Modeled performance of non-chlorinated substitutes for CFC-11 and CFC-12 in centrifugal chillers
- Oak Ridge National Lab., TN (United States)
- Electric Power Research Inst., Palo Alto, CA (United States)
Current scientific evidence indicates that stratospheric chlorine concentrations below two parts-per-billion will be necessary to reverse and prevent ``ozone hole`` formations over the Earth`s polar regions each spring. This makes it unlikely that HCFC alternatives with non-zero ozone depletion potentials (ODPs), no matter how small, will be accepted as refrigerants or blowing agents for foamed insulations for the long term. Pressure to eventually eliminate all high volume uses of chlorine containing refrigerants provides a strong incentive to find HFC or alternative, chlorine-free compounds with P-V-T characteristics similar to R-11 and R-123 for new and existing large centrifugal chiller applications. Stable chlorine-free compounds with normal boiling points near CFC-11 and HCFC-123 are found in the fluorinated propane or butane or fluorinated ether families. These larger molecules have larger vapor phase heat capacities (Cp), molecular weights, and lower critical temperatures which thermodynamically decrease their volumetric capacity and coefficient of performance in simple cycle applications. Larger molar latent heats of vaporization caused by hydrogen bonding in the ethers may improve their net refrigerating effect over CFC-11 and HCFC-123, however. Consideration was given to the effects of acoustic velocity in the refrigerant, rotational mach numbers, the application of superheat to avoid ``wet isentropic compression,`` and liquid subcooling before isenthalpic expansion. The results indicate that there are several chlorine-free compounds that give modeled chiller performance comparable to CFC-11 and HCF-123 and better that CFC-12 and HFC-134a. Blends of these refrigerants may be required to mitigate the flammability of some of the alternatives which show the best performance, and modifications to the current chiller cycle such as liquid subcooling and suction gas superhead may offer unique advantages for more complicated, larger refrigerant molecules.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Electric Power Research Inst., Palo Alto, CA (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 10105739
- Report Number(s):
- CONF-911256-3; ON: DE92004350
- Resource Relation:
- Conference: International chlorofluorocarbon (CFC) and halon alternatives conference,Baltimore, MD (United States),3-5 Dec 1991; Other Information: PBD: [1991]
- Country of Publication:
- United States
- Language:
- English
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