Chapter 2: Problem 136
How is the order of a differential equation determined?
Chapter 2: Problem 136
How is the order of a differential equation determined?
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Get started for freeConsider a solid cylindrical rod whose side surface is maintained at a constant temperature while the end surfaces are perfectly insulated. The thermal conductivity of the rod material is constant, and there is no heat generation. It is claimed that the temperature in the radial direction within the rod will not vary during steady heat conduction. Do you agree with this claim? Why?
How do you distinguish a linear differential equation from a nonlinear one?
How do differential equations with constant coefficients differ from those with variable coefficients? Give an example for each type.
A heating cable is embedded in a concrete slab for snow melting. The heating cable is heated electrically with joule heating to provide the concrete slab with a uniform heat of \(1200 \mathrm{~W} / \mathrm{m}^{2}\). The concrete has a thermal conductivity of \(1.4 \mathrm{~W} / \mathrm{m} \cdot \mathrm{K}\). To minimize thermal stress in the concrete, the temperature difference between the heater surface \(\left(T_{1}\right)\) and the slab surface \(\left(T_{2}\right)\) should not exceed \(21^{\circ} \mathrm{C}\) (2015 ASHRAE Handbook-HVAC Applications, Chap. 51). Formulate the temperature profile in the concrete slab, and determine the thickness of the concrete slab \((L)\) so that \(T_{1}-\) \(T_{2} \leq 21^{\circ} \mathrm{C}\).
Consider a medium in which the heat conduction equation is given in its simplest form as $$ \frac{1}{r} \frac{d}{d r}\left(r k \frac{d T}{d r}\right)+\dot{e}_{\text {gen }}=0 $$ (a) Is heat transfer steady or transient? (b) Is heat transfer one-, two-, or three-dimensional? (c) Is there heat generation in the medium? (d) Is the thermal conductivity of the medium constant or variable?
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