Calif. State Univ., Sacramento CE135 Hydraulics Lab

Dept of Civil Engineering Instructor MEH

OBJECTIVES:

- Introduce flow measurement by constriction meters

Calibrate a constriction flow meter

Compare a few different flow meters

APPARATUS: Sketch your system, including key dimensions for at least the following items

- Flow manifold with orifice, nozzle, and venturi meters

Differential manometer

Weighing scale with collection tank

Clock to read at seconds

EXPERIMENTAL PROCEDURE:

- Set up equipment
- Open the surge tank valve.
- Turn on the water supply pump and purge air from the pipe system and the manometer tubing.
- Make sure the differential manometer is connected to the meter you want to calibrate
- Record the water temperature and essential geometric variables such as the pipe diameter and constriction meter throat diameter.
- Record the heads on the differential manometer tubes. If Δh fluctuates, use an average over time.
- Gravimetrically determine the flow rate by collecting the flow in a container and measuring the weight of water captured in a measured amount of time
- Run these steps for a range of flows spanning the capacity of the supply pump or the differential manometer, whichever is more limiting.
- Sketch the equipment from the inflow control valve to the weighing tank
- Establish flows through the three flow meters at the same time
- Observe flows through the clear plastic sections
- Sketch the differences in flow patterns and turbulence among the three devices

Establish a steady flow through one of the flow meters

Compare flow patterns in the orifice, nozzle, and venturi meters

Turn off the pump and close the surge tank valve.

Sacramento State University Dept. of Civil Engineering

CE 135 Hydraulics Lab
Instructor MEH

CONSTRICTION FLOW METERS IN PIPES: RESULTS

FORMAT: Memo Report

[Refer to class hand-out for style]

- Present the key results and describe any major deviations from the printed procedures and why you changed them.

You do not need to turn in the lab procedure sheet with your report, but it is ok to add it as an attachment. Attach your hand drawn sketch of the apparatus even if you put a computer drawing in the body of the report.

RESULTS:

- For the graphs & final table{s), convert flows to cubic feet per second (cfs) and heads to feet. Compute the Reynolds numbers (Re) associated with the flows. (Note which diameter you use in the Reynolds number.) The data shown on the graphs should be in the body of the report but detailed tables of input and calculated data should be attachments.
- Constrained exponent: Determine a best fit equation in the form Q=KA(2g Δh)
^{1/2}(I.e., find a best fit K value for this equation). [Note that you must use one variable (use Δh) as the "known" and the other (Q) as the "unknown".]

- Unconstrained exponent: Determine a best fit equation in the form Q=KA(2g Δh)
^{x}(Here, you find both K and x values for the equation). [Again use Δh as "known".]

- Plot Q against Δh on log-log scale, using (a) the values of Q and Δh from the experimental data (at points) and (b) the two best-fit equations just calculated (as curves).
- Which curve – constrained or unconstrained – fits the experimental data better. How do you judge “better”? Compare your results with literature on constriction meters.

Calculate rating curves for a device you tested. You are to determine the discharge coefficient (K) with the exponent constrained (1/2) and unconstrained (x) as follows:

Using K values computed for each run (as constrained), plot K (y-axis) against Re (x axis). Is K constant over the range of Re in this experiment?

- How well do your K values compare with those in the literature, e.g., Figure 13.13 of Roberson, et al, 1997?

ATTACHMENTS:

- Attach your sketch of the experimental set-up and copies of your input data and calculated results.

Write out the key equations used in calculating the results, with one sample calculation for each equation.

Calif. State Univ., Sacramento CE135 Hydraulics Lab

Dept of Civil Engineering Instructor MEH

CONSTRICTION FLOW METERS IN PIPES

EXPERIMENTAL DATA

Lab Team Members: Date of Experiment:

__CONSTANT DATA__

Constriction Type (Orifice, Nozzle, or Venturi) & Diameter _________ inch

Pipe Diameter _________ inch

Water Temperature _________º F

__VARIABLE DATA__

Data from the differential manometer, the weighing scale, and a clock or stop watch.

Run enough samples to span the available range of flows

Manometer | Scale Weights | Time | ||||
---|---|---|---|---|---|---|

Run | H1 | H2 | Start | End | Start | End |

No. | ------------ (in) ------------ | ------------ (lbf) ----------- | ----------- (sec) ----------- | |||

1 | ||||||

2 | ||||||

3 | ||||||

4 | ||||||

5 | ||||||

6 | ||||||

7 |

References:

- Roberson, J.A. and C. T. Crowe, Engineering Fluid Mechanics, 6th ed., John Wiley and
Sons, 1997, Ch. 13 Flow Measurements

ASME Fluid Meters Research Committee, "The ISO-ASME Orifice Coefficient Equation", Mechanical Engineering, July, 1981, pp 44-45. (Magazine available in CSUS Library)

US Bureau of Reclamation, Water Measurement Manual, www.usbr.gov/pmts/hydraulics_lab/pubs/wmm (all you want to know & then some)