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Thermal Chamber in Standard Nineteen-Inch Rack

IP.com Disclosure Number: IPCOM000120303D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 4 page(s) / 140K

Publishing Venue

IBM

Related People

Hansen, MW: AUTHOR

Abstract

A chamber operation is described in three sections. First, there is the path the airflow is traced as it makes a round trip through the chamber. Each major subassembly is described as it is encountered. The next section outlines some of the key features of the chamber. The last section outlines, at a high level, the steps taken to ramp temperature, either up or down.

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This is the abbreviated version, containing approximately 48% of the total text.

Thermal Chamber in Standard Nineteen-Inch Rack

      A chamber operation is described in three sections.
First, there is the path the airflow is traced as it makes a round
trip through the chamber.  Each major subassembly is described as it
is encountered.  The next section outlines some of the key features
of the chamber.  The last section outlines, at a high level, the
steps taken to ramp temperature, either up or down.

      A side view of the chamber is provided in Fig. 1. Refer to this
for all sections of this article.

      Starting with the blowers 1.  The air is pushed through
insulated tubing up to the top plenum 2.  There are two centrifugal,
each capable of generating 462CFM.  The blowers 1 were chosen for
their ability to overcome the high static pressure generated by the
many restrictions in the chamber.

      The air now makes its way through the dut chamber 3 and into
the front plenum 4.  At this point, the air can take one of two
paths.  If cooling is required, the damper 5 is put in the vertical
position.  The air then flows through the air conditioner 6.  If the
damper 5 is in the horizontal position, the air flows in a duct above
the air conditioner 6.  The air conditioner 6 is industrial grade,
capable of 16,000 BTU.  It was chosen for its size, cooling capacity
and price.

      The air now enters the heater plate plenum 7.  The heater plate
plenum 7 consist of 6 heaters.  The heaters are wired to enable
either two, four or six heaters to be energized.  Each heater
generates 650 watts when energized.

      Ramp Time Reductions:
   1.  Blower ON/OFF Control.  The capability was added for the
blowers 1 to be turned OFF during ramp down times when the air
conditioner 6 is on.  The blowers 1, within the air conditioner 6,
provide adequate airflow.  Turning the blowers 1 off eliminates the
heat that the electrical motors generate.  This creates less heat for
the air conditioner 6 to overcome and the ramp down time is decreased
by 25 percent.
   2.  Redirecting the Airflow.  A damper 5 is used to redirect the
airflow.  This enables the heated air to bypass the cooling coils in
the air conditioner 6.  This saves ramp time in two cases: when
ramping up the heated air does not have to overcome the cold air
conditioner coils, and when ramping down the heated air is directed
to the already cold air conditioner coils (still cold from the last
cycle), which brings about a very quick drop in chamber air
temperature.
   3.  Additional Heaters.  The chamber employs 2x the number of
heaters needed to maintain set temperature.  The heater plate plenum
7 contains 6 650-watt heaters.  During ramp up, all six of these
heaters are enabled.  When the chamber temperature is within 5
percent the setpoint, 4 of the heaters are disabled.  This method
gives very fast ramp times, 25 to 60 degrees Celsius in less than 5
minutes. Overshoot is reduced to less than 1 degree Celsius.

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