Heat Transfer

Heat transfer oil, also called thermal fluid, carries heat from a fired or electric heater around a closed loop to jacketed vessels, presses, dryers, reactors and process equipment, allowing high process temperatures without the pressure a steam system would require.

That last point is the main attraction: a thermal fluid system can run well above 200 degrees at close to atmospheric pressure, which removes the need for a pressure vessel and its associated inspection regime. The demand on the fluid is severe, since it is held at high film temperature continuously. Thermal stability and oxidation resistance decide service life, and degradation shows up as light-end cracking, carbon deposits on heater tubes and rising viscosity.

Keep the expansion tank cool and blanketed, avoid air ingress, and sample the fluid periodically for viscosity and flash point change.