Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.3/2259
Título: Thermophysical Properties of Alternative Refrigerants.
Autor: Gurova, A. N.
Barão, M. T.
Sousa, Ana T.
Nieto de Castro, Carlos A.
Mardolcar, Umesh V.
Fialho, Paulo
Palavras-chave: Thermal Conductivity
Data: 1994
Editora: SG Editorali
Citação: Gurova, A.N.; Barão, M. T; Sousa, Ana T; Nieto de C. C. A; Mardolcar, Umesh V; Fialho, Paulo. (1994). "Thermophysical Properties of Alternative Refrigerants", In «CFC'S, the day after. Joint Meeting of IIR commissions B1, B2, E1 and E2 (Padova, 21-23 September 1994)»: 393-401. ISBN: 8886281099.
Resumo: The need for new environrnentally acceptable refrigerants, with low or zero ozone depletion potential and low global warming potential, led the industrial and the scientific community to launch a significant research effort on the thermophysical properties of these compounds. It is the purpose of this paper to give an overall view of the current research in this field, started in 1990 by our group, in collaboration with the LIMHPCNRS, Villetaneuse, France, and the NIST, Boulder, USA. The effort has been concentrated in developing equipments to measure density dielectric constant and thermal conductivity in the liquid phase, covering the temperature and pressure ranges necessary for the normal duty of these fluids. The dielectric constant and the thermal conductivity of three provisional replacements, HCFC 123, HCFC 141b, HCFC 142b and two c1ass A fluids, HFC 134a and HFC 152a, have been measured in the temperature range 200 to 300 K and pressures up to 20 MPa, using a direct capacitance method, by measuring the capacitance of a cylinder filled with the sample and in vacuum, using an impedance analyzer, and the polarized hot wire technique. The density of HCFC 142b, HCFC 22 + HCFC 142b and HCFC 14lb was measured with a vibrating fork densimeter, calibrated with toluene, 2,2,4-trimethylpentane and vacuum. The instruments are capable of obtaining the dielectric constant with an absolute uncertainty of 0.1 %, the thermal conductivity with 0.5 % and the density with 0.1 %. An Hard Sphere De Santis equation of state has been used to develop an universal estimation scheme for the density of pure refrigerants and of their mixtures, based only upon the properties of pure fluids, capable of calculating the density of the liquid phase with an uncertainty better than 1.5 % for T/Tc < 0.9. The density dependence of the dielectric constant has been studied using the concept of Eulerian strain and the Onsager-Kirkwood theories. The dipole moments of the several refrigerants in the liquid phase were obtained.
Descrição: Proceedings of International Conference of CFC'S, the Day After. Padua, Italy, 21-23 September 1994.
Peer review: yes
URI: http://hdl.handle.net/10400.3/2259
ISBN: 8886281099
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