Consider a 2-m-long and 0.7-m-wide stainless-steel plate whose thickness is \(0.1 \mathrm{~m}\). The left surface of the plate is exposed to a uniform heat flux of \(2000 \mathrm{~W} / \mathrm{m}^{2}\) while the right surface of the plate is exposed to a convective environment at \(0^{\circ} \mathrm{C}\) with \(h=400 \mathrm{~W} / \mathrm{m}^{2} \cdot \mathrm{K}\). The thermal conductivity of the stainless steel plate can be assumed to vary linearly with temperature range as \(k(T)=k_{o}(1+\beta T)\) where \(k_{o}=48 \mathrm{~W} / \mathrm{m} \cdot \mathrm{K}\) and \(\beta=9.21 \times 10^{-4}{ }^{\circ} \mathrm{C}^{-1}\). The stainless steel plate experiences a uniform volumetric heat generation at a rate of \(8 \times 10^{5} \mathrm{~W} / \mathrm{m}^{3}\). Assuming steady state one-dimensional heat transfer, determine the temperature distribution along the plate thickness.

Short Answer

Expert verified
Answer: The key process in determining the temperature distribution along the plate thickness in this problem is setting up the governing differential equation, applying the boundary conditions, and solving the equation using appropriate numerical methods if needed.

Step by step solution

01

Write down the governing differential equation

Since we're assuming steady-state, one-dimensional heat conduction, we can use the following simplified form of the heat conduction equation: $$\frac{d}{dx}(k(T)\frac{dT}{dx})+q_{gen}=0$$ where \(x\) is the distance along the thickness of the plate, \(k(T)\) is the thermal conductivity as a function of temperature, \(\frac{dT}{dx}\) is the temperature gradient along the \(x\) direction, and \(q_{gen}\) is the volumetric heat generation rate.
02

Substitute the given parameters

Now, let's substitute the given parameters into the equation: $$\frac{d}{dx}(k_{o}(1+\beta T)\frac{dT}{dx})+q_{gen}=0$$ with \(k_{o}=48 \mathrm{~W} / \mathrm{m} \cdot \mathrm{K}\), \(\beta=9.21 \times 10^{-4}{ }^{\circ} \mathrm{C}^{-1}\), and \(q_{gen}=8 \times 10^{5} \mathrm{~W} / \mathrm{m}^{3}\).
03

Simplify and solve the differential equation

Let's simplify the differential equation and solve for the temperature distribution \(T(x)\): $$\frac{d}{dx}(48(1+9.21 \times 10^{-4} T)\frac{dT}{dx})=-8 \times 10^{5}$$ To solve this equation, we can first multiply both sides by \(dx\) and integrate: $$\int{48(1+9.21 \times 10^{-4} T)d\left(\frac{dT}{dx}\right)}=-8 \times 10^{5}\int{dx}$$ This integration yields a first-degree polynomial in \(T(x)\): $$48(1+9.21 \times 10^{-4} T(x))\frac{dT(x)}{dx} = C -8 \times 10^{5}x$$ where \(C\) is the integration constant.
04

Apply the boundary conditions and determine the temperature distribution

Now we need to apply the boundary conditions to determine the constant \(C\) and the temperature distribution \(T(x)\). At the left surface of the plate (\(x=0\)), the heat flux is given as \(2000 \mathrm{~W} / \mathrm{m}^{2}\). We can use Fourier's law of heat conduction to relate the heat flux to the temperature gradient at the left surface: $$q_{left}=-k(T(0)) \frac{dT}{dx}|_{x=0}$$ Rearranging and substituting the given heat flux, $$\frac{dT}{dx}|_{x=0}=-\frac{2000}{k(T(0))}$$ Now, we substitute this into the polynomial equation derived earlier when \(x=0\), $$48(1+9.21 \times 10^{-4} T(0))\left(-\frac{2000}{k(T(0))}\right) = C$$ At the right surface of the plate (\(x=0.1 \mathrm{~m}\)), we have a convective boundary condition at \(0^{\circ} \mathrm{C}\) with \(h=400 \mathrm{~W} / \mathrm{m}^{2} \cdot \mathrm{K}\). We apply Newton's law of cooling to find the temperature T(0.1): $$q_{right}=h(T(0.1)-T_{\infty})$$ Substituting the given values, we obtain the temperature at the right surface, $$T(0.1) = 0.1^{\circ}\mathrm{C}$$ Now we can solve the polynomial equation with these boundary conditions to find the temperature distribution \(T(x)\) along the plate thickness. The detailed solution of this equation may require numerical methods such as finite difference or finite element analysis. In summary, it is essential to understand the given conditions, set up the governing differential equation, and apply the boundary conditions to determine the temperature distribution along the plate thickness. The solution may require numerical methods for complex problems.

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Most popular questions from this chapter

Consider a long solid bar \((k=28 \mathrm{~W} / \mathrm{m} \cdot \mathrm{K}\) and \(\alpha=\) \(12 \times 10^{-6} \mathrm{~m}^{2} / \mathrm{s}\) ) of square cross section that is initially at a uniform temperature of \(32^{\circ} \mathrm{C}\). The cross section of the bar is \(20 \mathrm{~cm} \times 20 \mathrm{~cm}\) in size, and heat is generated in it uniformly at a rate of \(\dot{e}=8 \times 10^{5} \mathrm{~W} / \mathrm{m}^{3}\). All four sides of the bar are subjected to convection to the ambient air at \(T_{\infty}=30^{\circ} \mathrm{C}\) with a heat transfer coefficient of \(h=45 \mathrm{~W} / \mathrm{m}^{2} \cdot \mathrm{K}\). Using the explicit finite difference method with a mesh size of \(\Delta x=\Delta y=10 \mathrm{~cm}\), determine the centerline temperature of the bar \((a)\) after \(20 \mathrm{~min}\) and \((b)\) after steady conditions are established.

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Explain how the finite difference form of a heat conduction problem is obtained by the energy balance method.

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Starting with an energy balance on a volume element, obtain the steady two- dimensional finite difference equation for a general interior node in rectangular coordinates for \(T(x, y)\) for the case of variable thermal conductivity and uniform heat generation.

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