Bulls-eye: High Accuracy Refrigerant Charging in Scientific Cooling Systems

A leading multinational manufacturer of medical devices and cooling systems for scientific applications came to us with the following question: how to get an accuracy of 2/10 of a gram (0.2 g) on an 80 g charge, which works out to be ±0.003%! Like all refrigeration systems, the smaller the charge, the more accurate it needs to be for the system to perform at its peak efficiency. “Standard” refrigerant filling systems can usually be as accurate as 0.5 g, for a small charge (under 200 grams) or 1% over 200 grams.

We approached the problem from two sides: first we needed to guarantee a very precise tolerance in the refrigerant supply pressure; this was accomplished through the use of VTech’s Refrigerant Supply system including a special sensor that would identify any trace of vapor in the refrigerant supply line.

Secondly, we adjusted our PLC resident algorithms that control charging accuracy and increase the number of “counts” in our optical targets metering system. In the end, the VTech 101 Refrigerant Charging System hit the “bull’s eye” of 0.2 g accuracy!

It might be of interest to know that unlike most of our competitors, VTech standard metering device is not a “mass-flow” based system. Our proprietary technology allows us to achieve exceptional results as exemplified in this case study, while being extremely price competitive. In our opinion, Mass-Flow technology is a viable technology only for very specific applications, but

cannot be economically justified for traditional refrigerants and blends.