Types And Modes Of Heat Transfer

1557 Words Jun 2nd, 2016 7 Pages
1.2 Types or modes of heat transfer
1.2.1 Conduction
It is basically a microscopic level phenomenon. In this process, highly energetic particles of its substance transfer their energy to their less energetic neighbour .Conduction shown in fig. 1.1

Fig.1.1 One Dimension Heat Conduction(snapshot)
T1: Hot temperature(k)
T2: Cold tempreture(k)
Q: The heat flow by conduction in the x-direction (W) A : The area through which the heat flows, normal to the x-direction (M) dT/dx: This is temperature gradient in the x-direction (K/m)
These terms are related by Fourier 's Law, a model proposed as early as 1822:
Q = -KAdT/dx or q= -dT/dx
A significant feature of this equation is the negative sign. This recognises that the natural direction for the flow of heat is from high temperature to low temperature, and hence down the temperature gradient.The additional quantity that appears in this relationship is K the thermal conductivity (W/m K) of the material through which the heat flows. This is a property of the particular heat-conducting substance and, like other properties, depends on the state of the material, which is usually specified by its temperature and pressure.The dependence on temperature is of particular importance. Moreover, some materials such as those used in building construction are capable of absorbing water, either in finite pores or at the molecular level, and the moisture content also influences the thermal…

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