1. Conservation of Mass, Flow Rates
So Far:
Conservation of Mass, Flow Rates
Fluid Flow, Re No., Laminar/Turbulent
Pressure Drop in Pipes
Bernoulli’s Equation
Flow Measurement, Valves
Total Head, Pump Power, NPSH
This Week:
Pump Sizing, Types of Pumps
Conservation of Energy

2. Pump Sizing
Volume Flow Rate (m3/hr or gpm)
Total Head, h (m or ft)
2a. P (bar, kPa, psi)
Power Output (energy added to fluid) and Input (mechanical shaft power from motor)
NPSH Required

3. Pumps Centrifugal Impeller spinning inside fluid
Kinetic energy to pressure
Flow controlled by Pdelivery
Positive Displacement
Flow independent of Pdelivery
Many configurations

4. Centrifugal Pumps
Delivery
Impeller
Volute Casting
Suction

5. Centrifugal Pumps
Flow accelerated (forced by impeller)
Then, flow decelerated (pressure increases)
Low pressure at center “draws” in fluid
Pump should be full of liquid at all times
Flow controlled by delivery side valve
May operate against closed valve
Seal between rotating shaft and casing

6. Centrifugal Pumps
Advantages
Simple construction, many materials
No valves, can be cleaned in place
Relatively inexpensive, low maintenance
Steady delivery, versatile
Operates at high speed (electric motor)
Wide operating range (flow and head)
Disadvantages
Multiple stages needed for high pressures
Poor efficiency for high viscosity fluids
Must prime pump

7. Increasing Impeller Diameter
Centrifugal Pumps
H-Q Chart
Increasing Impeller Diameter
Head
(or P)
A B C
Volume Flow Rate

8. Increasing Efficiency
Centrifugal Pumps
H-Q Chart
Increasing Efficiency
Head
(or P)
Required NPSH
A B C
Volume Flow Rate

9. Centrifugal Pumps
H-Q Chart
Head
(or P)
A B C
Volume Flow Rate

10. Required Flow Capacity
Centrifugal Pumps
H-Q Chart
Required Flow Capacity
Head
(or P)
Actual Flow Capacity
Required Power
Volume Flow Rate

11. What if available NPSH is less than required NPSH?
Centrifugal Pumps
What if available NPSH is less than required NPSH?
Increase Available NPSH
1. Increase suction static head (pump location)
2. Increase suction side pressure
3. Decrease fluid vapor pressure
4. Reduce friction losses on suction side
Decrease Required NPSH
1. Reduce pump speed
2. Select a different pump

12. Centrifugal Pumps
Curves created for specific speed, viscosity and density
Often, use more charts or correction factors to “fine tune” pump selection
Variable speed motor has same effect as impeller size
Multiple pump/impeller combinations may work

13. Centrifugal Pumps
Closed Impeller
Most common, low solids
Water, beer, wort
Flash pasteurization
Refrigerants
Open Impeller
Lower pressures
Solids okay
Mash to lauter turn
Liquid yeast, wort, hops

14. Positive Displacement Pumps
Theory: Volume dispensed independent of delivery head
Practice: As delivery head increases, some slippage or leakage occurs
Speed used to control flow rate, use of valves could cause serious damage
Self-priming
Good for high viscosities, avoiding cavitation

15. Positive Displacement Pumps
Piston Pump
Volumetric Efficiency High Pressures
Metering hop compounds, detergents, sterilents
Suction Valve
Delivery Valve

16. Positive Displacement Pumps
Peristaltic Pump

17. Positive Displacement Pumps
Gear Pump
High Pressures
No Pulsation
High Viscosity Fluids
No Solids
Difficult to Clean

18. Positive Displacement Pumps
Lobe Rotor Pump
Both lobes driven
Can be sterilized
Transfer
Yeast
Trub
Bulk Sugar Syrup

19. Laws of Thermodynamics
First Law – Energy is conserved
Second Law – Energy has quality, processes go in certain directions only
Forms of Energy
Potential energy = mgh
Kinetic energy = (0.5)mv2
Internal energy (U) – microscopic forms
Conservation of Energy

20. Heat transfer – Temperature difference
Energy Interactions
Heat transfer – Temperature difference
Work – Shaft, electrical, boundary, etc.
Mass flow – U + PV = Enthalpy (H)
Closed System Energy Equation
No Phase Change

21. Open System Energy Equation
for steady flow systems or

22. A 500 gallon water tank is filled with 220 gallons of hot water at 80C and 280 gallons of cold water at 10C. Assume that the specific heat of water is 4.2 kJ/kg.K.
Determine the temperature in the tank after it has been filled.
How much heat must be added to the tank to bring its temperature to 65C?
If a 30 kW electric heater is used, how long will the heating process take?

23. 500 kg of grain (25C) is mixed with hot (80C) and cold (10C) water for mashing. The water to grain ratio (by weight) is 3:1 and the specific heat capacities of the water and grain are 4.2 and 1.7 kJ/kg.K, respectively.
a) If the desired “mash in” temperature is 38C, how much hot and cold water should be added?

24. (Continued) A three step mashing process, with 20 minute-long rests at 50, 62 and 72C, is desired. The mash should be heated quickly, but not too quickly between rests; with an optimal rate of 1C per minute. Neglect heat losses to the surroundings.
b) Plot the mash temperature vs. time.
c) Determine the heating power required, in kW.
d) Determine the total heat required for the mashing process, in kJ.

25. Two types of heat sources are available for mashing, electric resistance heaters and steam. The steam enters a heating jacket around the mash as dry, saturated steam at 300 kPa and it exits the system as wet, saturated steam at the same pressure (enthalpy of vaporization = 2150 kJ/kg).
(e) What is steam flow rate required, in kg/s?
(f) If steam is used, what is the total mass of steam required, in kg?

26. At the location of our brewery, electricity costs $0
At the location of our brewery, electricity costs $0.14/kW-hr and the steam can be generated for $0.03 per kg.
(g) What is the mashing cost when electric resistance heaters are used?
(h) What is the cost with steam?

27. Explain the term “net positive suction head” and discuss its importance in the pumping of liquids in a brewery.
A centrifugal pump with an NPSH of 5 m is pumping wort from a whirlpool, open to the atmosphere, to a wort cooler. If the wort is at 95C and has a vapor pressure of bar, calculate the minimum distance below the whirlpool outlet that the pump must be positioned to prevent cavitation. Data on board…