services and products

Double wall heat exchanger

A double wall heat exchanger keeps your drinking water separated from the medium on the other side, because two plate walls sit back to back between the two flows. If one of those walls develops a leak, the leaking water emerges visibly on the outside instead of ending up in the drinking water. That is why this is the usual version for domestic hot water. HEXCHANGE supplies the double wall models of UNEX from its own stock in Oosterhout.

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Frame detail of a double-wall heat exchanger

When do you need a double wall heat exchanger?

As soon as drinking water runs on one side of the exchanger and the other side carries a medium that must not get into it, separation between the two flows is required. The Dutch rules for drinking water installations address exactly this: drinking water must be protected so that no other medium can flow back into it. A single wall plate is then one barrier; if it fails, there is no second one.

In practice this mainly applies to collective domestic hot water installations and commercial buildings, where the consequences of contaminated drinking water affect an entire building. If you are unsure whether your situation qualifies, put the application to your installation consultant or to us — we are happy to take a look.

Domestic hot water heat exchanger: how the double wall works

In an ordinary plate heat exchanger, a single plate separates the two media. In a double wall version there are two, back to back, with a narrow gap between them that opens to the outside. As long as everything is intact, nothing happens there and the heat simply passes through both plates. If one of the two walls develops a leak, the medium runs out through that gap to the outside instead of crossing to the other side. Drinking water and heating water can therefore never mix.

The price you pay for that is a slightly lower heat transfer per plate, because the heat has to pass through two walls instead of one. During selection that is compensated with somewhat more surface area.

Close-up of the plates of a heat exchanger

Double wall plate heat exchangers from our own stock

Double wall models are not quickly available everywhere, because they are less common than single wall ones. That is why we keep them in stock ourselves in Oosterhout, matched to what is in demand in the Netherlands. If the type you are looking for is not among them, we will think along about an alternative or order it with a clear lead time attached. Either way, you get an answer within one working day, with a quotation.

Drinking water heat exchanger: what to look for when choosing

In a drinking water application, separation is the starting point, but a few other factors then determine which model it becomes:

The temperatures on both sides and the required capacity in kW
The permitted pressure drop, which helps determine the number of plates
The connection size and the space available in the installation
Whether insulation is needed, and whether it concerns heating or cooling
The local water quality, in connection with the material choice

Insulation and the brazed version

Insulation can be supplied along with it on request: insulation boxes against heat loss or cold insulation against condensation. You can read more about the brazed version that the double wall models belong to on the brazed plate heat exchanger page.

Have your double wall heat exchanger calculated

If you do not yet know the required capacity, there is no need to guess. Pass on the temperatures, flow rate and medium of both sides via the calculation form; our specialists will make the calculation and send a matching quotation the same working day. Bear in mind that a double wall version turns out somewhat larger than a single wall one at the same capacity — so do not size it like an ordinary exchanger.

Prefer to discuss the application first? Call +31 (0)162 429 068 or request heat exchanger advice.

heat exchanger calculation