Inside of the heat exchanger of automobile, first the water flow comes into the inlet chamber and streams into many branch passages. Through these passages, the hot water is cooled by the surrounded air. Then the cooled water merges into the outlet chamber and flow out from the heat exchanger. As the heat exchanger is consisted of bends and tubes, the flow field in the heat exchanger is very complicated because of the presence of flow reversal and separation. Only a few reports are available to date concerning the mal-distribution of the flow rate and the technical remedy to obtain uniform flow distribution. This study aims to predict the flow patterns in a heat exchanger. Flow visualization, velocity measurement and numerical analysis are applied to the water flow in the tube array model. The results in laminar flow region show that the flow rates and patterns in tube array greatly depend on the mutual position of the tube arrays to the flow inlet and outlet of the model. It is shown that the uniform flow distribution in each branch passage can be realized by increasing the volume of the outlet chamber.
The X-shaped intersecting ducts have a structual defect in engineering because of extra ducts at both the confluent and branching sides. However, the results are interesting when researchers apply the characteristics of flow around the intersecting region with the use of newly developed apparatuses. In this paper, experiments were performed to investigate the changes of energy, resistance and flow rates in two intersecting vertical ducts. The flow visualization study was conducted using a recirculating flow loop with an intersecting duct installed between two head tanks of different heads. It is disclosed that the changes of energy and hydraulic gradient in the intersecting vertical ducts are as almost same as those in the intersecting plane ducts. The flow rates in the intersecting ducts with the angle of 60° are found to be of great interest, that is, their flow rates at the end of downstream ducts are almost same regardless the water levels in the upper tanks.
The three-dimensional particle tracking velocimeter (3-D PTV) is a powerful tool for measuring the instantaneous three-dimensional distributions of the velocity vectors. Despite of its significant ability, it can be applied only to the flow field in a simple geometry, because of its complex camera calibration procedure. Although there have been made some modifications that handle the refraction at the glass walls implicitly in the camera parameters, but their applications are still limited to the case of parallel planes. Presently, a new method is proposed that calculates all the refractions at any surface explicitly. Thus, one can avoid the complexity in the camera calibration and can measure any flow field in the complex geometry, if the shape of which is known by the numerics. The principle of the new camera calibration technique and the procedures for the practical measurement in a circular curved pipe is shown in this study.