Specific Heat Measurements on Aqueous Lithium Bromide

Abstract

In the design and application of lithium bromide (LiBr) based absorption machines, McNeely's correlation for enthalpy is widely used. This correlation is derived from vapor pressure and specific heat data. The McNeely correlation applies in the range of mass fraction of aqueous LiBr from 45% to 75% and temperature from 5°C to 175°C. Therefore, high-temperature applications require a new correlation. In addition, after a literature survey on aqueous LiBr specific heat data, it was found that the data are limited and inconsistent. The need for consistent data, including high-temperature data, motivated us to measure specific heat in the full range of mass fraction of liquid aqueous LiBr and the temperature range from 5°C to 260°C. The new data were then used to create an updated correlation as discussed in a companion paper. The measurements of specific heat discussed here were performed using a Setaram C80 calorimeter. The accuracy of the measurement method is estimated to be better than ±2% based on comparisons with high-accuracy data for pure water and estimates of uncertainty in the other variables. Comparison of our specific heat data with other data sources indicates that reasonable agreement is obtained over the central range of the independent variables with larger deviations near the extremes of temperature and mass fraction. A main contribution of this study is the extended temperature and mass fraction range of this new specific heat data set.