The Problem

The operational costs of current Data Centers are rising with the increase in computing density and energy costs. High density computing places a significant amount of stress on modern Data Centers. Fully populated racks can draw between 6kW and 35kW of power per rack. Being that heat given off is proportional to the amount of power consumed, traditional cooling systems cannot efficiently meet the demands of growing data centers. The reason current cooling systems are so inefficient is because air itself is a thermal insulator. With a low level of thermal conductivity (0.025 W/m-K), air is a poor median for heat exchange.

Traditionally, Data Center cooling systems use Computer Room Air-Handlers (CRAH) to handle the cooling of multiple racks. These systems function in three phases: •First, server fans and heat sinks draw heat away from the components inside the individual servers.•Second, cooled air is delivered through a raised floor system forcing the hot air to exhaust through the ceiling, essentially utilizing the entire room as a heat exchanger.•Third, the hot air is interfaced with an external heat exchanger, usually a chiller, to be cooled and re-circulated

Our design reduces the number of exchange systems from three to two, and thus reduces the amount of power consumed by up to 12 percent. The system is contained to a modified rack in which antifreeze cools a nonconductive liquid that fills the rack. The antifreeze is then re-cooled by an external heat exchanger and once again pumped through the system.

The Solution

This new design allows for the servers to be completely immersed in a non-conductive fluid which is then interfaced with a heat exchanger, passing the heat into an external environment. Our ILC cooling solution also allows current data center to take advantage of the cost savings through seamless integration with current chilling

systems; which amounts to about 12% off of operational costs or ~ $8.6 million USD per year just by eliminating Computer Room Air Handlers. In addition to the new advances in green data center technology can save up to 30% of operational costs of a modern data center.

Background

Experiment

In order to show that Mineral Oil was a better median for heat transfer than Air we conducted an experiment where we applied a constant voltage and current to an electro thermal heating element in a solution of mineral oil, water, and finally air. As shown in the graph above, we found that the heating element heated up fasted in air, then water, and finally mineral oil,. This confirmed our hypothesis that Mineral Oil was a far better median for heat transfer than air, or even water.

Design Requirements•The cooling configuration and design should not impede the servicing of the encased IT equipment•The design should meet or exceed current server density per square foot•The unit should be able to be retrofitted into current data centers by making use of traditional water chillers•The fluid to be used must be a good electrical insulator as well as an excellent thermal conductor•The fluid must be non-volatile, highly resistant to thermal breakdown under expected operating conditions, and safe for contact with human operators

Heat Exchanger

& Coolant

Reservoir

Innovation & Design

Original Production Model

The original design shown above houses four 1U servers and three aluminum cooling plates. The servers are to be inserted back to back into the empty slots with the CPU facing the cooling plate. An external pump would then drive a cooled liquid solution of water or antifreeze through the cooling plates, drawing heat away from the system. The design was abandoned due to fabrication complexity and limited funding, however it is scalable to support real world implementation.

Microcontroller

The entire system is monitored and controlled by an Arduino microcontroller. The PID controller monitors the current temperatures at a number of critical points in the system. Based on the input temperature, the controller can vary the flow rate into the system thus maintaining a sustainable thermal environment for the enclosed servers.

Group Members: John Daily Jr.William BestNathaniel Slinin

Design Advisor:Dr. Stuart Tewksbury

Website:BridgingClouds.com

IMMERSIVE LIQUID COOLING