Numerical and experimental investigations on the performance of coiled adiabatic capillary tubes

The objective of this study is to investigate the performance of coiled adiabatic capillary tubes both numerically and experimentally by comparison with the straight capillaries. With the developed model including metastable both liquid and two-phase regions, three methods (M&N equation, M&N + Giri method and developed C–M&N method) are discussed to calculate friction factors for coiled capillary tubes. A one-pass-through experiment apparatus is set up for model verification. Mass flow rate through the capillary is measured with different tube geometries and under various operating conditions. Compared with the present experimental data and that in literature, the developed C–M&N method gives the best prediction with the average deviation of ±5%. The test results show that mass flow rate in a capillary tube increases with increase of coiled diameter (D), but changes little beyond D = 300 mm. And the mass flow rate with coiled diameter of 40 mm is approximately 10% less than that of straight capillary tube.