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The literature of heat transfer generally recognizes distinct modes of heat transfer. How many modes are there?
There are three modes of heat transfer i.e. radiation, convection and conduction.
Consider system A at uniform temperature t and system B at another uniform temperature T (t > T). Let the two systems be brought into contact and be thermally insulated from their surroundings but not from each other. Energy will flow from system A to system B because of
Greater the temperature imbalance the higher would be the rate of energy transfer.
An oil cooler in a high performance engine has an outside surface area 0.12 m^{2} and a surface temperature of 65 degree Celsius. At any intermediate time air moves over the surface of the cooler at a temperature of 30 degree Celsius and gives rise to a surface coefficient equal to 45.4 W/ m 2 K. Find out the heat transfer rate?
: Q = (T_{2} – T_{1}) A h = 0.12 (6530) 45.4 = 190.68 W.
Unit of heat transfer is Joule but rate of heat transfer is joule per second i.e. watt.
Convective heat transfer coefficient doesn’t depend on
It is denoted by h and is dependent on space, time, geometry, orientation of solid surface.
The rate equation used to describe the mechanism of convection is called Newton’s law of cooling. So rate of heat flow by convection doesn’t depend on
It is directly proportional to all of above except time.
Forced, natural and mixed convection.
Thermal conductivity of diamond is 2300 W/m K.
A radiator in a domestic heating system operates at a surface temperature of 60 degree Celsius. Calculate the heat flux at the surface of the radiator if it behaves as a black body
As, q = Q/A
= 5.67 * 10^{8} (273+60)^{4} = 697.2.
Which of the following is an example of forced convection?
In forced convection the flow of fluid is caused by a pump, fan or by atmospheric winds.
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