Development of a thermal management system for a chemical reactor utilizing axial heat pipes


Аuthors

Borshchev N. O.1, 2*, Kochegarova A. V.1, 2

1. Joint Institute for High Temperatures of the Russian Academy of Sciences, 13, Izhorskaya str., Moscow, 125412, Russia
2. Moscow Power Engineering Institute, Moscow, Russia, Russian Federation

*e-mail: www.moriarty93@mail.ru

Abstract

Axial and loop heat pipes are increasingly used for thermal management of high-energy equipment due to their extremely low thermal resistance, achieved through the evaporation-condensation cycle and high capillary-porous pressure. Axial heat pipes are employed in temperature control of nuclear chemical reactors and metallurgical furnaces, and have found extensive application in the nuclear industry and aerospace engineering.
The operating principle of a heat pipe is as follows: heat input causes part of the working fluid saturating the wick to evaporate. Due to the vapor pressure difference between the evaporator and condenser, the vapor is transported to the condenser. The condensation section is connected to a structural element whose temperature is lower than that of the evaporation section. Heat is transferred from the condensing working fluid to the condensation section. From the evaporator section of the heat pipe, heat is transferred to the outer wall of the wick, while part of it is conducted along the heat pipe wall to the condensation section. Evaporation of the working fluid occurs from the wick surface [6–9]. Subsequently, the vapor carries heat to the condensation zone. In the condensation zone, heat is transferred to the wick, and then through the wick and the wall of the heat pipe's condenser section. Finally, heat is rejected to the environment via convective cooling of the condensation zone.
This study presents a thermal management system for a chemical reactor operating on gaseous nitrogen. The reactor is temperature-controlled by a toroidal axial heat pipe equipped with two wicks. A thermal physico-mathematical finite element model of mass transfer within a sodium-based axial heat pipe, which provides thermal control for the chemical reactor, is proposed. The computational results were compared with a thermophysical experiment where 400 W was supplied to the evaporation zone via ohmic contact heating on one side of the heat pipe, while gaseous nitrogen at 300 K was pumped through for drainage cooling on the other side. Cooling of the condensation zone was achieved by supplying air through a ventilation cooling system.
The validation results of the axial heat pipe (AHP) thermal model showed a temperature difference of 8 °C between the evaporation and condensation zones for this design, with a local temperature of 389 °C in the heat input zone. The absolute error in temperature determination at the sensor location be-tween the simulation and experiment did not exceed 0.5%.

Keywords:

axial heat pipe, sodium, finite element method, high-enthalpy heat flow, chemical reactor, vapor-liquid mixture

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