Overall Heat Transfer Co-efficients
Overall heat transfer coefficents (ohtc) from a number of sources given in kW/m2/K for a quadruple effect evaporator train
The coefficients from Tongaat-Hulett Sugar were reported in a paper by Meadows and Love (SASTA 1999, pg 211) and are derived from plant measurements over a number of years. One would expect, however, that heat transfer coefficients would depend on heating steam temperature and juice/syrup brix, and since these are not stated one must assume usual conditions, namely: heating steam temperature is 120°C, final effect vacuum at 13kPa abs, juice and syrup brix respectively 12° and 65°. If the conditions you are designing for are not similar to these these figures must be used with caution.
In chapter 11 of Sugar Technology by Van der Poel, Schiweck and Schwartz ohtc is given as a function of juice/syrup temperature and brix, the function given is
- kis ohtc in kW/m2/K
- Tjsis juice or syrup temperature in °C and
- Bjsis juice or syrup brix.
This function is used in the online design of a robert evaporator