DENSITY OF LIQUID REFRIGERANTS By T SHYAMKUMAR 14TH14F I sem, M Tech Thermal Engineering

CONTENTS Introduction Methods of measuring density Literature Review ISH correlation Rackett equation Rackett equation by Yamada and Gunn Spencer and Danner modification of Rackett method(RSD) Hankinson and Thomson (HT) method(COSTALD) Reidel method NM Correlation Programming Results Conclusion

INTRODUCTION Designing refrigeration cycles require thermodynamic properties of refrigerants, i.e., liquid density, vapour density, enthalpy of vaporization and vapour pressure Liquid density is needed for process simulation and equipment design. Equations of state (EoS) are used in commercial simulation software for predicting phase behavior and thermodynamic properties.But, equations of state are not accurate enough for a wide range of applications. The popular EoSs such as SRK and PR predict liquid density with an average absolute error of about 8%, much higher than the correlations. correlations have wider range of applicability and accuracy.

TWO SINKER DENSIMETER Based on the Archimedes' buoyancy principle. Both sinkers have the same mass, the same surface area, and the same surface material, but a considerable difference in volume.

Continue... This sinker support is connected to a commercial analytical balance ( resolution 10 μg) by a thin wire via a magnetic suspension coupling. “apparent mass difference” Δm* = (m D * − m S *) of the sinkers. By means of the magnetic suspension coupling, the suspension force is contactlessly transmitted from the pressurized measuring cell to the balance at ambient conditions. ρ = (Δm* − Δm Vac ) / (V S − V D ), where Δm Vac = ( m D − m S ) corresponds to the very small mass difference of the two sinkers which is accurately determined by weighing in the evacuated measuring cell.

CORIOLIS FLOW METER Based on coriolis principle. An exciter causes tube to oscillate constantly Sensors are located at inlet & outlet Phase shift during flow is a measure of mass flow rate. Oscillating frequency is a direct measure of density..

LITERATURE REVIEW (a) ISH correlation (Iglesias et al [1]) n=0.5 and β is the scaling exponent having a value between 0.32 and 0.34 = (2.1) = 0.03 – (2.1.a) = (1 -) – 1 - (2.1.b) =

Rackett equation Rackett(1970),[2] proposed the following correlation......(Eq 2.2) is critical compressibility factor. =

Modified Rackett equation by Yamada and Gunn Yamada and Gunn (1973), [2] proposed.....(Eq 2.3) Acentric factor W represents accentricity or nonsphericity of a molecule.For monoatomic gases w =0. For higher hydrocarbon w increases. = ] - 1

Spencer and Danner modification of Rackett method By Kh.Nasrifar et al[3] Popularly known as RSD equation.....(Eq 2.4) Z RA = w = ( )

Hankinson and Thomson (HT) method By Hankinson et al[4] (Eq 2.5) a = ; b = ; c = ; d = ; e = ; f = ; g = ; h = ; is the characteristic volume ( ) = [1-] = 1+a +b+c +d =

Reidel method Reidel [3] suggested the following correlation......(Eq 2.6) is the slope of vapour pressure at critical temperature = = (1- + ( ) = (1- + ( )

NM Correlation KhashayarNasrifar and Mahmood Moshfeghian proposed the following correlation [5] d 1 = d 2 = d 3 = d 4 = δ is the characteristic parameter for each compound. c 1, c 2 and c 3 are vapour pressure dependent parameters = [1+ ] = =<1 = >1

CorrelationSuitable refrigerantsComments ISH R22, R123, R134a, R152a, R290, R600, R600a, R717, R718, R12 Rackett R22, R32, R123, R125, R134a, R152a, R290, R600, R600a, R717, R718, R1270 R143a, R12 For all compounds with Zc > 0.22 Yamada & Gunn R22,R32,R123,R125,R134a,R152a, R290,R600,R600a,R717,R718,R1270 R143a,R12 Spencer& DannerR22,R290,R600,R600a,R717,R718,R1270 Hankinson & Thomson R22, R290, R600, R600a, R717, R718, R1270 Applicable when 0.25 < Tr < 0.98 Reidel R22,R32,R123,R125,R134a,R152a, R290,R600,R600a,R717,R718,R1270 R143a,R12 NM R22,R32,R123,R125,R134a,R152a, R290,R600,R600a,R717,R718,R1270 R143a,R12

PROGRAMMING Coding language:MATLAB The program reads input data from excel sheet, calculates saturated liquid densities and percentage deviation from ASHRAE values for temperature ranges specified in ASHRAE data hand book and writes it back to another excel sheet.Average absolute percentage deviation is also calculated. Two plots for each refrigerant:  Density vs temperature  %error vs temperature

ERROR ESTIMATION Percentage deviation from ASHRAE values, δ =(ρ s –ρ exp )* (Eq 7) Average absolute percentage deviation = 1 /N*Σ|δ|..(Eq8) Where N is the number of data points.

RESULTS calculated densities calculated densities

Refrigerant ISHRackett Yamada & Gunn RSDHTReidelNM Best correlation R NM R NM R Yamada & Gunn R Reidel R134a NM R152a NM R HT R NM R600a HT R ISH R RSD R HT R143a Reidel R NM Average absolute percentage deviations

CONCLUSIONS NM correlation has been found the best the for prediction of saturated liquid densities for R22, R32, R134a, R152a, R600 and R12 with a maximum AAPD of % for R12 Equation predicted by Hankinson and Thomson.et al is best suited for R290, R600a and R1270 Reidel’s correlation can be applied to R143a and R125 Modified Rackett equation by Yamada and Gunn and Spencer and Danner gives fairly accurate results for R123 and R718 respectively. ISH correlation is best suited for R717 with AAPD of 0.555%.

REFERENCES [1] Gustavo A Iglesias-Silva,Kennath.R.Hall,”A saturated liquid density equation for refrigerants”,Fluid Phase Equilib 131(1997) [2]The properties of Gases and Liquids, Fifth Edition, Bruce E poling, John M Prausnitz John P O’Conell, McGraw Hill, ’Rackett equation’( ) [3]Khashayar Nasrifar, Mahmood Moshfeghian, ”Evaluation of saturated liquid density prediction methods for pure methods”, Fluid phase Equilib (1999), [4]Risdon W Hankinson, George H Thomson, AIChE Journal (vol25, no4) (1979), [5]Khashayar Nasrifar, Mahmood Moshfeghian, “A saturated liquid density equation in conjunction with the Predictive-Soave–Redlich – Kwong equation of state for pure refrigerants and LNG multi component systems”, Fluid phase Equilib 153(1998),

[6]Kh.Nasrifar,Sh.Ayatollahi,M.Moshfeghian,”An extended saturated liquid density equation”,Fluid phase Equilib166 (1999), [7]Kh.Nasrifar,Sh.Ayatollahi,M.Moshfeghian,”Generalised saturated liquid density prediction method for pure compounds and multi-component mixtures”,Fluid phase Equilib168(2000),71-90 [8]”Refrigerants-Physical properties”, [9] “Liquid density by volume translated method- Part1”, density-by-volume-translated-method-%e2%80%93-part-1-pure-compound/ [10]“Liquid density by volume translated method- Part2”, density-by-volume-translated-method-%e2%80%93-part-2-recent- development/