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I have a metal plate and I need to transfer heat out of the metal plate to the atmosphere. Hence, I can use a double pipe heat exchanger which contains 2 pipes. But what if I just use one pipe and let water flow through it. I can still bring the heat out right? Why is there a need for 2 pipes instead of just one pipe? My main point is a heat exchanger is used to transfer heat but a heat exchanger means having like two pipes separated by a metal wall. Why not just use one pipe and take the heat out?? Why have 2 pipes where in one pipe hot water flows in and turns cold at the end of the pipe and in another pipe cold water flows in and turns hot at the end of the pipe?

Thanks a lot in advance!

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  • $\begingroup$ @santiago I see.. I did not know where this questions belong the best. Hence, I posted on both. Anyway, I have deleted the one in chemistry now $\endgroup$ – Vin Apr 22 '15 at 8:59
  • $\begingroup$ No problems at all - hope you get a good answer $\endgroup$ – user77400 Apr 22 '15 at 9:00
  • $\begingroup$ If you have no access to a cooling liquid stream, then you should use an air cooled radiator (single pipe) like John Rennie suggests. If you do have access to a cooling liquid stream, then it is pretty self-evident that you should use it because bringing cold liquid in contact with the hot stream will cool it faster than just air cooling it. Was that your question? $\endgroup$ – pentane Apr 22 '15 at 13:22
  • $\begingroup$ @pentane my question was more like what is the difference in using a heat exchanger and just a single pipe. Because I would like to use a heat exchanger. Is it possible to use a heat exchanger in this case? $\endgroup$ – Vin Apr 28 '15 at 7:08
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You're basically describing a car radiator. I can't see any reason why you'd need a more sophisticated heat exchanger.

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  • $\begingroup$ But maybe having 2 pipes can enable the cooling process to be repeated? Like when the first pipe absorbs the heat from the plate and transfers it to the second pipe, the first pipe cools down and hence cold water comes out. The second pipe releases hot water. And this cold water can be inserted again and again into the process? If it is one pipe, then only heated water comes out which cant be let it to flow again since it will will not help absorb the heat from the plate. This is just my assumption. Could this be right? $\endgroup$ – Vin Apr 22 '15 at 9:36
  • $\begingroup$ No, I don't see why two pipes are necessary. Hot water enters the radiator, is cooled by the air, then leaves the radiator as cold water. I don't see any benefit to having an intermediate step. $\endgroup$ – John Rennie Apr 22 '15 at 10:24
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If you have hot water that you want to cool with air (especially ambient air), you would want to use a car radiator, as John Rennie pointed out. For a more industrial approach, you will often have a hot process stream (e.g., hydrocarbon) that you want to cool with cooling water. The cooling water is in a closed loop, so it comes from the cooling tower at approximately 80 deg F, goes through the heat exchanger, and goes back to the cooling tower at approximately 110 deg F, where the heat is expelled to the atmosphere. Since your employer has to pay for "make up" water (to make up for what evaporates, and for what is "blown down" to get rid of contaminants), you want to minimize how much water you purchase and you don't want a lot of water puddles all over the place, leading to the closed-loop circulation. On the process side of the heat exchanger, the hydrocarbon is either an intermediate substance or your product, and it is very flammable and/or explosive, so you don't want to get sloppy with this either. Due to these constraints, where you don't want to waste either water or process fluid, and you don't want either fluid to mix with the other, you would use something like a double pipe heat exchanger.

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