Week 1 Unit Conversions Conservation of Mass Ideal Gas Newtonian Fluids, Reynolds No. Pressure Loss in Pipes Week 2 Fluid Flow Examples Flow Measurement and Valves Pump Calcs and Sizing

1000 gallons of wort is transferred to a kettle through a 15 m long, 4 cm diameter pipe with a roughness of 0.01 mm. The wort flows at a velocity of 1.2 m/s and assume that its physical properties are the same as those of water. 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, assuming that the wort remains at 72  C. d) Would  P change if the wort were at 20  C?

Head vs.  P Head/Pressure loss in Fittings and Valves Reference Sheet

Consider the previous example. How would the pressure drop change if the pipework includes twelve 90  elbows and one half- open globe valve?

Valves – Brewery Applications Product Routing – Tight shutoff, material compatibility, CIP critical Butterfly and mixproof Service Routing – Tight shutoff and high temperature and pressure Butterfly, Ball, Gate, Globe Flow Control – Precise control of passage area Globe (and needle), Butterfly Pressure Relief – Control a downstream pressure

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 – Mix-proof Double Seat Two separate sealing elements keeping the two fluids separated. 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

Bernoulli Equation Notice how this works for static fluids.

Flow Measurement – Oriface Meter C d accounts for frictional loss,  0.65 Simple design, fabrication High turbulence, significant uncertainty P1P1 P2P2

Flow Meas. – Venturi Meter Less frictional losses, C d  0.95 Low pressure drop, but expensive Higher accuracy than orifice plate P1P1 P2P2

Flow Meas. – Variable Area/Rotameter Inexpensive, good flow rate indicator Good for liquids or gases No remote sensing, limited accuracy

Flow Measurement - Pitot Tube Direct velocity measurement (not flow rate) Measure  P with gauge, transducer, or manometer P1P1 P2P2 1 2 v

Flow Measurement – Weir Open channel flow, height determines flow Inexpensive, good flow rate indicator Good for estimating flow to sewer Can measure height using ultrasonic meter

Flow Measurement – Thermal Mass Measure gas or liquid temperature upstream and downstream of heater Must know specific heat of fluid Know power going to heater Calculate flow rate

Pumps z = static head h f = head loss due to friction Pump SuctionDelivery

Pumps

Calculate the theoretical pump power required to raise 1000 m 3 per day of water from 1 bar to 16 bar pressure. If the pump efficiency is 55%, calculate the shaft power required. If the electrical efficiency is 95%, calculate the electrical power required. Denisity of Water = 1000 kg/m 3 1 bar = 100 kPa

Pumps A pump, located at the outlet of tank A, must transfer 10 m 3 of fluid into tank B in 20 minutes or less. The water level in tank A is 3 m above the pump, the pipe roughness is 0.05 mm, and the pump efficiency is 55%. The fluid density is 975 kg/m 3 and the viscosity is Pa.s. Determine the total head and pump input and output power. Tank A Tank B 8 m 15 m 4 m Pipe Diameter, 50 mm Fittings = 5 m

Pumps Need Available NPSH > Pump Required NPSH Avoid Cavitation z = static head h f = head loss due to friction

Pumps A pump, located at the outlet of tank A, must transfer 10 m 3 of fluid into tank B in 20 minutes or less. The water level in tank A is 3 m above the pump, the pipe roughness is 0.05 mm, and the pump efficiency is 55%. The fluid density is 975 kg/m 3 and the viscosity is Pa.s. The vapor pressure is 50 kPa and the tank is at atmospheric pressure. Determine the available NPSH. Tank A Tank B 8 m 15 m 4 m Pipe Diameter, 50 mm Fittings = 5 m

Pump Sizing 1. Volume Flow Rate (m 3 /hr or gpm) 2. Total Head,  h (m or ft) 2a.  P (bar, kPa, psi) 3. Power Output (kW or hp) 4. NPSH Required

Pumps Centrifugal Impeller spinning inside fluid Kinetic energy to pressure Flow controlled by P delivery Positive Displacement Flow independent of P delivery Many configurations

Centrifugal Pumps Impeller Suction Volute Casting Delivery

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

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

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

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

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

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

Centrifugal Pumps Pump sizing example. Let’s say we need a pump for the following application: Total head: 8 m Flow rate: 25 m 3 /hr NPSH available: 2 m Fluid: Water at 20  C Start with APV Crepaco Model 6V 2 at 1750 rpm. Select an impeller size and it’s corresponding efficiency, flow capacity, and power (kW)

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

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

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

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 EfficiencyHigh Pressures Metering hop compounds, detergents, sterilents Suction Valve Delivery Valve

Positive Displacement Pumps Peristaltic Pump

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

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

Liquid-Solid Separation Types of Filtration Gravity, Vacuum, Pressure, Centrifugal Driving Force MechanicalDialysisElectrostaticMagnetic FiltrationSedimentation

Filtration Media Glass fiber Paper fabric Monofilament cloth Metal or plastic mesh or screen Pack beds Bridging effect of filter cloth Filter cake buildup becomes “filter media”

Filtration Performance of Filters Ability to retain solids (high surface area) Low flow resistance Mechanical strength Low cost Inert to cleaning/processing chemicals Brewery applications of filtration Mash or Lauter tun – gravity filtration Filtering wort and beer – pressure filtration Separating beer from yeast – pressure filter

Liquid-Solid Separation Sedimentation – gravity or centrifugal Terminal settling velocity – time required TSV increases with: Larger particles Greater density difference between fluid, particle Lower fluid viscosity Weight Drag Force