What is the emissivity of a black body ?
What is the emissivity of a black body ?
A. 0
B. 1
C. 0.5
D. 0.90
Similar Posts
With increase in temperature, the thermal conductivity of steel___________________?
With increase in temperature, the thermal conductivity of steel___________________?A. Increases
B. Decreases
C. Remains unchanged
D. Increases exponentiallyTemperature profile in steady state heat transfer is________________?
Temperature profile in steady state heat transfer is________________?A. Asymptotic
B. Hyperbolic
C. Parabolic
D. LinearThree materials A, B and C of equal thickness and of thermal conductivity of 20, 40 & 60 kcal/hr. m. °C respectively are joined together. The temperature outside of A and C are 30°C and 100°C respectively. The interface between B and C will be at a temperature of ____________ °C?
Three materials A, B and C of equal thickness and of thermal conductivity of 20, 40 & 60 kcal/hr. m. °C respectively are joined together. The temperature outside of A and C are 30°C and 100°C respectively. The interface between B and C will be at a temperature of ____________ °C?A. 40
B. 95
C. 70
D. 501000 Kg of liquid at 30°C in a well stirred vessel has to be heated to 120°C, using immersed coils carrying condensing steam at 150°C. The area of the steam coils is 1.2 m2 and the overall heat transfer co-efficient to the liquid is 1500 W/m2.°C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.°C, the time taken for the liquid to reach desired temperature will be__________________?
1000 Kg of liquid at 30°C in a well stirred vessel has to be heated to 120°C, using immersed coils carrying condensing steam at 150°C. The area of the steam coils is 1.2 m2 and the overall heat transfer co-efficient to the liquid is 1500 W/m2.°C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.°C, the time taken for the liquid to reach desired temperature will be__________________?A. 15 min
B. 22 min
C. 44 min
D. 51 minWhen does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?
When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?A. At high fluid velocity
B. At low velocity
C. When fluid flows past a smooth surface
D. None of theseIn a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will___________________?
In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will___________________?A. Increase
B. Decrease
C. Remain unchanged
D. Either increase or decrease; depends on the coolant flow rate