In a tube heat exchanger, if the heat exchange tubes are replaced from carbon steel to stainless steel, how does the heat exchange area change?
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This post was last edited by INJQZ on 2019-3-17 at 13:40. In the shell-and-tube heat exchanger, the heat exchange tubes have been replaced from carbon steel to stainless steel; the diameter and wall thickness of the tubes remain unchanged； The thermal conductivity of stainless steel is 1/3 that of carbon steel; as the heat transfer coefficient decreases, the heat exchange area needs to be increased. To ensure an effective heat exchange, by how many times is the heat exchange area usually increased?
I think the heat exchange area should remain unchanged
What you’re asking is: if the heat exchange tubes are replaced from carbon steel with stainless steel tubes, and the diameter and wall thickness of the tubes remain unchanged, by how much does the heat exchange area need to increase in order to achieve the same heat exchange efficiency as before? Because if only the material is changed while all other factors remain the same, the heat exchange area stays unchanged.
I usually add a factor of 1.5, but stainless steel pipes are generally much thinner than carbon steel pipes, so it’s okay to use a smaller value. In any case, it’s just an estimate; it’s best to recalculate based on the actual operating conditions
Yes. Ensure optimal performance. Do we need to increase the heat exchange area? By how much?
The material of the heat exchange tubes has been changed from carbon steel to stainless steel, and the thermal conductivity of this material varies (stainless steel has a lower thermal conductivity). With all other conditions remaining unchanged, the higher the thermal conductivity, the greater the overall heat transfer coefficient. Therefore, switching to stainless steel will result in an increase in the required area; however, the exact amount of increase can only be determined through heat transfer calculations. It is certain that the increase will not be significant.
Increasing it by 1.5 times means it becomes 2.5 times the original area?
This post was last edited by zjq1962 on 2019-3-17 at 13:44. Using the formula for calculating K, aside from the change in rw in the denominator, all other values remain constant; this allows one to determine how much more area is needed.
This post was last edited by INJQZ on 2019-3-17 at 13:48
GB/T151 Appendix F