is longer and the heat transfer coefficient increases. ； With the same heat transfer area, long tubes have fewer tube passes, smaller pressure drops, and lower heat transfer area ratios. ☆ arrange: There are two types of configurations: square and triangular. The triangular configuration is conducive to shell-side turbulence, and the square configuration is conducive to shell-side cleaning.
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