Published: 2015-09-18
ISBN: 978-91-7685-955-1
ISSN: 1650-3686 (print), 1650-3740 (online)
Many dynamic models of vapor compression systems experience nonphysical variations in the total refrigerant mass contained in the system when common modeling approaches are used. Ratherthan use the traditional state variables of pressure and specific enthalpy, the use of density as a state variable can eliminate these variations. A set of test models is developed in Modelica to study the effect of the state variable selection on the overall system charge, and results indicate that this alternative approach has significant benefits for maintaining a specified mass of refrigerant in the cycle.
V. Aute and R. Radermacher. Standardized polynomials for fast evaluation of refrigerant thermophysical properties. In International Refrigeration and Air-Conditioning Conference at Purdue, 2014.
A. Bejan. Advanced Engineering Thermodynamics. Wiley, 3 edition, 2006.
J. Bonilla, L.J. Yebra, and S. Dormido. Chattering in dynamic mathematical two-phase flow models. Applied Mathematical Modeling, 36:2067–2081, 2012.
G.E.P. Box and N.R. Draper. Empirical Model-Building and Response Surfaces. Wiley, 1987.
F. Casella, M. Otter, K. Proelss, C. Richter, and H. Tummescheit. The Modelica Fluid and Media library for modeling of incompressible and compressible thermo-fluid pipe networks. In Proceedings of the 5th Modelica Conference, 2006.
L. Cecchinato and F. Mancini. An intrinsically mass conservative switched evaporator model adopting the movingboundary method. International Journal of Refrigeration, 35:349–364, 2012.
J.M. Corberan, I. Martinez-Galvan, S. Martinez-Ballester, J. Gonzalvez-Macia, and R. Royo-Pastor. Influence of the source and sink temperatures on the optimal refrigerant charge of a water-to-water heat pump. International Journal of Refrigeration, 34:881–892, 2011.
H. Elmqvist, H. Tummescheit, and M. Otter. Object-oriented modeling of thermo-fluid systems. In Proceedings of the 3rd Modelica Conference, 2003.
R. Franke, F. Casella, M. Sielemann, K. Proelss, M. Otter, and M.Wetter. Standardization of thermo-fluid modeling in Modelica.Fluid. In Proceedings of the 7th Modelica Conference, 2009.
C. Laughman. A comparison of transient heat pump cycle simulations with homogeneous and heterogeneous flow models. In International Refrigeration and Air Conditioning Conference at Purdue University, 2014.
P. Li, Y. Li, J.E. Seem, H. Qiao, X. Li, and J. Winkler. Recent advances in dynamic modeling of HVAC equipment. Part 2: Modelica-based modeling. HVAC&R Research, 20(1): 150–161, 2014a.
P. Li, H. Qiao, Y. Li, J.E. Seem, J. Winkler, and X. Li. Recent advances in dynamic modeling of HVAC equipment. Part 1: Equipment modeling. HVAC&R Research, 20(1):136–149, 2014b.
Modelon AB. Air Conditioning Library User Guide, 2015. v1.9.0.
S.V. Patankar. Numerical Heat Transfer and Fluid Flow. Hemisphere Publishing Co., 1980.
H. Tummescheit. Design and Implementation of Object-Oriented Model Libraries using Modelica. PhD thesis, Lund Institute of Technology, 2002.
