Gas content in the tubes of a forced-circulation evaporator and optimal flow rate
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What is the gas volume fraction inside the heating tubes of a conventional forced-circulation evaporator? What is the optimal flow rate range for effective heat transfer and to prevent scaling? And what is the relationship between the evaporation rate and the circulation rate in forced circulation?
This post was last edited by FORREST_GUMP on 2015-12-4 09:02; the fluid inside the forced-circulation heat exchange tube is superheated fluid； The evaporation chamber at the upper part of the heat exchanger contains a certain amount of fluid, and it is the pressure of this fluid that causes bubbles to emerge when they reach near the liquid surface.
No crystal precipitation or low solid content; the flow velocity inside the tube is around 1.5 m/s； It has a high solid content; to reduce the energy consumption of the circulation pump, the flow rate is appropriately reduced to around 1.2 m/s.
If the heat transfer temperature difference for external heating is not large and weak nucleate boiling occurs inside the tube, are there any literature sources that provide formulas for calculating the heat transfer coefficient in such cases?
In a forced-circulation evaporator, the circulation rate has no direct relationship with the evaporation rate! The main parameter is the flow velocity inside the tube; a value of 1.2 to 1.5 meters per second is recommended.