We have been posting some “behind-the-scenes” and educational information about Heat Exchangers, how they work, what is the science behind them, etc. And now we want to take a look at “flow arrangement” and how we classify flow arrangement when fabricating our Heat Exchangers.
Basically, there are two primary classifications of heat exchangers according to their flow arrangement. In parallel-flow heat exchangers (at left), the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side.
In counter-flow heat exchangers (at right) the fluids enter the exchanger from opposite ends
. The counter current design is most efficient, in that it can transfer the most heat from the heat (transfer) medium.
For efficiency, heat exchangers are designed to maximize the surface area of the wall between the two fluids, while minimizing resistance to fluid flow through the exchanger. The exchanger’s performance can also be affected by the addition of fins or corrugations in one or both directions, which increase surface area and may channel fluid flow or induce turbulence.
In a cross-flow heat exchanger (at left), the fluids travel roughly perpendicular to one another through the exchanger.
The driving temperature across the heat transfer surface varies with position, but an appropriate mean temperature can be defined. In most simple systems this is the “log mean temperature difference” (LMTD). Sometimes direct knowledge of the LMTD is not available and the NTU (Number of Transfer Units) method is used.
If you would like more information about our Bendel heat exchanger design and fabricating program, please call us at 866-596-5112 or contact Vince Petrucci or Vivek Patel at Bendel.
