The effect of inclination angle on the heat transfer and pressure drop characteristics of brazed aluminum heat exchangers having louvered fins is experimentally investigated. Three samples having different fin pitches (1.25, 1,5 and 2.0 mm) were tested. Results show that heat transfer coefficients are not affected by the inclination angle. Friction factors, however, increase as the inclination angle increases, with negligible difference between the forward and the backward inclination. Both the heat transfer coefficient and the friction factor are the smallest at F p = 1.5 mm, followed by 2.0 mm and 1.25 mm. Possible explanation is provided considering the louver layout. Comparison of the present data with existing correlations is also made.
The refrigerant R-134a flow distributions are experimentally studied for a round header/ten flat tube test section simulating a brazed aluminum heat exchanger. Three different inlet orientations (parallel, normal, vertical) were investigated. Tests were conducted with downward flow for the mass flux from 70 to 130 kg/m2s and quality from 0.2 to 0.6. In the test section, tubes were flush-mounted with no protrusion into the header. It is shown that normal and vertical inlet yielded approximately similar flow distribution. At high mass fluxes or high qualities, however, slightly better results were obtained for normal inlet configuration. The flow distribution was worst for the parallel inlet configuration. Possible explanation is provided based on flow visualization results.
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