In this thesis, heat transfer coefficient and pressure drop during condensation of R-404A inside horizontal tube and coiled wire inserted tubes has been investigated experimentally. The experimental set-up which was used in this study was a well instrumented vapor compression refrigeration cycle which utilized R-404A as refrigerant. This set up consist of a test condenser which was a 1000-mm long double-tube counter-flow heat exchanger while, the refrigerant flowed in the inner copper and cooling water flowed in the annulus and all the experiments were carried out on it. In addition there is a primary condenser and secondary condenser to achieve the required vapor qualities in order to investigate the effect off vapor quality on heat transfer and pressure drop. All these condensers are double pipe counter flow water cooled heat exchangers which refrigerant flows inside the internal cooper tube, while water flows in the annulus. The experimental investigation was carried out in the plain tube and five coiled wire inserted tube that data were collected for different mass velocities of 71.2, 89, 106.8, 124.6 and 142.4 (kg/m 2 s) and in each mass velocities for six different vapor quality. At each experiment several parameters were measured, such as refrigerant mass velocity, inlet and outlet water temperatures, inlet and outlet refrigerant temperatures, etc. First category included springs with 10-mm coil pitch and 0.5, 1.0 and 1.5-mm thickness and exhibited effect of wire diameter on heat transfer and pressure drop during condensation of R-404A inside horizontal coiled wire inserted tubes, and second which had springs with equal diameter of 1.0-mm thickness and variant coil pitch of 8, 10 and 13-mm showed effect of spring pitch on heat transfer and pressure drop during condensation of R-404A inside horizontal coiled wire inserted tubes. Heat transfer coefficients were calculated by use of the collected data. Also, pressure drop between the inlet and outlet of test condenser is measured by differential pressure transmitter. In order to verify integrity of the experimental set up, Comparison between plain tube results and exiting correlation was done. Result of experiments showed using coiled wire increases average heat transfer coefficient up to 60% with compare to plain tube . From results, it was found that the coiled wire inserts increase the pressure drop up to 1200% relative to the plain tube values on a nominal area basis. Investigation of the results for coiled wire inserted tube shows that for the same mass velocity wire diameter increment and coiled pitch reduction increase both heat transfer coefficient and pressure drop. Also increase of mass velocity and vapor quality increase heat transfer and pressure drop. A new correlation for the prediction of heat transfer coefficient and pressure drop were developed by utilizing the gained results for the coiled wire inserted tubes. Finally performance evaluation was done and it is observed that at all conditions using coiled wire inserts are unfavorable. However, coiled wire inserts can be employed in specific application such as when because of limited space, compact heat exchangers are needed and higher pumping power is reasonable. Key words :Heat Transfer Increase, Condensation, coiled wire, Pressure Drop