Classic Heat Exchanger




Designing and building a heat exchanger can be complex. Especially if it has to be compact, if it has to have a large cooling / heating capacity or if the efficiency plays a crucial role.

However, in many applications neither criterium is extremely critical.

This instructable will show you how to build a "classic" heat exchanger. Classic because you can find calculations and guidelines about them in almost any basic engineering book and it is darn simple to build. 
The materials are cheap (PVC drainage pipe) and it can be easily enlarged or reduced to fit your cooling or heating capacity.

I used mine to protect the inlet of a vacuum pump by condensing liquid from an air stream.

Step 1: What Do You Need?

The basis is a "one shell, one pass" type of exchanger. If you require more cooling / heating capacity you can lengthen the assembly, or choose to increase the number of passes (by widening the outer tube for which this procedure does not change).

* 1 outer pipe PVC, 32 mm. If you require more passes, choose a large size.
* 1 inner pipe (Aluminium OD 10 mm).
* 2 T-pieces (PVC, 32 mm))
* 4 pieces of PVC pipe (4 cm long). These are the connectors between the T-piece and the end caps.
* 4 end caps (PVC, 32 mm)
* 4 spacers (rings diameter 30 mm, 10 & 12 mm hole)
* 2 water pipes (Copper OD 12mm)
* 4 self made Rubber plugs (Alternatively: cork of a champagne bottle, styropor/styrofoam or polystyrene).
* PVC glue.

Step 2: The Inner & Outer Tube

Picture 1
 Glue the 2 T-pieces directly onto the PVC pipe (in this stage pay attention to the configuration).

From now on, the procedure will describe only one half of the heat exchanger as the other one is identical.

Picture 2, 3 &4
Place the two spacers into both sides of the T-piece. Glue the PVC connectors in the T-piece and thus locking the spacers in place.

Picture 5
Insert the Aluminium pipe. This will nicely stay in place due to the spacers.

Step 3: Closing the Heat Exchanger

Picture 1
Fabricate the rubber plugs (or cork of a champagne bottle, styropor/ styrofoam or polystyrene). Ensure a very tight fit as they will act as a sealing plug.
Drill holes in the end caps. 

Picture 2
Fit the rubber plug over the Aluminium pipe and push it (hard!) into the connector.
Apply glue to the end section of the PVC connector and apply a large blob of glue to the wall of the Aluminium pipe. Slide the cap, whilst rotating, over the connector. Once it is dry, you can start with the water connection.

Picture 3
Install the water pipe, install the plug, and glue in the similar way as described here above.

Step 4: The Connections

Rig up the hoses, test for water leaks and go !!
Best is to operate the heat exchanger in a counterflow mode (bottom to top).



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    14 Discussions


    1 year ago

    That's a good idea, you got there. It's very much like the ones I built one time when I broke my foot where I worked. They didn't believe in lost time injuries. So I was stuck in the shop making a lot of these things but, ours were all copper. As they were used to push steam heated oil into a blast furnance to keep the iron pool hot. The things worked like a charm.


    Reply 4 years ago on Introduction

    That depends on a lot of factors: temperature difference, flow rate, direction of flow, type of fluid...

    I haven't measure it but since it is a classical heat exchanger, you should be able to find on line calculators to predict the cooling rate under certain conditions.


    7 years ago on Introduction

    Many thanks, bertus52x11, for inspiring me to build one of these contraptions. You can see it on my home chemistry instructable on step 7. I will post my distilling apparatus instructable at some point and will give you all the credit for the heat exchange tube. 

    5 replies

    If your distilling anything to be consumed, aluminium would not be wise.
    Sorry if you already know this but I thought I'd say just in case.

    In short: it leaves with the water.

    It's a heat exchanger, so it exchanges heat from one medium to another.
    In this case, hot air enters in the right handside of the exchanger and flows through the Aluminium tube to the left handside exit. Meanwhile cold water flows through the copper tube into the PVC chamber (from below to the top). Heat is transferred from the hot air stream through the Aluminium pipe to the water stream.
    The air is cooled, the water is heated. 

     ok, thanks. So heat goes in through the air, transfers to the water. Air going out is cool and the water going out is hot. Okay. No need for reply.