GATE CH topic:heat-transfer PYQs & Answers — Page 4

Questions 31–40 of 57. Imported answers require independent review unless marked reviewed.

For a shell-and-tube heat exchanger, the clean overall heat transfer coefficient is calculated as 250 W m

for a specific process condition. It is expected that the heat exchanger may be fouled during the operation, and a fouling resistance of 0.01 m

K W

is prescribed. The dirt overall heat transfer coefficient is _____ W m

Your answerChoose one option.

100

150

200

250

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

A straight fin of uniform circular cross section and adiabatic tip has an aspect ratio (length/diameter) of 4. If the Biot number (based on radius of the fin as the characteristic length) is 0.04, the efficiency is ________ % (round off to nearest integer).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

A double-effect evaporator is used to concentrate a solution. Steam is sent to the first effect at 110 °C and the boiling point of the solution in the second effect is 63.3 °C. The overall heat transfer coefficient in the first effect and second effect are 200 W m

and 1500 W m

, respectively. The heat required to raise the temperature of the feed to the boiling point can be neglected. The heat flux in the two evaporators can be assumed to be equal.

The temperature at which the solution boils in the first effect is ________ °C (round off to nearest integer).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

Consider a solid slab of thickness 2L and uniform cross section A. The volumetric rate of heat generation within the slab is

(W m

). The slab loses heat by convection at both ends to air with heat transfer coefficient

. Assuming steady state, one-dimensional heat transfer, the temperature profile within the slab along the thickness is given by:

where

is the thermal conductivity of the slab and

is the surface temperature. If

K, ambient air temperature

K, and Biot number (based on L as the characteristic length) is 0.5, the maximum temperature in the slab is ________ K (round off to nearest integer).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

Ratio of momentum diffusivity to thermal diffusivity is

Your answerChoose one option.

Reynolds number

Prandtl number

Nusselt number

Peclet number

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

Leidenfrost phenomenon refers to

Your answerChoose one option.

the condensation of vapour on a cold surface

the exchange of heat between two solids

the melting of frost

film boiling and evaporation of liquid droplets falling on a very hot surface

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

A hollow cylinder of equal length and inner diameter (i.e.,

) is sealed at both ends with flat plate, as shown in the figure. Its inner surfaces,

, and

radiate energy.

denotes the fraction of radiation energy leaving the surface

which reaches the surface

. It is also known that

. Which one of the following is correct?

Diagram for Chemical Engineering question 35

Your answerChoose one option.

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

A fluid is heated from 40 °C to 60 °C in a countercurrent, double pipe heat exchanger. Hot fluid enters at 100 °C and exits at 70 °C. The log mean temperature difference, i.e. LMTD (in °C), is __________ (round off to 2 decimal places).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

Consider an infinitely long rectangular fin exposed to a surrounding fluid at a constant temperature

. The figure shows the fin.

Diagram for Chemical Engineering question 42

The steady state one dimensional energy balance on an element of the fin of thickness

at a distance

from its base yields

where

is the temperature of the fin at the distance

from its base in °C. The value of

is 0.04 cm

and the temperature at the base is

. The temperature (in °C) at

cm is ________ (round off to 1 decimal place).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

An aqueous suspension at 60 °C is fed to the first effect of a double effect forward feed evaporator with a mass flow rate of 1.25 kg s

. The sum of the rates of water evaporated from the first and second effects is 1.0 kg s

. Temperatures of the exit streams from the first and the second effects are 100 °C, and 60 °C, respectively. Consider the specific heat of the aqueous suspension, and the latent heat of phase change for water to be 4 kJ kg

and 2200 kJ kg

, respectively, over this temperature range. The steam economy (in kg per kg) is ________ (round off to 2 decimal places).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

GATE CH topic:heat-transfer PYQs

Question 8

Question 43

Question 44

Question 45

Question 18

Question 20

Question 35

Question 41

Question 42

Question 45