Here are 1000 MCQs on Heat Transfer (Chapterwise).
1. What is heat transfer?
a) Flow of thermal energy from low-temperature reservoir to high-temperature reservoir
b) Flow of energy in the form of heat from high-temperature reservoir to low-temperature reservoir
c) Flow of thermal energy irrespective of reservoir temperature
d) None of the above
View Answer
Explanation: Heat transfer is a branch of thermal engineering which deals with the study of transfer of energy from a high-temperature reservoir to low-temperature reservoir.
2. Which of the following is a method of heat transfer?
a) Convection
b) Radiation
c) Conduction
d) All of the mentioned
View Answer
Explanation: Methods of heat transfer are:
i) Conduction: Heat is transferred by solid materials.
ii) Convection: Heat is transferred by gases.
iii) Radiation: Heat is transferred by electromagnetic waves.
3. Heat transfer takes place according to which of the following law?
a) Newton’s second law of motion
b) First law of thermodynamics
c) Newton’s law of cooling
d) Second law of thermodynamics
View Answer
Explanation: The total entropy of an isolated system (the thermal energy per unit temperature that is unavailable for doing useful work) can never decrease, according to the second law of thermodynamics.
4. Which of the following is the rate of heat transfer unit?
a) Watt
b) Pascal
c) Joule
d) Newton
View Answer
Explanation: The joule is the unit of heat transfer, while the rate of heat transfer is measured in joules per second, i.e., watts.
5. Which of the following is an example of steady-state heat transfer?
a) Electric bulb cools down by the surrounding atmosphere
b) Chilling effect of cold wind on a warm body
c) Boilers and turbines
d) Cooling of I.C engine
View Answer
Explanation: The system is a perfect black body.
6. Which way is heat transfer believed to take place in a long, hollow cylinder that is kept at consistent but varied temperatures on its inner and outer surfaces?
a) Unpredictable
b) Radial only
c) No heat transfer takes place
d) Axial only
View Answer
Explanation: On the periphery of the cylinder, the ambient temperature is uniform, and the temperature is uniform. As a result, it only occurs in the radial direction.
7. Which of the following is correct regarding one dimensional heat transfer?
a) Steady – f (x, y, t), Unsteady – f (x)
b) Steady – f (y, z), Unsteady – f (y)
c) Steady – f (x, t), Unsteady – f (x)
d) Steady – f (x), Unsteady – f (x, t)
View Answer
Explanation: In a one-dimensional heat flow, steady state is determined solely by the x coordinate, whereas unstable state is determined solely by the x coordinate and time.
8. A person prefers to sit by a fire during the cold winter months. Which of the following heat transfer types gives him with the most heat?
a) Convection and radiation together
b) Radiation will provide quick warmth
c) If it is near the fire, convection sounds good
d) Conduction from the fire
View Answer
Explanation: Even when separated by a medium that is colder than both of them, heat transmission by radiation can occur between two bodies.
9. On which of the following, convective heat transfer coefficient doesn’t depend on?
a) Orientation of solid surface
b) Time
c) Surface area
d) Space
View Answer
Explanation: As we know, Q = h x A x (temperature difference), the total heat transfer is affected by the surface area, but the coefficient itself is not. Coefficient is independent of the surface area. The coefficient is denoted by h and is dependent on space, time, geometry, orientation of solid surface.
10. In liquids and gases, heat transmission is primarily caused by
a) Convection
b) Radiation
c) Conduction
d) Conduction as well as convection
View Answer
Explanation: Convection is the transfer of thermal energy between a solid and a fluid flowing through it.
11. For conduction heat transfer, the heat energy propagation will be minimal for __________
a) Copper
b) Air
c) Water
d) Lead
View Answer
Explanation: It’s because air has the lowest heat conductivity of all the possibilities.
12. A 25 mm diameter egg roll (k = 1 W/m degree) is roasted with the help of microwave heating. For good quality roasting, it is desired that temperature at the center of roll is maintained at 100 degree Celsius when the surrounding temperature is 25 degree Celsius. What should be the heating capacity in W/m 3 of the microwave if the heat transfer coefficient on the surface of egg roll is 20 W/m2 degree?
a) 613.31 k W/m3
b) 93.31 k W/m3
c) 6713.31 k W/m3
d) 213.31 k W/m3
View Answer
Explanation: t max = t a + q g R/2h + q g R2/4k.
13. The rate of heat transfer for a plane wall of homogenous material with constant thermal conductivity is given by which of the following equation?
a) Q = 2k/δ x
b) Q = 2kAδx
c) Q = kA (t1-t2)/δ
d) Q = 2kAx/ δ
View Answer
Explanation: The value of the temperature gradient can be substituted into the general equation to compute heat flow. The heat flow is independent of x in some way.
14. The appropriate rate equation for convective heat transfer between a surface and adjacent fluid is prescribed by which law?
a) Newton’s law of cooling
b) Kirchhoff’s law
c) Newton’s first law
d) Wein’s displacement law
View Answer
Explanation: When a solid surface is cooled by a fluid, the rate equation used to describe the mechanism of convection is called Newton’s law of cooling.
15. A wire of radius 3 mm and 1.25 m length is to be maintained at 60 degree Celsius by insulating it by a material of thermal conductivity 0.175 W/m K. The temperature of surrounding is 20 degree Celsius with heat transfer coefficient 8.5 W/ m2 K. Find percentage increase in heat loss due to insulation?
a) 124.23 %
b) 100.00 %
c) 12.55 %
d) 134.46 %
View Answer
Explanation: Q = 8.5 (2 π 0.003 1.25) (60 – 20) = 8.01 W. % increase = (18.78 – 8.01/8.01) (100) = 134.46 %.
16. Why fins are provided on a heat transfer surface?
a) Pressure drop of the fluid should be minimized
b) Increase turbulence in flow for enhancing heat transfer
c) Surface area is maximum to promote the rate of heat transfer
d) Increase temperature gradient so as to enhance heat transfer
View Answer
Explanation: Fins are added to the surface of a heat exchanger to improve heat transmission by increasing the surface area exposed to the environment.
17. A heating unit is made in the form of a vertical tube of 50 mm outside diameter and 1.2 m height. The tube is fitted with 20 steel fins of rectangular section with height 40 mm and thickness 2.5 mm. The temperature at the base of fin is 75 degree Celsius, the surrounding air temperature is 20 degree Celsius and the heat transfer coefficient between the fin as well as the tube surface and the surrounding air is 9.5 W/m2 K. If thermal conductivity of the fin material is 55 W/m K, find the amount of heat transferred from the tube without fin
a) 118.44 W
b) 98.44 W
c) 8.44 W
d) 908.44 W
View Answer
Explanation: Q = h A d t = h (π d 0 H) (t 0 – t INFINITY).
18. What is the rate of heat transfer from the fin in case of fin insulated at the tip?
a) (h P k)1/2 (t 0 – t a) tan h ml
b) (h P A)1/2 (t 0 – t a) tan h ml
c) (h P k A)1/2 (t 0 – t a) tan h ml
d) (h k A)1/2 (t 0 – t a) tan h ml
View Answer
Explanation: It should contain all the terms i.e. h, A, P, k.
19. Consider the following statements pertaining to heat transfer through fins
(i) They must be arranged at right angles to the direction of flow of working fluid
(ii) The temperature along the fin is variable and accordingly heat transfer rate varies along the fin elements
(iii) Fins are equally effective irrespective whether they are on the hot side or cold side of the fluid
(iv) Fins are made of materials that have thermal conductivity higher than that of wall
Identify the correct statements
a) i and ii
b) iii and iv
c) i and iv
d) ii and iii
View Answer
Explanation: The statements made in serial number 3 and 4 are incorrect. Fins are seen on the side of the body when the convective coefficient is low.
20. In which of the following cases provision of fins on a given heat transfer surface will be more effective?
a) Fewer but thin fins
b) Large number of thin fins
c) Large number of thick fins
d) Fewer but thick fins
View Answer
Explanation: Increase in ratio of perimeter P to be cross-sectional area A C brings about improvement in the effectiveness of fins.
21. What are the relevant boundary conditions in case of heat transfer from a bar connected to two heat sources at different temperatures?
a) α = α 1 at x = 1 and α = α 2 at x = 2L
b) α = α 1 at x = 0 and α = α 2 at x = infinity
c) α = α 1 at x = 0 and α = α 2 at x = L
d) α = α 1 at x = infinity and α = α 2 at x = 1
View Answer
Explanation: It should be at x = o and x = L.
22. Radiation heat transfer is characterized by
a) Movement of discrete packets of energy as electromagnetic waves
b) Due to bulk fluid motion, there is a transport of energy
c) There is the circulation of fluid by buoyancy effects
d) Thermal energy transfer as vibrational energy in the lattice structure of the material
View Answer
Explanation: EM waves is characterized by radiant heat transfer.
23. A thin metal plate of 4 cm diameter is suspended in atmospheric air whose temperature is 290 K. This plate attains a temperature of 295 K when one of its faces receives radiant energy from a heat source at the rate of 2 W. If heat transfer coefficient on both surfaces of the plate is stated to be 87.5 W/m 2 K, workout the reflectivity of the plate.
a) 0.15
b) 0.55
c) 0.25
d) 0.45
View Answer
Explanation: Heat loss by convection from both sides of the plates = 2 h A d t = 1.1 W. Energy lost by reflection = 2.0 – 1.1 = 0.9 W.
24. Which of the following is the unit of coefficient of radiant heat transfer?
a) W/m2
b) W/m K
c) W/m2 K
d) W/K
View Answer
Explanation: Its value can be calculated from the heat flux equation for any configuration.
25. The radiant heat transfer from a plate of 2.5 cm2 area at 1250 K to a very cold enclosure is 5.0 W. Determine the emissivity of the plate at this temperature
a) 0.544
b) 0.144
c) 0.044
d) 0.244
View Answer
Explanation: Emissivity = E/σ A T4 = 0.144.
26. The calculation of heat transmission by convection is based on the determination of a Nusselt number or convective film coefficient. To that goal, which of the following strategies have been proposed
(i) Non-dimensional analysis and experimental correlations
(ii) Hydrodynamic concept of velocity boundary layer
(iii) Reynolds similarity between the mechanism of fluid friction in the boundary layer and the transfer of heat by convection
Identify the correct one
a) ii and iii
b) i and iii
c) i, ii, and iii
d) i and ii
View Answer
Explanation: It should be a dimensional analysis and experimental correlations.
27. The non-dimensional parameter known as Stanton number is used in which of the following heat transfer?
a) Natural convection heat transfer
b) Unsteady state heat transfer
c) Condensation heat transfer
d) Forced convection heat transfer
View Answer
Explanation: It’s the ratio of the heat transfer coefficient to the heat flow per unit temperature rise caused by fluid velocity. It can only be used for forced convection heat transfer.
28. The convective heat transfer coefficient in the laminar flow over a flat plate __________
a) Decreases with increase in free stream velocity
b) Increases if a denser fluid is used
c) Increases with distance
d) Increases if a higher viscosity fluid is used
View Answer
Explanation: It mostly increases if a denser fluid is used.
29. Maximum heat transfer rate in a modern boiler is about
a) 4 * 10 5 W/m2
b) 5 * 10 5 W/m2
c) 3 * 10 5 W/m2
d) 2 * 10 5 W/m2
View Answer
Explanation: Greater importance has recently been given to the boiling heat transfer.
30. In spite of the large heat transfer coefficient in boiling liquids, fins are used advantageously when the entire surface is exposed to
a) Nucleate boiling
b) Film boiling
c) Transition boiling
d) All modes of boiling
View Answer
Explanation: Here all modes of boiling i.e. film, transition and nucleate are of great importance.
31. The condensate film runs down a vertical flat surface where saturated steam is allowed to condense. Condensation’s local coefficient of heat transfer
a) Increases with increasing thickness of film
b) Increases with increasing temperature differential between the surface and vapour
c) Decreases with increasing distance from the top of the surface
d) Remains constant at all heights of the surface
View Answer
Explanation: It decreases with increasing thickness of condensate film.
32. A steam condenser is transferring 250 k W of thermal energy at a condensing temperature of 65 degree Celsius. The cooling water enters the condenser at 20 degree Celsius with a flow rate of 7500 kg/hr. If overall heat transfer coefficient for the condenser surface is 1250 W/m2 K, what surface area is required to handle this load?
a) 7.08 m2
b) 5.08 m2
c) 4.08 m2
d) 1.08 m2
View Answer
Explanation: Q = U A α m. So, A = 7.08 m2.
33. What is the value of overall heat transfer coefficient ammonia condensers?
a) 200-750 W/m2 K
b) 250-2500 W/m2 K
c) 1500-1750 W/m2 K
d) 800-1400 W/m2 K
View Answer
Explanation: It is an electrical device that stores a vast amount of energy.
34. Which of the following is having highest value of overall heat transfer coefficient?
a) Steam
b) Steam condensers
c) Feed water heaters
d) Alcohol condensers
View Answer
Explanation: Feed water heaters have an overall heat transfer coefficient of 8500 W/m2K, whereas steam, alcohol condensers, and ammonia condensers have heat transfer coefficients of 5000 W/m2 K, 630 W/m2 K and 1400 W/m2 K.
35. For laminar film condensation on a vertical plate, the local heat transfer coefficient at the lower edge of the plate is given by
a) [k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.125
b) [k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.1
c) [k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.25
d) [k 3 p 2 g h f g /4 δ l (t sat – t s)] 0.5
View Answer
Explanation: The rate of condensation heat transfer is higher at the upper end of the plate than at the lower end.
36. The outer surface of a vertical tube is 1.25 m long and outer diameter is 50 mm is exposed to saturated steam at atmospheric pressure. If the tube surface is maintained at 80 degree Celsius by the flow of cooling water through it, determine the rate of heat transfer to the coolant
a) 32397 W
b) 19879 W
c) 48476 W
d) 25234 W
View Answer
Explanation: h v = 0.943 [k 3 p 2 g h f g/δ l (t sat – t s)] 0.25 = 5046.8 W/m 2 k and heat flow rate = 19879 W.
37. What is the value of the overall heat transfer coefficient for air to heavy tars and liquid?
a) As low as 25 W/m2 K
b) As low as 15 W/m2 K
c) As low as 45 W/m2 K
d) As low as 55 W/m2 K
View Answer
Explanation: It is an incompressible fluid which has constant volume independent of pressure.
38. Exhaust gases (c P = 1.12 k J/kg K) flowing through a tubular heat exchanger at the rate of 1200 kg/hr are cooled from 400 degree Celsius to 120 degree Celsius. This cooling is affected by water (c P = 4.18 k J/kg K) that enters the system at 10 degree Celsius at the rate of 1500 kg/hr. If the overall heat transfer coefficient is 500 k J/m2 hr degree, what heat exchanger area is required to handle the load for counter flow arrangement?
a) 1.758 m2
b) 6.758 m2
c) 8.758 m2
d) 3.758 m2
View Answer
Explanation: m h c h (t h 1 – t h 2) = m c c c (t c 2 – t c 1).
39. What is the value of the overall heat transfer coefficient for air condensers?
a) 250-900 W/m2 K
b) 200-1950 W/m2 K
c) 350-780 W/m2 K
d) 200-350 W/m2 K
View Answer
Explanation: It consists of an air coil which is used to remove heat from fluids.
40. Heat transfer coefficients for natural convection across the surface of a vertical pipe and a vertical flat plate at the same height. What could be the cause(s) of this?
(i) Same height
(ii) Both vertical
(iii) Same fluid
(iv) Same fluid flow pattern
Select the correct answer
a) iii and iv
b) iv
c) i and ii
d) i
View Answer
Explanation: The fluids must be same so their flow pattern.
41. Which of the following is having the lowest value of overall heat transfer coefficient?
a) Feed water heaters
b) Air condensers
c) Air to low viscosity liquids
d) Steam condensers
View Answer
Explanation: Overall heat transfer coefficient for air condensers is 780 W/m2 K while that of steam condensers, air to low viscosity liquids and feed water heaters are 5000 W/m2 K, 600 W/m2 K and 8500 W/m2 K.
42. A cross-flow type air heater has an area of 50 cm2. The overall heat transfer coefficient is 100 W/m2 K and the heat capacity of both hot and cold streams is 1000 W/m K. The value of NTU is
a) 0.2
b) 6
c) 1000
d) 5
View Answer
Explanation: NTU = A U/C MIN = 5.
43. An oil cooler in a high-performance engine has an outside surface area 0.12 m2 and a surface temperature of 65 degree Celsius. At any intermediate time air moves over the surface of the cooler at a temperature of 30 degree Celsius and gives rise to a surface coefficient equal to 45.4 W/ m 2 K. Find out the heat transfer rate?
a) 564.98 W
b) 324.67 W
c) 190.68 W
d) 768.43 W
View Answer
Explanation: Q = (T2 – T1) A h = 0.12 (65-30) 45.4 = 190.68 W.
44. Which of the following statement is incorrect according to heat transfer?
a) Heat flow doesn’t depend on temperature
b) A material medium is not necessary for heat transmission
c) The process of heat transfer is an irreversible process
d) For heat exchange, a temperature gradient must exist
View Answer
Explanation: Heat flows from higher to lower temperature.
45. Consider a convective heat flow to water at 75 degree Celsius from a cylindrical nuclear reactor fuel rod of 50 mm diameter. The rate of heat generatioN is 50000000 W/m3 and convective heat transfer coefficient is I kW/m2 K. The outer surface temperature of the fuel element would be
a) 400 degree Celsius
b) 625 degree Celsius
c) 700 degree Celsius
d) 550 degree Celsius
View Answer
Explanation: t w = t a + q g R/ 2h.
46. For a cylindrical rod with uniformly distributed heat sources, the thermal gradient at half the radius location will be
a) One half
b) One fourth
c) Four times
d) Twice
View Answer
Explanation: t = t w + q g (R2 – r2)/4k. (d t /d r) r = R/2 = 1/2(d t/d r) r = R.
47. Water (specific heat = 4 k J/kg K) enters a cross flow exchanger (both fluids unmixed) at 15 degree Celsius and flows at the rate of 7.5 kg/s. It cools air (C P = 1 k J/kg K) flowing at the rate of 10 kg/s from an inlet temperature of 120 degree Celsius. For an overall heat transfer coefficient of 780 k J/m2 hr degree and the surface area is 240 m2, determine the NTU
a) 1.2
b) 8.2
c) 6.2
d) 5.2
View Answer
Explanation: NTU = U A/C MIN = 5.2.
48. A heat exchanger to preheat oil for a furnace was designed without considering the possibility of scale formation, and the overall heat transfer coefficient based on the fuel oil side was 3200 k J/m2 hr degree. What would be the corrected coefficient of heat transfer if a fouling factor of 0.00025 m2 hr degree/k J for the fuel oil is taken into account?
a) 1222.78 k J/m2 hr degree
b) 1555.78 k J/m2 hr degree
c) 1777.78 k J/m2 hr degree
d) 1233.78 k J/m2 hr degree
View Answer
Explanation: U = 1/ (R + 1/h S).
49. Which of the following is the value of fouling factor for engine exhaust?
a) 0.001 m2 K/W
b) 0.002 m2 K/W
c) 0.003 m2 K/W
d) 0.004 m2 K/W
View Answer
Explanation: Its unit is m2 hr K/kcal and it represents the reciprocal of the scale coefficient i.e. heat transfer.
50. The value of fouling factor for industrial liquids is ______
a) 0.0002 m2 K/W
b) 0.0001 m2 K/W
c) 0.0003 m2 K/W
d) 0.0004 m2 K/W
View Answer
Explanation: Its unit is m2 hr K/kcal and it represents the reciprocal of the scale coefficient i.e. heat transfer.
51. Which of the following is the value of overall heat transfer coefficient for steam condensers?
a) 2000-9500 W/m2 K
b) 1500-5000 W/m2 K
c) 200-9000 W/m2 K
d) 3000-5500 W/m2 K
View Answer
Explanation: It’s a rotating mechanism that works in the same way as a motor to control power flow in electric power transmission.
52. The value of overall heat transfer coefficient for air to low viscosity liquid _______
a) As high as 700 W/m2 K
b) As high as 900 W/m2 K
c) As high as 600 W/m2 K
d) As high as 800 W/m2 K
View Answer
Explanation: It is made up of tiny vibrating particles of matter which are held together by intermolecular bonding.
53. Mark the system where heat transfer is given by forced convection
a) Heat flow from hot pavement to the surrounding atmosphere
b) Heat exchange on the outside of cold and warm pipes
c) Chilling effect of cold wind on a warm body
d) Fluid passing through the tubes of a condenser and other heat exchange equipment
View Answer
Explanation: Forced convection occurs when the fluid motion involved in the process is produced by some external means.
Chapterwise Multiple Choice Questions on Heat Transfer
- Definitions and Basic Concepts
- Fourier Equation and Thermal Conductivity
- Steady State Conduction
- Conduction with Heat Generation
- Heat Transfer from Extended Surfaces
- Transient (Unsteady State Heat Conduction)
- Radiation : Processes and Properties
- Radiation : Exchange between Surfaces
- Convection : Processes and Properties
- Dimensional Analysis
- Empirical Correlations for Free and Forced convection
- Condensation and Boiling
- Hydrodynamic and Thermal Boundary Layers
- Heat Exchangers and Mass Transfer
1. MCQ on Definitions and Basic Concepts Heat Transfer
The section contains multiple choice questions and answers on steady and unsteady types of heat transfer and various heat transfer modes.
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2. Heat Transfer Multiple Choice Questions on Fourier Equation and Thermal Conductivity
The section contains questions and answers on various properties of fourier equation and thermal conductivity which include fourier equation, heat conduction equation and thermal conductivity of different materials.
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3. Heat Transfer MCQ on Steady State Conduction
The section contains MCQs on conduction through various mechanisms which include plane wall, composite wall, cylindrical wall and a sphere. It also contains questions and answers on shape factor, variable conductivity effect and critical thickness of insulation.
4. Heat Transfer Multiple Choice Questions on Conduction with Heat Generation
The section contains multiple choice questions and answers on heat generations through various mechanisms which include plane wall, cylinder and a sphere. Additionally, the section also contains questions on dielectric effect.
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5. Multiple Choice Questions on Heat Transfer from Extended Surfaces
The section contains questions and answers on concepts of fins, steady heat flow along a rod, performance of fin, design consideration for fins, thermometric well properties and heat dissipation from a long fin and a fin which is insulated at the tip.
6. Heat Transfer MCQ on Transient (Unsteady State Heat Conduction)
The section contains MCQs on thermocouple response, time constant, heat conduction in solids using various mechanisms like infinite thermal conductivity, finite conduction and infinite thick solids. The section also contains questions and answers on biot number and periodic variation.
7. Heat Transfer MCQ on Radiation : Processes and Properties
The section contains multiple choice questions and answers on various concepts which include transmissivity, absorptivity, reflectivity, black body concepts, planck’s law, stefan-boltzman’s law, wein’s law, kirchoff’s law, radiation intensity and solar radiations.
8. Heat Transfer Multiple Choice Questions on Radiation : Exchange between Surfaces
The section contains questions and answers on Black body heat exchange, shape factor concepts, Non black body heat exchange, radiation shield, gaseous radiation, fouling factor, physical and geometrical property symbols, adiabatic surface, reradiating surface and other network approaches.
9. Heat Transfer MCQ on Convection : Processes and Properties
The section contains MCQs on flow types, convection types, nusselt number, reynolds number and newton rikhman law.
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10. Heat Transfer Multiple Choice Questions on Dimensional Analysis
The section contains multiple choice questions and answers on Dimensional System and Homogeneity, rayleigh and buckhingam methods, model simulation and studies, dimensionless group importance and advantages and disadvantages of dimensional analysis.
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11. Heat Transfer MCQ on Empirical Correlations for Free and Forced convection
The section contains questions and answers on laminar flow, turbulent flow and various correlations for forced convection.
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12. Heat Transfer Multiple Choice Questions on Condensation and Boiling
The section contains MCQs on boiling, nucleate boiling, free convection boiling, condensation concepts and bubble growth.
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13. Heat Transfer MCQ on Hydrodynamic and Thermal Boundary Layers
The section contains multiple choice questions and answers on reynolds analogy, pohlhausen equation, thermal boundary layer, hydrodynamic boundary layer and von-karmal equation.
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14. Multiple Choice Questions on Heat Exchangers and Mass Transfer
The section contains questions and answers on heat exchanger classification, mean temperature difference, discrete time system implementation, specific heat, heat transfer coefficient, transfer units number and heat exchanger effectiveness.
Wish you the best in your endeavor to learn and master Heat Transfer!
