In this research, we have introduced a computational fluid dynamics (CFD) model in two dimensions to examine the thermal efficiency of a single-loop cryogenic Pulsating Heat Pipe (PHP). The operating orientation is bottom heat mode, and the PHP comprises a condenser section positioned at the top and an evaporator unit at the bottom. The capillary tube possesses inner and outer diameters of 1.5 mm and 3.16 mm, respectively. The lengths of all three sections are all set at 40 mm, resulting in an overall PHP length of 120 mm. The tube wall is constructed from stainless steel, and nitrogen serves as the operational fluid. The liquid–vapor phase interface is monitored by utilizing the volume of fluid (VoF) model, and the phase interaction is addressed by employing the Lee model. The evaporator segment experiences a heating power of 0.5 W, while the condenser section is subjected to a constant temperature of 75 K. The transient behavior of evaporator and condenser temperature has been monitored over time. Additionally, the evolution of the PHP flow pattern is examined. The estimated effective thermal conductivity for the PHP is almost four times the thermal conductivity of pure copper at 77 K temperature.