I´ve found a webpage where the following problem is solved in detail, together with the substitution of numerical values into the pertinent formulas:(adsbygoogle = window.adsbygoogle || []).push({});

A plate is of cross-section thickness L = 0.1 m and has an initial temp of To = 250°C.

It is suddenly immersed into an oil bath of temperature Ta = 50°C.

The material properties are:

thermal conductivity k = 204W/m°C

heat transfer coefficient h = 80W/m^2°C

density rho = 2707 kg/m^3

specific heat Cp = 896 J/kg°C .

It is required to determine the time taken for the slab to cool to a temperature of 200°C.

The formula used to solve the problem is of the form

(T(t)-Ta)/(To-Ta) = e^-(mt)

where m is a function of h, rho, Cp and L.

The solution is then worked out for the conditions stated above. I had no problem in understanding the steps to solve the problem.

But now, suppose the same problem, but instead of submerging the plate into an oil bath at Ta = 50°C, leave the plate to cool into ambient air at Ta = 20°C.

My specific question is this:

Which coefficients and constants should I change to take care of the air instead of the oil

and which are their numeric values?

Your help will be greatly appreciated.

Thank you.

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# Heat transfer sample problem.

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