Data approach, at the cost of wasted

Data centers are
computing infrastructure facilities that house large amounts of information
technology (IT) equipment used to process, store, and transmit digital
information. This equipment
is housed within electronic cabinets or racks of standardized dimensions.
Data centers need power equipments to maintain reliable and high-quality power
as well as HVAC to maintain the proper temperature and humidity conditions
within the facility. Presently, data centers are managed based on best
practices, which often lead to an overly conservative thermal management
approach, at the cost of wasted cooling resources. Reducing energy consumption
and carbon footprint of data centers, on the other hand, requires fundamental
principles based approach. The data center manager now has to supplement prior
experience with conceptual understanding of heat transfer, fluid flow,
thermodynamics, computational modeling, metrology, and
data acquisition and processing. The electrical power consumed by the IT
or telecommunications equipment is converted entirely into heat and must
ultimately be rejected to the environment. Since the  beginning of 
the  past decade,  the 
American Society  of  Heating Refrigeration and Air-Conditioning
(ASHRAE) has played a pioneering role in identifying the trends in power
densities, operating environmental guidelines, and cooling of data centers.
This has been pursued through the formation of a technical committee (TC 9.9) dedicated to
identifying and updating emerging environmental and heat load requirements and
best energy management practices for mission critical IT equipment and
facilities. An early survey of multiple equipment manufacturers of IT
and telecommunications equipment resulted in the historical trends and power
density projections, showed in Figure 1 1.

Figure 1. Power dissipation projections for various IT racks or cabinets; adapted
from 1

 

Guidelines for
air-cooled data centers specifying dry-bulb air temperature and relative
humidity levels at the inlets of the IT equipment have been a focus of the
ASHRAE TC 9.9 Committee. In 2011, ASHRAE further revised the guidelines and
enlarged both the “recommended” and “acceptable” regions of
operation 2. This expansion allows for reduced energy consumption for cooling
as well as extension of conditions for which “free cooling” such as
the use of economizers is possible. These regions are shown in Figure 2.

Figure 2. ASHRAE environment
guidelines for the cooling air at the inlet of IT racks 2
 

Physical access to
operating data centers for the purpose of thermal characterization is usually limited
due to security and high reliability constraints. Also, large variations in
data center architectures limit the extendibility of measurements across
facilities. As a result,
the most common characterization approach utilizes computational fluid dynamics
and heat transfer (CFD/HT) to predict airflow and heat transfer. These
simulations can enable identification of potentially dangerous local hot spots
and provide rapid evaluation of cooling alternatives, as the facility IT loads
or equipment change. With
continual upgrades, the optimal arrangement of new heterogeneous IT equipment
needs to be determined to minimize its effect on neighboring equipment.
Additional constraints imposed by the grouping of IT equipment by functionality
and cabling requirements often conflict with thermal management strategies and
data center managers need to provide localized supplemental cooling to
high-power racks. Thermal simulations are the best way to determine these
requirements.

The first published
results for data center airflow modeling appeared in 2000 3. The various CFD/HT
modeling efforts since then have ranged from individual component modeling to
rack and power layouts and can be classified into the following main categories
4:

1. Raised floor
plenum (RFP) airflow modeling to predict perforated tile flow rates

2. Thermal
implications of CRAC and rack layout and power distribution

3. Alternative
airflow supply and return schemes

4. Energy
efficiency and thermal performance metrics

5. Rack-level
thermal analysis

6. Data center
dynamics: control and lifecycle analysis.

Figure 3
presents a summary of the various types of thermal modeling activities
undertaken for data centers 4. The three main thrusts are evaluation of  global 
cooling  schemes,  investigating 
the  effects  of 
local  and  supplemental cooling schemes, and improving
energy efficiency at all levels of the data center.

Figure 3. Data center
thermal management organizational chart 4

 

This study is to 3D
modeling of cooling process in a sample data center. It is really important to review international
design standard and air?ow performance index at first, in order to objectively
evaluate data center’s air distribution efficiency. Different design
alternatives based on the standard module can be analyzed, such as cooled air
supply and return location, raised ?oor height, ceiling height etc., and
cooling systems variables, such as CRAC unit’s supply air temperature, physical
containment of cold aisle or hot aisle, etc, but we tried to model actual
situation of room.  Sample center
properties, are adjusted for Computational Fluid Dynamics (CFD) simulations including
standard modules. Last, air management system’s performance is derived and
compared with experimental data.