A. General

Wide variations in condensing coefficients occur along the condensation path as a result of changing vapor velocity and condensate quantity. Condenser design thus requires evaluating the coefficients and temperature difference as a function of the vapor fraction (or heat load) and integrating numerically or graphically to determine the surface area. These stepwise and iterative calculations are solved by means of complex computer programs, which are proprietary.

The condensation equations used are for the local average coefficient; that is, at a given axial position along the tube, the coefficient is the circumferential average coefficient and not a local point coefficient.

For convenience, we summarize below the condensing coefficient equations used in condenser design, but Section 32, on condensation, should be consulted for more detail and discussion. Depending on the type of coolant and condenser design, the following sections need be consulted for the calculation of coolant coefficients and pressure drop:

  2.3 Multiphase fluid flow
  2.5 Single-phase convective heat transfer
  2.7 Boiling and evaporation
  3.3 Shell-and-tube exchanger design: sensible heat transfer
  3.5 Evaporators
  3.6 Shell-and-tube reboilers
  3.8 Air-cooled heat exchangers