Want to learn more about thermal fluid heating systems? Here are five frequently asked questions about such systems as well as the no-nonsense answers you seek.
Q: Is there a minimum flow requirement for a thermal fluid heater?
A: A minimum flow rate is required in order to maintain the appropriate velocities through the heater (typically 10 to 12 ft/sec). If the velocity is too low, the film temperature could increase, potentially destroying the fluid.
Q: What are the primary components in a thermal fluid system?
A: A typical system includes the heater, circulation pump, expansion tank and the user. Depending on the temperature requirements and the system design, control valves may also be utilized.
Q: How do I choose a thermal fluid?
A: The required operating temperature along with the physical properties (specific heat, maximum operating temperature, vapor pressure, specific gravity and coefficient of thermal expansion) of the fluid should be evaluated when choosing a thermal fluid. It is important to choose a fluid specifically designed for heat transfer as opposed to a multi-purpose of turbine oil.
Q: Can thermal fluids be mixed?
A: Mixing different fluids and subjecting them to high temperatures can have unpredictable results. In addition, once fluids have been mixed, the baseline analysis of the fluid is no longer applicable, making it difficult to perform an annual analysis of the fluid for degradation.
Q: Why is an expansion tank required?
A: All thermal fluids expand as they are heated. The amount of expansion is based on the operating temperature, system volume and the coefficient of thermal expansion of the fluid. An expansion tank must be provided to accommodate the increased system volume at operating temperature. Note that different heat transfer fluids expand at different rates, so the system design should be tailored to your specific process and equipment criteria.