A hot water pipe (D = 4 cm, Do = 6 cm, L = 2 m, k = 12 W/m K) made of "Plain Carbon Steel" is being moved into a running cold water to heat up the cold water and cool down the hot water. Hot water flows inside the pipe at a temperature of Thw = 90 C, with a convection coefficient h = hhw = 200 W/m K - The cold water is outside the pipe at a bulk temperature Tcw = 20 C, and a flow rate ucw, = 0.1 m/sec. a) { Please construct a thermal circuit for this heat transfer system. Please label all the resistors and the temperatures before and after each resistor. (hint: Where does the heat come from and go? How many thermal resistors, and what are they? Are they in series or parallel? What geometry / coordinate?) e) Tow T20 C New Mut 0.1 m/s b) If the pipe is placed such that the cold water flows across the pipe (Figure 1). What is the outer convection coefficient, hout? What is the total heat transfer rate for the pipe? What are the surface temperatures at the outer and inner surfaces of the pipe? Imagine the hot water was running in the pipe for long time before the pipe is being submerged into cold water. In other words, Tpipe = Thw = 90 C at the time of submerging (time Assume the properties of stainless steel do not change with temperature, how long would it take for the outer surface temperature to cool down to 50 C? (hint: non-steady state problem) c) = 0). d) -Now, the pipe is placed along the same direction of cold water (Figure 2). Approximating the outer convection as a flat plate, please use calculation to show if the heat transfer rate becomes higher or lower than the case in b). What about the inner and outer surface temperatures of pipe? hot water W cold water how-200K Tw=90 C TowTout 20 C cold Mut= 0.1 m/s water (Fig. 1) cold water hot water Do D W 200- mK The 90 C (Fig. 2) ) If the only thing that can be changed is the pipe length, do you think at certain length, say 200, 2000 m or more, the parallel flow in d) will have a higher heat transfer than the cross flow in b)? Briefly explain why.