- Author
-
Kedzierski, M. A.
- Title
- Investigation of an Additive to Improve the Boiling Performance of R245fa.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Trane Co., La Crosse, WI
- Report
-
Letter Report
February 4, 1999
17 p.
- Keywords
-
additives
|
heat transfer
|
hydrocarbons
|
refrigerants
- Identifiers
- binary mixtures; enhanced heat transfer; fluid heating; pool boiling
- Abstract
- This letter reports work outlined in project CN-1514 entitled, "Investigation of an Additive to Improve the Boiling Performance of R245fa," which was initiated in June 1998. The focus of the study was to measure and compare the pool boiling heat transfer performance of pure HFC-R245fa (1,1,1,3,3-pentafluoropropane) to that of an R245fa/isopentane (99.5/0.5) % by mass mixture. Both fluids were boiled on a flattened Turbo-BIII (tm) -LP low-pressure boiling surface. The results indicate that the addition of 0.5 % mass isopentane to R245fa increases the heat flux by no more than 11% above the heat flux of pure R245fa when the entire surface was actively boiling. By contrast, the heat flux of the R245fa/isopentane mixture was as much as 50% greater than that of pure R245fa for a partially boiling-active surface. Although not outlined in the research plan of project CN-1514, pure R123 pool boiling data was taken on the same Turbo-BIII (tm)-LP surface that was used with R245fa and the mixture. The ratio of the pure R245fa heat flux to the pure R123 heat flux was independent of the fraction of the surface that was actively boiling. This is consistent with the hypothesis that isopentane acts to enhance the site density. That is, the addition of 0.5% isopentane limits the heat transfer degradation that results from the loss of active sites by increasing the number of active sites in the actively boiling regions. From 8 kW/m2 to 100 kW/m2 and for fixed superheat, the R245fa heat flux was 27% greater than that for R123. Considering only the boiling heat transfer characteristics of R245fa, it appears to be a good replacement for R123.