Fluid Lab - Pump in Parallel and Series

OBJECTIVES    

To demonstrate pump performance when connected in series and parallel To show shut off point of pump in parallel and series. To study about the fluid flow rate and efficiency in parallel and pump series. To determine required net head by solving energy equation in parallel and pump series.

INTRODUCTION A pump is a device to move fluid through mechanical action. Pumps consume energy to perform mechanical work in order to move the fluid the frictional force and gravitational force. A pump can serve to move liquid, as in a cross country pipeline, to lift liquid as from a well or to the top of a tall building; or to put fluid under pressure as in a hydraulic brake. In chemical plants and refineries pumps transfer or circulate oil and a great variety of fluids. These two types of pumps have their own advantage and disadvantage. In serial operation the heads of the pumps are added and in parallel operation the flow rates (capacities) of the pumps are added. Shortly said, pumps in series tend to increase head but pumps in parallel tend to increase capacity. EQUIPMENT 

Pump in Series and Parallel Apparatus

PROCEDURE For single pump: 1) Turn on valve 1 and 4.

Make sure valve 2 and 3 are closed. The

pressure reading were taken from pumps P1 and P2. 2) The volume flow rates were set to be 20, 40 ,60, 80 and 90 liter per minute. Make sure the volume flow rate is set to 0 before taking reading for different values of volume flow rate. 3) For each reading, two set of measurement were taken. 4) Average pressure reading from both sets were calculated and the difference in the two pressure pumps was determined

For series pump: 3) Turn on valve 1, 3 and 4. Make sure valve 2 is closed. Take the pressure reading from pumps P1, P3 and P4. 4) Repeat step 4-6 as for single pump.

For parallel pump: 3) Turn on valve 1,2 and 4. Make sure valve 3 is closed. Take the pressure reading from pumps P1, P2 and P4. 4) Steps 4-6 as for single pump were repeated, but the volume flow rates were set to be 40, 80, 120, 160 and 180 liter per minute. RESULT Single pump : Volume

Pressure

Net Head

Pump

Average

Average

flow rate

Drop

loss

efficiency,

velocity

velocity

(L/min)

(kPa)

(m)

ηpump

(m/s)

pressure

20 40 60 80 90

152.72 131.35 119.97 106.18 96.53

15.57 13.39 12.23 10.82 9.84

0.14 0.23 0.32 0.38 0.39

0.68 1.36 2.04 2.72 3.06

(kPa) 103.85 178.64 244.74 288.81 295.38

Series pump : Volume

Pressure

Net Head

Pump

Average

Average

flow rate

Drop

loss

efficiency,

velocity

velocity

(L/min)

(kPa)

(m)

ηpump

(m/s)

pressure

20 40 60 80 90

380.94 344.74 309.92 262.00 234.42

38.83 35.14 31.59 26.71 23.90

0.34 0.62 0.83 0.94 0.94

0.68 1.36 2.04 2.72 3.06

(kPa) 259.04 468.85 632.24 712.64 717.33

Parallel pump : Volume

Pressure

Net Head

Pump

Average

Average

flow rate

Drop

loss

efficiency,

velocity

velocity

(L/min)

(kPa)

(m)

ηpump

(m/s)

pressure

1.36 2.72 4.07 5.43 6.11

(kPa) 231.15 403.21 540.17 636.45 663.48

40 80 120 160 180

169.96 148.24 132.72 117.21 108.59

17.33 15.11 13.53 11.95 11.07

0.30 0.53 0.71 0.84 0.87

CALCULATIONS 1 psi = 6.895 kPa Diameter of pipe = 1 inch = 0.025m SINGLE PUMP Pressure drop :

ΔP = 22.15 psi

6.895 kPa 1 psi ) = 152.72 kPa ¿

Average velocity :

Vavg =

´v = A

20

L 1 m3 1 min ( ) min 1000 L 60 s ( 0.025 m )2 π( ) 4

(

)

= 0.68 m/s

Head loss : N m2 1 kPa

( ) 1000

hL =

∆P ρg

152.72 kPa =

(

1000

= 15.57 m

kg m 1N 9.81 2 ( ) 3 m s 1 kgm s2

)(

)

ηpump :

ηpump =

ρVg h bh p

=

(

)(

kg m 1000 3 0.000333 s m

average velocity pressure: P = Vavg (ΔP) = 0.68 m/s (152.72 kPa) = 103.85 kPa

3

)(9.81 ms )(15.57 m) =¿ 2

3

0.37285 ×10 W

0.14

Volume flow rate vs Pressure drop 400.0000 300.0000 Single pump Series pump

Pressure drop 200.0000

Parallel pump

100.0000 0.0000 0

50 100 150 200

volume flow rate

Volume flow rate vs Pump efficiency 1 0.8

pump efficiency

0.6

Single pump

0.4

Series pump Parallel pump

0.2 0 0

50

100 150 200

volume flow rate

DISCUSSION Through this experiment we can know which of the pumps is more efficient. We also can know the advantage and the disadvantage of the pumps. Pumps are important to provide mechanical work to the fluid to move against the friction and gravitational force.

Based on the result that we obtained, we can see that the fluid flow rate remain constant no matter what is the pipe diameter. The total net head of pumps in series can be calculated by adding up of all pumps head. Usually pump in series produces higher pressure than pump in parallel. Besides, pump in parallel produces high volume of flow rate. In parallel pump, the water going into each of the pumps is at exactly the same state and the pump may be analyzed individually. What we can say that, as the volume flow rate increases, the pressure also increase. The pressure drop when the series pump is bigger than the pump in parallel. Since the result showed that pump in series connection can increase net head while pump in parallel can increase volume flow rate. Therefore, we can say that parallel pump is much more efficient than the pump in series. Among the safety precautions that should be taken are :In series operation, we can get greater discharge pressure. In all cases we have to be very careful to have the correct safety interlocks to protect the pumps from a malfunction of the other pump. Also, we have to be sure the pumps have the necessary maximum operating pressure capability so the first pump does not overpressure the second pump. Next, never operate the pump when there is no liquid in the pipeline because it will cause damage to the pump which may lead to the error. Other than that, never operate the pump above its limit of operation.

CONCLUSION Through this discussion we finally can demonstrate the pumps performance when connected in parallel in series. We also finally know about the fluid flow rate and efficiency in parallel and pump series. For series pump, the total shutoff is the sum of each individual pump while in parallel pump their individual flow rate is summed. The free delivery of the combined pumps is equal to the sum of the free delivery of each individual pump. We

also can determine required net head by solving energy equation in parallel and pump series. All in all, the objectives of this experiment are achieved.

REFERENCE 1) Lab Manual, Biotechnology Engineering Lab 2, BTE 2222 2) Cengel YA, Cimbala JM. Fluid mechanics third edition in SI units.McGraw Hill Education. Chapter 5 and 8. 3) mimoza.marmara.edu.tr/~orhan.gokyay/enve311/ch7.pdf 4) http://www.alicat.com/alicat-blog/accuracy-and-repeatability/whats-upwith-pressure-drop/