In supercritical carbon dioxide(S-CO_2) Brayton cycle and other thermal mass circulation transportation processes

there is a flow heat transfer process between cold and hot carbon dioxide under supercritical pressure

and its heat transfer characteristics are important to the performance of corresponding systems. In this paper

by using a tube heat exchanger as a prototype

numerical simulation on the heat transfer characteristics between cold and hot carbon dioxide under supercritical pressure is carried out. The effects of inlet temperature of hot fluid

inlet mass flow rate of cold and hot fluid on the heat transfer characteristics and distribution of heat transfer characteristics in the circumferential direction are mainly studied. The results show that

with the change of inlet temperature of the hot fluid

the local heat transfer coefficients of hot side and cold side will change and fluctuate correspondingly. At the same time

the heat transfer of cold side will appear enhancement obviously when the cold side mainstream temperature approaches the pseudocritical temperature. In addition

the increase of mass flow rate of hot side will enhance the heat transfer coefficient of hot side

meanwhile the peak value of cold side heat transfer coefficient decreases and moves to the inlet of cold fluid. As the mass flow of the cold side increases

the peak value of the heat transfer coefficient at the cold side increases and moves towards the cold fluid outlet. Due to the horizontal arrangement of the heat exchanger

the heat transfer characteristics have obvious unevenness in the circumferential direction

which is related to the increase and decrease of the local turbulence effect of fluid density change under the action of gravity. This research has guiding significance for the development and design of new carbon dioxide Brayton cycle and other thermal mass circulation transportation processes.