So, what do we need to know about H.T.?3.8.1 Forms of heat energy3.8.2 Heat transfer mechanisms3.8.3 Conduction3.8.4 Convection3.8.5 Multi-Component Barrier3.8.6 Boiling and Condensation3.8.7 Radiation3.8.8 Heat Exchanger Sizing3.8.9 Plate Heat Exchanger Design3.8.10 Plate Heat Exchanger Applications3.8.11 Jacketed Vessels3.8.12 Shell and Tube Applications3.8.13 Insulation

Forms of Heat EnergySpecific Heat CapacityLatent Heat (enthalpy of vaporization)Exothermic Heat (chemical to sensible)Examples of these in brewery

Heat transfer mechanisms• Conduction – contact between atoms/mol.• Convection – in fluid, natural or forced• Radiation – electromagnetic waves

Conduction –• Thick walled tubes – Area increases with radius. Log mean radius.• Fouling – Thin layer of low k material.

Convection – What is it?• Natural vs. forced convection• Effect of velocity, turbulence (vel profile)• Film heat transfer coefficient

Some Heat Transfer Equations for multi-component systems (MANY APPLICATIONS):

€

˙ Q = UoAΔT

€

Rconduction = xk

€

Rconvection = 1hinsidewoutsideo hk

xhU

111

Boiling and CondensationNucleate vs. film boilingCopper – well wetted surfaceStainless steel – less-well wettedLarger bubbles on stainless (larger surface

tension)Smaller bubbles better (conductivity of

liquid greater than vapor)Effect of delta T between boiling liquid and

heat transfer surface

RadiationFactors effecting radiation heat transferAreas of brewery where rad is significant

Heat exchange – conservation of energyRate of Ein – Rate of Eout = Rate of E Accumulation

WortH2O

0,,,, 22222 outOHinOHOHpOHOHin TTcmQ

0,,,, outwortinwortwortpwortwortout TTcmQ

0,,,,,, 2222 outOHinOHOHpOHoutwortinwortwortpwort TTcmTTcm

Log Mean Temperature DifferenceParallel Flow Counter Flow

Length

Tem

pera

ture

T1 T T2

Length

Tem

pera

ture T1

TT2

Log Mean Temperature Difference

2

1

21

lnTT

TTTm

€

˙ Q = UoAΔTm

Plate Heat Exchangers• Construction, Components, and Configuration• Function of Plate Patterns• Typical Heat Transfer Coefficients• Importance of Gaskets, Divider Plates• Parallel and Series Passes to Match Flow and Heat Requirements• Typical Approach Temperatures• Calculation of Area, Number of Plates

Plate heat exchanger (wort, beer cool, pasteurize)

Use of Plate Heat Exchangers in:• Wort cooling (both single and 2 stage)• Beer chilling• Pasteurizaton• Importance of fouling/ scaling problems• CIP techniques• Process and instrumentation arrangement• Leakage protection

Two-stage wort cooler

Single-stage stage wort cooler

Hot Wort 85C

Hot Water 80C

Cool Wort 15C

Cold Water 10C

2nd Refrig. -5C

Cold Wort 0C

2nd Refrig. 10C

Hot Wort 85C

Cold Wort 7-15C

Cold Water 10C

2nd Refrig. -5C

Colder Water 2C

Hot Water 80C

CIP of Plate Heat Exchanger

Jacketed Vessels

Shell and Tube (steam raising, calandria)

Insulation• Above ambient temp – open pore

• Fiberglass• Below ambient temp – closed pore

• Plastic foams• Air is good (low conductivity)• Convection is bad (tiny air pockets)• Water is bad (higher k than air)

Right Now

Heat transfer problems.

Readings for Next Tuesday

CD, Section 3.8

Review BS+T pp. 102-113

Read BS+T pp. 115-143

Read Kunze pp. 232-235, 289-319, 347-352, 816-821