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

1000 gallons of wort is transferred to a kettle through a 100 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 included twelve 90  elbows and one fully open globe valve?

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

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

Flow Measurement Principle: Bernoulli Equation Notice how this works for static fluids.

Flow Measurement – Orifice 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

Flow Measurement – Magnetic Faradays Law Magnetic field applied to the tube Voltage created proportional to velocity Requires a conducting fluid (non-DI water)

Flow Measurement – Magnetic

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. 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. Both tanks are at atmospheric pressure. 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-V 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

Pump Sizing Example Requirements 100 gpm 45 feet of head Choose the proper impeller Determine the power input to the pump