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| 3. |
- Berntsson, Thore, 1947, et al.
(författare)
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Some aspects of using mixtures
- 1994
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Ingår i: Presented at IEA HP Centre Workshop, Consequences of (H) CFC Replacement in HVAC Applications, Gothenburg, September 7-8, 1994. - 1103-2952.
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Konferensbidrag (refereegranskat)
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| 4. |
- Fransson, Eva, 1967, et al.
(författare)
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The Abdoul-Rauzy-Peneloux Group Contribution Equation of State Extended to CFC-Containing Mixtures
- 1993
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Ingår i: Chemical Engineering Science. ; 48:10, s. 1753-1759
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Tidskriftsartikel (refereegranskat)abstract
- This study contributes to the development of new thermodynamic models, useful for the prediction of refrigerant-mixture properties. Mixtures are considered to be potential substitutes for the environmentally harmful chlorofluorocarbons. Here the Abdoul—Rauzy—Pénéloux (ARP) equation of state (EOs) is used, which combines a group contribution excess Helmholz energy model with traditional cubic EOSs. This EOS, initially developed for different petroleum mixtures, has been extended to cover also certain compounds containing chlorine and fluorine. A predictive method for PVT modelling of mixtures containing CFCs, HCFCs, HFCs, FCs and hydrocarbons has thus been developed. From experimental data for 31 different binary systems, 19 general group parameters were estimated. the error on the calculated vapor pressure for these systems does not exceed 5.1% for any of the considered mixtures. This demonstrates the effectiveness of the method since the traditional mixing rules would have demanded 31 specific interaction parameters to describe the same number of systems, without the possibility of extending their validity to other mixtures. In order to verify the predicting capacity of the method, it has also been applied to a ternary and an azeotropic system, that have not been included in the estimation procedure of the parameters. The results from these applications are deviations on the calculated pressure of 0.7 and 26% for the ternary and the azeotropic system, respectively.
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| 5. |
- Gabrielii, Cecilia, 1969, et al.
(författare)
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Changes in optimal design of a dry-expansion evaporation when replacing r22 with r407c
- 1998
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Ingår i: International journal of Refrigeration. - 1103-2952. ; 21:7, s. 518-534
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Tidskriftsartikel (refereegranskat)abstract
- An investigation was made on whether the optimal distribution of heat exchanger area between the evaporator and the suction gas heat exchanger, at a given cost, will change when R22 is replaced with the non-azeotropic mixture R407C. A comprehensive computer program was used to simulate a refrigeration plant, originally designed for R22, where the tube-and-shell evaporator is of dry-expansion type. The simulations show that for R22, the area distribution in the original design is optimal for every set of conditions simulated. For R407C it is, in most of the cases simulated, favourable to move some heat exchanger area from the evaporator to the suction gas heat exchanger. The improvement in COP can be up to 3.4%. Further, it was observed that the optimal area distribution for R407C corresponds to the maximum use of the glide in the evaporator, and for R22 to the minimum pressure drop in the evaporator. The superheat at the evaporator exit is an important parameter, especially for the non-azeotropic mixture.
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| 6. |
- Gabrielii, Cecilia, 1969, et al.
(författare)
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Changes in optimal distribution of heat exchanger area between the evaporator and suction gas heat exchanger when replacing r22 with r407c
- 1998
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Ingår i: International Journal of Refrigeration. - 1103-2952. ; 21:6, s. 440-451
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Tidskriftsartikel (refereegranskat)abstract
- An investigation was made on whether the optimal distribution of heat exchanger area between the evaporator and the suction gas heat exchanger, at a given cost, will change when R22 is replaced with the non-azeotropic mixture R407C. A comprehensive computer program was used to simulate a refrigeration plant, originally designed for R22, where the tube-andshell evaporator is of dry-expansion type. The simulations show that for R22, the area distribution in the original design is optimal for every set of conditions simulated. For R407C it is, in most of the cases simulated, favourable to move some heat exchanger area from the evaporator to the suction gas heat exchanger. The improvement in COP can be up to 3.4%. Further, it was observed that the optimal area distribution for R407C corresponds to the maximum use of the glide in the evaporator, and for R22 to the minimum pressure drop in the evaporator. The superheat at the evaporator exit is an important parameter, especially for the non-azeotropic mixture. q1998 Elsevier Science Ltd and IIR. All rights reserved.
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| 9. |
- Gabrielii, Cecilia, 1969, et al.
(författare)
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Mixtures To Replace R22 in High-Temperature Heat Pumps
- 1999
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Ingår i: presented at the 20th International Congress of Refrigeration “Refrigeration into the Third Millennium” Sydney, Australia, 19-24 September 1999 (REF).. - 1103-2952.
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Konferensbidrag (refereegranskat)
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| 10. |
- Gabrielii, Cecilia, 1969, et al.
(författare)
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Replacement of R22 in tube-and-shell condensers: experiments and simulations
- 1997
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Ingår i: International Journal of Refrigeration, 1997. ; 20:3, s. 165-178
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the change in condenser overall heat transfer coefficient when replacing R22 with one of the three mixtures R407C, R404A and R410B was made, both experimentally and theoretically. Measurements have been carried out on a full-scale test plant consisting of a horizontal shell-side condenser. According to the measurements the decrease in overall heat transfer coefficient for the non-azeotropic mixture R407C was very large, up to 70% compared to R22, while for the near-azeotropic mixture R404A the decrease was less than 15%. Simulations of the condenser were done with a comprehensive computer program, calculating the condensation heat transfer with an approximate method including a correction for mass resistance. The calculation model was not able to predict this large degradation for the non-azeotropic mixture, while the predictions agreed rather well with the measurements for the pure fluid and the near-azeotropic mixtures.
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