Densities and Heat Capacities of the Ammonia + Water + NaOH and Ammonia + Water + KOH Solutions

Abstract

Ammonia + water + sodium hydroxide and ammonia + water + potassium hydroxide mixtures were chosen as potential candidates for absorption chillers driven by low-temperature heat sources. Heat capacity and density were studied between (293.15 and 353.15) K at a constant pressure of 1.8 MPa for these solutions using a heat flux Calvet-type calorimeter and a vibrating-tube densimeter, respectively. Measured data were well-correlated with temperature and composition using simple polynomial equations. The relative deviations between the experimental and calculated values in the density and heat capacity measurements were 0.20 % and 0.49 % for NH3 + H2O + NaOH solutions and 0.10 % and 0.36 % for NH3 + H2O + KOH solutions, respectively. Also, two density prediction methods were checked using the experimental data. Previously, it was necessary to measure the density of ammonia and hydroxide aqueous solutions in similar conditions. The results showed that both methods are suitable for predicting the density of these solutions.

Molar Volumes and Heat Capacities of Aqueous Solutions of Potassium Hydroxide and for Water Ionization up to 573 K at 10 MPa

“…The high temperature data of both Mashovets et al and Corti et al, obtained at close-to-saturation pressure, are reasonably consistent with the present values. At low temperatures (≤373 K) all of the available data are broadly consistent with the exception of the results reported by Salavera et al…”

“…The high temperature data of both Mashovets et al 39 and Corti et al, 42 obtained at close-to-saturation pressure, are reasonably consistent with the present values. At low temperatures (≤373 K) all of the available data are broadly consistent with the exception of the results reported by Salavera et al 44 For heat capacities, there are few data available in the literature, mainly at low temperatures and only at atmospheric pressure (Table 1). Despite the significant pressure difference the present C pϕ values (at p = 10 MPa) of KOH(aq) at low temperatures (≤373 K) fit seamlessly with the data of Roux et al, 45 measured using a Picker flow calorimeter at p = 0.1 MPa and 278.15 ≤ T/K ≤ 328.15.…”

“…Deviations (Δ V ϕ = V ϕ exp – V ϕ fit ) of present and literature apparent molar volumes, V ϕ , of KOH­(aq) from the overall fit of all data using eq : ●, this work; violet + , Akerlof and Bender; ▽, Mashovets et al; blue ▼, Tham et al; red × , Herrington et al; □, Corti et al; green ▲, Sipos et al; ⧫, Salavera et al; ○, Roux et al; ◇, Patterson et al Deviations as a function of as a function of (lower box) temperature, T , and (upper box) molality, m .…”

“…With regard to V ϕ (Figure 7), the most striking feature of the data is the almost constant differences between KOH(aq) Akerlof and Bender 37 0.01 0.06 Mashovets et al 39 0.11 0.36 Tham et al 40 −0.50 0.50 Roux et al 45 0.12 0.17 Herrington et al 41 −0.10 0.12 Corti et al 42 0.24 0.58 Sipos et al 43 −0.01 0.07 Patterson et al 46 −0.17 0.39 Salavera et al 44 2.24 2.24 this work 0.00 0.02 48 1.0 2.0 Roux et al 45 0.0 2.3 Patterson et al 46 −0.1 1.5 this work 0.0 1.4 (represented by the zero line in the plot) and NaOH(aq) and CsOH(aq), at least up to 525 K and irrespective of concentration. These differences essentially reflect the differences in the hard-sphere volumes of the cations (r(Cs + ) > r(K + ) > r(Na + )).…”

Simulation research on absorption refrigeration system based on NH3-H2O-LiBr vapor-liquid equilibrium calculation model

“…There are many options for adding a third component to the ammonia+water system. The hydroxile in the solution will make the ammonia ionization equilibrium move towards the direction of ion reduction [8] , thus adding alkali into the ammonia+water system can significantly reduce the concentration of ammonia in the liquid phase at the vapor-liquid equilibrium [9][10][11][12] . Besides adding alkali, there are lots of researches of adding soluble salt in ammonia+water solution.…”