6.6.2   Condensing section

 

The condensing section uses the method of calculating LMTD as illustrated in Fig 3.51 (d) but with

T1 - T2 = TS ,

the saturation equivalent of the pressure in the condensing section. The effect of the 28°C of superheat may be neglected as its effect on the surface area will be small. The overall heat transfer coefficient is dependent on the condensing heat transfer process and can be found by reference to BEAM A 1968 [13] or ТЕМА 1978 [12]. The baffle pitch is determined by the need to distribute the steam throughout the condensing section and is usually about the maximum permissible without the risk of tube vibration. The length of the condensing section is determined from the heat transfer surface needed, the external area of the tube per unit length and the number of tubes.

In a two-flow U-tube heater, as illustrated in Fig 3.44, the condensing section includes the return bend of the 'U' and part of the bottom return leg.

 

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