Algebraic solution of capillary tube flows: Part I: Adiabatic capillary tubes

Capillary tube flows have been solved through both numerical and analytical approaches. The former requires a reasonable understanding of the governing equations of heat and fluid flow, thermodynamic relations, numerical methods, and computer programming, and therefore are not the suitable approach for most refrigeration and air-conditioning practitioners. Some simpler procedures based on different strategies for analytically solving the capillary tube flow have been proposed in the literature, although iterative loops for calculating the mass flow rate are still required. The aim of this work is to advance a semi-empirical algebraic model to solve adiabatic capillary tube flows using a relatively simple set of thermodynamic relations and being explicit for the mass flow rate calculation. Comparisons with a comprehensive experimental data set, taken with the refrigerants HFC-134a and HC-600a, has shown that the model predicts more than 90% and nearly 100% of all data within ±10% and ±15% error bands, respectively.