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Calculate heat transfer area for a plate-type condenser

Q: We need to distill PoCl₃, which is present in reaction mass. We increase the temperature and distill with 1 tar pressure through a plate-type condenser. For 250 kgs to be distilled with cooling water as utility for condenser jacket, what capacity of plate-type condenser do we need? At what pressure we can pass water through jacket? How do we calculate the heat transfer area? How do we know the thermal conductive?

A: The distillation of POCl₃ at 1 bar (~1 atmosphere) would result in a saturated vapor temperature of about 105ºC if it is a pure component. The capacity of the condenser is determined by the rate at which you desire to distill off the POCl₃. The latent heat of POCl₃ must be utilized along with the specific heat of the liquid and desired amount of subcooling in order to determine the total enthalpy change per Kg of POCl₃. This data, along with other physical and transport properties, can be obtained from the literature although a comprehensive source like DIPPR would be more reliable.

The pressure of water through the jacket can be whatever is required to overcome the pressure drop across the unit. The flow rate of water should be set so as not to exceed about 50°C discharge temperature to prevent carbonate scale fouling (dependent on water quality).

Heat transfer area must be calculated by starting with a trial design, calculating individual film coefficients and log mean temperature difference (LMTD). Using these data with the general heat transfer equation: Q = U x A x LMTD. This process is iterative until the desired heat duty (Q) is achieved.