Therminol VP-3 Heat Transfer Fluid


Therminol VP3 heat transfer fluid is a synthetic heat transfer fluid that was specially developed to allow vapour phase heat transfer at lower temperatures than are practical with traditional diphenyl oxide (DPO)/biphenyl constituted fluids like Therminol VP-1.

Performance Benefits

  • Easy to Handle—Therminol VP-3 has a normal boiling point of 243°C (469°F), 14°C (26°F) below the normal boiling point of Therminol VP-1. Laboratory thermal stability testing suggests a recommended continuous operating temperature of 330°C (625°F) in the liquid or vapor phase. A crystallisation point of 2°C (36°F) makes Therminol VP-3 easy to handle and may eliminate the need for costly heat tracing in moderate climates.
  • Low Odor—The odor of Therminol VP-3 is milder than other vapour phase organic heat transfer fluids. Therminol VP-3 is a mixture of phenylcyclohexane and bicyclohexyl. It contains virtually no biphenyl.
  • Class III b Combustibility—With an open cup flash point of 104°C (219°F), Therminol VP-3 is a Class III b combustible fluid under the definitions of the U.S. National Fire Protection Association (NFPA) . As with any other combustible material, proper system design and operation are important to safe operation. Leaks of vapour could condense into a stable mist suspension that may be explosive in certain concentrations in air.

Typical Properties

PropertyTest MethodTypical Value, Units
AppearanceAbove 2.4°C (36°F) clear, sediment-free liquid
Composition Phenylcyclohexane + bicyclohexyl
Recommended Bulk Temperature330 °C (625 °F)
Maximum Film Temperature360 °C (675 °F)
Normal Boiling Point243 °C (469 °F)
Flash Point COCASTM D92104 °C (219 °F)
Autoignition TemperatureASTM E659
DIN 51794
360 °C (680 °F)
351 °C (664 °F)
Heat of Vaporisationa263.9 kJ/kg (113.6 Btu/lb)
Coefficient of thermal expansion @ 200°C0.001204 /°C (0.000669 /°F)
Viscosity, Kinematic
@ 40°C

ASTM D 445

2.04 cSt, mm2/s
Liquid Density
@ 15ºC
@ 25°C

ASTM D 4052
ASTM D 4052

935 kg/m3 (7.8 lb/gal)
930 kg/m3 (7.76 lb/gal)
AcidityASTM D 664<0.2 mg KOH/g
Molecular Weight (Average)161
Pseudocritical temperature406 °C (764 °F)
Pseudocritical pressure38.5 bar (558.4 psia)
Pseudocritical density352 kg/m3 (22 lb/ft3)
Copper CorrosionASTM D 130<<1a
Moisture Content, maximumASTM E-203150 ppm
Dielectric Constant @ 23°CASTM D-9242.48
Surface Tensiona @ 25°C43.2 dynes/cm
Properties reported here are typical of average lots.

Key Attributes

  • Low odour
  • Easy to handle
  • Class III b Combustibility


  • Extruding
  • Fibers
  • HTF – fine chemicals
  • Polyamide
  • Polyester (PET)
  • Specialty and batch chemical production
  • Specialty chemicals
  • Specialty heat-sensitive polymers

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