The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is_____________________?

A. 11.2 kW/m2
B. 12.0 kW/m2
C. 14.6 kW/m2
D. 16.5 kW/m2

Related Mcqs:

Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because___________________?
A. Convection becomes important B. Conduction becomes important C. Radiation becomes important D. Sub-cooled boiling occurs...
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 min...
It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30°C. The boiling point of the solution is 110°C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/kg.K. The rate at which the heat has to be supplied in (kJ/min) to the evaporator is____________________?
A. 3.06 × 105 B. 6.12 × 105 C. 7.24 × 105 D. 9.08 × 105...
Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately ?
A. 32 B. 37 C. 45 D. 50...
With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer ?
A. Decreases B. Increases C. Increases exponentially D. Remain unaffected...
The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is – 5°C. The outside wall temperature is___________________?
A. 25°C B. 30°C C. 35°C D. 40°C...
Stefan-Boltzmann law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K) ?
A. t4 B. T4 C. 1/t4 D. 1/T4...
The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by ______________ times, when the number of tube passes is increased to 8?
A. 20.8 B. 40.8 C. 40.4 D. 20.4...
The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C- 1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.°C-1. The rate of heat loss from the outer surface in W.m-2is__________________?
A. 165.4 B. 167.5 C. 172.5 D. 175...
A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________________?
A. Greater than that for un-insulated steam pipe B. Less than that of the un-insulated steam pipe C. Equal to that of the un-insulated steam pipe D. Less than the steam pipe with 5 cms insulation...