Master Brewer Program (6 Weeks) 1. Fluids fundamentals and equipment. 2. Fluids test. Heat transfer...
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Transcript of Master Brewer Program (6 Weeks) 1. Fluids fundamentals and equipment. 2. Fluids test. Heat transfer...
Master Brewer Program (6 Weeks)
• Fluids fundamentals and equipment.
• Fluids test. Heat transfer fundamentals and equipment.
• Heat transfer test. Insulation, steam, refrigeration.
• Heat exchanger/steam/refrigeration test. Materials, process control.
• Materials and process control test. Instrumentation, pasteurization, filtration and process gases.
• Instrumentation, pasteurization, filtration and process gas test. Wrap-up.
How this Relates to the IBD Syllabus3.1 Packaging Materials3.2 Unit Packaging Operations3.3 Sterile Filtration and Pasteurization3.4 Packaging Line Design3.5 Quality3.6 Process Gases3.7 Fluid Flow3.8 Principles of Heat Transfer3.9 Steam3.10 Refrigeration3.11 Materials of Construction3.12 Process Control and Instrumentation
So, what do we need to know about fluids
3.7.1 Forms of fluid and fluid energy
3.7.2 Properties of moving fluids
3.7.3 Friction loss
3.7.4 Pumps
3.7.5 System design
3.7.6 Cavitation and NPSH
3.7.7 Valves
Qualitative and Quantitative
• Liquids – take shape of container, but have finite volume (incompressible)
• Gases – are compressible, take size and shape of container
• Shear force will always deform a fluid
• Mass and volume flow rates
• Newtonian Fluid – Shear resistance proportional to relative velocity between fluid layers
• Newtonian – Water, air, beer
• Non-Newtonian – Gelatin, blood, milk, mash, wort
Example: Water with density of 1000 kg/m3 flows through a 10.0 cm diameter pipe at a velocity of 5 m/s. The pipe size is then reduced to a 5.0 cm diameter. Determine the mass and volumetric flow rates and the velocity of the water in the 5.0 cm pipe.
Bernulli’s equation:
Applications• No-flow• Flow through orifice plate, venturi meter
“Head” = Pressure
Determine the absoluteP in the tank using themanometer (water)
constant2
1 2 gzvP
ghP
PTank
18 cm
Fluid Statics
Example: Water fills a 10 m deep tank with a 10 cm diameter butterfly valve at the bottom. Calculate the gauge pressure at the valve and the force acting on the valve, assuming that it is round.
Example: Water with density of 1000 kg/m3 flows through a 10.0 cm diameter pipe at a velocity of 5 m/s. The pipe size is then reduced to a 5.0 cm diameter. Determine the mass and volumetric flow rates and the velocity of the water in the 5.0 cm pipe.
atmgaugeabs PPP AFP
Reynolds NumberLaminar flow - “low” flow rates, viscous forces most significantTurbulent flow - “high” flow rates, inertial
forces most significant
Re < 2300 Laminar2300 < Re < 5000 TransitionalRe > 5000 Fully Turbulent
D
mD
4
Re
Laminar flow velocity profile (mean / max = 0.5)
Turbulent flow velocity profile (mean / max = 0.8)
22 v CD
LP f
500 gallons of wort at 70C is transferred to a boil kettle through a 25 m long, 5 cm diameter pipe. The wort flows at a velocity of 1.2 m/s, the pipe roughness is 0.005 mm the wort density is 950 kg/m3 and it’s viscosity is 0.0008 Pa.s.
a) Determine the time required to transfer all of the wort to the boil kettle, in min.
b) Determine the Reynolds Number.
c) Determine the pressure drop in the pipe.
d) Would P change if the wort were at 20C?
Example E.2
Beer flows in a straight horizontal pipeline, diameter 100 mm such that two sensitive pressure gauges 25 m apart register a pressure difference of 240 Pa (N/m2). The density of the beer is 1.001x103 kg/m3, its viscosity is 0.001 Ns/m2 and the relative roughness of the pipe is 0.0003. Calculate the velocity and volumetric flow rate of beer.
Flow Measurement – Oriface Meter
Cd accounts for frictional loss, 0.65
Simple design, fabrication
High turbulence, significant uncertainty
P1 P2
Flow Meas. – Venturi Meter
Less frictional losses, Cd 0.95
Low pressure drop, but expensive
Higher accuracy than orifice plate
P1P2
Flow MeasurementNon-Linear – Venturi, orifice, nozzle meters
4:1 Rangability
2% f.s. accuracy
Flow Meas. – Variable Area/Rotameter
Inexpensive, good flow rate indicator
Good for liquids or gases
No remote sensing, limited accuracy
WeightDragForces
mgvCdrag 2
2
10
vAV
Flow Measurement - Pitot Tube
Direct velocity measurement (not flow rate)
Measure P with gauge, transducer, or manometer
P1
P2
1 2
2
2
21v
PP
v
Flow MeasurementMagnetic – Faraday’s Law (Conductor moving
through magnetic field, voltage produced)
40:1 Rangability
0.5% of f.s. accuracy
No obstructions
Fluid must conductNo good for
• Pure water• Gases• Hydrocarbon fuels
External elec/mag fields
Flow MeasurementTurbine – magnetic pulse as turbine wheel spins
20:1 Rangability, 0.25% f.s. accuracy
Easy to interface with control system
Pumps – Add energy to liquid to move it
Pump power output =
Pump power input =
Pump power requirements includeHeight fluid must be pumpedFriction losses through fittings, equipmentVapor pressure of fluid, tank pressures
Total head, NPSH eqations
€
˙ V ΔP
€
˙ V ΔP
η
Pump Sizing Example
A pump, located at the outlet of tank A,must transfer 20 m3 of fluid into tank B in 30 minutes or less. The piperoughness is 0.005 mm, and the pumpefficiency is 55%. The fluid density is 975 kg/m3 and the viscosity is 0.00075Pa.s. The vapor pressure is 10 kPa andthe tank is at atmospheric pressure.Determine the total head, pump inputand output power and available NPSH.
Tank A
Tank B
8 m
15 m
4 m
Pipe Diameter,
25 mm
Fittings = 12 m
Centrifugal Pumps• Fluid enters at center and forced radially• Open or closed impeller
• Closed higher efficiency• Open handles solids better
Advantages• Available, cheap, adaptable, simple, reliable• Handle wide range of fluids, including solids• Discharge can be completely blocked
Disadvantages• Operate at high speed, high shear stress• Limited delivery pressure• Cannot meter flow
Positive Displacement Pumps• Reciprocating (Piston, Diaphram)• Rotary (Gear, peristaltic, lobe)
Advantages• High delivery pressure• Accurate for metering flows
Disadvantages• Pulsating delivery• Tight tolerance, so not good for solids
(except for mono pump)• Serious damage if discharge valve closed• Bigger and more costly for given application
Cavitation• Formation of bubbles• Pressure drops below vapor pressure
(friction losses)Effects
• Surface pitting and erosion• Loss of performance (changed tolerances)• High shear stresses
Particular concern when pumping wort from kettle to cooler
NPSH Required – Pump characteristicNPSH Available – Configuration characteristic
Considerations for Brewery Fluid HandlingMulti-component – sugars, proteins, etc.
Multi-phase – liquids, solids and/or gases
Biologically active – Sensitive to temperature, pressure, pH, contaminants, etc.
Sensitive to oxygen
• Surface area exposed, still or wavy
• Temperature and pressure
• Avoid less than full flow
• Avoid filling tanks from the top
Sensitive to shear forces
Centrifugal Pumps – Principle of Operation
Constantρgzρv2
1P 2
Impeller
SuctionVolute Casting
Delivery
Centrifugal Pumps – Principle of Operation
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
Centrifugal Pumps – Impeller Designs
Closed ImpellerMost common, few solidsWater, beer, wortFlash pasteurizationSecondary refrigerants
Open ImpellerLower pressuresSolids okayMash mixer to lauter tunLiquid yeast, wort, hops
Centrifugal Pumps
Materials - Can be made of many materialsWhat do you think is used in brewery?
Shaft seal – Must seal between rotating shaft and volute casting, effects efficiency
Hygiene Considerations – No valves, crevices, can be CIP. Mechanical seal between two faces (impeller shaft and volute casting) faces kept together with spring.
Centrifugal Pumps
Control – Valve on delivery side or change pump speed (not always available, “VFD”)
Self-Priming – Centrifugal pump will not work when “air-bound.” Can self-prime by supplying a reservoir with a “bleed supply” of liquid. Air from pipework and liquid from reservoir moves through pump until it is flooded by liquid from suction pipework. Used for CIP fluid return.
Centrifugal Pumps
Multiple pumps connected in series required for high pressures (flash pasteurization)
Curves created for specific speed, viscosity and density
Variable speed motor has same effect as impeller size
Multiple pump/impeller combinations may work
Centrifugal PumpsH-Q Chart
Head
(or P)
Volume Flow Rate
Increasing Impeller Diameter
A B C
Centrifugal PumpsH-Q Chart
Head
(or P)
Volume Flow Rate
A B C
Increasing Efficiency
Required NPSH
Centrifugal PumpsH-Q Chart
Head
(or P)
Volume Flow Rate
A B C
Centrifugal PumpsH-Q Chart
Head
(or P)
Volume Flow Rate
Required Flow
CapacityActual Flow
Capacity
Required Power
Centrifugal PumpsAdvantages
Simple construction, many materialsNo valves, can be cleaned in placeRelatively inexpensive, low maintenanceSteady delivery, versatileOperates at high speed (electric motor)Wide operating range (flow and head)
DisadvantagesMultiple stages needed for high pressuresPoor efficiency for high viscosity fluidsMust prime pump
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
Positive Displacement Pumps
Piston Pump
Volumetric Efficiency High Pressures
Metering hop compounds, detergents, sterilents
Suction Valve
Delivery Valve
Positive Displacement Pumps
Diaphragm Pump – Similar to piston pump, diaphragm contacts fluid
Not as accurate as piston pump, particles okay
Transfer trub, yeast, tank bottoms
Suction Valve
Delivery Valve
Positive Displacement PumpsPeristaltic Pump
Tubing compressed in stagesHygienic, easily cleaned (new tubing)Can be run dryLaboratory applications, sampling,
dosing
Positive Displacement Pumps
Gear Pump
High Pressures
No Pulsation
High Viscosity Fluids
No Solids
Difficult to Clean
Not common in brewery, oil feed to boiler
Positive Displacement Pumps
Lobe Rotor Pump
Both lobes driven
Can be sterilized(steam)
TransferYeastTrubBulk Sugar Syrup
Positive Displacement Pumps
Screw or Mono PumpHelical worm rotates inside elastomeric stator
Seal between worm and stator
Fluid is forced downstream
Variety of fluids, slurries.
Cannot be steam sterilized, cannot run dry
Used to transfer yeast and trub slurries
Flexible Vane Pump
Flexible rubber impeller rotates
Sampling and dosing detergents, sterilents
Centrifugal Pumps• Fluid enters at center and forced radially• Open or closed impeller
• Closed higher efficiency• Open handles solids better
Advantages• Available, cheap, adaptable, simple, reliable• Handle wide range of fluids, including solids• Discharge can be completely blocked
Disadvantages• Operate at high speed, high shear stress• Limited delivery pressure• Cannot meter flow
Positive Displacement Pumps• Reciprocating (Piston, Diaphram)• Rotary (Gear, peristaltic, lobe)
Advantages• High delivery pressure• Accurate for metering flows
Disadvantages• Pulsating delivery• Tight tolerance, so not good for solids (except
for mono pump)• Serious damage if discharge valve closed• Bigger and more costly for given application
Pump Selection Considerations• Head and flow requirements• Characteristics of fluid (density, viscosity, etc.)• Materials (sterilization, erosive nature of slurries)• Crevices where solids can accumulate• Hygienic design, seals• Pressure relief• Interchangability (spares)
Cavitation and NPSH• What causes cavitation?• What are the effects of cavitation?• Factors that cause cavitation?• NPSH Available vs. NPSH Required• Particular problems for breweries
Centrifugal Pumps
What if available NPSH is less than required NPSH?
Increase Available NPSH1. 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 NPSH1. Reduce pump speed
2. Select a different pump
Valves – Globe Valve
Single Seat- Good general purpose- Good seal at shutoff
Double Seat- Higher flow rates- Poor shutoff (2 ports)
Three-way- Mixing or diverting- As disc adjusted, flow to one channel increased, flow to other decreased
Valves – Butterfly Valve
Low Cost
“Food Grade”
Poor flow control
Can be automated
Valves – Mixproof Double Seat Valve
Two separate sealing elements
Keeps fluids from mixing
Immediate indication of failure
Automated, Sanitary apps
Easier and Cheaper than using many separate valves
Valves – Gate Valve
Little flow control, simple, reliable
Valves – Ball Valve
Very little pressure loss, little flow control
Other ValvesDiaphram – Flexing membraneNon-return – Flow in one direction only
ApplicationsProduct - Butterfly and mix-proof common,
diaphram. Hygiene critical.Service – Butterfly, globe, gate, ball. High temperature, pressure.Flow control – Globe, modified globe and modified butterfly.Pressure reduction – Spring loaded pressure
reducing valve. Often for steam.Pressure relief – Spring or weight loaded.
Valves – Considerations
Duty – What the valve is designed to do (on/off, product routing, pressure reduction, etc.)
Process – Corrosion of valve body, seals
Temperature – Closed valve, solidifying product
Pressure – Max and min, do not overpressure
Capacity – Flow for given pressure
Leakrate – Maximum allowable leakage
Connections – Flanges, NPT, tubing, hose, etc.
Actuator – Torque, fail open or closed
Feedback – Signal indicating valve’s position
Valves in Breweries
Product Routing – Tight shut-off, CIP, material compatibility (elastomer seals). Butterfly and mixproof common.
Service Routing – Tight shut-off, high temperature and pressure. Globe, gate, ball.
Flow ControlWater temperature controlSteam flow rate control in wort boilingFermentation vessel temperature controltank gas top pressure controlCO2 addition during in-line carbonationwater addition during high gravity brewing
Readings for Next Week
BS+T – Chapter 1 (if you don’t read anything else, read this)
Singh – Chapter 2
Kunze – 10.5.1, 6.1.2, 6.1.3, 3.3.3, 3.3.4