Parsimonious constitutive expressions with good accuracy and suitable for modelling the properties of aqueous sodium chloride in solar ponds

• Published in: Solar energy 2015-12, Vol.122, p.617-629
• Main Authors: Abdullah, A.A., Lindsay, K.A., AbdelGawad, A.F.
• Format: Article
• Language: English
• Subjects: Aqueous sodium chloride; Aqueous solutions; Atmospheric pressure; Constitutive expression; Heat conductivity; Salinity; Salt-gradient; Solar pond; Thermodynamics; Viscosity
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2015.09.015

•Parsimonious constitutive equations with good accuracy are constructed for aqueous NaCl.•Data sources on the properties of aqueous NaCl are cleaned and collected in one place.•Constitutive equations focus on regions of state space relevant to solar ponds.•Salinity is expressed as a particle density unlike molality or weight fraction.•Most constitutive expressions in the literature are unsuitable for modelling. Parsimonious constitutive expressions with good accuracy are developed for the fundamental thermodynamic and mechanical properties of aqueous sodium chloride in the ranges of temperatures and salinities arising in the operation of a salt-gradient solar pond. Specifically expressions for density, thermal conductivity and diffusivity, solubility, boiling point, specific heat and enthalpy at atmospheric pressure, dynamic viscosity and vapor pressure are expressed as functions of Celsius temperature and salinity (particle concentration) in kg/m3 by contrast with the commonly used measures of molality or weight fraction. The constitutive expressions are constructed from data drawn from specialist articles spread around the literature and are parsimonious in the respect that at most floor(log(N)) adjustable parameters are allowed in each expression, where N is the number of data used in the estimation. A number of competing expressions are considered for each property with the expression of choice being that which minimizes mean relative error.