A novel boil-off calorimeter with measurements on water, toluene and methylcyclohexane

Abstract

A novel fluid boil-off calorimeter, the first of this type to use electrical techniques, was developed. This calorimeter was calibrated with water from 17 psia to 2325 psia pressure and 142(DEGREES)F to 511(DEGREES) in temperature. The estimated maximum total uncertainty in the enthalpy measurement is (+OR-) 0.7% at 1112(DEGREES)F and (+OR-) 0.35% at 212(DEGREES)F. A comparison of the experimental results with the literature showed a maximum absolute difference of 4.5 BTU/lb (3.9%), with an average difference or 1.5 BTU/lb (0.82%) for the liquid and maximum absolute difference of 11.3 BTU (0.96%) with an average difference of 5.7 BTU/lb (0.47%) for the vapor. Enthalpy data were obtained experimentally for toluene and methylcyclohexane. Toluene was investigated in the region 17-1365 psia and 152-433(DEGREES)F. Methylcyclohexane data were obtained from 17 to 1365 psia and from 172(DEGREES) to 442(DEGREES)F. Pressure-enthalpy, specific heat-temperature, enthalpy-temperature and temperature-entropy diagrams were prepared for each compound and included both vapor and liquid phase regions. Some of the advantages of the calorimeter are: avoidance of actual measurement of flow rate of Freon-11 and the unnecessity for an accurate, independent value of heat of vaporization and density of Freon-11 at 25(DEGREES)C (77(DEGREES)F). Finally, when the system was at steady state, no sampling of Freon-11 was required and with all digital read-outs, data could be secured in a minimum time.