Browsing by Author "Tsai, Jhong-Syuan"

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Characteristics of flow distribution in compact parallel flow heat exchangers, part I: Typical inlet header
(2011-11-01)
Wang, Chi-Chuan
;
Yang, Kai-Shing
;
Tsai, Jhong-Syuan
;
Chen, Ing Youn
;
機械工程學系
This study experimentally and numerically investigates the single-phase flow into parallel flow heat exchangers with inlet and outlet rectangular headers having square cross section and 9 circular tubes. The effects of inlet flow condition, tube diameter, header size, area ratio, flow directions (Z and U-type), as well as the gravity are investigated. The experimental results indicate that flow distribution for U-type flow is more uniform than Z-type flow. Depending on the inlet volumetric flow rate, the flow ratio at the first several tubes can be lower than 50% of the last tube for Z-type arrangement, and this phenomenon becomes more and more pronounced with the rising velocity at the intake conduit. The mal-distribution can be eased via reducing the branching tube size or increasing the entrance settling distance at the intake conduit. It is found that the influence of gravity on mal-distribution is negligible and the mal-distribution is associated with the jet flow pattern. (C) 2011 Elsevier Ltd. All rights reserved.
Characteristics of flow distribution in compact parallel flow heat exchangers, part II: Modified inlet header
(2011-11-01)
Wang, Chi-Chuan
;
Yang, Kai-Shing
;
Tsai, Jhong-Syuan
;
Chen, Ing Youn
;
機械工程學系
This study presents the experimental results of liquid flow distribution in compact parallel flow heat exchanger through a rectangular and 5 modified inlet headers (i.e., 1 trapezoidal, one multi-step, 2 baffle plates and 1 baffle tubes header). The basic header has a rectangular shape with 9 x 9 mm cross section and 90 mm long header length having a 4 mm inlet tube for flow into the header and distributed to nine 3 mm parallel tubes with 400 mm length. A jet stream induced at the header inlet associated with vortexes affecting the flow distribution to the front tubes. The flow distribution in the header highly depends on the header shape and the total flow rate. Normally the first several tubes have the lowest flow ratios for the conventional headers and the flow distribution is significantly improved by lifting the jet stream using the modified header with baffle tube, followed by the baffle plate and multi-step header. The baffle tube yields the best flow distribution for it removed the vortex flow, and it is applicable for all the flow rates. (C) 2011 Elsevier Ltd. All rights reserved.