Levenberg-Marquardt application to two-phase nonlinear parameter estimation for finned-tube coil evaporators

Abstract

A procedure for calculation of refrigerant mass flow rate isimplemented in the distributed numerical model to simulate theflow in finned-tube coil dry-expansion evaporators, usually foundin refrigeration and air-conditioning systems. Two-phaserefrigerant flow inside the tubes is assumed to beone-dimensional, unsteady, and homogeneous. In the model theeffects of refrigerant pressure drop and the moisture condensationfrom the air flowing over the external surface of the tubes areconsidered. The results obtained are the distributions ofrefrigerant velocity, temperature and void fraction, tube-walltemperature, air temperature, and absolute humidity. The finitevolume method is used to discretize the governing equations.Additionally, given the operation conditions and the geometricparameters, the model allows the calculation of the refrigerantmass flow rate. The value of mass flow rate is computed using theprocess of parameter estimation with the minimization method ofLevenberg-Marquardt minimization. In order to validate thedeveloped model, the obtained results using HFC-134a as arefrigerant are compared with available data from the literature.