EXPERIMENTAL AND NUMERICAL INVESTIGATION OF METASTABLE FLOW OF REFRIGERANT R-22 THROUGH CAPILLARY TUBE

Abstract

This study presents an experimental investigation of metastable region take place for
refrigerant flow through adiabatic and non-adiabatic capillary tube of window type air
conditioner. Large numbers of experiments are carried out to explain the effect of length of
straight and helical capillary tube on metastable region under adiabatic and non-adiabatic
conditions. for the case of adiabatic capillary tube, three different length are selected
(70,100 and 150) cm and two helical capillary tube, the length of each tube is 100 cm with
two coil diameters (2 and 6) cm. For the non-adiabatic capillary tube, the straight capillary
tube suction line is 150 cm while the length of non-adiabatic helical capillary tube is 200 cm
with 8 cm coil diameter. The results show that the length is the most influence parameters
on beginning of metastable region. In addition the helical coil tube effect on the beginning
of metastable region. As well as for the adiabatic and non-adiabatic capillary tube it is
concluded that mass flow rate is the main parameters on beginning of metastable region.
Also effect of length and coiling on both pressure drop and mass flow rate are discussed.
The CFD commercial code, ANSYS CFX 16.1 based on finite volume method using Kturbulence
model considering the homogeneous flow between phases applied to straight
capillary tube. The present numerical data has been validated with the present work
experimental data and with other researchers. A good agreement is obtained which can be
lead to use ANSYS CFX 16.1 in the design and optimization of capillary tube in airconditioner.