Flow rate prediction for an adiabatic capillary tube in a transcritical CO₂ system: an analytic approach

Transcritical nature of the CO₂ refrigeration cycle makes the capillary tube behavior distinctly different compared with a conventional subcritical system. A novel closed-form analytical solution is proposed to simulate the flow characteristics of an adiabatic capillary tube. Such an analytical solution is being proposed, for the first time, for the transcritical--superheated--two phase region in a CO₂-based transcritical heating--cooling system. Improved K value relations based on Gaussian function for CO₂ are obtained employing MATLAB-based tools. Predictions by the proposed analytical model have been validated against carefully obtained test data and the observed agreement is fairly good. Copyright The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org, Oxford University Press.