This paper presents numerical and experimental results of the flow characteristics of R134a flowing through adiabatic helical capillary tubes. The local pressure distribution along the length of the capillary tubes is measured at inlet pressures ranging from 10 to 14 bar, mass flow rates from 8 to 20 kg $h^{-1}$, and degrees of subcooling from $0.5^{circ}C$ to $15^{circ}C$. The theoretical model is based on conservation of mass, energy and the momentum of the fluids in the capillary tube. The model is divided into three regions: subcooled liquid region, metastable liquid region and equilibrium two-phase region and can be applied for various tube geometries, new alternative refrigerants and critical or noncritical flow conditions. The model is validated by comparing results from the present experimental data with that of the available literature. Based on the comparison results, the model used in the present study provides reasonable agreement with the experimental data.