Measurement of the thermal conductivities of 2-amino-2-methyl-1,3-propanediol (AMP), 2-amino-2-hydroxymethyl-1,3-propanediol (TRIS) and the mixture (AMP+TRIS, mole ratio 50:50) in the temperature range from 20°C to their supermelting temperatures
Introduction
Some substances such as 2-amino-2-methyl-1,2-propanediol (AMP), 2-amino-2-hydroxymethyl-1,3-propanediol (TRIS), neopentylglycol (NPG), pentaerythritol (PE) and trihydroxymethylethane (PG) are being considered as potential candidates for the thermal storage of energy. Owing to the considerable enthalpy of a solid–solid transition in the temperature range from 20 to 200°C, these substances are attractive to both chemists and engineers. Murrill and Breed (1970) reported on the transition parameters in the compounds CR1R2R3R4, where Rs were methyl, methylol, amino and carboxy, by differential scanning calorimetry. Zhang et al., 1988, Zhang and Yang, 1989, Zhang and Yang, 1990a, Zhang and Yang, 1990b measured the heat capacities and transition parameters for a series of polyalcohols having solid–solid transition, by an adiabatic calorimeter. For example, the solid–solid transitions were found for AMP at 80.1°C and for TRIS at 134.3°C. The enthalpies of solid–solid transition were determined to be 23.46 kJ mol−1 for AMP and 33.42 kJ mol−1 for TRIS. However, the thermal conductivities of the potential materials for the thermal storage of energy do not appear to be in the literature. Therefore, as a part of the series of measurements of thermal conductivity, this paper will report the thermal conductivities on AMP, TRIS and the mixture (AMP+TRIS) in the temperature range from 20°C to the supermelting temperatures of the substances.
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Apparatus and procedure
The principle and the construction of the apparatus used in the study were described by Wang and Yang (1995). In order to satisfy the special conditions of the study, some improvements were made on the apparatus. Basically, it is composed of a thermal conductivity cell, an electrical bridge circuit and a thermostated oil bath. The thermal conductivity cell is made of 1-mm-thick silica tube and is 40 mm long and 15 mm in inner diameter. Due to a wide temperature range needed in the study, two
DISCUSSION
The experimental method applied in this study is a relative method. Basically, the uncertainty of the thermal conductivities measured in the study depends on the accidental change in the experimental conditions and the uncertainty of thermal conductivities of the reference substances used in the calibration of the apparatus. The former will result in the accidental uncertainty of the measurement and the latter will bring systematic uncertainty to the experimental results. The relative standard
Acknowledgements
This research was supported by the Shann’ Xi Education Commission Foundation under contract 98 JZK-10.
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