Abstract
The relationship between the performance ratio and the overall heat transfer coefficients of thecondensers in a multi-stage flash evaporator was investigated theoretically and experimentally. Asimplified equation between the performance ratio and the overall heat transfer coefficient wasobtained by the approximate calculation of the theoretical heat and mass balance of the evaporator.
The experimental tests were carried out using a 100m3/d, 10-stage plant and a 1 m3/d, 5-stageplant. The performance ratio and the overall heat transfer coefficient of each plant were examinedat the operations with and without polyphosphate additive for scale prevention. The experimental data on the performance ratio and the overall heat transfer coefficient werecompared with the values calculated using the simplified equation. The experimental data of theperformance ratio agreed well with the calculated values before the heat transfer tubes of thecondensers in the plants were extremely fouled by the deposition of scales and sludges. From theresults of the experiments, it was cleared that the simplified equation was capable of applicationto the commercial plants. The fouling factors of the tubes are given using the overall heat transfercoefficients calculated from the experimental data of the performance ratio by the simplified equation, and the conditions of the tube cleaning are estimated.
