Submittal

WW-CPWP-09, Rev.0, 09/2009

Deploying a Vertical Exhaust System

to Achieve Energy Efficiency and Support Sustainability Goals

In a raised-floor environment with ceiling returns, CRAH units distribute cool air underneath a raised floor,

allowing air to enter the room through perforated floor tiles located in cold aisles. Active equipment within

cabinets is positioned such that the equipment fans draw cool air through the equipment from the cold-aisle side

and release exhaust into the hot aisle at the rear. Finally, the equipment exhaust air exits the room and returns

back to the CRAHs via a ceiling plenum and return ducts.

The current trend in data centers is toward greater equipment densities, and these higher densities are pushing

the capability of raised floor cooling systems to their limits. Raised floor systems with ceiling returns can

typically deliver enough air to remove 7-8 kW of heat per cabinet, provided that the CRAH units have adequate

thermal capacity and best thermal management practices are employed. These best practices include a 24-36

inch (60-90 cm) raised floor height, a hot aisle / cold aisle arrangement for cabinet rows, properly sized

perforated floor tiles or grates, a proper return airflow path, proper positioning of power and data cables, and the

use of raised floor air sealing grommets and blanking panels.

Data center consolidation and virtualization efforts are resulting in higher density cabinets with each cabinet

holding several servers. These high server densities can generate heat loads of 8-12 kW per cabinet; and as

equipment is added and upgraded, especially high heat-generating blade server configurations, cabinet heat

loads can exceed 25 kW. Without effective thermal management strategies in place risks multiply quickly:

• Increased risk of downtime and lost revenue due to equipment failures

• Reduced Mean Time Between Failure (MTBF)

• Increased costs associated with maintenance

• Increased operational expenses due to overcooling

Innovative, Cost-Effective Improvements in Data Center Cooling

Budget constraints and escalating energy costs are forcing data center stakeholders to review all available heat

removal options in order to improve operational efficiency and maintain business continuity. UPI-based cooling

conservation solutions are finding increasing adoption in data centers as a reliable, cost-effective and eco-

friendly option for addressing high heat loads. These innovative solutions use precision cooling techniques to

optimize airflow and protect active equipment without adding power-hungry cooling units that drive capital costs

up and introduce additional operational costs (see Table 1 for a quantitative comparison).

Table 1. Comparison of Supplemental Cooling Methods in the Data Center

Method Capital Costs Operational Costs Points of Failure

Passive Systems $ None None

In-Cabinet Fans $$

3 3

Overhead Cooling Units $$$

3 3

Rear Door Heat Exchanger $$$

3 3

Boost CRAH Capacity $$$

3 3

As part of a holistic UPI-based approach, precision cooling elements can be planned and deployed from initial

startup or modularly added when needed, enhancing agility by integrating with existing cabinet layouts to allow

cooling capacity to scale as business requirements change and grow. This flexibility allows data center

stakeholders to provision equipment as needed without adding CRAH units or overtaxing the raised floor

cooling system.