Chocolate pattern on plates of heat exchangers

Let’s talk about Chocolate pattern, which in our sector means talking about plate heat exchangers. One of the mostly asked questions we receive is what is the best configuration of the connections distribution on plate heat exchangers.

Plate heat exchangers of latest generation have for the majority parallel connections, which means primary fluid on the right and secondary fluid on the left, or viceversa. Since a few years ago there were also exchangers with crossed connections. We are then very often asked if crossed connections, on the perspective of the distribution of the fluid within the plate, is not better than parallel ones.

In fact it can be natural to think crossed connections are better than parallel ones, when looking at the design of a plate and at how plate heat exchangers do work. Just because, especially with large sized plates and maybe with lower flow rates of the fluids, the distribution doesn’t happen on the overall thermal transfer surface of the plate but only on the side where connections are.

Clearly, having crossed connections it doesn’t happen, because the fluid gets automatically distributed upon the whole surface of the plate.

This kind of implication has been studied indeed, leading to the famous Chocolate pattern design. Looking carefully to photographs of the triangular area between the nozzles, it is possible to observe a very peculiar design that reminds the one of chocolate bars, from which it gets its name. This system has been designed and engineered in order to allow a uniform distribution of the fluid upon the whole surface of the plate.

Looking with further attention, one can see that the channels that distribute the fluid upon the whole width of the plate have differentiated passage sections. This allows to foster the correct distribution of the fluid upon the whole width of the thermal transfer surface. And finally, see also how this kind of distribution design is equally applied to small size plates.

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