Keeping pace

A peek inside a pair of high-tech facilities reveals plumbing and HVAC strategies that integrate successfully with technology-driven projects
August 11, 2010

As the march of technology advances, it's a constant curve to deliver buildings capable of meeting end users' needs. Nowhere is this more telling than in computer-intensive facilities such as telecom and data centers, hospitals and research laboratories where state-of-the-art equipment is sometimes outdated by the time it's actually installed. Some things, however, are constant: the need for water and heating and cooling. And although these mechanical systems tend to be fairly unchanging as far as the technology curve, high-tech facilities often demand greater results than what can be produced via traditional plumbing and HVAC practices. But the design community has responded, as the following examples illustrate.

Concrete plumbing solution

Located on the campus of the University of Wisconsin in Madison, the Waisman Center has been involved in multidisciplinary research for developmental disabilities for 30 years. Calling it a multiuse facility is an understatement. The first floor alone houses a magnetic resonance imaging scanner, a positron emission tomography scanner and a linear accelerator. The second floor contains an auditorium, lecture halls, administrative services and the main mechanical equipment room for a new tower addition. Auditorium and mechanical space occupy what would be the third floor, and the fourth floor is a biomanufacturing facility where products for clinical phase-one trials are made. The fifth and sixth floors include bench laboratories and support spaces, including researcher offices and warm and cold rooms.

Although it might be one of the least important functions one would associate with such high-tech equipment, the plumbing system is the core for all of the building's operations, at least when in came to the center's latest addition. According to Tom Boehnen, with Madison-based mechanical/electrical/plumbing engineer Arnold & O'Sheridan, the building team could not think just about one floor. Rather, the interrelation of all functions and spaces had to be at the forefront of planning. Expansion also had to be factored in.

Furthermore, he says a solid plumbing scheme was critical because much of the building's piping systems would be locked in concrete. The existing building's structural system — which uses concrete waffle slabs — was not carried into the addition. Collaboration with the architect, Bowen, Williamson and Zimmerman, Madison, and structural engineer SRI Design, Madison, became critical and resulted in a concrete joist system that allowed greater integration of the horizontal plumbing distribution necessary to reach the various lab locations without compromising valuable ceiling or floor space.

For example, branch plumbing drain lines are installed in the depth of concrete joists. Plumbing systems, themselves, include piping for domestic hot and cold water, purified water, specialty gases and nuclear injectables, as well as vacuum systems and steam piping.

The piping networks are accommodated by a central vertical riser near the elevator. Collector mains and stacks for chemical drain lines were purposely located on the outside walls at columns, says Boehnen, and the structural design accommodates stack location by connecting concrete joists on the side of the columns. This arrangement leaves a space at the column face to sleeve the stacks through the floor.

Plumbing and piping systems above the first floor are distributed through floor trenches, access flooring and suspended ceilings. Throughout the rest of the building, plumbing and piping systems have vertical risers and horizontal distribution above suspended ceilings. Plumbing stacks are located at permanent vertical elements such as columns and elevators, so that if functions in the building change, the plumbing stacks won't need to be relocated. (For more on the lab specialty piping systems, visit www.bdcmag.com.)

Tower of Cool

Another building type constantly fighting to keep abreast of the technology curve is the telecom/data center. Having experienced this firsthand, RTKL Associates Inc., Baltimore, has adapted its design technology to better serve clients needs.

"Server room cooling systems have remained virtually unchanged since the inception of the raised floor," says Stephen Spinazzola, an RTKL vice president. "Traditional methods of cooling data centers are no longer adequate to keep pace with the increasing power and heat load densities we're seeing today and expect to see moving forward."

Indeed, he points to anecdotal evidence which shows that conventional data-center cooling design becomes ineffective as power density exceeds 150 watts per square foot — or approximately 3.8 kilowatts per computer/equipment rack. With this in mind, RTKL proceeded with a plan to raise the cooling effectiveness of air-conditioning systems for data centers and computer rooms. The result is a custom computer rack, dubbed the "Tower of Cool" (TOC), that conveys cool air directly to electronic equipment via specially designed doors. Specifically, Spinazzola explains the computer rack isolates the heat load of the electronic equipment from the rest of the space. "Conveying cooling air directly to and from the electronic equipment, instead of mixing the cooling air in the space to cool the electronic equipment doubles the cooling effectiveness of the air-conditioning equipment," he says.

After picking up equipment heat, return air discharges from the TOC directly to a ceiling plenum where it is conveyed to a computer room air-conditioning unit (CRACU) — units designed and manufactured specifically for the raised-floor data-center environment.

Spinazzola notes this increases the effectiveness of the cooling system because standard temperature air can be used to cool equipment, but higher temperature air (around 95 F) returns to the CRACU. This is so because heat transfer across the cooling coil of the CRACU is raised by a process known as high Delta-T cooling (HDTC) (see "Typical computer room using high Delta-T Cooling," page 44).

Conventional data-center air-conditioning design, adds Spinazzola, delivers 55 F air to the space that houses electronic equipment, where it mixes with 110 F air discharged from the equipment, producing approximately 70 F air to cool equipment. Air returns to the CRACUs at approximately 75 F.

That 20-degree differential, says Spinazzola, means each CRACU can provide twice the cooling heat transfer for the same airflow. In other words, the number of CRACUs for a particular facility can be reduced by half. This, of course, leads to significant reductions — as much as 16 percent — in operating costs for a data center's cooling plant, and as much as 7 percent in construction costs because less overall space is required, he says.

According to its testing, RTKL claims the HDTC concept is effective in cooling approximately 7.4 kilowatts of electronic equipment in one rack, and that the TOC can operate without adverse effects through normal day-to-day operations of an active data center. This, of course, begs the question as to how such testing translates into real-world numbers and benefits. With that in mind, the firm developed a cost model based on a server farm prototype it designed for a large telecommunications company in 1999 (see table, opposite).

The use of HDTC, according to Spinazzola, should allow electronic equipment density to increase as the result of more effective cooling. Therefore, for this analysis, he says, two circuits per cabinet, consuming approximately 191 watts per square foot — a 38 percent increase above the base prototype — were used to reflect the increased density of equipment.

RTKL also used the size of the electrical service for the electronic equipment to serve as the constant between the base and the HDTC alternate. Spinazzola says this was decided because electrical service is typically the highest cost element of such projects. The variables, he adds, are the size of the building, the number of cabinets and the size of the cooling plant, given the associated quantity of electronic equipment circuits is also constant.

In the test case, calculating the electrical service size to be fixed at 6,600 circuits, and using two circuits per cabinet in the HDTC prototype, Spinazzola says the cabinet count was reduced by more than 1,500 from the base prototype. Additionally, the implementation of the HDTC prototype would also reduce the quantity of CRACUs from 122 to 61. This, he says, not only lowers the cost of the mechanical system, but also brings down the cost of the electrical system significantly. Furthermore, he argues the use of HDTC technology — at least in this case — would reduce power requirements by approximately 450 kilowatts.

Of further benefit, Spinazzola postulates the reduction of CRACUs will reduce the size of data center chiller plants by reducing fan motor heat. The test case resulted in a net reduction in the power requirements of approximately 360 kilowatts. These combined factors resulted in a total power reduction of 810 kilowatts.

"The bottom line is that the TOC concept will allow owners and operators of data centers to install more electronic equipment into each TOC and cool it more effectively and efficiently," says Spinazzola.

         
 

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