Effect of holding time on temperature field and residual stress in the vacuum brazing process of titanium alloy plate-fin heat exchangers

The power and environmental control systems of high-end equipment, such as aerospace, submarine and aircraft carrier, were commonly in service under extreme environment of high pressure, heavy load, strong vibration and elevated temperature corrosion, which put forward an urgent demand for efficient and high-strength plate-fin heat exchanger. However, due to low production yield, large residual stress and deformation for titanium alloy plate-fin heat exchanger, the corresponding efficient and reliable brazing technology need further breakthrough at present. Therefore, a thermal-solid coupling model was carried out in this paper for the vacuum brazing process of titanium alloy plate-fin structure. The temperature uniformity and the distribution characteristics of residual stress were explained, the influence of holding time on the temperature field and residual stress of the vacuum brazing process of titanium alloy plate-fin heat exchanger was verified. The results showed that the temperature of the plate-fin structure was higher on both sides and lower in the middle. Extending the insulation time could effectively improve the temperature uniformity of the plate-fin structure. The residual stresses were mainly concentrated on the upper surface of the fins and the middle of the back side of the spacer, and there were obvious stress concentrations at the brazing seam and the clamping point. When increasing holding time, the residual stresses decreased. The simulated residual stress during vacuum brazing process agreed with the test results, and the relative errors were 5.3%, verifying the accuracy of the model.