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| 2. |
- 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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| 3. |
- Högberg, Marine, 1962, et al.
(författare)
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Calculation methods for comparing the performance of pure and mixed working fluids in heat pump applications
- 1993
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Ingår i: International Journal of Refrigeration. ; 16:6, s. 403-413
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Tidskriftsartikel (refereegranskat)abstract
- Three methods for comparing cycle performance of working fluids, pure as well as non-azeotropic mixtures, are investigated for two applications and for two mixture pairs, HCFC22-CFC114 and HCFC22-HCFC142b, and their pure components. The methods differ in the way of calculating the heat exchange processes. They assume, respectively, equal minimum approach temperatures, equal mean temperature differences and equal heat transfer areas. Changes of coefficient of performance (COP) with composition are explained for all methods. It is shown that transport properties must be taken into account when making rigorous comparisons between working fluids. To predict the relations between fluids with high accuracy, one must use the method with equal heat transfer areas. By the method with equal mean temperature differences, the COP can be estimated with the same accuracy for mixtures as for pure fluids, and can be used for rough estimations of the COP level with different fluids. The method of equal minimum approach temperatures should be avoided for non-azeotropic mixtures.
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| 4. |
- Linden, M. Mc., et al.
(författare)
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The need for, and availability of, working fluid property data: Results from Annexes XIII and XVIII
- 1993
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Ingår i: Presented at The 4th International Energy Agency Heat Pupm Coference Maastrict, The Netherlands, April 26-29.1993.
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Konferensbidrag (refereegranskat)abstract
- In these days of transition to new, more environmentally friendly working fluids, there is a definite need for good data and models of basic thermodynamic and transport properties of both pure compounds and mixtures to be used for cycle calculations and equipment redesign.Two annexes of the IEA Program on Advanced Heat Pumps have dealt with such data, namely Annex XIII-State and Transport Properties of High Temperature Working Fluids andNonazeotropic Mixtures and Annex XVIII-Thermophysical Properties of the Environmentally Acceptable Refrigerants. In this paper, highlights of these two annexes are presented.A sensitivity analysis (from Annex XIII) gives an estimate of how accurately these basic data need to be known to reach a certain accuracy in heat pump coefficient of performance (COP) and heating or cooling capacity calculations. This analysis points out the importance of measured property data. Other projects to be highlighted are a comparison of equations of state with experimental density, vapor pressure, and heat capacity data for mixtures (XIII), a survey of current research on the properties of the "new" refrigerants (XVIII), and an evaluation of equations of state for R134a and R123 which will lead to an international bulletin for the properties of these two alternative refrigerants (XVIII).
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| 6. |
- Vamling, Lennart, 1954
(författare)
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Factors of importance in cycle performance estimations
- 1993
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Ingår i: Presented at the International Seminar on Heat Transfer, Thermophysical Properties and Cycle Performance of Alternative Refrigerants Kitakyushy, Japan, December 6-8, 1993.
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Konferensbidrag (refereegranskat)
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