The present work experimentally investigates the effect of the geometrical parameters of a conically coiled tube in tube (CCTIT) evaporator and its operating conditions on the coefficient of performance (COP) of a vapour compression refrigeration system (VCRS). The CCTIT evaporator is oriented vertically, through which refrigerant R134a flows in its internal tube, while pure water flows in its annulus as heating mediums, in a counter-flow configuration. Twelve CCTIT evaporators with different taper angles (0135) and pitch ratios (0.07770.1311) are constructed. Totally 72 test runs are performed on the twelve evaporators for heating water flow rates from 1.8 to 14 l/min, which are equivalent to Dean number in the evaporator annulus from 119.8 to 756.4. The experimental results demonstrate that increasing the taper angles and the pitch ratio of the CCTIT evaporator in addition to decreasing the Deev,w augments both the COP of the VCRS. Finally, an experimental correlation is developed to predict the COP of the VCRS as a function of the investigated parameters.