SYSTEM PERFORMANCE
13
Rev C
HOW TO DETERMINE RATE OF FLOW FROM THE MERLIN SYSTEM - NORTH AMERICAN
Example
Inlet Water TDS (measured)
300 ppm
Inlet Water Temperature
50°F
Inlet Pressure
60 psi
3/8-inch Tubing
15 ft long
Obstructions in Permeate Line
One 90° elbow
Elevation Difference Between Merlin and Faucet
6 ft.
Post Filter?
Yes
Faucet? Yes
Assigned Values
Pressure Drop per Obstruction
0.5 psi
Pressure Drop per Postfilter
3 psi
Pressure Drop in Elevation
0.43 psi per ft
(feet Faucet is above Merlin)
1.
Determine the Inlet TDS =
300 ppm
2.
Determine the Inlet Water Temperature =
50 °F
3.
Determine the Net Driving Pressure of the Merlin system
Net Driving Pressure = Inlet Pressure - System Pressure Drop (Follow instructions below)
3A.
Calculate the Flow Rate Adjustment Factor
This factor will be used with Table 1 to adjust the TDS of Inlet Water from 750 ppm to 300 ppm.
-0.0002 (300 ppm) + 0.15 =
0.09 gpm
3B.
Calculate the Tubing Pressure Drop
Inlet Pressure
= 60 psi
Water
Temp
=
50°F
Use Table 1 to estimate flow rate, 750 ppm NaCl @ 50°F and 60 psi =
0.49 gpm
Adjust Table data for actual TDS using the Flow Rate Adjustment Factor 0.09 gpm
Tubing Flow Rate = 0.49 gpm
+ 0.09 gpm = 0.58 gpm @ 300 ppm NaCl
Use Figure 4 to determine the pressure drop for 1 ft. tubing = 0.138 psi
Tubing Pressure Drop for 15 ft = 15 x 0.138 psi =
2.07 psi
3C.
Calculate the Obstruction Pressure Drop
1 obstruction (the elbow) X (0.5 psi) =
0.5 psi
3D.
Calculate Elevation Pressure Drop
6 ft elevation X 0.43 psi/ft =
2.58 psi
3E.
Calculate Postfilter Pressure Drop
1 postfilter X 3 psi =
3 psi
3F.
Calculate Faucet Pressure Drop
60 psi - 2.07 psi - 0.5 psi - 2.58 psi - 3 psi = 51.85 psi
Use Table 1 to estimate flow rate, 750 ppm NaCl @ 50°F and 51.85 psi = 0.40 gpm
Adjust Table Data for actual TDS using the Flow Rate Adjustment Factor 0.09 gpm
0.36 gpm + 0.09 gpm
= 0.45 gpm @ 300 ppm NaCl
e 8 and the Inlet Flow Rate of 0.49 gpm to estimate the Faucet Pressure Drop =
4.5 psi
3G.
Calculate the System Pressure Drop
(System Pressure Drop = Tubing PD + Obstruction PD + Elevation PD + Postfilter PD + Faucet PD
2.07 psi + 0.5 psi + 2.58 psi + 3 psi + 4.5psi =
12.65 psi
3H.
Determine the Net Driving Pressure Drop
(
Net Driving Pressure = Merlin Inlet Pressure - System Pressure Drop)
60 psi - 12.65psi =
47.35 psi
4.
Determine the Merlin Flow Rate
Use Table 1 to estimate flow rate, 750 ppm NaCl @ 47.35psi and 50°F = 0.38gpm
Adjust Table Data for actual TDS using the Flow Rate Adjustment Factor 0.09 gpm
0.38 gpm + 0.09 gpm = 0.47 gpm
TOTAL MERLIN FLOW RATE = 0.47 gpm
g
gp
p
p
p
p
p
p
p
p
Actual results may vary. Membrane performance may vary ± 15%.
