Some
processes such as air conditioning absorption systems have
been developed as a feasible and economical alternative to help reduce
the consumption of fossil fuels and prevent the impact of gas emission
produced by electrical air conditioning. However, a main disadvantage
of these systems is the absorbent’s crystallization phenomenon
in the working mixture, which occurs when the absorbent concentration
is higher than the saturation point. Among the aqueous working mixtures,
NaOH solution shows several advantages for absorption system applications.
The aim of this paper is to propose new mathematical correlations
to predict or estimate the NaOH concentrations and refractive index
in aqueous solutions (H2O–NaOH) for an air conditioning
absorption system application. The experimental measurements of NaOH
concentration and refractive index were made in situ from aqueous
solutions with concentrations from 20 to 50% (weight/weight %, with
increases of 5%) and temperatures between 10 and 60 °C (with
increments of 1 °C). Two correlations for predicting the concentration
of NaOH and refractive index based on cubic regression models with R
2 of 0.99704 and 0.99918, respectively, are
presented for the first time. The normalized error for NaOH estimation
using experimental data lies between −0.026 and 0.040, and
for refractive index, the estimation lies between −0.002 and
0.001. Both correlations present a good fit to predict the NaOH concentration
between 25 and 45% of concentration ratio.