Comparative Study of Heat Transfer Parameter Estimation Using Inverse Heat Transfer Models of a Trailing Liquid Nitrogen Jet in Welding

Abstract

Welding induces distortions and stresses in welded structures. A heat sink trailing the weld arc is one among the methods used to reduce the stresses and distortions. Researchers have made use of cooling agents like atomized water and liquid nitrogen (LN2) jet as trailing heat sinks. As the inclusion of a heat sink alters the temperature distribution, estimation of heat removal due to cooling jet is a prerequisite for the study of the effects of the heat sink on stresses and distortions. Analytical methods for the estimation of heat transfer parameters are complicated due to nonuniform cooling by the impinging jet, boiling heat transfer of cooling jet, stray fluid particles on the work-piece surface, and the sharp localized temperature gradient on the work piece due to weld heat input. Therefore, an inverse heat transfer (IHT) method is adapted to estimate the heat transfer parameters due to heat sink. Experiments were conducted using automated tungsten inert gas welding apparatus on a low-carbon steel work piece with an LN2 trailing jet, and transient temperature history was recorded at select points. A finite-element method is used as a solution procedure for IHT method. The heat transfer parameters are estimated by comparing the temperature history at a point from the experiment with the temperature history of the same point in the finite-element model by an iterative method. The heat transfer coefficient, heat flux of LN2 jet, and effective radius of the jet are estimated using two-dimensional and three-dimensional models.