Is the water in your Sub Zero heat transfer fluid system costing you money?
Water causes extensive plant reliability problems and is a major cause of plant failure and production loss. Synthetic fluids are used as a heat transfer medium at temperatures down to –100°C and up to 400°C and water causes problems through the whole range. Sub Zero systems are particularly susceptible to problems.
In order to reduce system water content, we have designed a range of mobile and fixed drying units based on ‘nitrogen stripping’ and ‘distillation’ principles.
The units can dry fluid down to below 10 parts per million while in continuous production at Sub Zero temperature or in stand alone batch processing.
The water saturation point of heat transfer fluids varies with the fluid type and the operational temperature.
Free water, above the saturation point, will circulate as ice particles which will deposit themselves on heat exchanger surfaces, in chiller heat exchangers and in expansion tanks.
It should be noted that the surface temperature on heat exchangers will be far lower than the circulating fluid and that the refrigerant temperature should be taken into consideration. Allow at least 10°C lower than the fluid requirement.
As systems are closed loop, eliminating water is not easy. Cycling chillers and allowing individual reactors jackets to warm to release water still leaves the problem of removal or the water will simply deposit itself elsewhere in the system.
How does water get in?
What can be done?
Our units, available for hire or purchase, are connected to the system as a side stream, taking a proportion of the flow through a heat exchanger to a temperature below the boiling point of the HTfluid and above 100°C.
The fluid is passed through a ‘flash chamber’, over a series of micromeshes, cooled and returned to the system. Nitrogen is passed through the ‘flash chamber’ to pick up the released vapours and passed through a condenser.
The condensate can be collected for safe disposal or further reconditioning.
A recent example
Reduction in water content in a 20,000 litre system of Dowtherm Syltherm 800
Starting content: 2520ppm
Finishing content: 36ppm
System content: 20,000 litres
Rig operated: 24 hours per day
System content: 20,000 litres of
Drying cycle: 42 hours
Water removed: 68 litres
Water content: 2520 ppm dried
to 36 ppm