The technology advances cited (augmentation of threaded joints with O-rings, use of improved sealants, increased leak testing, and use of condensing purges with vapor recovery) are means to reduce refrigerant releases rather than increase efficiency. There is some tie between them, since optimal efficiency is degraded with charge leakage.

The primary measures to reduce refrigerant releases were redesign to minimize the number of joints, shift to welded or brazed joints where feasible, and improvements in service practices. The best new chillers attain annual loss rates less than 1/2%, compared to more than 35% for the worst cases thirty years ago.

The performance increases also were dramatic. The most efficient new chillers use less than half the energy for the same capacity as some old machines still in use; replacement usually provides an attractive cost payback. Combining improved effi-ciency, reduced refrigerant releases, and use of environmentally friendly refrigerants minimizes the impacts on both stratospheric ozone depletion and global warming.

On the matter of R-123 (an HCFC), the article suggests that its future is in doubt. This refrigerant offers low-pressure operation to minimize leakage, very low ODP, a much lower GWP than other centrifugal chiller options, and the highest efficiency among current centrifugal choices. There is a strong environmental rationale to exempt R-123 from phaseout for use in chillers. Several studies published in prestigious engineering and scientific journals document its environmental advantages and the harm of phasing it out. I would be pleased to send some of these studies to News readers who request them by e-mail to jmc@ JamesMCalm.com.

I made these points in my comments, but also noted that the Montreal Protocol currently requires that R-123 production halt by 2030 in developed countries and 2040 in developing (more accurately Article 5.1) countries. Ample service quantities will be available long after those dates with prudent planning and equipment maintenance. Additional amounts will become available through recovery from other R-123 chillers as they age.

Although still a long way off, I encourage the industry to seek recon-sideration of R-123 phaseout as a chiller refrigerant. That is consistent with a key premise of the Montreal Protocol, to continue scientific assessments and base actions on the findings. The rationale for a reprieve recognizes the dire outlook for global warming, which was not addressed in framing the earlier HCFC stipulations. I am optimistic rather than doubtful on the outcome.

Finally, the article cited my com-ments on absorption chillers (not adsorption chillers, as your article stated). It is their lower thermal efficiency, rather than use of water and lithium bromide as refrigerant and absorbent, respectively, that increases their global warming impacts. There are sound economic and engineering reasons to use absorption chillers in some applications.

However, absorption chillers typically result in higher net greenhouse gas emissions — some-times described as total equivalent warming impact (TEWI), life-cycle-warming impact (LCWI), or life-cycle climate performance (LCCP) — than their vapor-compression counterparts.

Thank you allowing me to clarify these points.

James M. Calm, P.E. Engineering Consultant Great Falls, VA

Publication date: 03/05/2001