Chiller

One of the conditions in system design is – the sample should be conditioned to the temperatures as required by the analysers. What then is this required temperature?

As per the standards this temperature should be 25 ± 1 Deg.C. The analysis needs to be done at these temperatures.

There are two ways of looking at this issue :

1.  To cool the sample with the available cooling water temperature (cooling water is generally available between 32 to 36 Deg.C, if it is from cooling towers). With this cold water, one can cool the sample to (say) 40 Deg.C. This sample can be fed to analysers which in turn sense it and interpret  the results as if the sample is at 25 Deg.C. A temperature compensation algorithm is used for this purpose inside the analyser.

2.  To cool the sample to 25 ± 1 Deg.C. Some users and consultants believe in this method. They argue that if they are investing in a sampling system for conditioning the sample, why not do the complete job in the sampling system itself ? Why leave some part of this function to analysers ?

Use of chilled water becomes necessary in such cases. This is because cooling water available on site is not capable of cooling the sample to 25 ± 1 Deg.C. The normal practice is to make use of available cooling water for extracting as much as  possible heat from the sample and using the chilled water for  removing the remaining fraction of heat.  Thus it becomes two stage sample cooling. In the first stage, one can use available cooling water and in the second stage – chilled water.

Chiller with isothermal bath is a compact unit which saves a lot of space.  In this the chiller unit provides the chilled water to a container called isothermal bath in which the sample coils are immersed.  Thus one can save the use of individual heat exchangers.  The SWAS vendor who can manufacture chillers / isothermal baths is an ideal choice with a single point responsibility.