As a guide, prepare a similar table showing the order of magnitudes of the thermal resistances of a unit area for convection between a surface and various fluids.

GIVEN
• The order of magnitude of convective heat transfer coefficient ( h c)
FIND
• The order of magnitudes of the thermal resistance of a unit area (A Rc) SOLUTION
The thermal resistance for convection is defined by Equation as


The thermal resistance for convection is defined as



Therefore the thermal resistances of a unit area are simply the reciprocal of the convective heat

transfer coefficient



As an example, the first item in Table 1.4 is ‘air, free convection’ with a convective heat transfer

coefficient of 6–30 W/(m2 K). Therefore the order of magnitude of the thermal resistances of a unit

area for air, free convection is



The rest of the table can be calculated in a similar manner

Physics & Space Science

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