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Types of Thermal Transfer Fluids

At Thermal Fluid Systems, we specialize in the supply and servicing of thermal fluid heating systems. In addition to standalone heater units, we provide ancillary components for complete solutions and replacement parts for existing systems, such as pumps, valves, tanks, economizers, stacks, and more.

Thermal fluid heating systems are indirect heat transfer systems that control temperature conditions by circulating a thermal fluid throughout the equipment. This process allows for fine-tuned cooling or heating using a single thermal transfer fluid. However, the fluid employed must be carefully chosen to accommodate the system’s processing requirements for the operation to proceed effectively and efficiently.

Below, we provide an overview of the thermal fluids we use in our systems, including what they are and what unique properties they offer.

Mineral Oil

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Types of Thermal Transfer Fluids

Mineral oil is used as a heat transfer medium for a variety of applications. Compared to some of the synthetic fluids available, it offers better thermal stability at high temperatures, easier maintenance and disposal requirements, and a smaller environmental impact. It also generally comes at a lower price point.


CALFLO is a line of heat transfer fluids engineered for use in non-pressurized indirect heating systems. CAFLO LT is recommended for use in systems operating at bulk temperatures of 520° F, while CAFLO HTF is designed for use in systems operating at bulk temperatures of 620° F. CALFLO AF is suitable for systems that require oxidative resistance and thermal stability at continuous operating temperatures up to 600° F. PURITY FG is formulated for greater longevity in operations involving food-grade product at bulk temperatures up to 620° F.


Chevron heat transfer oils are mineral-based heat transfer fluids designed for use in indirect or secondary heating systems. They are non-toxic, non-corrosive, and long-lasting. Numerous formulations are available to accommodate different operating temperatures. For example, Grade 46 is recommended for bulk temperatures up to but not exceeding 550° F, while Grade 22 is suitable for bulk oil temperatures up to 600° F.

Dowtherm & Dowfrost

DOWTHERM and DOWFROST are heat transfer fluids manufactured by Dow Chemical. Both contain copper inhibitors and other additives that improve their corrosion resistance in heat transfer applications. DOWTHERM is an organic heat transfer fluid that demonstrates thermal stability at temperatures up to 750° F. It can be used in either its liquid or vapor phase. DOWFROST is a propylene glycol-based medium with low acute oral toxicity, which makes it suitable for use in food and beverage applications. DOWFROST HD offers freeze protection to temperatures of less than -60°F and burst protection to temperatures below -100° F.


In heat transfer applications, glycol is generally used in one of two forms: ethylene glycol water (EGW) or propylene glycol water (PGW). EGW has a high boiling point, low freezing point, thermal stability over a broad temperature range, and excellent specific heat and thermal conductivity. PGW offers an even lower specific heat and a smaller risk of oral toxicity. The latter quality makes it suitable for use in food and beverage applications and locations with enclosed spaces.


Marlotherm® heat transfer fluids are suitable for indirect heating and cooling applications. They are available in several formulations for pressurized and non-pressurized systems, all of which help achieve and maintain safe operating conditions, lower operating costs, and reduce maintenance costs.


Mobiltherm heat transfer oils are lubricants developed for use in cold-oil sealed, closed-loop or open-loop, indirect heating and cooling systems. They contain refined base stocks that provide resistance to chemical oxidation and thermal cracking. Other key properties include excellent thermal stability, good heat transfer efficiency, and fast startup in cold systems. As they prevent the buildup of sludge and coke within equipment, they help improve system longevity and reduce maintenance costs.


Multitherm® heat transfer fluids are available in several formulations to suit different applications. For example, MultiTherm IG-1® is a refined, hydro-treated mineral oil designed for closed-loop heat transfer systems equipped with expansion tanks. It can accommodate bulk temperatures up to 550° F and film temperatures up to 600° F.


Paratherm heat transfer fluids are designed for non-pressurized, closed-loop heat transfer systems. The product line includes high-temperature, low-temperature, food-grade, and synthetic heat transfer fluids and supports industrial processing temperatures between -126.4° F to 649° F, depending on the formulation.


Petro-Therm is a thermal transfer oil formulated for use in non-pressurized, liquid-phase, closed-loop heat transfer systems operating at bulk temperatures up to 599° F. It demonstrates excellent thermal efficiency and resistance to oxidative and thermal degradation. The PPD variation is suitable for startup operations in cold systems at low ambient temperatures.


Shell heat transfer fluids are used in indirect fluid heat transfer systems with closed-loop configurations. They can accommodate bulk temperatures up to 608° F. Shell THERMIA® oils offer excellent oxidative and thermal stability, fluidity, and heat transfer properties, good solvency, low vapor pressure, and easy disposal requirements.


SYLTHERM heat transfer fluids are silicone-based heat transfer mediums. They are available in a variety of formulations to accommodate different heating and cooling applications. SYLTHERM XLT is suitable for systems with operating temperatures up to 500° F. SYLTHERM HF is designed for use in temperatures ranging from -100° F to 500° F. SYLTHERM 800 is a high-temperature formulation used for systems with operating temperatures between -40° F and 750° F.


Texatherm® is a highly refined paraffinic petroleum oil formulated for closed-loop and open-loop thermal fluid systems with forced circulation and operating temperatures up to 608° F. It contains selective additives that enhance its oxidative and thermal stability, which helps prevent coke and sludge buildup and contributes to longer service life. Other key properties include excellent fluidity at low temperatures (facilitates startup in cold systems) and low vapor pressure at elevated temperatures (minimizes the risk of evaporation, vapor lock, and pump cavitation).


Therminol® heat transfer fluids are designed for use in indirect heat transfer systems with single-station or multi-station configurations. They are available in synthetic, synthetic-organic, and mineral formulations, each of which offers excellent thermal stability across a specific operating temperature range. In the right system, they allow for better operation, lower maintenance requirements, and greater temperature control.


Water has a high heat capacity and excellent thermal conductivity, both of which make it suitable for heating and cooling applications. When using water for such applications, it is important to consider the source of the water and its purity. For example, while tap water is convenient and inexpensive, it is likely to contain impurities that could cause corrosion and/or clog fluid channels. As such, it is important to use good quality water treatment to ensure the system operates as intended.


XCELTHERM® is a line of products that encompasses a variety of synthetic and hot oil heat transfer fluids developed using cutting-edge technologies and high-quality raw materials. They are suitable for use in petroleum refineries, synthetic fiber plants, and many other manufacturing environments.

Thermal Transfer Fluid Types Utilized by Thermal Fluid Systems, Inc.

Thermal Fluid Systems, Inc. is an experienced provider of thermal fluid heaters and hot oil systems for customers in the process industries. Equipped with extensive experience and a partner network of German technology companies, we have the knowledge and skills necessary to supply an appropriate solution for nearly any process requirement. In addition to our sales capabilities, we provide a variety of after-sales support services, including on-site technical service and support, parts replacement, and systems and controls upgrades.

For additional information about our thermal transfer fluid systems and/or how to choose the right fluid type for your needs, contact us or request a quote today.