Thermal conductivity of pure water and aqueous SrBr2 solutions at high temperatures and high pressures

Abstract

Accurate thermal conductivity measurements were made on pure water and H 2 O + SrBr 2 solutions at pressures up to 100 MPa over the temperature range 293-473 K with a parallel-plate apparatus. The concentrations studied were between 2.5 and 20 mass%. The estimated accuracy of the method is about 1.6%. The pressure, temperature, and concentration dependences of the thermal conductivity have been studied. The thermal conductivity shows an almost linear dependence on pressure and concentration. Along each isobar, at a given concentration, the λ s o l -T curves show a thermal conductivity maximum at temperatures between 405 K and 420 K depending on pressure and concentration. The measured values of thermal conductivity at atmospheric pressure were compared with values reported by other authors and values calculated with the use of various correlation equations and prediction techniques. The experimental and calculated values from IAPWS formulation of thermal conductivity for pure water show excellent agreement within their experimental uncertainties (AAD = 0.38%). The experimental results have been correlated in terms of the polynomials of x, T, P for practical use. The concentration dependence of the relative thermal conductivity λ s o l /λ H 2 O was studied. The values of apparent and partial molar thermal conductivity were derived from the measured values of thermal conductivity for solutions λ s o l and pure water λ H 2 O . Derived apparent molar thermal conductivities were extrapolated to zero concentration (x → 0) to yield partial molar thermal conductivity values Φ ∞ λ of electrolyte (SrBr 2 ) at infinite dilution.