Abstarct: The development of high-efficiency electronic equipment requires high-capacity heat transfer devices. Heat pipes are a good option for this purpose due to their two-phase heat transfer. The background of the researches in this field shows that many experimental studies and analyzes have been done in relation to open and closed heat pipes and oscillating pipes. The results reported by different researchers show relative differences between experimental and theoretical observations. Therefore, in the present study, using numerical and simulation methods (Camsol software) to numerically study the thermal behavior and flow regime of a single-loop oscillating heat pipe for a CLPHP mode. The two-phase current is compared to the other models presented. The results of this study are as follows: • Different types of flow pattern were observed in the oscillating heat pipe mechanism. • The start-up time is reduced by reducing the setting angle due to the reduced gravity effect. There was also a slight and sudden change in temperature during start-up. • The drying state was not observed in any of the installation angles in the research. • By decreasing the setting angle from 90 ° (vertical) to 30 ° (inclined), the thermal resistance increases. • The oscillating heat pipe operated in all four positions from the angle of establishment, and in it, a rotating movement was also seen, which changed its direction from time to time. • The performance of the heat pipe in the 90 mode was better than in other modes of gravity, and the heat transfer in the operator and condenser in the vertical position was optimal. • By changing from 90 ° to 30 °, the effect of gravity helps the liquid move less and less and reduces the intensity of the liquid. • For the fluid to move continuously, a minimum of time is required when less than that time no movement is seen inside the oscillating heat pipe.