Optimization Arrangement of Two Pulsating Impingement Slot Jets for Achieving Heat Transfer Coefficient Uniformity

Abstract

In this paper, an optimization was performed to achieve uniform distribution of convective heat transfer coefficient over a target plate using two impinging slot (air) jets. The objective function is the root mean square error (Erms) of the local Nusselt distribution computed by computational fluid dynamic (CFD) simulations from desired Nusselt numbers. This pattern search minimized this objective function. Design variables are nozzle widths, jet-to-jet distance, jet-to-target plate distance, frequency of pulsations (for pulsating jets), and the flow rate. First, an inverse design is performed for two steady jets for simplicity and the obtained errors for three different desired Nusselt numbers, NuD = 7, 10, and 13, were 20.73%, 20.08%, and 22.92%, respectively. Uniform distribution of heat transfer coefficient for two steady jets was not achieved. Thus, two pulsating jets are considered. The range of design variables for pulsating state is as same as steady-state and heat transfer rates increased about 400% over steady-state due to the effects of pulsations in inlet velocity. Thus, in the pulsating state, optimization must be performed for the desired Nusselt numbers around four-times NuD in the steady-state, i.e., NuD = 28, 40, and 52. The Erms reduced less than 0.01% and distribution of heat transfer coefficient for all cases was uniform. An experimental study using an inverse heat conduction method (conjugate gradient method with adjoint equation) has been performed and the experimental results for the case of NuD = 52 are presented. The estimated distribution of Nusselt number on the target plate with the numerical distribution has around 3.2% relative error with optimal configuration.

A detailed analysis of flow and heat transfer characteristics under a turbulent intermittent jet impingement on a concave surface

“…It was shown that the Nusselt number of a surface with the lower curvature was higher than the other one. Twin jets were employed by Farahani et al [13] to uniform the heat transfer coefficient distribution (HTC) on a flat surface. They evaluated the variation of the inlet nozzle width, jet-to-surface and jet-to-jet distances, pulsation frequency, and Reynolds number on heat transfer.…”

Estimation of distribution of moving heat source during milling of AISIH13 by inverse heat conduction method

“…Due to limitations and difficulties of direct measurement at the interfaces, inverse methods are suitable to estimate temperature and heat flow at the tool/work-piece interface. The inverse heat conduction problem involves parameter estimation (Kowsary and Farahani, 2010;Farahani et al, 2011) using some temperatures measured from locations within or on the surface of the body, and inverse design (Farahani et al, 2016). IHCPs are highly sensitive to random noise, inherently based on measured temperature data.…”

Interaction of dual sweeping impinging jets at different Reynolds numbers

“…1, a secondary stagnation region with an upwash flow may appear in the space between the jets, hindering the impingement effect (Can 2003;Hewakandamby, 2009;and Chander and Ray 2007). For this reason, unsteady jets with optimized phase differences are introduced, including pulsed jets (Hewakandamby, 2009 andFarahani et al, 2016) and synthetic jets (Greco et al, 2016;105105-2 Wen et al Phys. Fluids 30, 105105 (2018) FIG.…”