Patent Application
20160081220
The present disclosure relates to airflow cooling of rack mounted electronics.
In a front-to-back air cooling network rack, holes are strategically placed in the faceplate of network line cards to allow cooling air to enter the line cards. One design challenge is to provide sufficient cool air into the system with maximum input/output (I/O) ports and adequate electromagnetic interference (EMI) containment. As the performance of integrated circuits and processing power increases, the balance between port count and perforation size/area forces a tradeoff between switching capacity and thermal management. For a given footprint, such as a one rack unit (RU) line card, as the port density increases, the area available for perforations in the faceplate decreases, and less cool air is able to be drawn into the system.
An apparatus is presented herein comprising a frame and one or more heat generating elements supported by the frame. A plurality of ports are located at the front portion of the frame, and are electrically coupled to the heat generating elements. A faceplate is coupled to the front portion of the frame and includes one or more port openings to allow access to the ports and a plurality of airflow openings. Each of the airflow openings comprises a bottom edge aligned with the front portion of the frame and a top edge aligned with the top portion of the frame The top edges of the airflow openings are set back a predetermined distance from the front portion of the frame.
One factor in bringing cooling air through a faceplate in a rack mounted electronics system, such as a network line card, is the projected intake area. A higher projected intake area permits a lower pressure drop and a higher airflow rate through line cards mounted in a rack. One example of an intake area comprises slots stamped into the faceplate of the line card, e.g., above the ports of the line card. According to the techniques presented herein, the projected area is increased by retracting the top edge of the intake slots. In another example the projected area of stacked line cards (e.g., line cards mounted above and below each other in a rack) is increased by chamfering the bottom of the faceplate, which is aligned with the intake slots of the line card below.
The design of the faceplate described herein provides approximately a 20% improvement on the pressure drop at the intake due to the increased area of the intake slots. The chamfered bottom of the faceplate contributes approximately an additional 5% improvement. The electronics modules described herein fully utilize the effective intake area of the faceplate without sacrificing electromagnetic interference (EMI) performance. The faceplate allows maximum Input/Output (I/O) port count or signal capacity, while minimizing any thermal choking concerns. Additionally, the faceplate design described herein minimizes costs due to the lack of costly additional features, e.g., hex honeycomb air intake holes, custom EMI shielding gaskets, and/or computer numerical controlled (CNC) machining.
Referring to
An EMI shield 140 drops down onto the top of module over the ports 120 and prevents unacceptable levels of EMI from passing through the relatively large intake slots 115. The EMI shield 140 presses down against an EMI gasket on the inside front of the faceplate 110 and on top of the cage that surrounds the ports 120. Heat generating elements 150, such as a central processing unit (CPU), are coupled to the PCB 105. Heat sink 155 is placed in thermal contact with heat generating element 150 to provide a larger surface area for cooling air to interact with.
Referring to
Faceplate 110 also includes one or more openings 220 to allow access to elements (e.g., ports 120) on the electronics module 100. Webbing 225 may provide structure for the faceplate 110 on the sides of the openings 220, and may include air intake holes to provide some cooling air into the electronics module 100. Rack-mount locking mechanisms 230 may be attached to the faceplate, and secure the faceplate 110 and the attached electronics module 100 to an electronics rack.
Referring to
The corner where the front face of the faceplate 110 and the bottom face of the faceplate 110 is replaced with a chamfer 240 that extends from a predetermined point on the front face to a predetermined point on the bottom face. In one example, the chamfer 240 is a linear chamfer, extending from a point 0.1 inches up from the bottom face along the front face to a point 0.38 inches back from the front face along the bottom face. In other examples, the chamfer 240 may be a combination of multiple linear segments, or the chamfer 240 may be non-linear. The chamfer 240 allows a larger opening for air to enter an electronics module positioned below the current electronics module, as will be discussed below with respect to
In one example, the faceplate 110 shown in
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Another measure of the improved pressure drop characteristics is the increase in volumetric flow rate that a lower pressure drop allows. Table I shows the overall pressure drop and the volumetric flow rate of air through an individual electronics module with intake slots modified as described herein. The volumetric flow rate of air is given in units of cubic feet per minute (CFM) and the pressure is given in inches of water gauge (in. w.g.). The flow rate through the module with modified intake slots is approximately 20% higher than that typically achieved at normal operating conditions for network line cards.
Referring to
In summary, the techniques presented herein maximize the projected intake area on the faceplates of electronics modules, such as network line cards, by enlarging and retracting the slots on top of the faceplate along with chamfering the faceplate's bottom edge. The increased projected intake area permits high air flow rates and lower pressure drops within the system. This allows more space for ports on the faceplate without sacrificing the ability to provide cooling capacity to heat generating elements, such as processors, memory, or application specific integrated circuits (ASICs).
In one example, the techniques presented herein provide for an apparatus comprising a frame and one or more heat generating elements supported by the frame. A plurality of ports are located at the front portion of the frame, and are electrically coupled to the heat generating elements. A faceplate is coupled to the front portion of the frame and includes one or more port openings to allow access to the ports and a plurality of airflow openings. Each of the airflow openings comprises a bottom edge aligned with the front portion of the frame and a top edge aligned with the top portion of the frame. The top edges of the airflow openings are set back a predetermined distance from the front portion of the frame.
In another example, the techniques presented herein provide for a system comprising an electronics rack to hold a plurality of electronics modules. Each of the electronics modules comprises a frame and one or more heat generating elements supported by the frame. A plurality of ports electrically coupled to the heat generating elements are located at the front portion of the frame. A faceplate coupled to the front portion of the frame further comprises one or more port openings to allow access to the ports, a plurality of airflow openings aligned with the top portion of the frame, and a chamfered bottom aligned with the bottom portion of the frame. A first electronics module selected from the plurality of electronics modules is mounted above a second electronics module, such that the chamfered bottom of the faceplate on the first electronics module is substantially aligned with the airflow openings of the faceplate on the second electronics module.
In a further example, the techniques presented herein provide for a method comprising installing a plurality of electronics modules in an electronics rack. Each of the electronics modules comprises one or more heat generating elements. The method also comprises providing power to the heat generating elements in the plurality of electronics modules. Air is forced between a chamfered bottom of a faceplate on a first electronics module selected from the plurality of electronics modules and a plurality of airflow openings in a second electronics module. The heat generating elements of the second electronics modules are cooled with the forced air.
The above description is intended by way of example only. Any material described is only an example of a material that may be used. Other materials can be substituted without leaving the scope of the present invention. It is also to be understood that terms such as “left,” “right,” “top,” “bottom,” “front,” “rear,” “side,” “height,” “length,” “width,” “upper,” “lower,” “interior,” “exterior,” “inner,” “outer” and the like as may be used herein, merely describe points or portions of reference and do not limit the present invention to any particular orientation or configuration. Further, the term “exemplary” is used herein to describe an example or illustration. Any embodiment described herein as exemplary is not to be construed as a preferred or advantageous embodiment, but rather as one example or illustration of a possible embodiment of the invention.
