This study experimentally investigates the effect of the geometrical parameters of a vertical conically coiled tube in tube (CCTIT) evaporator/condenser and their operating conditions on their effectiveness and on the coefficient of performance (COP) of a vapor compression refrigeration system (VCRS). Twelve CCTIT evaporator/condenser of different taper angles (0-135) and torsions (0.0777-0.1311) are tested for different water Dean numbers in their annuli, while R134a flows in their internal tube. The results demonstrate that increasing the evaporator/condenser taper angles and torsions in addition to decreasing their water Dean numbers augment the evaporator/condenser effectiveness and the COP of the VCRS and. However, the coils taper angles have the more dominant effect than the other studied parameters. Finally, experimental correlations are developed to predict the COP of the VCRS and the effectiveness of the evaporator and condenser as a function of the investigated parameters.