In this study, the effects of the leakage flow between the baffle and tube bundles on the performance of a shell and tube heat exchanger (STHE) were examined using the commercial software ANSYS FLUENT v.14. A computational fluid dynamics model was developed for a small STHE with five different cases for the ratio of the leakage cross-sectional area to the baffle cross-sectional area, ranging from 0 to 40%, in order to determine the optimum leakage flow corresponding to the maximum outlet temperature. Using fixed tube wall and inlet temperatures for the shell side of the STHE, the flow and temperature fields were calculated by increasing the Reynolds number from 4952 to 14858. The present results showed that the outlet temperature, pressure drop, and heat transfer coefficient were strongly affected by the leakage flow, as well as the Reynolds number. In contrast with a previous researcher's finding that the leakage flow led to simultaneous decreases in the pressure drop and heat transfer rate, the present study found that the pertinent leakage flow provided momentum in the recirculation zone near the baffle plate and thus led to the maximum outlet temperature, a small pressure drop, and the highest heat transfer rate. The optimum leakage flow was shown in the case with a ratio of 20% among the five different cases. † Corresponding Author,
The split-type air conditioners are widely used in high-rise apartment buildings in the major urban areas, especially Ho Chi Minh City - Vietnam, because of its convenience. In the apartments with limited space, the installation of outdoor units not in accordance with technical guidelines will affect the performance of the air conditioning system and the aesthetics of the apartment building. The aim of this study is to propose the technical room in apartments for properly installing outdoor units of air conditioning systems. The CFD method is utilized through Ansys Fluent software to determine the inlet air temperature of condensers and COP corresponding to the louver angle of 0o, 10o, 20o, 30o và 40o. The results obtained from the simulations show that increasing the louver angle results in rising the inlet air temperature of condensers and reducing COP. The average temperature of the air which entering the condensers does not change significantly when the louver angle increases from 0o to 30o. When the louver angle is more than 30o, the inlet air temperature of outdoor units exceeds the continuous operating temperature of 48oC. To maintain the high performance of the air conditioner during operation, the louver angle is adjusted as small as possible and limited to a value of about 30o.
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