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/* |
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Initial model of a simple mixture, to get the procedure right. This |
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is in preparation for a general algorithm to find mixing conditions |
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in the ideal-mixture case. |
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|
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Started May 28, 2015 |
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*/ |
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|
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#include "../helmholtz.h" |
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#include "../fluids.h" |
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#include "../fprops.h" |
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#include "../refstate.h" |
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#include "../sat.h" |
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|
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#include <stdio.h> |
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#include <assert.h> |
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#include <math.h> |
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|
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/* TODO: maybe add nice colors from `color.h', later. |
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Too much of a distraction to figure it out now. */ |
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|
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extern const EosData eos_rpp_nitrogen; |
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extern const EosData eos_rpp_ammonia; |
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extern const EosData eos_rpp_carbon_dioxide; |
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extern const EosData eos_rpp_methane; |
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extern const EosData eos_rpp_water; |
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|
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/** |
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Calculate overall mass density of a mixture of components, given mass |
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density of components. |
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|
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@param nPure number of pure components |
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@param x mass fractions of components |
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@param rhos mass density of each component |
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@return mass density of mixture |
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*/ |
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double mixture_rho(unsigned nPure, double *x, double *rhos){ |
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double rho_mix; |
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|
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int i; |
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for(i=0,rho_mix=0.0;i<nPure;i++){ |
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rho_mix += x[i]*rhos[i]; /* mixture mass density is simply sum of each mass density weighted by the mass fraction */ |
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} |
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return rho_mix; |
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} |
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|
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/** |
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Get data for the fluids I want available for the mixture: |
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nitrogen |
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ammonia |
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carbon dioxide |
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methane |
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water |
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|
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Then, establish mixture conditions, and find individual densities |
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*/ |
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int main(void){ |
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enum FluidNames {N2,NH3,CO2,/*CH4,H2O,*/NFLUIDS}; |
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ReferenceState ref = {FPROPS_REF_REF0}; |
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|
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const EosData *IdealEos[NFLUIDS]={ |
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&eos_rpp_nitrogen |
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, &eos_rpp_ammonia |
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, &eos_rpp_carbon_dioxide |
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// , &eos_rpp_methane |
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// , &eos_rpp_water |
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}; |
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|
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char *FluidNames[NFLUIDS]={ |
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"nitrogen", "ammonia", "carbondioxide"/* , "methane", "water" */ |
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}; |
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|
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PureFluid *Ideals[NFLUIDS]; |
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PureFluid *Helms[NFLUIDS]; |
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|
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FpropsError err = FPROPS_NO_ERROR; |
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int i; |
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for(i=N2;i<NFLUIDS;i++){ |
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Ideals[i] = ideal_prepare(IdealEos[i],&ref); |
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Helms[i] = fprops_fluid(FluidNames[i],"helmholtz",NULL); |
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} |
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|
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/* Mixing conditions, in temperature and pressure */ |
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double T=300; /* K */ |
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double P=1e5; /* Pa */ |
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double x[NFLUIDS] = {0.5, 0.3, 0.2}; /* mass fraction */ |
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/* Density is found as ideal-gas density for now */ |
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double rho[NFLUIDS]; |
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for(i=N2;i<NFLUIDS;i++){ |
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rho[i] = P / Ideals[i]->data->R / T; |
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printf("\n\t%s%s is : %.4f kg/m3", "The mass density of ", FluidNames[i], rho[i]); |
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} |
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|
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/* mixture properties */ |
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double rho_mx = mixture_rho(NFLUIDS, x, rho); |
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double p_mx=0.0, /* pressure and enthalpy, calculated from mixture mass densities */ |
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h_mx=0.0; |
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|
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/* Calculate pressures and enthalpies with the Ideal model (ideal-gas mixture) */ |
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double p_i, h_i; /* these will hold individual pressures and enthalpies */ |
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printf("\n The ideal-gas case:"); |
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for(i=N2;i<NFLUIDS;i++){ |
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p_i = ideal_p(T, rho[i], Ideals[i]->data, &err); |
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h_i = ideal_h(T, rho[i], Ideals[i]->data, &err); |
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printf("\n\t%s %s\n\t\t%s %g Pa;\n\t\t%s %g J/kg.\n", |
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"For the substance", FluidNames[i], |
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"the pressure is :", p_i, |
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"the enthalpy is :", h_i); |
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p_mx += x[i] * p_i; |
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h_mx += x[i] * h_i; |
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} |
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printf("\n\t%s\t\t:\t %f kg/m3\n\t%s\t:\t %g Pa\n\t%s\t\t:\t %g J/kg\n", |
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"The density of the mixture is", rho_mx, |
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"The average pressure of the mixture is", p_mx, |
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"The enthalpy of the mixture is", h_mx); |
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|
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/* Calculate pressures and enthalpies from Helmholtz model */ |
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printf("\n The non-ideal-gas case:"); |
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p_mx=0.0; /* reset mixture pressure and enthalpy to zero */ |
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h_mx=0.0; |
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for(i=N2;i<NFLUIDS;i++){ |
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p_i = fprops_p((FluidState){T,rho[i],Helms[i]}, &err); |
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h_i = fprops_h((FluidState){T,rho[i],Helms[i]}, &err); |
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printf("\n\t%s %s\n\t\t%s %g Pa;\n\t\t%s %g J/kg.\n", |
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"For the substance", FluidNames[i], |
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"the pressure is :", p_i, |
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"the enthalpy is :", h_i); |
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p_mx += x[i] * p_i; |
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h_mx += x[i] * h_i; |
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} |
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printf("\n\t%s\t\t:\t %f kg/m3\n\t%s\t:\t %g Pa\n\t%s\t\t:\t %g J/kg\n", |
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"The density of the mixture is", rho_mx, |
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"The average pressure of the mixture is", p_mx, |
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"The enthalpy of the mixture is", h_mx); |
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|
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/** |
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Now I drop the assumption that densities can be calculated from the |
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ideal-gas model, and use a root-finding method to find the densities |
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that each component must have to be at the pressure P. |
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|
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That is, since ideal-solution mixing is isobaric (constant pressure), the |
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density of each component is found by assuming it is at pressure P before |
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mixing, and solving for the density that will satisfy that condition. |
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*/ |
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return 0; |
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} |
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