Used to heat the same medium (with the same heat load), heated by superheated steam and saturated steam at the same temperature; heat exchange area...
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For the same application, when heating the same medium with 1.0 MPa superheated steam at 215°C and with 1.5 MPa saturated steam at the same temperature, which requires a larger heat exchange area under the same heat load?
This post was last edited by lupg on 2016-1-15 14:23. In the formula Q=K.A.ΔT, Q and ΔT are specified. The temperature difference for superheated steam varies, while that for saturated steam remains constant. In the original poster’s question, the K value is also changing. Closely related to this is the medium speed. 2 For superheated steam, the temperature changes but it remains in the gas phase, so it has little effect on the convective velocity ； When saturated steam loses heat, it converts to the liquid phase; its volume decreases significantly, its flow velocity drops, the Reynolds number falls, and the K value also changes. 3 To find out how the A value changes, several operating conditions can be listed for calculation
Premise: Since the poster mentioned that it is under the same heat load, this means that the process parameters on the cold side are identical, and the requirements regarding steam subcooling on the hot side differ little. Under these conditions, as stated by the poster, the difference in logarithmic temperature differences is small; hence, the effect of the heat transfer coefficient becomes more significant. The heat transfer coefficient for the condensation of superheated steam is lower than that of saturated steam; therefore, it is reasonable to estimate that a larger area is required for superheated steam.