Thermal Stress Induced by Inclined Impinging Heating Jet on a Flat Plate

Abstract

J ETS impinging normally on a flat plate have been extensively studied in terms of flow characteristics, wall temperature, and pressure distribution [1,2]. In some cases, a jet impinges on the plate with a certain degree of inclination with respect to the plate, resulting in the oblique impinging jet. In the case of a jet removing heat from the target plate (cooling jet), it has been established that the location ofmaximumheat transfer shifts increasingly toward the uphill side of the plate, and the maximum Nusselt number decreases as the inclination angle is decreased from the normal impinging position [3,4]. On the contrary, for a heating jet, such an inclination increases the maximum temperature (or heat transfer rate), leading to a significant temperature jump at all the points along the plate [5]. The upward shift of the maximum temperature is attributed to the reduction in effective entrainment of air on both the uphill and downhill sides of the target plate. Although a multitude of studies have been conducted to characterize theflowand heat transfer characteristics of an impinging jet [1– 7], there has not yet been a study devoted to the thermal stresses induced on the target plate by an inclined impinging heating jet. Several systems, including welding, laser heating, and electric discharge machining (EDM), are similar to the impinging heating jet in terms of heat transfer to the target plate and consequently have akin temperature profiles. Yadav et al. [8] used the Galerkin finite element formulation to simulate the EDM-induced temperature and thermal stresses on a target plate. High temperature gradient zones were found to correspond to regions of large stresses that may exceed the material yield strength. Sunar et al. [9] analyzed the temperature and thermal stresses developed in a sheet metal due to welding. The thermal stresses were found to be compressive in nature and follow a trend similar to the temperature distribution due to the high gradients near the center. The present study is concerned with the thermal stresses developed on a flat plate, due to an impinging heating slot jet, and their variation with jet inclination. For fixed separation distance and Reynolds number, and selected jet inclination angles, the measured temperature data are used as input for thermal stress modeling, using the sequential coupling finite element method (FEM). For a given set of thermal boundary conditions, thermal stresses are calculated for various inclination angles and physical boundary conditions of the plate. The study is limited to the steady-state responses of temperature and thermal stresses.