Materials Choice in Heat Exchanger | Stalwart International Pvt Ltd.

1. Materials Choice in Heat Ex-changer

2. From heat recovery to air coils and refrigeration to power plants, choosing the right material for heat ex-changers — particularly with reference to thermal qualities, resistance to sag during brazing and corrosion resistance — is key.Fortunately, choosing materials becomes easier once you have assessed the environment and the application. If the heat ex -changer will be operating outdoors, or in a processing plant with corrosive media, then a high corrosion resistance will be a necessity.In such an environment, the tubes must be made of an inert material, perhaps even an unconventional one that is non-metallic – such as glass.The two most commonly selected materials for heat ex-changer are aluminium and copper. Both metals have the optimum thermal properties and corrosion resistance to make them ideal choices, with most of the differences being application- specific.

3. Copper for Heat Ex-changers

4. Typical thermal conductivity of generic pure copper is 386.00 W/(m·K) at 20 degrees Celsius. This makes copper the most thermally conductive common metal, which, along with its relatively low specific heat — of approximately 0.385 J/(g·°C — underpins its popularity in heat ex-changers. These characteristics do bring with them a slightly elevated price. Most design engineers and product designers consider this one of the biggest deciding factors between copper and aluminium for smaller projects.

5. However, there are a few practical considerations to consider when using copper. The density of the material, for example, might mean that it is unsuitable for certain applications that require a lightweight heat exchanger. Copper has a lower flexibility than aluminum, making it more difficult to form into certain shapes. Because of this, design engineers working on a plate fin exchanger, which is a type of heat exchanger that uses plates and finned chambers to transfer heat between fluids, might find that aluminum is a better fit for the fins.

6. Aluminum for heat ex-changers

7. Boasting a thermal conductivity of 237 W/(m·K) for pure aluminum or ~160 W/(m·K) for most alloys, aluminum is the third most thermally conductive material and arguably the most cost-effective. Aluminum also offers a specific heat of 0.44 J/(g·°C), making it very nearly as efficient at diffusing heat as copper. Aluminum is also far more lightweight and flexible than copper, addressing many of the practical issues engineers might encounter with copper. It is far more malleable, so engineers designing a plate-fin exchanger for a gas furnace will find that it is better suited to the intricacies of the fins.

8. Aluminum does typically have lower sag resistance than copper, making it more prone to deformation during the brazing process and after repeated heat cycles. This can be counteracted by opting to specify an aluminum alloy that has been specifically formulated to bring the metal’s properties closer to that of copper, without significantly increasing the price.The characteristics of aluminum and copper are very closely matched in terms of suitability for heat exchangers, with the key deciding factor ultimately being the application’s practical requirements.

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