Nonequilibrium modeling of an ammonia-water rectifyng column via fundamental thermodynamic and transport relations

Brazilian Journal of Chemical Engineering

J. R. Figueiredo¹  B. L. Fernandes¹  R. J. R. Silverio¹ 

[1],UNICAMP FEM DECampinas SP ,Brazil

关键词: Rectifier;    Absorption refrigeration;    Ammonia-water;    Heat and mass transfer;    Non-equilibrium model;   

DOI  :  10.1590/S0104-66322006000400012

来源: SciELO

【 摘 要 】

A nonequilibrium heat and mass transfer model is presented for the steady-state operation of a rectifying column, employed in ammonia-water absorption refrigeration systems to dehumidify the ammonia vapor leaving the generator. The thermodynamic state relations of the mixture are derived from two equations representing the Gibbs free energy in terms of temperature, pressure and concentration for the liquid and the vapor phases. Two of the transport properties, surface tension and liquid diffusivity required original relations, as presented here in. The resulting nonlinear system of equations is solved by efficient use of the Newton-Raphson code that minimizes the order of the Jacobian matrix without losing any model information or the quadratic order of convergence of the numerical method. Accuracy tests are performed by grid refinement and by comparison with results in the literature. A sensitivity study is presented showing the influence of some alternative methods for estimation of the transport properties on the temperature and concentration profiles.

【 授权许可】

CC BY   
 All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License