Heat exchange capability of main heat exchangers in pressurized water test loop under low parameter conditions during fuel assembly irradiation

The steady-state irradiation test for fuel assemblies is a key aspect of nuclear reactor fuel development, for revealing irradiation resistance and verifying the safety of new fuel assemblies before engineering application. The impact of low parameter conditions on the heat transfer capacity of main heat exchangers in the the pressurized high-temperature water test loop was studied. A segmented fitting method for determining flow turning points was established, and proposals for series-parallel configurations and new regenerative heat exchanger designs were presented. It is shown that the total heat exchange power of two main heat exchangers operating in parallel is not always greater than that of a single unit. There exists a flow turning point, and above this point, operating the two main heat exchangers in parallel is beneficial. Through segmented fitting, the flow turning points at different inlet water temperatures can be obtained. The average difference in turning points obtained from fitting and calculations is only 0.6%, with a corresponding average power deviation of 1.8%. Besides, for low parameter operating conditions, the issues of insufficient heat exchange power can be addressed by using a series connection of the main heat exchangers and adjusting the heat exchange area of the regeneration section. • The heat exchange power can be expressed through segmented fitting curves • Heat exchange power enhancement in parallel is only evident above the flow turning point • Heat exchangers in series are suitable for improving the existing system's heat exchange capacity • Setting an adjustable area for the regeneration section can effectively enhance the heat exchange power under low parameter conditions.