Heat Transfer MCQs Archives

221. LMTD for counterflow and prallel flow heat exchanger will be the same, when the

Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)

Outlent temperature of both the hot and cold fluid are same

Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid

None of these

✅ The correct answer is option A.

222. Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the

Less corrosion problems

Flexibility possible in the baffle arrangement

Low pressure drop

High heat transfer co-efficient

✅ The correct answer is option B.

223. The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m². The flux, when the element temperature is increased to 1000°C for the same furnace temperature is

11.2 kW/m²

12.0 kW/m²

14.6 kW/m²

16.5 kW/m²

✅ The correct answer is option D.

224. In case of __________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid.

Nucleate

Pool

Low pressure

None of these

✅ The correct answer is option B.

225. A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number.

Condensation

Grashoff

Stantan

Brinkman

✅ The correct answer is option D.

226. (NRe.NPr)(D/L) is called the __________ number

Peclet

Stanton

Graetz

None of these

✅ The correct answer is option C.

227. In Fourier’s law, the proportionality constant is called the

Heat transfer co-efficient

Thermal diffusivity

Thermal conductivity

Stefan-Boltzman constant

✅ The correct answer is option C.

228. Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube

Exit-fluid temperature > wall temperature

Exit fluid temperature < wall temperature

Exit fluid temperature = wall temperature

Graetz number > 100

✅ The correct answer is option C.

229. Which of the following has maximum thermal conductivity at the same temperature?

Steel

Petrol

Air

All of the above

✅ The correct answer is option A.

230. An evaporator while concentrating an aqueous solution from 10 to 40% solids evaporates 30000 kg of water. The amount of solids handled by the system in kg is

4000

9000

4600

3000

✅ The correct answer is option A.