BREWING ENGINEERING part 2

1. BREWING ENGINEERING part 2

2. BREWING ENGINEERING • PUMPS • WHIRLPOOLS OBJECTIVES for part 2:

3. PUMPS • Fluids are moved through pipes or ducts using pumps, fans, blowers and compressors. • These devices: • 1. Move the fluid (increase its velocity) • 2. Increase the pressure in the fluid • 3. Lift the fluid vertically against the force of gravity BREWING ENGINEERING • We generally speak of pumps moving liquids, while fans, compressors, or blowers either move or compress gases.

4. PUMPS • Common brewery pumps • 1. Centrifugal pumps-- Most commonly used • 2. Air-operated Diaphragm pumps BREWING ENGINEERING

5. PUMPS • CENTRIFUGAL PUMP • 1. Achieves liquid movement and flow by “slinging” the fluid out of the impeller using centrifugal force. • 2. Two main parts of a centrifugal pump head: • - Impeller • - Diffuser (or volute). BREWING ENGINEERING

6. CENTRIFUGAL PUMP PUMPS BREWING ENGINEERING Flow rate that can be achieved is an inverse function of pressure: As back-pressure increases, flow decreases. Higher liquid flow rates will result in higher resistive pressure within the system due to pipe friction See graph next…

7. CENTRIFUGAL PUMP PUMPS Relationship between flow velocity, system pressure (blue curve) and centrifugal pump capability: BREWING ENGINEERING

8. CENTRIFUGAL PUMP • The intersection of the two curves is known as the “operating point “ for the system. PUMPS BREWING ENGINEERING

9. PUMPS • CENTRIFUGAL PUMP BREWING ENGINEERING • The system curve characteristics depend upon: • Height to which liquid must be pumped • Diameter • Length of the piping within the system • Number and types of fittings, valves, etc. within the system

10. CENTRIFUGAL PUMP PUMPS • We are able to manipulate the flow rate of liquid delivered by the pump by increasing or decreasing the total amount of back pressure within the system • 2. By closing or opening a valve BREWING ENGINEERING valve

11. PUMPS • Ways to modify the flow output of a centrifugal pump: • 1. Change impeller diameter • 2. Change impeller speed • 3. The relationship between impeller rotational velocity and flow, pressure head, and power requirements are know as the pump Affinity Laws. BREWING ENGINEERING

12. PUMPS • Ways to modify the flow output of a centrifugal pump: • Affinity Laws: BREWING ENGINEERING • Example Problem: Flow from a pump is measured to be 100 gpm. Delivered pressure head is 100 ftH2O. Power requirements are 5 h.p. The pump impeller rotational velocity is increased from 1750 rpm to 3500 rpm. What effect does increasing the impeller rotational velocity have on flow rate, delivered pressure and power consumption? • Doubling impeller velocity: • 1. Increases flow by factor of 2---200 gpm • 2. Pressure by a factor of 4 --- 400 ftH2O • 3. Power consumption by a factor of 8 --- 40 h.p.

13. In order for a pump to move liquid, it must do work on the liquid, and work requires energy. Doing more work requires more ENERGY. • The rate at which energy is used and work is done (work per unit time) is the definition of POWER. • The amount of POWER required to move a liquid is dependent upon the liquid flow rate, the back pressure within the system and the efficiency of the motor. • For a centrifugal pump, the equation that describes the relationship is: PUMPS CENTRIFUGAL BREWING ENGINEERING Where: P = Power (h.p.) Q = Flow rate (gallons/minute or gpm) DPtotal = total system pressure (pounds/in2 or psi) h = overall pump efficiency

14. Centrifugal pump manufacturers typically supply performance curves for each of their pumps. • These are normally referred to as “pump curves”, and are generally developed using water as the reference fluid. • Most centrifugal pump curves allow for direct reading or easy determination of: • System pressure (head) vs. flow rate for any fluid • Pump efficiency for any fluid • Pump energy (horsepower) requirements for a system pumping water PUMPS CENTRIFUGAL BREWING ENGINEERING

15. Here is an example of a pump curve provided by a manufacturer: PUMPS CENTRIFUGAL Efficiency BREWING ENGINEERING NPSH Impeller Diameter Developed Head Horsepower Flow Rate Brewery Engineering Lecture 1- P 15

16. Net Positive Suction Head (NPSH) • Net positive suction head (NPSH) is the pushing force at the intake of a pump. It is the force of the liquid pushing into the pump due to gravity, plus other head pressures • It can be thought of as the net positive pressure of the liquid entering the pump intake, and is determined by liquid head height or liquid head pressure + gravity pressure, minus friction loss. • NPSH is the head (pressure and gravity head) of liquid in the suction line of the pump that will overcome the friction resistive forces. PUMPS CENTRIFUGAL BREWING ENGINEERING Brewery Engineering Lecture 1- P 16

17. Net Positive Suction Head Required (NPSHR) • NPSHR is the minimum amount of liquid pressure required at the intake port of a pump • Net Positive Suction Head Available (NPSHA) • is the amount of positive pressure head available at the pump intake after pipe friction losses and head pressure contribution has been accounted for • It is very important that NPSHA > NPSHR • Why…..? PUMPS CENTRIFUGAL BREWING ENGINEERING Brewery Engineering Lecture 1- P 17

18. When a centrifugal pump is pulling liquid in through the suction side of the impeller it is creating a large low-pressure situation immediately upstream of the impeller • If liquid is unable to flow into the pump intake fast enough, this low-pressure situation can become a VERY low-pressure situation. • If the pump suction is strong enough, a pump can create a vacuum that is so strong that the pressure within the pipe immediately upstream of the impeller is low enough for the liquid to begin to boil • This situation is given the name “cavitation” • Cavitation decreases pump performance and can cause damage to the pump. PUMPS CENTRIFUGAL BREWING ENGINEERING Brewery Engineering Lecture 1- P 18

19. To avoid this situation, ensure that centrifugal pumps are properly specified and installed in a location that maximizes available suction head (i.e. near the low-point within the piping system). PUMPS CENTRIFUGAL BREWING ENGINEERING ü Tank #1 Tank #2 Pump Pump X Tank #1 Tank #2 Brewery Engineering Lecture 1- P 19

20. Another kind of pump that is often found in breweries is an Air Operated Diaphragm (AOD) pump. • An Air Operated Diaphragm pump uses a combination of the reciprocating action of one or more diaphragms and internal inlet and outlet check valves to move fluid. • AOD pumps use compressed air to provide the energy needed to move fluids. • Air supply is shifted from one internal chamber to another to cause the diaphragm(s) to flex back and forth. Check valves open and close as internal pressure pushes the liquid through the pump. PUMPS Air OperatedDiaphragm BREWING ENGINEERING Brewery Engineering Lecture 1- P 20

21. Here are some examples of AOD pumps ……. PUMPS Air OperatedDiaphragm BREWING ENGINEERING Brewery Engineering Lecture 1- P 21

22. ……… and a view of the internals………….. PUMPS Air OperatedDiaphragm Discharge Manifold BREWING ENGINEERING Air Chamber Air Distribution System Liquid Chamber Outer Diaphragm Inner Diaphragm Diaphragm Check-Valve Ball Intake Manifold Check-Valve Seat Brewery Engineering Lecture 1- P 22

23. ……… and a view of the internals PUMPS Air OperatedDiaphragm BREWING ENGINEERING Brewery Engineering Lecture 1- P 23

24. 1 2 3 NM NM NM NM NM NM 4 5 NM NM GIF Animation of AOD Pump NM = No Movement Liquid Flow Direction Air Flow Direction NM NM

25. AOD pumps differ from centrifugal pumps in several important ways: • Energy source: • Centrifugal: Electric motor • AOD: Compressed air • Effect of system head pressure • Centrifugal: flow varies with system head pressure • AOD: flow remains constant with changing system pressure • Inlet Condition Requirements • Centrifugal: Liquid must be in pump head; not self-priming • AOD: Liquid not needed at inlet; self priming PUMPS Air OperatedDiaphragm BREWING ENGINEERING Brewery Engineering Lecture 1- P 25

26. Like centrifugal pumps, AOD pumps also have performance curves, but the things that AOD pump performance curves describe are different • The physical parameters that affect AOD pump performance are • Compressed air inlet pressure • Compressed air consumption rate • These parameters affect AOD pump performance and determine the output parameters for the pump. • AOD pump output parameters are: • Discharge pressure • Liquid flow rate PUMPS Air OperatedDiaphragm BREWING ENGINEERING Brewery Engineering Lecture 1- P 26

27. What, exactly is a whirlpool? • The first thing that I think of is the appliance manufacturer……….. WHIRLPOOLS BREWING ENGINEERING Brewery Engineering Lecture 1- P 27

28. ….but that’s not really exactly what we are talking about today. WHIRLPOOLS BREWING ENGINEERING Brewery Engineering Lecture 1- P 28

29. Here are several definitions of a Whirlpool: • a swirling body of water that is produced by the meeting of currents flowing in opposite directions • water in swift, circular motion, as that produced by the meeting of opposing currents, often causing a downward spiraling action • a vortex, spinning around a central point • It seems that most people can agree that a whirlpool is “swirling water” WHIRLPOOLS BREWING ENGINEERING Brewery Engineering Lecture 1- P 29

30. A whirlpool occurs when two currents are moving in opposing directions, or at an angle to each other in such a way as to allow friction between the two currents to cause the water to spin, creating the whirlpool. WHIRLPOOLS BREWING ENGINEERING 3 1 2 Brewery Engineering Lecture 1- P 30 4 5

31. A whirlpool can also be generated by inducing a liquid to swirl around, either from mechanical agitation (stirring): • or by tangentially directing the flow of a fast-moving stream within the bulk of the liquid: WHIRLPOOLS BREWING ENGINEERING Side Top Side Top Brewery Engineering Lecture 1- P 31

32. WHIRLPOOLS BREWING ENGINEERING • In many breweries, “whirlpooling” is a specific step in the brewing process. • Whirlpooling is done in order to help separate suspended solids (hop particles, hot-break material, trub etc.) from the liquid wort • Whirlpooling, if performed, is done right after the boil: Brewery Engineering Lecture 1- P 32

33. Barley Water Yeast Hops Adjuncts Energy Milling Ground Barley Yeast Starter Grind Settings Strain More Yeast Amount Mashing Temp. Wort Water to Grist Ratio Temp. Sparging Rate Wort Water to Grist Ratio Boiled Wort Boil Temp. Isomerized a-acids Time Maillard Reaction Products Type Finings Addition / Whirl pooling Hot Break Amount Time Wort Cooling Method Cooled Wort Temp. Time Wort Aeration Method Oxygenated Wort Amount Transfer to Fermenter Method Wort in Fermenter Transfer Rate Yeast Pitching Fermentation Temp. CO2 Time Beer Dry Hopping Time Conditioning Temp. CO2 Secondary Ferment Beer Lagering Packaging & Carbonating Packaged Beer Keg Finished Beer Carbonated Beer Bottle Time Storage Temp. Finished Beer (ageing) Light Exposure Consumption Temp. Joy ! Amount

34. Breweries sometimes even have tanks that are specifically designated for whirlpooling. Here’s a PFD to illustrate this: WHIRLPOOLS BREWING ENGINEERING Brewery Engineering Lecture 1- P 34

35. The moving liquid in a whirlpool causes suspended particulate matter to move to the center of the tank and form a cone: WHIRLPOOLS BREWING ENGINEERING Brewery Engineering Lecture 1- P 35

36. WHIRLPOOLS BREWING ENGINEERING • But why does this happen? • Why does rotating liquid within a tank cause suspended particulate matter to move inward? • Shouldn’t centrifugal force cause the particulate matter to be slung outward toward the tank wall? • What’s going on…….? Brewery Engineering Lecture 1- P 36

37. WHIRLPOOLS • First of all, lets talk through a simple, representative physical system (one that has been extensively analyzed) and discuss the forces at work within it. Let’s talk about tea in a teacup. Specifically, loose leaves being stirred in a teacup. • When the tea leaves are being stirred, they are rotating around the bottom of a cup, following the motion of the water that is induced by stirring. When the spoon is removed, the leaves begin to move towards the center and collect on the bottom of the cup (just like our trub collects in the center of the whirlpool). BREWING ENGINEERING Brewery Engineering Lecture 1- P 37

38. This can be explained by the fact that the pressure (and water level) near the side walls of the cup is higher than the pressure in the center when the water is rotating. • Note that the shape of the surface of the water, while the tea is rotating, is concave from the viewpoint of the drinker. • This pressure variation is the result of the centripetal acceleration that balances the centrifugal acceleration of the rotating liquid water. • It is this pressure gradient that induces a vortex effect within the system • But why does this pressure gradient exist? WHIRLPOOLS BREWING ENGINEERING Brewery Engineering Lecture 1- P 38

39. WHIRLPOOLS • The pressure gradient exists because water near the bottom of the cup cannot move as freely as the rest of the water within the cup. • The water moves much more slowly near the bottom of the cup because of frictional resistance to the movement. • The water touching the wall of the cup also experiences a similar frictional effect. • As a consequence of fluid friction, the angular momentum of the water near the bottom is not enough to oppose the effect of the radial pressure field created by the rotating water away from the bottom boundary layer. • The pressure variation is such that it pushes the water near the bottom of the cup towards the center. BREWING ENGINEERING Brewery Engineering Lecture 1- P 39

40. WHIRLPOOLS BREWING ENGINEERING • Because mass is conserved in this flow, the water that is caused to move towards the center of the cup then turns upward towards the surface. • When the water is near the surface, it then turns towards the side wall and finally moves down towards the bottom, replenishing the water that was originally there. • The tea leaves recirculate with the water and eventually become entangled with one another near the bottom-center of the cup. • Once they are clumped together, the upward movement of the water near the center is no longer sufficient to create a buoyant force that can overcome the force of gravity acting upon the leaves. When this happens, the leaves remain on the bottom at the center of the cup. Brewery Engineering Lecture 1- P 40

41. WHIRLPOOLS BREWING ENGINEERING • To summarize: • Moving water and tea leaves (or wort and trub) do experience centrifugal force, but the whirlpool effect "overpowers" the centrifugal force and circulates everything toward the center of the vessel in question. The fluid friction at the bottom of the vessel is actually responsible for this. • A vortex is induced because the water near the top is pushed out harder due to higher centrifugal force and less friction at the top of the liquid. • The water near the bottom is pushed out with less force because there is more friction and a lower centrifugal force near the bottom to push it out. • The weaker centrifugal force at the bottom of the vessel induces a pressure gradient that creates an inward recirculation flow. Brewery Engineering Lecture 1- P 41

42. WHIRLPOOLS BREWING ENGINEERING • For a commercial brewer, there are several factors that are important to consider when operating a whirlpool vessel: • vessel geometry, • feed velocity, and • rotation time Brewery Engineering Lecture 1- P 42

43. WHIRLPOOLS BREWING ENGINEERING • Vessel geometry is an important consideration for a whirlpool vessel because it directly impacts the fluid dynamics within the system and thus directly affects the systems ability to establish a good vortex. Commercial breweries usually use cylindrical or slightly cone-bottomed vessels with a depth:diameter ratio of between 1:1 to 1:5. • Feed velocity also affects the final results of the whirlpool. If the initial rotational velocity is too low, a poorly compacted trub cone (or no cone at all) will be formed. If the initial rotational velocity is too high, the trub cone may not hold together. Initial rotational velocities generally are determined by trial and error. • Rotation time is important because all of the fluid-dynamic-induced forces must have time to work their magic. Generally, commercial breweries allow a rotation time of between 10 and 40 minutes. Smaller tanks generally require less rotation time. Brewery Engineering Lecture 1- P 43

44. WHIRLPOOLS BREWING ENGINEERING • The optimum rotational velocity and rotation time for a whirlpool system depends on: • the geometry of the vessel, • the amount of friction between the wort and the vessel and • the clumping properties of the trub that is being formed into a cone within the whirlpool. • Optimal rotational velocity also depends (to a small extent) on the O.G. of the wort; whirlpool effectiveness decreases as the O.G. of the wort increases due to the fact that the relative density-differential between the wort and the trub decreases with increasing wort O.G. Brewery Engineering Lecture 1- P 44

45. WHIRLPOOLS BREWING ENGINEERING • When we began this discussion, we said that whirlpooling is done by brewers in order to help separate suspended solids (hop particles, hot-break material, trub etc.) from the liquid wort. • But aren’t there other ways to separate suspended solids from liquids? • What about simply filtering the wort? Wouldn’t that work? • What about just allowing the particles to settle out naturally using gravity? Wouldn’t that work? • The answers are “Yes” to all of the above questions, but there are reasons why brewers whirlpool anyway…… Brewery Engineering Lecture 1- P 45

46. WHIRLPOOLS BREWING ENGINEERING • Filtration is certainly a viable way to remove suspended solids. Filtering beer or wort is a good option for some styles of beer, but there are numerous reasons why this may not be the best choice: • Filtering removes flavor and color-producing compounds from the beer. • Filtering is also likely to increase the rate of oxidation of the beer by exposing it to more air than an equivalent unfiltered beer. • Filters cost money to purchase, cost money and time to operate and maintain, and can be a potential source for contamination within the brewery. • Using gravity to allow the particles to naturally settle is also a viable way to remove suspended solids, but this can be a very slow process when very small particles are involved. Brewery Engineering Lecture 1- P 46

47. WHIRLPOOLS BREWING ENGINEERING • Summary: • Whirlpools are used in the brewery to separate solid, particulate matter from liquid wort. • Whirlpools work the way they do because friction forces within the vessel create pressure differentials within the liquid that affect flow patterns and velocities within the whirlpool vessel • Factors that affect whirlpool vessel operation include: • vessel geometry, • liquid feed velocity, and • rotation time Brewery Engineering Lecture 1- P 47

48. Centrifuge Instead of Whirlpool? BREWING ENGINEERING • Can we use centrifuge similar to the one we use when filtering finished beer instead of a whirlpool? Brewery Engineering Lecture 1- P 48

49. Centrifuge Instead of Whirlpool? BREWING ENGINEERING • Yes! In fact there are dedicated “decanters” that are similar to a centrifuge designed exclusively for hot side trub and hop removal. • What are some pros and cons of using a centrifuge instead of a whirlpool? Brewery Engineering Lecture 1- P 49