Subtopic: Concentration and drying of liquid foods – evaporators, tray, drum and spray dryers
Question Statement:
Boiling Point Elevation ($BPE$) of concentrated food liquid solutions in an evaporator causes:
Options:
(A) A reduction in the effective temperature driving force ($\Delta T$) available for heat transfer
(B) An increase in the steam economy of the evaporator
(C) A decrease in liquid viscosity
(D) An increase in the overall heat transfer coefficient
Answer Key:
A
Step-by-Step Solution & Explanation
Because dissolved solutes increase the boiling point of the solution above that of pure water ($T_b = T_{sat} + BPE$), the temperature difference between condensing steam and boiling juice is reduced ($\Delta T_{eff} = T_{steam} - (T_{sat} + BPE)$), which reduces the heat transfer capacity.