A. Convection heat transfer by stirring the fluid and cleaning the heating surface
B. Conduction heat transfer by reduction in the material thickness and increase in the thermal
conductivity
C. Radiation heat transfer by increasing the temperature and reducing the emissivity
D. None of these
Related Mcqs:
- A furnace is made of a refractory brick wall of thickness 0.5 metre and thermal conductivity 0.7 W/m.°K For the same temperature drop and heat loss, this refractory wall can be replaced by a layer of diatomaceous earth of thermal conductivity 0.14 W/m.K and thickness ______________ metre?
A. 0.01
B. 0.1
C. 0.25
D. 0.5 - What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively ?
A. 2
B. 8
C. 10
D. 40 - A steam pipe is intended to be insulated with two layers of insulating materials of different thermal conductivities. For minimum heat transfer to take place_________________?
A. The better insulation material should be put just next to pipe (i.e., inside)
B. The better insulating material should be put outside
C. Either of the insulating material could be put on either side
D. Steam temperature is considered before deciding as to which insulating material is to be put
inside (i.e., just next to the pipe) - Cold cracking in the heat affected zone of a high strength steel weld can take place because of the___________________?
A. Retained austenite
B. Martensite formation
C. Relatively high sulphur content in the base metal
D. Sufficient hydrogen present in the welding arc - Temperature of hot gases flowing in a pipe is measured by a thermocouple inserted in the thermal well. The thermal well made of ______________ will facilitate the most accurate measurement of the temperature ?
A. Copper
B. Steel
C. Aluminium
D. Brass - Thermal diffusivity of a substance is proportional to (where, k = Thermal conductivity) ____________________?
A. 1/k
B. k
C. k2
D. 1/k2 - The refractory brick which has good thermal shock resistance at high temperature but cracks on cooling below 400°C is__________________?
A. Magnesite
B. Chrome
C. Silica
D. Fireclay - Work required for compression of a gas contained in a cylinder is 7000 kJ. During compression, heat interaction of 3000 kJ causes the surroundings to be heated. Internal energy change of the gas during the compression is __________________ kJ ?
A. +4000
B. -4000
C. 10000
D. -10000 - Transition from laminar flow to turbulent flow in fluid flow through a pipe does not depend upon the___________________?
A. Length of the pipe
B. Diameter of the pipe
C. Density of the fluid
D. Velocity of the fluid - One face of a furnace wall is at 1030°C and the other face is exposed to room temperature (30°C). If the thermal conductivity of furnace wall is 3 W. m-1. k-1 and the wall thickness is 0.3 m, the maximum heat loss (in W/m) is____________________?
A. 100
B. 900
C. 9000
D. 10000
