**5. Conclusions**

A time and temperature dependent three-dimensional multi-phase simulation with dynamics boundary conditions determined experimentally has been developed to characterize the thermal, inertial, and phase-transition details of refrigerant R404a in a water-cooled condenser at startup conditions. Given the complicated geometrical configuration of the system, where the secondary fluid (refrigerant) is concentric and flows inside the copper jacket in contact with the primary fluid (water), it becomes a challenging task to capture experimental information about the phase-transition details of the refrigerant using common optical or fluid field experimental methods such as optical tagging, particle image velocimetry, or tomography techniques. Therefore, indirect methods have been applied to obtain temperature and pressure values at the inlet and outlet sections of the condenser.

The numerical solution showed the condensing and evaporating oscillatory nature of the phase-transition throughout the spiral tubbing as well as the progression of saturated liquid at the outlet of the refrigerant line. Condensation occurs due to the temperature differences between the water and the refrigerant. Evaporation takes place given the body and inertial forces present in the system that prevent further bubble nucleation to sustain the condensation process.

The velocity profiles for both water and refrigerant show vortices developing at the inlet and outlet zones due to the curvatures and elbows present in the geometry. Nusselt numbers show that heat transfer can be optimized by slightly increasing the diameter of the refrigeration line without inducing a disruption in the flow regime or affecting the manufacturability of the part.

*Numerical Analysis of a Water-Cooled Condenser at Startup Conditions for Refrigeration… DOI: http://dx.doi.org/10.5772/intechopen.97203*
