1

ECU flow study and flow through PXL

version 0 11/14/2013

2

Topics

• ECU flow measurements• ECU Pressure vs Flow measurements• Determination of expected PXL maximum cooling air flow with ECU• ECU measurement of flow and pressure vs fan RPM

Testing of AirInnovations ECU, air cooling system for the PXL detector

3

The flow out of the ECU was measured with a pair of venturi meters using the setup shown

This was checked against flow measured by the timed filling of a large plastic bag.

Venturi mass flow meters

ECU out

Flow measurement with venturi meter and bag inflation

4

Bag: 37 ft long, 280 ft3

Agreement between venturi meters and bag filling time is good to 2% to 3%

The ECU front panel flow meter is way off. It reads a factor 2.4 to 3.4 too high.

The flow measurement was made using the setup on page 3 at two different blower speeds. The flows were 290 CFPM and 348 CFPM, the higher value was at the maximum blower speed of 5940 RPM

5

Measure of ECU pressure as a function of flow

ECU output pressure measured here

Flow was varied by adjusting restrictions at the exhaust. Pressure and flow values were recorded.Flow was determined using the two venturi mass flow meters.

This set of measurements was made at full blower speed, 5940 RPM

6

Measure of ECU pressure as a function of flow

7

Determination of expected PXL maximum cooling air flow from the ECU

The flow was measured with the setup shown at full blower RPM.

PXL detector withdrawn from the PST.

When the PXL detector is inserted into the PST there will be additional back pressure due to the turning around of the air back in the opposite direction over the outside of the PXL cluster. The back pressure is expected to be 1 or 2 times the dynamic pressure, . There will, however, be a reduction in pressure if the venturi meters are removed. The measured flow in the setup shown is modified using the predicted back pressure according to the pressure vs flow fit shown in slide 6.

Flow measured: 387 CFPM

Flow predicted: 351-388 CFPM

Requirement: 410-580 CFPMECU Specification: 600 CFPM

Thermal tests with real sectors will determine if the predicted flow is sufficient.

𝑝=12 𝜌 𝑣

2

8

Measurement of ECU flow and pressure vs fan RPM

These measurements were done using the setup shown in slide 3. The flow values were obtained using the venturi mass flow meters.

9

Summary

• The venturi mass flow meters provide a very accurate measure of flow• The ECU front panel flow meter is as much as 3.4 times the true flow• The ECU will only reach 0.59 to 0.65 of the flow specification, however, this may be in part

due to greater PXL back pressure than was estimated. This will be checked when PXL is installed in the PST.

• Thermal tests with real sectors will be done to determine if the reduced performance of the ECU is sufficient for PXL cooling needs