Session: 05-03 Advanced Cooling Technologies 2

Paper Number: 97446

97446 - Computational Models of Additive Manufactured Heat Spreading Device for Enhanced Localized Cooling 

Our heat sink design uses round jet nozzles that impinge on a hot surface in efforts to cool hot spots. Two designs with different internal geometries are investigated. The internal flow in these geometries is dependent on various parameters. Hussain et al. [1] analyzed conventional design techniques with microchannel heat exchangers validating the influence of channel geometry on the performance of flow. Effectively optimizing channel geometry, they concluded the heat exchangers best performance was achieved when using circular channels. Marzec et al. [3] presented four different nozzle geometries to determine whether cylindrical or circular impingement nozzle configuration provides optimal flow characteristics and pressure drop.   

Jet impinging nozzle geometry influences fluid mixing paths, which, when optimized, increase the heat sink's heat transfer capacity. The study examines the effects of geometry-based optimization on a jet impinging heat sink design, focusing on the following: nozzle diameters, jet-to-jet spacing, nozzle aspect ratios, and nozzle impingement zone to target spacing. Based on our CFD model, we predict a reduction of pump power and an increase in thermodynamic efficiency.

The jet impinging heat sink design process is made more accurate, less costly and less time consuming by using CFD to develop a repeatable nozzle analysis process. The design process can provide jet array configurations with a variety of nozzle geometries. Various geometries of impingement zones (angles of separation, fluid velocity, jet impingement target distance) can be designed to achieve an optimal thermal performance efficiency operating with user-defined functions within ANSYS.

Our research aims to understand the direct effect of nozzle geometry on heat transfer at an impinging hot zone. We constructed configurations for uniform nozzle impingement zones and drafted outlet nozzle regions to determine when convergence occurs in design arrays the quickest. In areas of convergence, design comparisons showed that nozzle angles directly affect fluid flow behavior before and after nozzle elbows and changes in direction. Cross-flow mixing paths were found to be  influenced by channel cross sections as well as nozzle elbows, which provide optimal geometrical arrangements.           

In order to examine the effects of geometric parameters on jet array flow behavior, CFD simulations are conducted using the  k-epsilon turbulent model. Manifold control volumes of fluid that will flow and undergo convection are determined using user-identified boundary conditions. Internal manifold designs align nozzle locations with diode hot spots. Such alignments cater to the cooling of certain modules. In this device, jet impinging nozzles are aligned perpendicular to the hot spots. In a subsequent analysis, angled impingement zones shall be explored in order to determine the optimal sweep angle for each nozzle configuration as well as the performance of varying internal manifold models.

 The first generation AMHS device was tested using a flow loop setup, which allowed fluid to flow through its internal manifold. The fluid enters through the inlet of Figure 3 and travels through a circular channel, which directs flow into individual jet impinging nozzles. After entering the nozzles, water exits them by impinging on a surface, causing overflow into two outer channels that flow into a single outlet. This design encourages mixing flow paths that can be predicted with a computational analysis. We then study geometrical changes that increase flow performance and enhance pressure prediction on designs through computational experiments.

Currently, the investigation includes geometries with rounded nozzles and varying nozzle 'neck' angles. Simulations are conducted for jet Reynolds number (Re) of 12,000, nozzle diameter ranging from 14mm to 16mm, nozzle radius of curvature ranging from 8.5mm to 12.5mm and nozzle jet to jet spacing ranging from 20mm to 28mm.   When the impinging flow impacts the target surface, the velocity of the fluid throughout the AMHS will change. As a result, the speed, angle, and potential erosion of fluid flows are highly dependent on flow velocity. 

Presenting Author: Zion Clarke Howard University