Transactions of Nanjing University of Aeronautics & Astronautics
Gas Flow Development Through Tandem Heat Exchangers Inside Exhaust Nozzle by Using Porous Medium Model
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Abstract:
A computational study on the flow development through tandem double-U-shaped-tubes compact heat exchangers inside exhaust nozzle is presented. In order to simplify the computational process on modeling the flow field, the compact heat exchanger is modeled as a porous matrix by using an isotropic porous medium assumption, which makes two-dimensional numerical simulation realistic. With the use of an existed quadratic relation which connects the pressure drop with the inlet velocity in the external part of the heat exchanger, the permeability and drag coefficient in the porous medium model are determined and a corresponding computational method validation is also made. Two schemes of tandem double-U-shaped-tubes compact heat exchangers are numerically analyzed. In relative to the baseline scheme, the modified scheme is improved by smoothing the nozzle expansion, varying heat exchanger mounting angle and installing boattail ramp at the trailing edge of the last heat exchanger. The results show that the pressure losses due to the existence of local recirculation zones and inappropriate distribution of the flow field are reduced in the modified scheme. The pressure loss coefficient is decreased from 1.7% under the baseline scheme to 1.2% under the modified scheme.
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