Thermal Hydraulic Investigation of Sodium-Air Heat Exchanger
U. Partha Sarathya, K. Velusamyb, P. Selvarajc, P. Chellapandid and S. C. Chetale
Reactor Engineering Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India.
aups@igcar.gov.in
bkvelu@igcar.gov.in
cpselva@igcar.gov.in
dpcp@igcar.gov.in
echetal@igcar.gov.in
ABSTRACT
Post shutdown decay heat removal (DHR) should be assured with very high reliability in any nuclear reactor system. In Indian Prototype Fast Breeder Reactor (PFBR), this is achieved by providing Air Heat Exchangers (AHX), which reject heat directly to the atmosphere. AHX is a finned tube cross flow heat exchanger with hot sodium flowing through tubes. Ambient air passes over the tubes, absorbs heat from sodium and leaves to the stack. The tubes are long and slender. Air has to pass uniformly over the tubes to maximize the heat removal. Non-uniform air flow distribution results in reduction of the AHX heat removal capacity. This also results in higher local velocities and may cause FIV (flow induced vibration) related problems. Non-uniform temperature distribution between the rows of tubes leads to unequal expansion of tubes and thermal stresses at tube-header joints. In order to achieve a near uniform air flow distribution, detailed CFD analyses have been carried out. Based on the parametric study an optimum shape for the flow distributor has been identified. This paper discusses about the modeling and the results of CFD studies carried out. This paper also discusses about other modifications made in the design to increase the heat exchanger capacity.
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