Determining optimum tube dimensions for Robert evaporators

Experimental investigations were undertaken for three tube lengths and three tube diameters in a pilot evaporator to determine the optimum tube dimensions for Robert evaporators. The pilot evaporator was tested at operating conditions typically encountered in sugar factory evaporators. Juice of three brix levels were selected to mimic conditions for the first, third and fifth effect positions in a quintuple evaporator set. For each brix, the heat transfer coefficient was calculated at four juice levels, two headspace pressures and two pressure differences between the calandria and the head space. Of the four juice levels, one juice level was identified as the optimum juice level corresponding to the maximum heat transfer coefficient. In total, 432 tests were undertaken with nine tubes and 128 tests were replicated with four tubes. This paper highlights the maximum HTC and optimum juice level results from the experimental work, linked together with a capital cost model and sucrose loss considerations, to determine the optimum tube dimensions for the Robert evaporator at the first, third and fifth effect positions in a quintuple evaporator set