Thermo-Hydraulic Performance of Partially Blocked Metal-Foam Channels

Exponential growth of heat flux densities in commercial and industrial electronics, and compact heat exchangers demand surfaces and heat sinks with high dissipation rate capabilities. Among different technologies proposed to meet these demands, high-porosity metal foams have attracted the attention of many investigators due to their higher surface area densities as well as higher thermal performance due to the turbulence and tortuosity generated in the flow due to their structure. One of the disadvantages of such metal foams, however, is the attendant higher pressure drop or pumping power penalty. This thesis was undertaken to investigate whether channels partially filled with metal foams can reduce the required pumping power with a minimal loss in thermal performance. The thermo-hydraulic (T-H) performance factor J/F<sup>1/3, where J is the Colburn-J factor and F is the friction factor, was used to compare the relative performance of foams for various values of blocking fractions (B), where B is defined as the ratio of the height of the foam to the height of the channel. The metal foam samples considered were 10 PPI (pores per inch) 6101-T6 Aluminum, with porosity of ∼ 94 − 96%, and B of 1/6, 1/3, 2/3, 5/6, and 1. Each of these samples was attached to an aluminum slab embedded in one of the walls, which had a patch heater that acted as a heat source. A modification was made to all B < 1 configurations by attaching an aluminum plate on top, which then separated the foam-free and the foam-filled flows completely. These configurations are denoted by a 'P' in their names (e.g. B = 1/3P is the plated modification of B = 1/3). Experiments were conducted in an in-house designed wind tunnel, with a test section of 45" in length and a cross-section of 3"X3". Reynolds number (based on channel hydraulic diameter and inlet velocity) was varied from 1,000 to 15,000 to capture the flow domains from laminar to turbulent. The data obtained for the three scenarios namely - 1. Controlled-Flow Scenario 2. Pumping Power Variation with Temperature Difference, and 3. Fan-Based System were analyzed for their thermo-hydraulic performance. The extreme low blocking fractions are evaluated and compared against the dimpled/protruded surfaces, and were found to give superior performance, hence displaying potential as good turbulators. The plated configurations were found to perform better in almost all scenarios when compared to their non-plated counterparts. Furthermore, a new simplified analytical model is introduced that considers the flow in the partially-blocked region as two separate 'parallel' flows, one in the foam-free region and the other in the foam-filled region. The comparison between this novel approach and the analytical solution from the literature shows good agreement, suggesting that this simplified model may be appropriate. This model is then used for determining the foam-filled region flow ratios for the performed experiments, and a correlation is presented.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Mechanical Engineering

Department dc:contributor.department

Mechanical Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2023

Author dc:creator

• Sonavane, Prasad Deepak

Chair dc:contributor.committeechair

• Mahajan, Roop L.

Committee members dc:contributor.committeemember

• Boreyko, Jonathan B.
• Huxtable, Scott T.

• Metal Foams
• Heat Sinks
• Partially-Blocked Channels
• Thermal Management
• Electronics Cooling

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

vt_gsexam:36434

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/113602