Abstract: In order to investigate the flow and heat transfer performances of tandem double-U-shaped-tubes heat exchangers, model experiments were conducted. The effects of arrangement of the tandem heat exchangers on the nozzle pressure drop and recuperator effectiveness were obtained. The results show that the nozzle pressure drop is increased as the increase of heat exchanger inclined angle. The inclined angle of the last heat exchanger located adjacent the convergent nozzle exit has the most significant influence on the nozzle pressure drop. And the influence of the front heat exchanger located adjacent the nozzle inlet is next. In relative to the situation where a single heat exchanger is placed inside the nozzle, the influence of the inclined angle of the front heat exchanger on pressure drop is somewhat weakened when tandem heat exchangers is used. When the inclined angle of the front heat exchanger is small, the thermal recovery efficiency achieved by the front heat exchanger is very low, thus make it difficult to improve the overall thermal recovery efficiency of tandem heat exchangers. Among several arrangements of tandem heat exchangers in the present tests, the inclined angles of 30°-17°-13° corresponding to the three tandem heat exchangers appears to be more reasonable for obtaining optimum comprehensive flow and heat transfer performance.

Key words: U-shaped heat exchanger, tandem arrangement, mounting angle, pressure drop, thermal recovery efficiency, Model Experiment