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The heat flow (per unit area) through some thin layer, e.g. a boundary layer of water, is given by: $$ \frac{dQ}{dt} = \frac{K\Delta T}{d} $$ where $K$ is the thermal conductivity, $d$ is the thickness of the layer and $\Delta T$ is the temperature difference between the two sides of the layer. So a high thermal conductivity does indeed mean a high heat ...


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The incoming waves will terminate against each other in the corners of the square pipe, meaning there is a deficit of heat in the faces of the square. If that's true, we should add more corners, and waste less material. A square has 4 corners, with not a lot of heat on the center of the faces. An octagon has 8 corners, with $ 1 \over 2 $ of the ...


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the shape and area of the cross section of the pipe can change flow property along the stream. The fluid velocity in a pipe changes from zero at the surface because of the no-slip condition to a maximum at the pipe center. In fluid flow, it is convenient to work with an average velocity which remains constant in incompressible flow. Laminar flow in a round ...


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The equation: $$ dS = \frac{dQ}{T} $$ only applies to reversible processes. For an irreversible process $dS \gt dQ/T$. To see this start with the expression for the change in internal energy: $$ dU = dQ - dW $$ The internal energy is a state function, so this equation always applies whether the process is reversible or irreversible. So for a reversible ...


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The sign is governed by the convention - whether the volume is of your system in consideration or not. If you decrease the volume of your system - you increase the energy of your system, so you require for total energy change to be positive. If the volume is describing your system then $ dV <0 $ and so $dE=-PdV>0$ is the correct expression If the ...



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