So Far:Mass and Volume Flow Rates

Reynolds No., Laminar/TurbulentPressure Drop in PipesFlow Measurement, ValvesTotal Head, Pump Power, NPSH

This Week:Bernoulli’s Equation and its ApplicationPump Sizing, Types of PumpsConservation of Energy

Pump Sizing

1. Volume Flow Rate (m3/hr or gpm)

2. Total Head, h (m or ft)

2a. P (bar, kPa, psi)

3. Power Output (energy added to fluid) and Input (mechanical shaft power from motor)

4. NPSH Required

hgP

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

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

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 ImpellerMost common, low solidsWater, beer, wortFlash pasteurizationRefrigerants

Open ImpellerLower pressuresSolids okayMash to lauter turnLiquid 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 Efficiency High 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

TransferYeastTrubBulk Sugar Syrup