Session: 15-01-01: ASME International Undergraduate Research and Design Exposition

Paper Number: 100541

100541 - Enhancement of Two-Phase Immersion Cooling Using Submerged Synthetic Jet​ Impingement on Simulated High-Power Electronic Components​ 

Motivation and purpose of the research:

Electronic systems used in data centers and computing applications include high-performance servers that contain CPUs, GPUs, and power distribution elements. As the computing processors get faster, their power dissipation increases in direct proportion. Liquid cooling has emerged as the next step in the evolution of cooling technologies for high-performance electronics. There are two primary liquid cooling methods. (1.) Indirect liquid cooling involves placing a cold plate on top of the hot component and circulating liquid through it. (2.) Direct liquid cooling involves immersion cooling in which the entire server is fully immersed in dielectric fluid.

Contribution of the work toward advancing science and engineering:

The current project investigates the improvements to two-phase immersion cooling, in which the dielectric fluid is allowed to “boil” on the high-power component surfaces. Boiling occurs on the hot surface, causing vapor bubbles to form. The bubbles leave the surface by their own buoyancy, and fresh liquid flows in to replace the departing vapor. This research is investigating the enhanced performance of two-phase immersion cooling by forcing a liquid jet to impinge on a boiling vertical heated surface using a synthetic jet approach. The figure of merit will be the heat transfer coefficient on the boiling surface, defined as h = q"/(T_surface-T_sat).

A synthetic jet is a jet formed by providing a time-dependent flow into and out of a nozzle submerged in the fluid. The nozzle expels a jet flow in the forward stroke half cycle and ingests inflow during the backstroke half cycle. This periodic flow has no net mass flux but a positive momentum flux. A reciprocating piston connected to a nozzle is used to create synthetic jets. Our hypothesis is that the impinging jet will force the bubbles off the surface at a faster rate, thus accelerating the cycle of bubble formation which controls pool boiling. The objective of this experiment is to systematically evaluate the efficacy of submerged jet impingement on increasing two-phase heat transfer by documenting the increases in the heat transfer coefficient as a function of target heat flux and synthetic jet frequency, amplitude, and distance from jet to target.

Methodology used:

1-Design and prepare a tank made of polycarbonate sheets, a Kapton Polyimide heat source, a copper block, a condenser, a Bakelite block, 3M Novec 7100 Engineered fluid, a circulating bath, and type-K thermocouples.

2-Connect the circulating bath to the tank and a small pump. Attach the condenser to the lid of the tank and a Bakelite piece to the side of the tank to hold the heat source.

3-Connect the heat source to a data acquisition system, a power supply, and a shunt resistor.

4-Design and fabricate a reciprocating piston using PVC and a motor. Connect a nozzle to the piston to impinge onto the heated surface.

5-Use type-K thermocouples to measure the fluid temperature near the heat source and the surface temperature of the copper heat source.

6-Operate the system and study the efficiency of the synthetic jet for enhancing heat transfer during immersion boiling.

Preliminary results and conclusions:

An experimental apparatus consisting of a liquid tank, a condenser, a synthetic jet, and a target heated surface was designed and fabricated. Experiments are being conducted in water over a 1-inch x 1-inch copper surface suspended vertically in the water. To validate heat transfer coefficient measurements, experiments are conducted in a natural convection flow on a heated vertical plate without pool boiling. The measured heat transfer coefficients are within 15% of the expected empirical correlation for a vertical plate in water. Experimental measurements are underway in pool boiling both with and without the impinging synthetic jet. Video observations have shown that the synthetic jet has an immediate effect of enhancing heat transfer. Measurements of the heat transfer coefficient over a range of operating conditions for boiling and for the synthetic jet parameters are in progress.

Presenting Author: Elsaid Youssef Villanova University - College of Engineering

Presenting Author Biography: Elsaid Youssef is a mechanical engineering and research student at Villanova University with a minor in mechatronics. Elsaid is a dedicated, conscientious, and diligent student. He joined the Laboratory for Advanced Thermal and Fluid Systems to work with Dr. Alfonso Ortega’s team during his first year at Villanova University showing his inquisitiveness about advanced system-level and component-level thermal management. He is a Villanova Undergraduate Research Fellowship and Research Match Program scholar. Elsaid began his journey in the lab by assisting in building a thermosyphon system and a two-phase cooling system using cold plates and different refrigerants. He also joined the NovaVENT Project Sensor Development Team of Villanova to work on a low-cost, easily manufacturable ventilator in response to the COVID-19 pandemic. Elsaid is currently leading his research in the Center for Energy-Smart Electronic Systems (ES2) to investigate the “Enhancement of Two-Phase Immersion Cooling using Submerged Synthetic Jet Impingement on Simulated High-Power Electronic Components”.

Authors:

Elsaid Youssef Villanova University - College of Engineering
John Schofield Villanova University
Alfonso Ortega Villanova University - College of Engineering