Selecting Sheath Material, and Watt Density for Your Circulation Heater

It is important when selecting your circulation heater to choose the proper watt density and sheath material. If done correctly, selecting the right sheath material and watt density will provide your heater with a longer life and greater fluid integrity. Follow the guidelines below and use the information to help guide your decision making process.

Watt density, watts per square inch of element surface area, determines the heater’s operating temperature for a given set of conditions. For a more detailed explanation of watt density, please refer to our Watt Density article that explains how it is calculated and the affects it can have on a heater.

Watt density takes three factors into consideration:

1. Fluid flow rate

2. Maximum outlet temperature

3. Type of fluid that is being heated

They type of sheath material will depend on the type of fluid and the maximum temperature needed. A standard vessel material used is carbon steel but a stainless steel vessel may be required for higher temperatures or to provide better corrosion resistance.

The table below illustrates the maximum watt densities, sheath materials, and properties for Liquids:


When selecting the right circulation heater for your application, be sure to use this helpful guide to select the right watt density and sheath materials! Contact Accutherm today for more help on choosing the right heater for you, call toll-free 888-925-IDEA or email us at

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