A comparative study has been carried out on the adiabatic straight and helical capillary tube, using a CO2 and R22 refrigerant. The Numerical model for CO2 and R22 is developed using the basic principles of conservation of mass, momentum, and energy. Under similar geometric conditions, the comparison of the straight and the helical capillary tube has been carried out for CO2 and R22 refrigerant. Compared to the straight capillary tube, the percentage reduction in mass flow rate in the helical capillary tube is calculated with a change in coil diameter, tube diameter, and length. As the coil diameter increases from 30mm to 150mm, the percentage reduction in mass is from 5.8% to 2.2% in CO2, and 5% to 1.6% in R22. For helical capillary tube with 50mm coil diameter, as the tube diameter increases from 1 to 1.5mm, the percentage reduction in mass flow rate with CO2 refrigerant is from 2.65% to 4.96%, however, for R22 it is from 3% to 4.24%. Similarly, as the capillary tube length increases from 1.3m to 1.8m, the percentage reduction in mass with CO2, and coil diameter 50mm is 4.44% to 4.55%. however, the percentage reduction in mass with R22 is 3.71% to 3.85%. Moreover, Compared to the straight capillary tube, the percentage reduction in length in a helical capillary tube with coil diameter 50mm is 16.4% for CO2 and 9% for R22 refrigerant.