Browse Prior Art Database

Redundant Cooling of Computers

IP.com Disclosure Number: IPCOM000123896D
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2005-Apr-05
Document File: 2 page(s) / 105K

Publishing Venue

IBM

Related People

Christensen, SM: AUTHOR [+3]

Abstract

Availability and redundant features in computers, such as hot swap fans and redundant cooling, are moving from the high-end systems downward and are becoming more and more a standard feature/requirement. Hot swap fans and redundant cooling allow for a fan to fail and then to be replaced at a later time without ever shutting down or throttling the system. Redundant cooling is typically achieved by adding extra Air Moving Devices (AMDs), either fans or blowers, so that if one AMD fails sufficient cooling is provided by the remaining AMDs. Disclosed is a method of achieving redundant cooling, without increasing the number of AMDs, by increasing the AMD voltage beyond current levels after an AMD failure.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Redundant Cooling of Computers

   Availability and redundant features in computers, such as
hot swap fans and redundant cooling, are moving from the high-end
systems downward and are becoming more and more a standard
feature/requirement.  Hot swap fans and redundant cooling allow for a
fan to fail and then to be replaced at a later time without ever
shutting down or throttling the system.  Redundant cooling is
typically achieved by adding extra Air Moving Devices (AMDs), either
fans or blowers, so that if one AMD fails sufficient cooling is
provided by the remaining AMDs.  Disclosed is a method of achieving
redundant cooling, without increasing the number of AMDs, by
increasing the AMD voltage beyond current levels after an AMD
failure.  This methodology has not previously been exploited since
AMDs are typically powered by the maximum voltage provided by the
power supply.

   Fan speed control is typically employed in computers to
provide minimum acoustics in cool environments where less cooling is
required, while providing more cooling in hot ambients where
acoustics is typically of less concern.  For instance, in many
systems the power supply provides a maximum of 12 VDC to the system.
Fan speed control would typically vary fan voltage from approximately
8V in cool environments up to 12V in hot ambients.  When an AMD fails
all functioning AMDs would be driven to the maximum available voltage
of 12V.  Unfortunately, the system has less cooling capacity under
fan fail conditions than it has under normal operating conditions due
to the loss of the AMD  (N-1 fans at 12V vs N fans at 12V) and there
exists no way to compensate for this loss.  As such, extra AMDs are
added to the system to counteract this loss.  For instance, if 2 fans
are required to cool a given system without redundant cooling, the
following options would be considered for the same system if it
required redundant cooling:
  1.  Three fans upstream of the system
  2.  Three fans downstream of the system
  3.  Two fans upstream and 2 fans downstream of the system

   Providing redundant cooling by utilizing more AMDs than is
needed for a non-redundant case has several drawbacks including:
  1.  Cost of extra AMD(s) and associated hot-swap mounting and
      connector hardware
  2.  Cost of providing extra power supply capacity to drive
      the extra AMD(s)
  3.  Cost and complexity of the fan speed control circuitry
      to drive the extra AMD(s)
  4.  Volume must be allocated for the extra AMD(s).  This is a
      serious concern since the volume occupied by fans can not
      be used for electronics.

   This is especially serious if upstream and downstream fans
are...