Search
.Management Sciences
Category: Heat Transfer
The unit of overall coefficient of heat transfer is___________________?
A. kcal/m2
B. kcal/hr °C
C. kcal/m2 hr °C
D. kacl/m hr °C
E. kcal/m3 hr °C
Emissivity of a white polished body in comparison to a black body is________________?
A. higher
B. lower
C. same
D. depends upon the shape of body
E. none of the above
Depending on the radiating properties, a body will be white when_________________?
A. p = 0, x = 0 and a = 1
B. p=l,T = 0anda = 0
C. p = 0, x = 1 and a = 0
D. x = 0, a + p = 1
E. a = 0, x + p = 1.
where a = absorptivity, p = reflectivity, x = transmissivity
In counter flow heat exchangers_________________?
A. both the fluids at inlet (of heat ex¬changer where hot fluid enters) are in their coldest state
B. both the fluids at inlet are in their hot¬test 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
Thermal conductivity of wood depends on_______________?
A. moisture
B. density
C. temperature
D. all of the above
E. none of the above
The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit_______________?
A. temperature
B. thickness
C. area
D. time
E. area and time
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 the above
E. none of the above
Depending on the radiating properties, a body will be opaque when _________________?
A. p = 0, x = 0 and a = 1
B. p=l,x = 0anda = 0
C. p = 0, x = 1 and a = 0
D. x – 0, a + p = 1
E. a=0,x + p= 1.
where a = absorptivity, p = reflectivity, X = transmissivity
A perfect black body is one which_______________?
A. is black in colour
B. reflects all heat
C. transmits all heat radiations
D. abslprbs heat radiations of all wave lengths falling on it
E. fully opaque
Unit of thermal conductivity in M.K.S. units is ___________________?
A. kcal/kg m2 °C
B. kcal-m/hr m2 °C
C. kcal/hr m2 °C
D. kcal-m/hr °C
E. kcal-m/m2 °C
Recent Comments