Thermal Design & Thermal Loading Recommendations

This page explains how the passive cooling design of the cabinet works, gives some thermal load guidelines and summarises our recommendations on how to best configure equipment inside the AcoustiRACK® to optimise cooling.

How does Cooling Work in the AcoustiRACK®?

The equipment mounted inside the cabinet creates a low pressure area immediately behind the front door acoustic baffle, and a high pressure area immediately in front of the rear door sound baffle. Cool air is therefore drawn into the cabinet from the front, warmed by equipment, and expelled from the back of the cabinet around the rear door baffle.

Where necessary, for heavy thermal loads, this process can be enhanced by installing the Assisted Venting Roof (AVR) tray as an optional accessory (see the AcoustiRACK® Accessories page for more details). The AVR helps expel warm air in the upper parts of the cabinet behind installed equipment to the outside.

Thermal Guidelines

The passive air venting design of the AcoustiRACK® is driven by cooling fans inside the installed equipment or servers. This means the cooling potential of the soundproofed cabinet is related, in part, to the cooling efficiency of the various installed equipment, and the location/configuration of the equipment inside each cabinet.

As such, the thermal capacities given below must only be considered as guidelines to maximum thermal loading. The thermal capacity for each quiet cabinet is going to be as unique as the selected servers/equipment installed, and influenced by a number of other factors including arrangement, capacity, and the immediate environment.

Maximum Thermal Capacity Guidelines

	24U AcoustiRACK®	42U AcoustiRACK®
Product Code	AR-24U600x1000-G	AR-42U600x1000-G
Maximum Capacity* without Assisted Venting Roof	2.0kW	2.0kW
Maximum Capacity* WITH Assisted Venting Roof	3.0kW	3.0kW
This information is only a guideline for the systems being constructed and is not intended to be a substitute for system builder verification, validation, and testing on the reliability and effectiveness of a thermal solution. See the section 'Calculating Thermal Load' (below) for helpful comments on calculating thermal loads.
*The maximum capacity figures are based on the assumptions that the Thermal Recommendations (below) have been satisfied, namely that room temperature does not exceed 25°C, the AcoustiRACK® is fitted with front blanking plates blocking vertical gaps between equipment, equipment is mounted at the front of the cabinet, and no obstruction to free air movement into and out from the cabinet exist.

Thermal Recommendations

To achieve the best cooling efficiency inside the AcoustiRACK®, with or without the Assisted Venting Roof Tray, we recommend the following:

(i) Use of Blanking Plates for Empty Space

Ensure gaps between equipment in the front of the cabinet are filled using sound-proofed blanking plates wherever possible - this reduces re-circulation of warm air inside the cabinet. Blanking plates are available in 4U, 2U and 1U sizes, and add additional noise reduction because they are sound-proofed on the inside of the plate (using 7mm acoustic materials). Blanking plates are available as a reasonably priced optional accessory, because they are necessary for optimal thermal performance (see the AcoustiRACK® Accessories page for more details).

(ii) Mount Equipment towards the Front of the Cabinet

Ensure 19-inch equipment is mounted towards the front of the cabinet - which will also prevent air recirculation, and therefore maximize the cooling potential of the enclosure. The front vertical 19-inch steel brackets should be located in the front-most position (the first set of holes - as they are fitted upon delivery), and the rear brackets moved forward to adjust for different equipment depth if necessary. Avoid mounting equipment in both the front and the rear of the cabinet, unless equipment at the rear is very low thermal output and is not cooled using assisted airflow.

(iii) Air Conditioning/Room Temperatures

Ensure room air temperature does not range above 25°C if at all possible. Temperatures inside any air-cooled rackmount cabinet are directly related to the intake air temperature and therefore are dependant on the efficiency of any room/building air conditioning.

(iv) Allow Adequate Venting Space

Ensure the location of the AcoustiRACK® does not inhibit free air circulation in front, behind and above the cabinet. AcoustiRACK® cabinets can be co-located side-by-side to form a row of 19-inch low-noise enclosures. Locate the AcoustiRACK® enclosure in a space that does not have a heat-source nearby (such as a radiator). We recommend allowing more than 250mm free air space above the roof of the unit, unless there is a roof air conditioning facility (such as an air extraction unit/duct) directly above the cabinet. We recommend allowing more than 1m free space in front of and behind the quiet cabinet.

Calculating Thermal Load

This section aims to give comment on calculating thermal load, and provide some helpful links to key web resources.

Intel® Server Chassis SR2400 2U Technical information regarding maximum thermal loads is given in the majority of servers and 19-inch equipment documentation. It is noteworthy that the pace of change is high in the processor and memory market, and some thermal data may be out-of-date for some chassis given recent advances in chip and memory power.

See:

The total thermal load of a system is made up from heat directly dissipated from power-hungry components (such as central processing units - CPUs) and heat generated by losses that occur whenever electrical power is converted or transformed. The main processors in a system will normally account for the largest proportion of the total thermal load.

High-end CPUs can dissipate up to 110W per chip, so in a typical dual-processor server system this would equate to 220W for those infrequent periods of 100% CPU load. Although the thermal load at idle is variable between different processors, it is not uncommon for idle thermal dissipation to be up to 60% of the thermal guideline at 100% CPU load.

Overview of Server Processor Maximum Thermal Loads

Chip Manufacturer/Model	CPU Speed	Thermal Guideline (Max. Thermal Load)	Bus Speed	Cache Size	Manufacturing Process
Intel® Dual-Core Xeon®	3.0 – 3.76GHz	95-130W	667-1066MHz	4Mb	65nm
Intel® Xeon®	3.0 – 3.8GHz	110W	800MHz	2Mb	90nm
	2.8GHz	77-110W	533-800MHz	1-2Mb	90-130nm
	2.6GHz	60-71W	400MHz	512Kb	130nm
	2.4GHz	65-77W	400-533MHz	512Kb-1Mb	130nm
	2.0GHz	58W	400-533Mhz	512Kb	130nm
AMD Dual-Core Opteron™	2.6GHz	95-110W	n/a	2Mb	90nm
AMD Opteron™	2.8GHz	93-104W	n/a	1Mb	90nm
	2.6GHz	93-104W	n/a	1Mb	90nm
	2.4GHz	55-85W	n/a	1Mb	90-130nm
	2.0GHz	55-89W	n/a	1Mb	90-130nm
See Intel and AMD websites for figures relating to exact processor models. Links to specifications for the most popular server/workstation processors are given below.

Other contributions to thermal load occur from losses in the transformation of AC into DC power, and also in the voltage regulation modules (VRMs) on the system board that provide power to CPUs and other processors. Electrical power will eventually be transformed and, to a large extent disseminated as heat in a given system, so the total thermal load can be estimated from the electrical load.

Therefore, a fairly accurate estimation of the total thermal load for a system can be obtained by adding together the electrical power consumption of CPUs and other significant components, such as graphics processors (GPUs – not common in server systems), memory (DIMMs), and hard disk drives (HDDs).

Of note, is the recent emergence of Fully Buffered Memory Modules (FB-DIMMs) that have a much higher heat dissipation requirement than memory modules have previously required. Other components such as Hard Disk Drives (HDDs) can also make a significant contribution, particularly when they are present in high numbers as in storage systems.

The thermal load of a system is dynamic – it will vary with time given the processing load and other activities such as HDD read-write cycle activity.

Web Resources:

The Intel and AMD websites provide key thermal specification data and white papers of interest.

Intel

Intel® Processor Specification Finder: for the Xeon® single and Dual-Core Xeon® family of server/workstation processors

AMD (Advanced Micro Devices Inc.)

AMD Opteron™ Processor Specifications for Servers/Workstations at-a-glance
AMD Opteron™ Processor Information
"Power and Cooling in the Data Center" - Addressing today's and tomorrow's challenges with the AMD Opteron™ processor and AMD PowerNow!™ technology with Optimized Power Management (OPM) - 2005

Further Technical Support

If you have any questions regarding thermal loading, the configuration of your equipment inside an AcoustiRACK® quiet cabinet or any other technical questions please contact us by our contact page or email technical@acoustiproducts.com.

Thermal Loading Disclaimer

Whilst every care has been taken to produce a set of acoustic materials and cabinet design that will be appropriate for the majority of equipment configurations, it is the responsibility of the system builder/administrator to thoroughly test and monitor installed equipment including environmental parameters such as temperature. All equipment installed inside an AcoustiRACK® is done so at the risk of the installer.

Page Updated: April 5th, 2006

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