Numerical simulation and experimental investigation of heat pipe heat exchanger applied in residual heat removal system

Highlights: • The numerical simulation of HPHE applied in RHRS is proposed for the first time. • Heat transfer performance of 3-D HPHE with thermal resistance model. • The effects of diameters, Re and arrangements on heat transfer are discussed. - Abstract: The residual heat removal system (RHRS) discharges residual heat from the reactor core and other equipment when the nuclear power plant is shut down. Heat pipe heat exchanger (HPHE) has the characteristics of high reliability, stability, volume heat capacity and modular operation, which is suitable to be used in RHRS. In this paper, a three-dimensional numerical simulation and experimental study of HPHE under steady-state turbulent flow and heat transfer with thermal resistance network are performed. The simulation and experiments are completed under the operating condition of residual heat removal system. The validation of the computational model is performed by comparing the experimental data and empirical correlation of average Nu in condenser and evaporator. The maximum deviation is less than 10%, which means that the simulation is accurate enough. Then investigation compares heat transfer and turbulent flow of HPHE with two bundle arrangements, two types of heat pipe diameters and different Re. When the flow is in the state of vigorous turbulence (Re ≈ 10⁴), the heat transfer power of each heat pipe with diameter of 16 mm exceeds 2.65 kW. For heat pipe with the diameter of 19 mm, heat transfer performance of each is improved by about 3% to 6% than heat pipes with the diameter of 16 mm. The results show that HPHE not only has safety advantage of avoiding leakage of radioactive liquid, but also has good heat transfer performance applied in RHRS, which verified its feasibility.