Thermophysical properties of the equimolar mixture sodium nitrate-potassium nitrate from 300 to 600.degree.C

Abstract

260 33-7= 75 I I Literature Cited A DlBENZOTHIWWNE = 70 , I I I 0 FLUORENE 0 MENZOFURAN Q 60 (1) Amerlcan Petroleum Institute. "Selected Values of Properuee of Hydrocarbons and Related Compounds"; Chem. Thermodynamk Rop. Center, API Research Project 44, Texas A 6. M Unhrerdty: Colkge Station, TX, 1971. (2) Rleveechl, (3.; Ray, F. E. (10) k i m e r , S. F.; Murphy, R. V. The thermophydcal properties (viscosity, surface tension, a d dendty) of the equimolar mixture NaNo,-KNO, have been determined over the temperature range 300-600 OC in argon and in oxygen. The surface tendon is a linear function of the temperature and can be represented by the expression y(dyn/cm) = 133.12 -(6.25 X 10-2)T(oC). The viscosity may be calculated from the equatlon q(cP) = 22.714 -0.120T + (2.281 X 10-')T2 -(1.474 X 10-')Ta, for T in OC. The dendty of the equimolar mixture k given by p(g/cma) = 2.090 -(6.36 X 104)T('C). I n contrast to the surface tendon and the viscosity, the density k affected by the presence of nitrite, the thermal decomposition product of the nitrate anion.The equimolar moiten salt mixture NaN03-KN03 is being proposed as a heat-transfer fluld and a thermal-energy storage medium for various solar energy applications. I n these applications the maximum operating temperature will be in the range 500-600 OC. Industrial experience and previous experimental investlgations on this moiten salt mixture have generally been confined to temperatures below 450 OC. I n order to provkle data to solve various specific design problems associated with the use of these molten nitrate saits as heattransfer fluids, it is important that we know how the physical properties of these saits are affected by temperature and composition of the liquid and gas phases. I t is the purpose of this report to present and comment on the viscosity, surface tension, and density data which we have measured for equimolar NaN0,-KNO, over the temperature range 300-600 OC. Apparatus and Expertmental TechniqueThe thermophysical-property data for the equimolar NaN-O3-KNO3 mixture were taken by an instrument designed and bullt by the author at SNLL. This instrument is based on the principle of a damped, onedimenslonal, harmonic oscillator, i.e., the motion of a body suspended from a spring and Oscillating in a fluid. A description of the theoretical principles which govern the operating of this instrument, the details of construction, and its operation and response are discussed elsewhere ( 7 , 2). Only an abbreviated description of the various modes of operating of this instrument will be given here.The heart of the apparatus is a quartz spring oscillator, an electromagnet for remotely starting the spring oscillating, a position transducer for remote readout of the spring extension (ilnear variable differential transformer (LVDT)), and a gold plate suspended in a liquid whose vlscosity is being measured (see Figure 1). It is the viscous drag exerted on this plate by the liquid which causes damping of the oscillatory motion of the quartz spring.The rate of dampi...

Viscosity of Molten Sodium Nitrate

“…although the residual presence of the nitrite ion does not seriously affect the measured viscosity as previously reported by Nissen et al [14], at least at lower temperatures. …”

Latent heat augmentation of thermocline energy storage for concentrating solar power – A system-level assessment

“…For the current study, molten salt is represented with a commercial eutectic mixture known as Solar Salt (60 wt.% NaNO 3 , 40 wt.% KNO 3 ) which operates between 300 °C and 600 °C. Physical properties of the salt are known functions of temperature [13,14]. The specific heat is relatively constant across the stated temperature span and is approximated with an average value of 1520 J/kg-K.…”

Rheological Analysis of Binary Eutectic Mixture of Sodium and Potassium Nitrate and the Effect of Low Concentration CuO Nanoparticle Addition to Its Viscosity

“…Whilst the publication displayed large amounts of accumulated data for various salts, it did not provide a description of the setup used and the uncertainty in the measurements gathered was given to plus or minus ten percent. This was not the case with Nissen which provided a detailed description of the apparatus used to determine viscosity via the principle of dampening through the use of one-dimensional harmonic oscillator [2]. However much like Janz et al ., the effect of shear on the liquid was not investigated.…”