Cooling Requirements - HP E1399A User Manual

Cooling
Requirements
Note
Chapter 2
The VXIbus Specification requires module manufacturers to establish a
cooling specification for each of their modules. The specification is to
consist of: (1) the airflow required (in liters/second) for adequate cooling,
and (2) the pressure drop that occurs across the module when the specified
airflow is applied.
It is the user's responsibility to furnish adequate cooling for any module to
be used in a VXIbus system. Module cooling requirements are described in
the VXIbus Specification (Rev 1.3) in Section B.7.2.4. Mainframe cooling
requirements are discussed in Section B.7.3.5.
For ease of integration, you should label the airflow requirements for your
finished application circuitry on the module. For example, the label might
read: 0.3 liters/sec @ 0.2 mm/H
Due to the nature of a breadboard module, it is not possible to specify
cooling requirements without knowing the application and the amount of
power to be dissipated. Given the application, however, cooling
requirements may be estimated as follows:
1. Determine the airflow required as a function of power dissipation. To
maintain a 10ºC rise, approximately 0.08 liters/second are required
for every watt dissipated. For example, if a module dissipates 20
watts, 1.6 liter/second of airflow is required for cooling.
2. Establish the relationship between airflow and pressure drop. For a
breadboard loaded with typical components (such as ICs, relays, and
a few heat sinks), the curve in Figure 2-3 may be used to determine
the pressure drop across the module. Determine the pressure drop as
the intersection of the curve and the required airflow. For example, if
the airflow required is 1.6 liter/second, the pressure drop across a
typically populated breadboard will be approximately 0.05 mm H
Figure 2-3. Pressure vs. Airflow
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Configuring the HP E1399A 19
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