Chapter 5: Problem 2
What are the limitations of the analytical solution methods?
Chapter 5: Problem 2
What are the limitations of the analytical solution methods?
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Get started for freeConsider steady one-dimensional heat conduction in a composite plane wall consisting of two layers \(A\) and \(B\) in perfect contact at the interface. The wall involves no heat generation. The nodal network of the medium consists of nodes 0,1 (at the interface), and 2 with a uniform nodal spacing of $\Delta x$. Using the energy balance approach, obtain the finite difference formulation of this problem for the case of insulation at the left boundary (node 0 ) and radiation at the right boundary (node 2 ) with an emissivity of \(\varepsilon\) and surrounding temperature of \(T_{\text {sarr }}\).
Explain how the finite difference form of a heat conduction problem is obtained by the energy balance method.
Consider transient heat conduction in a plane wall whose left surface (node 0 ) is maintained at \(80^{\circ} \mathrm{C}\) while the right surface (node 6) is subjected to a solar heat flux of \(600 \mathrm{~W} / \mathrm{m}^{2}\). The wall is initially at a uniform temperature of \(50^{\circ} \mathrm{C}\). Express the explicit finite difference formulation of the boundary nodes 0 and 6 for the case of no heat generation. Also, obtain the finite difference formulation for the total amount of heat transfer at the left boundary during the first three time steps.
Hot combustion gases of a furnace are flowing through a concrete chimney \((k=1.4 \mathrm{~W} / \mathrm{m} \cdot \mathrm{K})\) of rectangular cross section. The flow section of the chimney is $20 \mathrm{~cm} \times 40 \mathrm{~cm}\(, and the thickness of the wall is \)10 \mathrm{~cm}$. The average temperature of the hot gases in the chimney is \(T_{i}=280^{\circ} \mathrm{C}\), and the average convection heat transfer coefficient inside the chimney is \(h_{l}=75 \mathrm{~W} / \mathrm{m}^{2} \cdot \mathrm{K}\). The chimney is losing heat from its outer surface to the ambient air at $T_{0}=15^{\circ} \mathrm{C}\( by convection with a heat transfer coefficient of \)h_{o}=18 \mathrm{~W} / \mathrm{m}^{2} \cdot \mathrm{K}$ and to the sky by radiation. The emissivity of the outer surface of the wall is \(\varepsilon=0.9\), and the effective sky temperature is estimated to be \(250 \mathrm{~K}\). Using the finite difference method with \(\Delta x=\Delta y=10 \mathrm{~cm}\) and taking full advantage of symmetry, \((a)\) obtain the finite difference formulation of this problem for steady two-dimensional heat transfer, (b) determine the temperatures at the nodal points of a cross section, and \((c)\) evaluate the rate of heat loss for a \(1-m\)-long section of the chimney.
What is a practical way of checking if the discretization error has been significant in calculations?
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