This study concerns the flow and heat transfer characteristics of a turbulent submerged circular air jet impinging on a horizontal flat surface when free stream turbulence exceeds 20 percent. The turbulent fluctuations of the free stream velocity are the primary aerodynamics influencing heat transfer. Two regions with distinct flow characteristics are observed: the stagnation region, and the wall-jet region. According to the linear form of the energy equation, the surface heat flux may be decomposed into laminar and turbulent components. An inverse methodology can determine the turbulent component of the heat transfer coefficient in the stagnation region and in the wall-jet region as a function of the root mean square value of the fluctuating component of velocity in the bulk flow direction.

An atomizer is a helpful tool that can be used to tailor the cooling rate of steel from the processing temperature in order to get desired properties. It is important to determine the temperature distribution in a specimen subjected to cooling by an atomized spray. A finite-element model for transient heat transfer and thermal-stress analysis is developed to determine the temperature and thermal-stress distribution. The results of the finite-element heat-transfer model are compared with a finite-difference model. The heat-transfer model describes the heat-transfer processes in an AISI 4140 steel cylinder subjected to controlled atomized spray cooling from an initial temperature of 1273 K. The temperature fields predicted by the model are used both to predict the resulting microstructure using continuous cooling transformation (CCT) diagrams and as an input for the thermal-stress model to predict the occurrence of quench cracks. The thermal-stress model incorporates temperature-dependent material properties, heat generation due to phase changes, elastoplastic behavior of steel, and the volumetric expansion associated with the formation of martensite. The results of the finite-element model are verified experimentally by recording temperature profiles, obtaining micrographs, and recording the occurrence of quench cracks.

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The solutions of the Inverse Heat Conduction Problem using the Monte Carlo method, Green’s Function Solution Equation and the Alternative Green’s Function Solution Equation are compared. The Monte Carlo method is a simple technique that provides a method of determining the source of error and placement of sensors. However, in comparison with the exact solution, if attainable, the cost is a higher error in the solution. All the three methods use the function specification method in the sense that a functional form for the surface heat flux or temperature is assumed and the parameters defining the function are evaluated by minimizing the error functional. In the alternative method, the functional form also satisfies the boundary conditions, the unknown quantity in the problem. The input data for this comparison are experimentally measured temperatures in a stainless steel disk subjected to spray cooling.