heat transfer MCQs

A. change liquid into vapour

B. change vapour into liquid

C. convert saturated steam into dry steam

E. convert water into steam and superheat it

A. kcal-m/hr C

B. kcal/hr m2 C

D. kcal/kg m2 C

E. kcal-m/m2 C

A. none of the above

B. may increase/decrease depending on temperature and thickness of insulation

D. increase

E. remain unaffected

B. all of the above

C. heating of building in winter

D. I.C. engine

E. air preheaters

A. convection

B. conduction and convection

C. conduction

E. convection and radiation

A. Film coefficient x Inside diameter Thermalconductivity

B. Equivalent thickness of film

C. none of the above

D. Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity

B. thermometer

C. thermistor

D. thermopile

E. radiatiouv pyrometer

A. Reynold number

B. Prandtl number

C. Weber number

D. Nusselt number

A. proportional to (k)

B. inversely proportional to k

C. none of the above

D. inversely proportional to k2

A. radiation

B. convection and radiation

D. conduction and convection

E. convection

A. transmissivity

B. reflectivity

C. absorptivity

E. emissivity

A. cold water inlet and outlet

C. hot medium inlet and outlet

D. hot medium outlet and cold water inlet

E. none of the above

A. 0.25

B. 0.5

D. I

E. 4

A. higher

B. depends upon the shape of body

C. same

E. none of the above

A. structure

B. porosity

C. density

E. composition

A. 0.5

C. 0.002

D. 0.1

E. 0.01

A. increases

B. decreases

C. remains constant

E. none of the above

B. dependent upon the material of the body

C. directly proportional to the temperature difference on the two faces of the body

D. directly proportional to the surface area of the body

E. inversely proportional to the thickness of the body

A. both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state

C. both the fluids .at exit are in their hottest state

D. one fluid is in hottest state and other in coldest state at inlet

E. any combination is possible depending on design of heat exchanger

A. heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces

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 1C

C. quantity of heat flowing in one second through one cm cube of material when opposite faces ^re maintained at a temperature difference of 1C

E. none of the above

A. useful in case of heat transfer by radiation

B. a dimensionless parameter

D. used as mathematical model

E. function of temperature

A. different heat contents

C. none of the above

D. different specific heat

E. different atomic structure

A. remains constant

C. may increase or decrease depending on temperature

D. decreases

E. none of the above

A. heat-transfer

B. thermal resistance

C. thermal coefficient

D. temperature gradient

A. unpredictable

B. remains constant

D. may increase or decrease depending on temperature

E. increases

B. 0.42

C. 0.23

D. 0.64

E. 0.1

B. radiation

C. convection and radiation

D. conduction

E. convection

B. kcal (heat).

C. C (temperature)

D. sqm (area)

E. hr (time)

A. boiling water

B. melting ice

C. steam

E. water

A. same

B. lower

C. depends on temperature conditions

E. depends on the area of heat exchanger

A. their atoms-are relatively far apart

B. they have high density

C. all of the above

E. they contain free electrons

B. electric heater

C. steam condenser

D. melting of ice

E. refrigerator condenser coils

A. heating of building

B. all of the above

C. blast furnace

E. cooling of parts in furnace

B. inferior insulation should be put over pipe and better one over it

C. both may be put in any order

D. whether to put inferior OIL over pipe or the better one would depend on steam temperature

E. unpredictable

B. increase the temperature of a liquid or vapour

C. change liquid into vapour

D. change vapour into liquid

E. convert saturated steam into dry steam

B. it is impossible to transfer heat from low temperature source to t high temperature source

C. rate of heat transfer depends on thermal conductivity and temperature difference

D. heat transfer by radiation requires no medium

E. heat transfer in most of the cases takes place by combination of conduction, convection and radiation

A. nature of the body

B. none of the above

C. its temperature

D. kind and extent of its surface

A. 1:01

B. 1:04

C. 2:01

E. 4:01

A. determined by the time taken to reach 100C from 0C

B. none of the above

D. the time taken to attain 50% of the value of initial temperature difference

E. the time taken to attain the final temperature to be measured

B. free electrons

C. low density

D. all of the above

E. atoms colliding frequency

A. kcal/m2 hrC

C. m2/hrC

D. kcal/m.hrC

E. kcal/m2 hr

A. k up the wrong case?

A. regular surfaces having non-uniform temperature gradients

B. two dimensional cases only

D. three dimensional cases only

E. irregular surfaces

A. liquids

B. enthalpy

C. entropy

D. energy

A. emissive power and absorptivity are constant for all bodies

B. ratio of emissive power to absorptive power is maximum for perfectly black body

D. radiant heat is proportional to fourth power of absolute temperature

E. emissive power depends on temperature

A. brass

C. lead

D. copper

E. steel

B. J/m K sec

C. J/m2 sec

D. A. and C. above

E. W/m K

A. convection

B. radiation

D. both convection and conduction

E. none of the above

A. conduction and convection

B. radiation

D. convection and radiation

E. conduction

A. less thermal conductivity insulator

B. all of the above

C. high thickness of insulation

D. high vapour pressure