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Two Phase Overview

Traditionally hiTRAN® Thermal Systems have been applied to single-phase heat exchanger services, but CALGAVIN®’s research and innovation have enabled vaporiser and condensers to benefit too.

The heat transfer of tube side boiling is very much a function of the observed flow pattern and boiling mechanisms. Dependant on the type of vaporiser, hiTRAN can give key benefits shown further down the page.

Likewise, for condensers, where condensing vapour forms a liquid film on the tube surface, the heat transfer coefficient is dependent on the flow conditions of both film and vapour phases. Where such flow behaviour is ineffective hiTRAN can be used to modify it and promote effective heat transfer.

Features & Benefits

Mitigates the constraints of multicomponent and Inert mixtures influence upon condensers

Ensures proper mixing of the vapour maintaining equilibrium conditions throughout the tube maximising mass transfer rates.

Effective vapour phase cooling

Increased vapour phase heat transfer cools the fluid quickly ensuring condensation proceeds as the dew point falls

Reducing condensate film thickness and increasing film turbulence

The effect of the hiTRAN geometry at the wall enables the draining of some of the condensate away from the wall and increases the turbulence of the remaining condensate film.

Removing phase stratification and non-equilibrium conditions

In two-phase services, the conditions of the phases can change independently, losing equilibrium resulting in mass transfer limitations. hiTRAN’s mixing maintains high mass transfer and convection rates for efficient heat transfer

Increased film turbulence

For falling film evaporators hiTRAN Thermal Systems can be designed to both improve fluid distribution at the wall and increase film turbulence.

Mitigating mist flow/entrainment

Increased bulk mixing ensures liquid droplets remain in contact with the highest vapour temperatures enabling complete vaporisation.

Suppressing film boiling

Successive contacts at the tube wall from hiTRAN breaks up the vapour blanket layer and redirects fluid to the hot tube wall. Critical heat flux is shifted to higher values with increased heat transfer, enabling reduced operating temperature differences.

Enhanced boiling

For thermosyphon reboilers, subcooled lengths can be reduced by hiTRAN, leaving longer lengths for boiling.

How it works?

At CALGAVIN® research has been undertaken both in our laboratory and at Universities to determine the effect of hiTRAN® Thermal Systems upon vaporisation and condensing exchangers.

The heat transfer mechanisms in action are often complex and may vary along the tube length from tube to tube and pass to pass. Our webinars titled ‘Total Vaporisation’, ‘Boiling with a low Delta T’ and ‘hiTRAN® Thermal Systems in tube side condensing processes’ detail how hiTRAN can help heat and mass transfer mechanisms, mixing, fluid distribution, drainage and de-entertainment.