Modeling of non-adiabatic capillary tube flows: A simplified approach and comprehensive experimental validation Christian J.L. Hermes a, *, Cla ´ udio Melo a , Joaquim M. Gonc ¸alves b,1 a POLO Research Laboratories for Emerging Technologies in Cooling and Thermophysics, Federal University of Santa Catarina, 88040-970 Floriano ´polis, SC, Brazil b Federal Center of Technological Education of Santa Catarina, Rua Jose ´ Lino Kretzer 608, 88103-310 Sa ˜o Jose ´, SC, Brazil article info Article history: Received 30 October 2007 Received in revised form 18 April 2008 Accepted 22 April 2008 Published online 1 May 2008 Keywords: Refrigeration system Capillary tube Mathematical modeling Non-adiabatic flow Experimental validation abstract A simplified computational model for simulating refrigerant flow through capillary tubes is proposed and validated using a dataset composed of more than 1400 experimental data points, including adiabatic flows of refrigerants CFC-12, HCFC-22, HFC-134a, HC-600a, R-404A, R-407C and R-507A, and non-adiabatic flows of refrigerants HFC-134a and HC- 600a, in both concentric and lateral capillary tube–suction line heat exchanger configura- tions. The model is based on the mass, energy and momentum conservation equations written according to their one-dimensional differential formulation. Some simplifications were added to the model in order to improve both numerical stability and computational performance. It was found that the model predicts 91.5% of the measured refrigerant mass flow rate for adiabatic and 79.3% for non-adiabatic flows within an error band of 10%. Also, the model solves non-adiabatic flows as fast as adiabatic ones. ª 2008 Elsevier Ltd and IIR. All rights reserved. Mode ´ lisation de l’e ´ coulement non adiabatique a ` l’inte ´ rieur des capillaires : approche simplifie ´ e et validation expe ´ rimentale comple `te Mots cle ´s : Syste ` me frigorifique ; Capillaire ; Modelisation mathematique ; Non-adiabatique e ´ coulement ; Valider expe ´ rimental 1. Introduction In refrigeration systems, a capillary tube is simply a small bore tube connecting the condenser to the evaporator. Liquid refrigerant flows into one end and expands until reaching the evaporating pressure. In doing so it maintains the refriger- ant at the desired mass flow rate. A capillary tube appears to be quite simple, but the refrigerant flow inside this * Corresponding author. Tel.: þ55 48 3234 5691; fax: þ55 48 3234 5166. E-mail addresses: hermes@polo.ufsc.br (C.J.L. Hermes), melo@polo.ufsc.br (C. Melo), joaquim@sj.cefetsc.edu.br (J.M. Gonc ¸alves). 1 Tel.: þ55 48 3381 2860; fax: þ55 48 3247 6542. www.iifiir.org available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/ijrefrig 0140-7007/$ – see front matter ª 2008 Elsevier Ltd and IIR. All rights reserved. doi:10.1016/j.ijrefrig.2008.04.002 international journal of refrigeration 31 (2008) 1358–1367