Prediction of Capillary Tube Adiabatic Flow Properties in the Absence of Precise Geometric Information

Abstract

Capillary tubes have been used in household refrigerators and other cooling systems for several decades. Complicated geometry, inevitable manufacturing variations, and complex twophase phenomena have been major prohibitory factors in the development of reliable and efficient modeling tools to analyze the flow properties inside capillary tubes. Friction factor correlations as are available in the open literature, and as examined by the author, unanimously fail to give an accurate analysis of the refrigerant flow. The delicate operation of a capillary tube makes experimentation cumbersome, time and cost intensive, and prone to errors. The present study introduces a method to utilize the data obtained from a standard nitrogen flow test for a given capillary tube to compensate for the geometric uncertainties and predict refrigerant flow properties through the tube at any desired spatial resolution, inlet state, and flow rate. Therefore, exploratory studies and capillary tube modifications for the purpose of system development and optimization can be greatly simplified.