Question

If _______ heating has higher heat transfer rates than _______ heating, then why is ________ difficult to be used.

(a) Direct, Indirect, no difficulty, they’re used

(b) Direct, Indirect, coil is difficult to clean and is prone to bacterial growth

(c) Indirect, Direct, no difficulty, they’re used

(d) Indirect, Direct, coil is difficult to clean and is prone to bacterial growth

The question was posed to me in an interview for internship.

I'm obligated to ask this question of Unit Operations topic in chapter Heat Transfer Equipment, Microwave Heating, Evaporation, Diffusion and Mass Transfer and Dehydration of Food Engineering

Answer 1

Correct choice is (b) Direct, Indirect, coil is difficult to clean and is prone to bacterial growth

The explanation is: Direct heating has higher heat transfer rates than indirect heating, but, the coil is difficult to clean and is prone to bacterial growth.