# Overall Heat Transfer Co-efficients

## Quadruple Effect

Overall heat transfer coefficents (ohtc) from a number of sources given in kW/m^{2}/K for a quadruple effect evaporator train

Tongaat- Hulett |
Honig | Baloh | Hugot | Clavijo | ||||
---|---|---|---|---|---|---|---|---|

First Effect | 2.500 | 2.160 | 3.410 | 2.800 | 4.050 | 2.330 | 2.790 | 3.014 |

Second Effect | 2.200 | 2.150 | 2.730 | 2.330 | 2.800 | 1.630 | 2.090 | 2.220 |

Third Effect | 1.700 | 1.360 | 2.050 | 1.800 | 1.820 | 1.160 | 1.630 | 1.907 |

Fourth effect | 0.700 | 0.680 | 1.020 | 0.770 | 1.120 | 0.700 | 0.930 | 1.255 |

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

k=0.465·T_{js}/B_{js}

where

- kis ohtc in kW/m
^{2}/K - Tis juice or syrup temperature in °C and
_{js} - Bis juice or syrup brix.
_{js}

This function is used in the online design of a robert evaporator