An "Open Access Project" Update

The Mestex "Open Access Project" continues to move forward so I thought I would provide a brief update on the current research activity and the plans for the next few months.

The installation at the Mestex facilities in Dallas has been brought up to the expected final configuration with a total of 120 servers, intelligent PDUs, and switches distributed over 4 cabinets.  We have separated the hot and cold aisles with a combination of a hard wall and flexible "curtains"...this has turned out to be one of the more important features of the installation.  The indirect/direct evaporative cooling system is fully functional although we have also found the need to increase the hot aisle exhaust pressure relief in order to reduce the "back pressure" in the hot aisle. 

In addition to the combination temperature and humidity sensors that are part of the standard Aztec control system, and used by the DDC control system to manage the operation of the Aztec unit, we have also installed 32, 10K thermistors.  These sensors are used to feed information to our data acquisition system that is running in the background collecting more granular detail about the system performance.  These sensors are located on the fronts and backs of the cabinets.

As I mentioned, we have spent some time resolving hot aisle/cold aisle separation issues.  Although the Aztec unit is monitoring cold aisle pressure and operating the supply fan to maintain a target positive pressure in the cold aisle we found that we still had hot aisle air migrating back into the cold aisle.  Over the last few days we have spent time filling small gaps and sealing around the cabinets more carefully and the results were immediately noticeable.  The cold aisle temperature was reduced by 5 to 6 degrees F. 

The other factor contributing to better separation was the reduction of the "back pressure" in the hot aisle.  We had addressed some of this earlier by removing the standard room exhaust grill and replacing it with a screen that had much greater free area.  While that made a measureable difference in server temperature rise we had simply moved the pressure issue from inside the data pod to the return air ductwork on the Aztec unit.  That has now been resolved by doubling the size of the pressure relief openings in the return ductwork.  Supply fan operation is now improved, server temperature rise is now on target, and supply fan motor power consumption has been reduced.  We monitor and report real time PUE for the pod and these changes have lowered the real time PUE to between 1.08 and 1.35, depending upon the system operating mode.

Now that we are beginning to see the kind of stable operation that we were anticipating we have started to plan the next phases of the research.

The Aztec unit is designed to operate in three modes, or some mixture of those modes, depending upon the sensor inputs.  The unit can operate in 100% fresh air cooling mode, in an indirect evaporative cooling mode, or in an indirect/direct evaporative cooling mode.  Each of those modes introduces characteristics that the data center industry wants to research. 

The next round of research will focus on two aspects of fresh air/evaporative cooling:

  • We will be installing coupons in the space to collect data on contaminants and their potential impact on the circuits in the servers.  This project is projected to run for at least 1 month and support is being provided by IBM.
  • Following the collection of this data (and possibly overlapping) we will be installing particle count measuring devices.  These devices will be installed upstream of the filters in the Aztec unit, downstream of the filters, within the cold aisle, and within the hot aisle.  The filter racks in the Aztec unit will allow us to evaluate filters of different MERV ratings and see how well they perform in a typical HVAC unit installation versus the controlled lab environment.

As you can tell, this site offers a unique opportunity for researchers to take their lab research findings and compare them to a real world application with real world equipment.  Mestex is pleased to be a part of this NSF sponsored research into data center cooling technologies.  We will be hosting a tour for the industry advisory board of the NSF-I/UCRC during their upcoming meeting at the University of Texas at Arlington.

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