V. LAS REPRESENTACIONES DEL PROFESORADO SOBRE SU PRÁCTICA
V.3. PERCEPCIONES SOBRE EL EEES Y LA EXPANSIÓN DEL CAPITALISMO
Following are recommendations for handheld digital meters that can measure temperature, relative humidity, and airflow velocity:
• A Kestrel 4000 or similar flow meter (with memory function to log data points for predetermined time intervals)
Appendix C Site Environmental Planning How to Measure Environmental Elements
• An Omega HHF81 or similar thermometer
About Measuring Temperature and Humidity
Air temperature and humidity level at the inlet of each chassis inside a cabinet are a true indication of environmental conditions. It may be difficult to take these measurements at each chassis, since it requires attachments of multiple probes inside the cabinet with the door closed.
As an alternative, the temperature and humidity levels at the chassis inlets can be derived by measurements taken outside the cabinet door, as illustrated in this section.
You can measure temperature and humidity with or without instrument readers. Without instrument readers
Place temperature and humidity probes approximately 0.64 cm (0.25 in.) in front of the opening near the bottom of the cabinet's front door.
With instrument readers
If using one of the instrument readers recommended under Environmental Measurement Instruments, orient the air flow impellers parallel to the door inlet vents, so that air going into the door opening will pass through the impellers and sensors.
Figure 29: Temperature and Humidity Measurement Locations Outside Cabinet
Cabinet_0041 Temperature and Humidity Probe Placement: 0.64 cm (0.25 in.) in front of vents
Humidity measurements taken outside and inside the cabinet door are generally the same. However, air temperature measurements taken outside and inside the door can differ. To estimate the maximum air temperature at the chassis inlets inside the cabinet door, the
Appendix C Site Environmental Planning How to Measure Environmental Elements
general rule is to take two readings outside the front door, calculate an average temperature, then add 5° C (9° F).
Note: Do not take temperature measurements at the rear of the cabinet, facing the hot aisle.
About Measuring Airflow
Air flow meters measure air velocity, in meters per second (m/s) or feet per minute (ft/min). The measurements for air velocity must then be converted to air flow rate, in cubic meters per second (m3/s) or cubic feet per minute (ft3/min).
Two methods for measuring air velocity and calculating airflow rate are: • Using an Alnor meter
• Using an airflow meter and handmade air capture hood
The Alnor flow rate meter is a specialized instrument that can be used to measure air flow rate. It has an air capture hood, and is instrumented to measure air flow rate in m3/s or ft3/ min. Once calibrated, it is very accurate. However, the Alnor meter has a list price of more than $1,200.
A cost-effective method to get reasonably accurate air flow rate measurements is to use a digital air flow meter and a handmade cardboard air capture hood. The accuracy of the measurements using the handmade air capture hood depends on the dimensions of the air hood, specifically the height, the placement of the air flow meter, and the air flow rates. Typically, measurements obtained using this method, with the height of the hood no less than 46 cm or 18 in, are accurate within 5-10% of those taken by a calibrated Alnor meter. A correction factor (CF) representing this discrepancy can be derived for a specific handmade air capture hood using an Alnor meter as calibration tool.
For detailed information on the recommended flow meter, the dimensions and fabrication of the hood, and the correction factor, contact your local Teradata Regional Technical Specialist (RTS), the Teradata Global Support Center (GSC), or Teradata Engineering. Measuring Air Flow Rate Using an Air Flow Meter and Handmade Air Capture Hood
This procedure for measuring air flow is specific to a raised floor environment. The air capture hood can be used to measure flow rate of an overhead air diffuser in an overhead air delivery environment, as long as the larger open end of the hood can cover the opening of the diffuser.
Appendix C Site Environmental Planning How to Measure Environmental Elements
Figure 30: Handmade Air Capture Hood and Measurement Locations
Important: Adhere to these dimensions for openings and height of hood. Airflow Meter at
the Exit Plane
Vented Tile Solid Tile Cabinet_0108
Flange 46 cm (18 in.) 61 cm (24 in.) 61 cm (24 in.) 46 cm (18 in.) 30.5 cm (12 in.) 30.5 cm (12 in.) Single Measurement Point in the Middle
Handmade Air Capture Hood for Flow Rate Measurement
Flow Rate = Measured Velocity x Top Opening Area
1 Make a four-sided cardboard air hood with two open ends:
• large end: 61 cm x 61 cm (2 ft x 2 ft) (standard floor tile size) • small end: 30.5 cm x 30.5 cm (1 ft x 1 ft)
2 Place the hood with the large open end over a vented floor tile.
Minimize air flow leakage by sealing seams on the hood, and by pressing the hood firmly against the floor.
3 Hold the air flow meter at the small open end of the hood, in the center, to get a reading
of the air velocity.
4 Convert the air velocity reading to the air flow rate.
The measurement in cubic feet per minute is:
flow rate (ft3/min) = flow velocity (ft/min) x area (1 sq. ft on small open end of hood)
If you need to calculate air flow rate in cubic meters per second (m3/s), the conversion factor is 4.719 x 104.
For example, to obtain air flow rate in m3/sec when measured air flow rate is X ft3/min (CFM), multiply X ft3/min by 4.719 x 104: X x 4.719 x 104.