Technical Info

What Is a Thermal Fluid System?

A thermal fluid system may also be referred to as a hot oil system or even a Downtherm system. The elements of thermal fluid system design involve a thermal transfer fluid that is recirculated through a heat exchanger (fired or electric) via a thermal heat pump system. Here, the fluid temperature is raised to be utilized in various heating processes. If you’re looking for more industry-specific terminology, please explore our enlightening thermal fluid system glossary.

What Are Some Typical Applications?

TFS has vast experience across numerous applications and industries for heating. Our examples of where thermal transfer fluid can be employed include:

• Heating press platens (OSB and plywood presses)
• Heating drying rolls (for non-wovens and papermaking felts)
• Heating chemical, petrochemical, and other process equipment (including reactors, heat exchangers, and evaporators)

If your specific application is not listed here; don’t worry. Please contact us as we can provide a bespoke solution tailored to your requirements. We have the capability to provide exceptional solutions for almost all indirect heating applications.

What Are the Advantages and Drawbacks of These Systems?

The core advantage on offer with a thermal heat pump system is its ability to operate at a very low pressure. This can be as the minimum pressure level required to pump the thermal transfer fluid around the system. As long as the thermal heat pump system is designed properly, high-temperature heat can be produced reliably and efficiently. The maintenance is simple; only the pump and burner will need frequent maintenance.

How Does the Heater Work?

Industrial thermal fluid heaters contain cylindrical coils that allow the recirculating thermal transfer fluid to pass through. The thermal transfer fluid is heated via a gas or oil-fired burner which fires into the middle of the cylindrical coil system. The temperature of the fluid will rise between 20 and 100 degrees Fahrenheit when traveling from the heater inlet to the outlet. Our TFS heater offers high efficiency thanks to its special three-pass flue gas arrangement.

What Kind of Burner Can Be Used?

TFS can supply any of the national brand burners firing gas, #2 through #6 oil, and waste fuels if required. The burner model is selected and the application is engineered to the exact needs of the particular industrial thermal fluid heater.

What Kind of Pump Can Be Used?

Up to 600 F inexpensive air-cooled mechanical seal pumps may be supplied. For higher temperatures water cooled or magnetically coupled pumps can be used. In some applications, API pumps may be preferred.

Are There Any Special Requirements for Isolation Valves?

TFS recommends the use of valves with a leakproof and maintenance-free metal bellows sealing arrangement. The initially higher cost over a packed valve is offset by the minimal maintenance requirements.

What Is the Pump Strainer For?

This strainer has a coarse mesh screen that stops solids bigger than about 1/8″ that could damage the pump. A side stream filter with a much smaller screen is sometimes used for systems that have small solids resulting from fluid breakdown in circulation.

What Is the Degasser For?

This is a specially designed tank located at the pump suction that helps to separate any air or vapors from the circulating fluid and vents them up to the expansion tank.

What Is a Temperature Blocking Vessel?

Our systems have a small buffer tank between the hot circulating thermal transfer fluid and the expansion tank which we call a Temperature Blocking Vessel. As the thermal heat pump system heats up, the system liquid expansion flows from the top to the bottom of the Temperature Blocking Vessel to the expansion tank. The initial cold contents of the Temperature Blocking Vessel buffer the expansion tank, reducing its temperature rise. After heat up, the expansion tank is effectively isolated from the system by the Temperature Blocking Vessel and it cools down to near ambient temperature.

How Big Does the Expansion Tank Need to Be?

All thermal transfer fluid manufacturers publish data for the volume expansion of their thermal transfer fluid from ambient to the system operating temperature. We calculate the initial system volume and apply this expansion factor, add an allowance for minimum and maximum tank fill, and select the tank size accordingly.

What Safety Controls Are in a Typical System?

TFS supplies a comprehensive set of safety controls in all of our thermal heat pump systems. All of our industrial thermal fluid heaters incorporate continuous flow monitoring with an orifice plate IN EACH HEATER COIL and differential pressure switches. We have redundant fluid outlet temperature alarms, a high stack temperature alarm, and an automatic interlock to allow minimum firing only during warm-up, when the oil flow may not be fully established. We provide low and (optional) high expansion tank level alarms. The burner is supervised by an electronic flame programmer with typically a UV flame scanner and the fuel trains come with low and high fuel pressure alarms and approved block and bleed valves.

Is a Drain Tank Always Required?

Small thermal heat pump systems (up to about 1,000 gallons) often are supplied without a drain tank as it is practical to fill directly from drums. With larger thermal heat pump systems the drain tank may be a smaller volume than the entire system as it is rarely necessary to drain the entire system at once.

System Checklist

The checklist link below is provided as a guideline for clients to minimize the time and associated costs for system startup. This will provide a general outline for preparing the thermal heat pump system and making sure it is essentially complete prior to the Field Engineer’s arrival on site for startup. If you need further information during this review, please contact TFS at (770) 425.5556.