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| Abstract No.: |
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Scheduled at:
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Tuesday, May 04, 2021, Hall 1 1:45 PM
Process & Quality Control
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| Title: |
Impact of substrate surface features on brazing of microchannel heat exchangers
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| Authors: |
Hui Zhao* / Creative Thermal Solutions, Inc;
University of Illinois at Urbana-Champaign, U.S.A
Pega Hrnjak / Creative Thermal Solutions, Inc./University of Illinois at Urbana-Champaign, USA
Stefan Elbel/ Creative Thermal Solutions, Inc./University of Illinois at Urbana-Champaign, USA
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| Abstract: |
Aluminum microchannel heat exchangers are widely used in the refrigeration and air conditioning systems. During the heat exchanger manufacturing, mircochannel tubes are joined to headers and fins by CAB brazing. The thin wall tube structure imposes challenges on the control of brazing process to prevent heat exchanger defects such as leak tubes due to excessive filler metal erosion. It is often found that extensive spreading of the liquid filler metal from the header to adjacent fins spreading over the microchannel tube surface may occur depending on the tube surface features, and brazing conditions. If in the interaction between the liquid filler metal flow and the tube surface erosion occurs it may cause catastrophic defect such as pin hole on tube wall. In this paper, the relation between the tube surface (external) features and tube wall erosion by filler metal is presented in detail. Based on a series of controlled atmosphere brazing tests performed under various brazing conditions it is demonstrated that certain surface feature or manufacturing defects on the tube wall may act as capillary channel for liquid filler metal to flow through and initiate the localized tube surface erosion. Brazing conditions (temperature, dwell time) play important role on erosion and pin-hole formation. The correlations between the brazing conditions and substrate dissolution rate are discussed based on experimental data.
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