Thermophysical Properties of 1,1,1,3,3,3-hexafluoro-2-methoxypropane (HFE-356mmz) in the Vapor Phase Measured by Using an Acoustic-Microwave Resonance Technique

Yuya Kano

doi:10.3390/en13205525

Abstract

Thermophysical properties of HFE-356mmz in the vapor phase were measured by means of an acoustic-microwave resonance method. HFE-356mmz, which is 1,1,1,3,3,3-hexafluoro-2-methoxypropane in chemical name, is expected to be used as a working fluid with low global warming potential for the Organic Rankine cycle (ORC). The sound velocity and dielectric permittivity were simultaneously measured by using a cylindrical acoustic-microwave resonator. The sound velocity data were analyzed to obtain the ideal-gas heat capacity at constant pressure. The integral of the ideal-gas heat capacity as a function of temperature derives the ideal-gas enthalpy, which is a fundamental and important energy property to simulate the thermodynamic cycle. Similarly, the analysis of the dielectric permittivity data leads to information on the ideal-gas molar polarizability, dipole moment, and density. The acquired thermophysical properties of HFE-356mmz were compared to those of R-245fa and n-pentane, which are the existing working fluids for the ORC system, to prospect a feasibility of HFE-356mmz as their alternative.

Highlights

The Organic Rankin cycle (ORC) is one of the important thermal energy systems to efficiently utilize a waste heat below 100◦ C
The sound velocity and the dielectric permittivity were simultaneously one of the characteristics to be associated with the solubility to the other molecule, so that the lubricant measured by using acoustic-microwave method
Compared with the thermophysical properties of R-245fa and n-pentane, which are the Several thermophysical properties of HFE-356mmz in the vapor phase were experimentally existing working fluids for the ORC system, HFE-356mmz has a lower value for the sound velocity determined in this study

Summary

Introduction

The Organic Rankin cycle (ORC) is one of the important thermal energy systems to efficiently utilize a waste heat below 100◦ C. R-245fa, has been used as a working fluid for the ORC. 1,1,1,3,3,3-hexafluoro-2-methoxypropane, which is known as HFE-356mmz, has been proposed as an alternative working fluid for the ORC system [3]. HFE-356mmz has a flammability limit around 8.46 vol% [4] that is regarded as mildly flammable; it has a low GWP of 14 [1] and is not toxic. Thermophysical properties of a working fluid to be used in the ORC represent an indispensable information for the evaluation of the performance of the thermodynamic cycle. Some researchers previously reported experimental data of some thermophysical properties of HFE-356mmz; for example, Sako et al [5] measured the critical properties and the normal boiling point, Alam et al [6] measured the thermal conductivity and the kinematic viscosity, and Chen et al [7]

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Conclusion