Low Thermal Inertia (Low Phi-Factor) Accelerating Rate Calorimeter (ARC) | Phi-TEC II | HEL Group

Phi-TEC II | Adiabatic Calorimeter for Vent Sizing & Thermal Runaway Testing

The ability to thoroughly simulate thermal runaway risks under
manufacturing plant conditions, at the laboratory scale, is a valuable
way of de-risking the process. Appropriate safety measures can be
designed and implemented before the final scale-up.

Plant-scale parameters from the laboratory

The Phi-TEC II is a more advanced type of adiabatic
calorimeter, which supports the use of low Phi factor
test cells. This capability means that very little of the
heat produced during a reaction or thermal runaway
is consumed in warming the test cell. As a result, the
runaway rate is not tempered.

The measured rate of pressure increase and final
temperature (Tend), along with the calculated Time to
Maximum Rate (TMR) and adiabatic temperature rise
(ΔTad), are representative of what would be expected
to occur during a manufacturing scale incident.
Thus, the Phi-TEC II enables the hazards to be fully
evaluated and explored, facilitating their mitigation
prior to scale-up.

Safety by design

The data generated by the Phi-TEC II can be used to
directly compare the impact of different operating
scenarios. From this, the necessary safety controls
for the manufacturing plant can be selected.
Examples of these are:
• Emergency and evaporation cooling
• Quenching
• Controlled depressurization
• Vent sizing (in accordance with DIERS

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The Phi-Factor

When it comes to safety, getting the right answers is a must. A second point to consider on calorimeters is the Phi-Factor.

In an exothermic reaction, a proportion of the energy released is absorbed by the test cell in which the test is performed – this is expressed in terms of the Phi-Factor. In a test in which the phi-factor is high, means a large amount of heat is lost to the test cell and this effectively slows down the temperature rise rate and reduces the final temperature. In a test allowing low phi-factor conditions, virtually all the energy of the reaction is retained in the sample, which is closer to the conditions of large scale plant and hence represents data that is ideal for scale-up simulation.

Phi-TEC II can be run under both low and high phi-factor conditions, depending on the application.

Only a low-phi factor calorimeter such as the Phi-TEC II can deliver the accurate, scalable safety vital for transferring processes from the lab to pilot or plant scale. For example, this low thermal inertia will enable vent sizing under runway conditions including situations where two-phase venting is involved.



The system will allow tests that might otherwise be performed in TSu & Phi-TEC I -type devices. Key data produced includes

  • So-called “Onset” Temperatures for exotherms
  • Runaway data, such as rates of pressure and temperature rise
  • Enthalpy of reaction
  • Reaction kinetics


Applications of the data include:

  • Determination of Venting behaviour (Gassy, tempered, hybrid)
  • Determination of Flow Regime (Two-phase or single-phase)
  • Kinetic data (eg for TMR, or TNR calculations)
  • Safe transport and storage prediction


Process Safety Scale Up Brochure 0620.pdf

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