Hello dear friends
There is two channels that one of them is finned and another one is simple and without fin(as attached file). The fluid mass flow rates and inlet fluid temperatures in both channels are equal. Conductivity of fin is larger then the fluid and the boundary conditions are shown in the attached figure. What is the difference between each channel's heat transfer rate. and why?
regards
The heat transfer is high in finned since they allow the highest log mean temperature difference between the hot and cold streams
Hello, If the overall entrance surface is equal for the two cases, the mass flow rate is equal, then the finned channel has a higher surface inside the channel through which heat can flow. Furthermore, it seems that the effective entrance surface of the finned case is lower, so that, with the same mass flow rate, the mean velocity is higher. This can increase the convective part of the heat transfer. Hence, the heat transfer rate is higher for the finned case.
The fluid pressure drop on the fined one (1) will be significantly higher than in (2) and it will have higher heat transfer. However, you must have equal pressure drop in two heat exchangers in order to make a meaningful comparison.
Hello,
Area-to-volume ratio is higher, so;
- Heat transfer is more effective in the finned channel ( depend on the competition between area of heat transfer and average velocity of fluid,
- Reynolds number is different (lower in finned channel)
- and pressure drop is higher in the finned channel.
In the finned channel, as mentioned by all, heat transfer will be more provided the mass flow rate is same as that of simple channel.
But in reality, in the finned channel,flow resistance will be more.As a result pressure drop will also be more.
Existing fan/other means currently being used in the system to induce the flow is no longer valid.Its operating point will change because of the increased flow resistance offered by finned channel. So the flow generated by the fan will come down.
But in order maintain the same flow rate, new fan has to be introduced.This is some important aspect to be considered when we make this comparison.
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