heat transfer objective questions with answers part1

Q1. Temperature of steam at around 540°C can be measured by
(A) thermometer
(B) radiatiouv pyrometer
(C) thermistor
(D) thermocouple

Q2. Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of
(A) 0.002
(B) 0.02
(C) 0.03
(D) 0.12

Q3. The time constant of a thermocouple is
(A) the time taken to attain the final temperature to be measured
(B) the time taken to attain 40% of the value of initial temperature difference
(C) the time taken to attain 63.2% of the value of initial temperature difference
(D) determined by the time taken to reach 100°C from 0°C

Q4. Thermal conductivity of air with rise in temperature
(A) increases
(B) decreases
(C) remains constant
(D) may increase or decrease depending on temperature

Q5. Heat flows from one body to other when they have
(A) different heat contents
(B) different specific heat
(C) different atomic structure
(D) different temperatures

Q6. The amount of heat flow through a body by conduction is
(A) directly proportional to the surface area of the body
(B) dependent upon the material of the body
(C) inversely proportional to the thickness of the body
(D) All of these

Q7. Which of the following has least value of conductivity
(A) glass
(B) water
(C) plastic
(D) air

Q8. Which of the following is expected to have highest thermal conductivity
(A) steam
(B) solid ice
(C) melting ice
(D) water

Q9. Thermal conductivity of glass-wool varies from sample to sample because of variation in
(A) composition
(B) density
(C) structure
(D) All of these

Q10. Thermal conductivity of a material may be defined as the
(A) quantity of heat flowing in one second through one cm cube of material when opposite faces ^re maintained at a temperature difference of 1°C
(B) quantity of heat flowing in one second through a slab of the material of area one cm square, thickness 1 cm when its faces differ in temperature by 1°C
(C) heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
(D) All of these

Q11. Which of the following has maximum value of thermal conductivity
(A) aluminium
(B) steel
(C) brass
(D) copper

Q12. Moisture would find its way into insulation by vapour pressure unless it is prevented by
(A) high thickness of insulation
(B) less thermal conductivity insulator
(C) a vapour seal
(D) All of these

Q13. Heat is transferred by all three modes of transfer, viz, conduction, convection and radiation in
(A) electric heater
(B) steam condenser
(C) refrigerator condenser coils
(D) boiler

Q14. According to Prevost theory of heat exchange
(A) it is impossible to transfer heat from low temperature source to t high temperature source
(B) heat transfer by radiation requires no medium
(C) all bodies above absolute zero emit radiation
(D) heat transfer in most of the cases takes place by combination of conduction, convection and radiation

Q15. The ratio of heat flow Q1/Q2 from two walls of same thickness having their thermal conductivities as ATj – 2K2 will be
(A) 1
(B) 0.5
(C) 2
(D) 0.25

Q16. Heat transfer by radiation mainly depends upon
(A) its temperature
(B) nature of the body
(C) kind and extent of its surface
(D) All of these

Q17. Thermal diffusivity is
(A) a dimensionless parameter
(B) function of temperature
(C) a physical property of the material
(D) useful in case of heat transfer by radiation.

Q18. Thermal conductivity of wood depends on
(A) moisture
(B) density
(C) temperature
(D) All of these

Q19. In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by
(A) convection
(B) radiation
(C) conduction
(D) both convection and conduction

Q20. Film coefficient is defined as Inside diameter of tube
(A) Equivalent thickness of film
(B) Thermal conductivity Equivalent thickness of film Specific heat x Viscocity
(C) Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity
(D) Film coefficient x Inside diameter Thermal conductivity