Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. •...

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Heat and mass Transfer MECH_KIOT_SALEM. Heat Transfer

Transcript of Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. •...

Page 1: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat and mass Transfer

MECH_KIOT_SALEM.

Heat Transfer

Page 2: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer

• Heat always moves from a warmer place to a cooler place.

• Hot objects in a cooler room will cool to room temperature.

• Cold objects in a warmer room will heat up to room temperature.

Heat Transfer

Page 3: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Question

• If a cup of coffee and a red popsickle were left on the table in this room what would happen to them? Why?

• The cup of coffee will cool until it reaches room temperature. The popsickle will melt and then the liquid will warm to room temperature.

Heat Transfer

Page 4: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer Methods

• Heat transfers in three ways:

–Conduction

–Convection

–Radiation

Heat Transfer

Page 5: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Conduction

When you heat a metal strip at one end, the heat

travels to the other end.

As you heat the metal, the particles vibrate, these

vibrations make the adjacent particles vibrate, and so on

and so on, the vibrations are passed along the metal and

so is the heat. We call this? Conduction Heat Transfer

Page 6: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Metals are different

The outer e______ of metal atoms drift, and are free to move.

When the metal is heated, this ‘sea of electrons’ gain k_____ energy and transfer it throughout the metal.

Insulators, such as w___ and p____, do not have this ‘sea of electrons’ which is why they do not conduct heat as well as metals.

lectrons

inetic

ood lastic

Heat Transfer

Page 7: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Why does metal feel colder than wood, if they

are both at the same temperature?

Metal is a conductor, wood is an insulator. Metal

conducts the heat away from your hands. Wood

does not conduct the heat away from your hands as

well as the metal, so the wood feels warmer than

the metal.

Heat Transfer

Page 8: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Convection

What happens to the particles in a liquid or a

gas when you heat them?

The particles spread out and become less dense.

This effects fluid movement.

What is a fluid? A liquid or gas.

Heat Transfer

Page 9: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Fluid movement

Cooler, more d____, fluids sink through w_____, less dense fluids.

In effect, warmer liquids and gases r___ up.

Cooler liquids and gases s___.

ense armer

ise

ink

Heat Transfer

Page 10: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Water movement

Hot water

rises Cooler

water sinks

Convection

current

Cools at the

surface

Heat Transfer

Page 11: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Why is it windy at the seaside?

Heat Transfer

Page 12: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Cold air sinks

Where is the freezer

compartment put in a fridge?

Freezer compartment

It is put at the top, because cool air sinks, so it cools the food on the way down.

It is warmer at the

bottom, so this warmer air rises and a convection current is

set up.

Heat Transfer

Page 13: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

The third method of heat transfer

How does heat energy get

from the Sun to the Earth?

There are no particles

between the Sun and the

Earth so it CANNOT

travel by conduction or

by convection.

? RADIATION

Heat Transfer

Page 14: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Radiation

Radiation travels in straight lines

True/False

Radiation can travel through a vacuum

True/False

Radiation requires particles to travel

True/False

Radiation travels at the speed of light

True/False

Heat Transfer

Page 15: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Emission experiment

Four containers were filled with warm water. Which

container would have the warmest water after ten minutes?

Shiny metal

Dull metal

Dull black

Shiny black

The __________ container would be the warmest after ten

minutes because its shiny surface reflects heat _______ back

into the container so less is lost. The ________ container

would be the coolest because it is the best at _______ heat

radiation.

shiny metal

radiation dull black

emitting

Heat Transfer

Page 16: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Absorption experiment

Four containers were placed equidistant from a heater. Which

container would have the warmest water after ten minutes?

The __________ container would be the warmest after ten

minutes because its surface absorbs heat _______ the best.

The _________ container would be the coolest because it is

the poorest at __________ heat radiation.

dull black radiation

shiny metal

absorbing

Shiny metal

Dull metal

Dull black

Shiny black

Heat Transfer

Page 17: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Convection questions

Why are boilers placed beneath hot water

tanks in people’s homes?

Hot water rises.

So when the boiler heats the water, and the hot water

rises, the water tank is filled with hot water.

Why does hot air rise and cold air sink?

Cool air is more dense than warm air, so the

cool air ‘falls through’ the warm air.

Heat Transfer

Page 18: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Radiation questions

Why are houses painted white in hot countries?

White reflects heat radiation and keeps the house cooler.

Why are shiny foil blankets wrapped around marathon

runners at the end of a race?

The shiny metal reflects the heat radiation from the runner

back in, this stops the runner getting cold.

Heat Transfer

Page 19: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

1. Which of the following is not a method of heat transfer?

A. Radiation

B. Insulation

C. Conduction

D. Convection

Heat Transfer

Page 20: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

2. In which of the following are the particles closest together?

A. Solid

B. Liquid

C. Gas

D. Fluid

Heat Transfer

Page 21: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

3. How does heat energy reach the Earth from the Sun?

A. Radiation

B. Conduction

C. Convection

D. Insulation

Heat Transfer

Page 22: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

4. Which is the best surface for reflecting heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black

Heat Transfer

Page 23: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

5. Which is the best surface for absorbing heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black

Heat Transfer

Page 24: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

CONVECTION HEAT TRANSFER

Modes

forced

flow induced by external agency e.g. pump

eg. forced-draught air cooler, evaporators

natural

fluid motion caused by temperature-induced

density gradients within fluid

Examples

air flow over hot steam pipe, fireplace

circulation, cooling electronic devices

Heat Transfer

Page 25: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

CONVECTION HEAT TRANSFER

Warm (lighter) air rises

Cool (more dense) air falls to replace warm rising air

Figure: Natural

convection flow

over a heated

steam pipe

Heat Transfer

Page 26: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Forced convection generally most-effective transport of

energy from solid to fluid.

Modelling Convection

SolidT

s Flowing

fluid

Tb

Q. Engineer's prime

concern

rate of convection

enables sizing of

equipment

Heat Transfer

Page 27: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Modelling Convection

h - convective heat transfer

coefficient.

Main problem

predict h value for:

• variety fluids & flow rates

• range of shapes

Experimentally found that:

s b

s b

Q A T T

Q A T Th

Heat Transfer

Page 28: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Rate equation Written in same form as Ohm’s Law:

Resistance Concept

Potential Difference V Current flow I =

Resistance R

s b s b

s b

T T T T Q A T T

1/ A Rh

h

(Ts-Tb)= driving force

(1/hA) – thermal resistance (R) for convection heat transfer.

Ts

hA

1

surf ace fluid

Q•

bT

Ts

bT

Q•

Heat Transfer

Page 29: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

TYPICAL UNITS FOR h

S.I.: W m-2

K-1

or J s-1

m-2

K-1

British: Btu hr-1

ft-2

(F deg)-1

Conversion: 1 W m-2

K-1

= 0.176 Btu hr-1

ft-2

(F deg)-1

Typical Values

free convection (air) 5 - 60

forced convection (air) 25 - 300

forced convection (water) 200 - 10,000

boiling water 2,000 - 25,000

condensing steam 4,000 - 110,000

Heat Transfer

Page 30: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Illustration 27.1

Air at 20°C is blown over an electrical resistor to keep it cool.

The resistor is rated at 40,000 ohm and has a potential

difference of 200 volts applied across it.

The expected mean heat transfer coefficient between the

resistor surface and the air is 50 W m-2K-1.

What will be the surface temperature of the resistor, which

has a surface area of 2 cm2?

R = 40,000

Air 20°C

h = 50 W m K

Potential = 200 V

Heat Transfer

Page 31: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

SOLUTION

Energy Balance

Generation = heat loss by convection

Rate of heat generation

Convective loss

2

2 2

4

P Q

VP VI V

R

V 200Q 1 watt

R 4x10

V

R

s b4

so

s

Q A(T T )

1 (50)(2x10 )(T 20)

T 120 C

h

Heat Transfer

Page 32: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Determining the size (H/T area) of the

exchanger

2 31 1 2 2 3 4

T T Q h A T T kA h A T T

x

Figure 1. Heat transfer between two flowing fluids

separated by a rectangular

1 4

1 2

T T overall driving forceQ

1 x 1 resis tances

h A kA h A

(10.25)

(10.26)

Heat Transfer

Page 33: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Determining the size (H/T area) of the

exchanger

i o

o

i

i i o o

i o

1 2 3

T T Q

rln

r1 1

h A 2 kL h A

T TQ

R R R

Figure 2: Heat transfer between

two flowing fluids separated by a

cylindrical wall (10.27)

Heat Transfer

Page 34: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Overall heat-transfer coefficient

2overall heat-transfer coefficient /o

where

U W m K

duty o

duty

o

Q U A T

T TQ

1 R

U A

As a short-hand method of describing heat-

exchanger performance, we use the overall heat-

transfer coefficient,

(10.28)

s bQ A T Th

Heat Transfer

Page 35: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Determining the size (H/T area) of the

exchanger

Heat Transfer

Page 36: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Illustration 27.2

Consider the kettle below. For the conditions given, find the flame

temperature for the following values of the heat transfer coefficients:

hi (boiling) = 4000 W m-2K-1 ho (gas flame) = 40 W m-2K-1

T

1

2

3

h

i

o

Water

Flam e

Q.

h

T

T

T

o

h

1

Q•

= 1.88 kW

hio

x

k

T0 1 2 3T = 100°CT T

1?

FLAME

BOILING WATER

Heat Transfer

Page 37: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Solution

Plane slab- area constant, eliminate A:

o o 1

1 1 x 1

U A h A kA h A

3

o

-2 -1o

1 1 1.2x10 1

U 40 204 4000

U 39.6 W m K

Heat Transfer

Page 38: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Solution

Q 1883 W (as before)

duty o o 3

dutyo 3

o

oo 3 2

oo

Q U A T T

QT T

AU1883

T T 1514K 1514 C3.14x10 39.6

T 1514 100 1614 C

-2 2A = 3.14x10 m (as before)

T

1

2

3

h

i

o

Water

Flam e

Q.

h

T

T

T

o

Heat Transfer

Page 39: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Determining the size (H/T area) of the

exchanger

• The term Tavg in equation 10.28 represents the temperature

difference between the hot and cold streams averaged.

• For single-pass exchangers, the appropriate form of Tavg is

the log-mean temperature difference, Tlog mean (often

abbreviated LMTD), defined as

(10.29)

duty o avg Q U A T (10.28)

log mean

1 2log mean

1

2

Log mean temperature difference T

T TT

Tln

T

Heat Transfer

Page 40: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Determining the size (H/T area) of the

exchanger

duty o avg Q U A T

(10. 30)

duty

o log mean

QA

U T

For shell-and-tube exchangers, the

inside area (Ai) of the tubes is smaller

than the outside area (Ao). However,

the differences between Ai and Ao will

be neglected.

Heat Transfer

Page 41: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Example

Hot

Cold

Saturated Steam,

280oF, mstream

Saturated water,

280oF, mstream

Oil, 110oF, 960 lbm/min Oil, 35oF, 960 lbm/min

Balance on cold stream:

p out in dutycold

omdutyo

m cold

duty

mC T T Q 10.24b

lb Btu960 0.74 110 35 F Q

min lb F

BtuQ 53,280

min

Heat Transfer

Page 42: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Example

How much area is required for the counter-current heat

exchanger in Example 10.5?

Hot

Cold

Saturated Steam,

280oF, mstream

Saturated water,

280oF, mstream

Oil, 110oF, 960 lbm/min Oil, 35oF, 960 lbm/min

o1

o2

olog mean

T 280 35 245 F

T 280 110 170 F

245 170T 205 F

245ln170

1

2

Heat Transfer

Page 43: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Example

o2

o2o

2

oBtu

hr ft F

U 150 Btu / hr ft F

53,280 Btu/min 60minA 104 ft

1hr150 205 F

From table 10.5

Heat Transfer

Page 44: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Example

How much area is required for the co-current heat exchanger

in Example 10.5?

Hot

Cold

Saturated Steam,

280oF, mstream

Saturated water,

280oF, mstream

Oil, 110oF, 960 lbm/min Oil, 35oF, 960 lbm/min

o1

o2

olog mean

T 280 110 170 F

T 280 35 245 F

170 245T 205 F

170ln245

1

2

Heat Transfer

Page 45: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Example

o2

o2o

2

oBtu

hr ft F

U 150 Btu / hr ft F

53,280 Btu/min 60minA 104 ft

1hr150 205 F

From table 10.5

Heat Transfer

Page 46: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Flow Patterns

• Parallel Flow

• Counter Current Flow

• Shell and Tube with baffles

• Cross Flow

Heat Transfer

Page 47: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Temperature Profiles

ΔT = Approach Temperature

Heat Transfer

Page 48: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Exchanger

Temperature Profiles

Heat Transfer

Page 49: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Flow Structure

incoldinhot

incoldoutcold

incoldoutcold

outhotinhot

TT

TTS

TT

TTR

RRS

RRSR

RS

SR

F

112

112ln1

1

1ln1

2

2

2

Q=U A F ΔTlm-counter

Heat Transfer

Page 50: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Overall Heat Transfer Coefficient

• Series of Resistances

• Basis

– Inside

– Outside

1

,, 1)ln(21)1(

ofoioowiio

i

oifo RhDDDkhDD

A

ARU

Inside

Tubes

Rf=fouling factors, inside and outside

See table 18.5 for range of U values for different cases. Heat Transfer

Page 51: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer inside a tube

Turbulent000,10Re

700,16Pr7.0

esmooth tub,60/

PrRe027.0

14.0

3/18.0

f

p

w

b

f

k

C

DL

k

hDNu

Also other correlations valid over wider ranges Heat Transfer

Page 52: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer outside of Tube

000,100Re40

300Pr67.0

2.525.0

Pr)Re06.0Re4.0(

25.0

4.03/25.0

f

p

w

b

w

b

f

k

C

k

hDNu

Also other correlations valid over wider ranges Heat Transfer

Page 53: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Thermal Conductivity

Heat Transfer

Page 54: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

What Temperature Approach

• Heuristic 26.

– Near-optimal minimum temperature approaches in heat exchangers depend on the temperature level as follows:

– 10°F or less for temperatures below ambient,

– 20°F for temperatures at or above ambient up to 300°F,

– 50°F for high temperatures,

– 250 to 350°F in a furnace for flue gas temperature above inlet process fluid temperature.

Heat Transfer

Page 55: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Where are the Heat Exchangers?

What is happening in each

Octane Reaction

2C2H4 + C4H10 C8H18

P= 20 psia, T=93C,

X=98% Conversion

TBP

C2H4 −103.7 °C

C4H10 +0.5 °C

C8H18 +125.52 °C

Heat Transfer

Page 56: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Where are the Heat Exchangers?

Heat Transfer

Page 57: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer With Phase Change

• Tricky Problems

– Examples

• Reboiler on Distillation Unit

• Condenser on Distillation Unit

• Flash Units

• Boilers

Heat Transfer

Page 58: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

A Word About Steam

• Simulator Assumptions

– Inlet – Saturated Vapor – Pressure

– 100% Vapor

– Outlet – Saturated Liquid

• Liquid Only Leaves via steam trap – Pressure = Pin- ΔP (1.5 psi, Heuristic-31)

– 100% Liquid

Heat Transfer

Page 59: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Where are the Tricky

Heat Exchangers?

Heat Transfer

Page 60: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Condensation Heat Transfer

• Drop Wise Condensation

– Special Case

• Very High Heat Transfer

• 5 to 10 x Film Condensation

• Film Condensation

– Laminar

4/13

)(4

)(

xTT

kHg

k

xhNu

wvl

lvapvll

l

xx

Heat Transfer

Page 61: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Laminar to Turbulent Condensate Flow

Heat Transfer

Page 62: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Boiling Heat Transfer Coefficient

Various correlations depending upon boiling mechanism

Highest Heat

Transfer Coef.

But hard to

control HX

operating here

Heat Transfer

Page 63: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heuristic 28

• Boil a pure liquid or close-boiling liquid mixture in a separate heat exchanger, using a maximum overall temperature driving force of 45 F to ensure nucleate boiling and avoid undesirable (low h) film boiling.

Heat Transfer

Page 64: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Effective Flow Conditions with Boiling in Thermo siphon

Heat Transfer

Page 65: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Kettle (Re)Boiler Design

Heat Transfer

Page 66: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Aspen - Zone Analysis ProMax – Heat Release Increments

• Heuristic 29. – When cooling and condensing a stream in a heat exchanger, a zone

analysis, described in Section 18.1, should be made to make sure that the temperature difference between the hot stream and the cold stream is equal to or greater than the minimum approach temperature at all locations in the heat exchanger. The zone analysis is performed by dividing the heat exchanger into a number of segments and applying an energy balance to each segment to determine corresponding stream inlet and outlet temperatures for the segment, taking into account any phase change. A process simulation program conveniently accomplishes the zone analysis.

Heat Transfer

Page 67: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Pressure Drop & Flow Rate

• Laminar vs. Turbulent

– Heuristic 31.

• Estimate heat-exchanger pressure drops as follows: – 1.5 psi for boiling and condensing,

– 3 psi for a gas,

– 5 psi for a low-viscosity liquid,

– 7-9 psi for a high-viscosity liquid,

– 20 psi for a process fluid passing through a furnace.

Heat Transfer

Page 68: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Controlling ΔP in Simulator

• Shell side – Nozzle diameter

• Inlet and Outlet

– Number of Baffles – Tubes

• Number, diameter, pitch, No. passes

• Tube side – Nozzle diameter

• Inlet and Outlet

– Tubes • Number, diameter, pitch, No. passes

Note interactions! Heat Transfer

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Shell Heads, Shell Type

• See ProMax Help/index “Shell, types”

Heat Transfer

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HX Cost

• Size Factor HX Area • CBase(6-2000)=exp[11.0545-0.9228*ln(A)+0.09861*ln(A)2]

• Purchase Price – CP-fob=FP(P)*FMaterial(A)*FL(L)*CBase*(CPI/394)

– CBM=FBM*CP-fob

– CBM=3.17*CP-fob

• Cost depends on HX Area • Pumping Cost

– Work = Q*ΔP

Heat Transfer

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Controlling A in Simulator

• A = Ntubes π Dtubes Ltubes

• Shell – Shell Diameter and pitch determines Ntubes

• Tubes – Dtubes

– Ltubes

– Tube pitch-The transverse pitch is the shortest distance from the center lines of two adjacent tubes.

– Tube pitch ratio 1.25 to 1.5 typically

Heat Transfer

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Other Issues

• Materials of Construction

– Strength at temperature, life time, heat conduction,

fouling

• Design layout

– Tube pitch, baffles, tube and shell diameters

Heat Transfer

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Heat Exchangers

• Heaters (sensible heat changes)

• Coolers (sensible heat changes)

• Condensers (also change of state, V to L)

• Evaporators (also change of state, L to V)

Heat Transfer

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Types of Heat Exchanger

• Shell and tube • Double pipe • Plate • Finned tubes/gas heaters • spiral • Vessel jackets • Reboilers and vapourisers/evaporators Etc • Direct/indirect

Heat Transfer

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Uses in chemical processes

• Chemical reactors (jackets, internal heat exchangers/calandria) • Preheating feeds • Distillation column reboilers • Distillation column condensers • Air heaters for driers • Double cone driers • evaporators • Crystallisers • Dissolving solids/solution • Production support services – HVAC, etc • Heat transfer fluids • etc

Heat Transfer

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continued

Important consideration in:

• Scale-up i.e. laboratory scale (‘kilo lab’) to pilot plant scale (250 litres) to full plant scale operation (10000 litres)

• Energy usage and energy costs

• Process design and development

Heat Transfer

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Heat transfer fluids

• Steam (available at various temperatures and pressures) • Cooling water (15oC) • Chilled water (5oC) • Brines (calcium chloride/water fp. -18 deg cent. at 20% by

mass; sodium chloride/water fp. -16.5 deg cent. at 20 % by mass)

• Methanol/water mixtures • Ethylene glycol/water mixtures • Propylene glycol/water mixtures (fp. -22 deg cent at a

concentration of 40% by mass) • Silicone oils (‘syltherm’)

Heat Transfer

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Low temperature heat transfer fluids

Considerations:

• Temperature(s) required

• Freezing point

• Viscosity

• Specific heat

• Density

• Hazardous properties

Heat Transfer

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Mechanisms for heat transfer

• Conduction

• Convection

• Radiation

Driving force for heat transfer is temperature difference. Heat will only flow from a hotter to a colder part of a system.

Heat Transfer

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Heat transfer by conduction

Fouriers law

dQ/dt = -kA(dT/dx)

dQ/dt – rate of heat transfer

k – thermal conductivity

A – area perpendicular to direction of heat transfer, x

dT/dx – temperature gradient in direction x

Heat Transfer

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Heat transfer by conduction (steady state)

Q = kmA (ΔT/x) or q = km (ΔT/x) q – heat flux, J/s m-2

Q - rate of heat transfer, J/s km – mean thermal conductivity, A – area perpendicular to the direction of heat transfer,

m2

ΔT – temperature change (T1 – T2), K x – length, m

Heat Transfer

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Thermal conductivity, k

k (300K), Wm-1 K-1

Copper 400

Water 0.6

air 0.03

Heat Transfer

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Conduction of heat through cylindrical vessels

Q = k2πLΔT/ln(r2/r1)

L – length of tube/cylinder

r2 external radius

r1 internal radius

Heat Transfer

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AL , log mean wall area

Q = kmAL (T1 – T2)

r2 – r1

where AL= 2πL (r2 – r1)

ln(r2/r1)

Heat Transfer

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‘thin walled tube’approximation

Assumptions:

• Thin wall and therefore xw is small and since k is large, term xw/kALis negligible compared to other terms

• Also A terms cancel as they are approximately equal

1/U = 1/h1 + 1/h2

Heat Transfer

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Fouling factors

Heat transfer surfaces do not remain clean. They become contaminated with dirt, scale, biofilms etc. This has the effect of reducing the overall heat transfer coefficient and reducing the rate of heat transfer. We take account of this by adding a term 1/Ahd for each deposit to the equation for the overall heat transfer coefficient, U, where hd is the fouling factor for the deposit and A is the corresponding area term. They represent an additional resistance to heat transfer.This will have the effect of reducing U and therefore Q.

Heat Transfer

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Heat flow (duty)

Q = hAΔT

or

Q = UAΔT

Heat Transfer

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Sensible heat changes

Q = mcpΔT

m mass flow, kg/s

Cp specific heat J kg-1 K-1

ΔT change in temperature of fluid

Heat Transfer

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Enthalpy balance

Enthalpy lost by hot fluid = enthalpy gained by cold fluid

(Assume negligible heat losses to surroundings)

Heat Transfer

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Simple double tube single pass heat exchanger

• Co-current operation

• Counter-current operation

• Temperature profiles

• LMTD

Heat Transfer

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Heat exchanger duty

Q = UAθlmtd

Heat Transfer

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Multi pass shell and tube heat exchangers

• LMTD correction factor, F

• LMTD value used is that for counter current flow with same fluid inlet/outlet temperatures

Q = UAθlmtdF

Heat Transfer

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Example – double pass

T1

T2

t1

t2

T1 = 455K; T2 = 388K; t1 = 283K; t2 = 372K

Heat Transfer

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continued

P = (372 – 283)/(455 – 283) = 0.52

R = (455 – 388)/(372 – 283) = 0.75

Therefore F= 0.87 (from graph)

To obtain maximum heat recovery from the hot fluid, t2 must be as high as possible.

T2 – t2 is known as the approach temperature.

Heat Transfer

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Dittus-Boelter equation

Used for calculating h values in circular tubes under turbulent flow conditions.

Nu = 0.023 Re0.8 Pr 0.4

Heat Transfer

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Heat transfer by radiation

q = eσ(T14 – T2

4)

q – heat flux

e – emissivity (0 to 1) – typically 0.9

σ – Stefan-Boltzmann const.(5.67 x 10-8 W m-2 K-4)

T1 – temp. of body (K)

T2 – temp. of surroundings

Heat Transfer

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Types of heat exchanger – shell & tube

• Passes

• shell

• Multiple tubes

• Baffles

• Co- and counter current operation

Heat Transfer

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Plate

• Individual separated thin corrugated parallel s.s. plates

• Gaskets separate plates • Gap approx. 1.4mm • Plate and frame arrangement • High h values at relatively low Re values and low flow

rates • Can operate with small ΔT • Reduced fouling • Easy cleaning

Heat Transfer

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Finned tubes

• Radial fins

• Longitudinal fins

• For air/gas heaters where film heat transfer coefficients on gas side will be very low compared with condensing steam on the other side of tube. Rate of heat transfer is increased by increasing surface area on side of tube with the limiting (low) heat transfer coefficient (gas side).

Heat Transfer

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References • An Introduction to Industrial Chemistry, Ed. C. A. Heaton

• Concepts of Chemical Engineering 4 Chemists, Ed. S. Simons, RSC, 2007

• Unit Operations of Chemical Engineering, W. L. McCabe et al

• Chemical Engineering Vol. 1, Coulson & Richardson

• Heat Transfer, R. Winterton

• Introduction to Heat Transfer, F. P. Incropera & D. P. DeWitt

• Ullmans Encyclopedia of Industrial Chemistry

• Engineering Thermodynamics

Heat Transfer

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Definition of Radiation

• “Radiation is an energy in the form of electro-magnetic waves or particulate matter, traveling in the air.”

Heat Transfer

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• Forces: There are many interactions among nuclei. It turns out that there are forces other than the electromagnetic force and the gravitational force which govern the interactions among nuclei.

• Einstein in 1905m showed 2 more laws: energy/mass, and binding energy

Heat Transfer

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Radioactivity: Elements & Atoms

Atoms are composed of smaller particles

referred to as:

– Protons

– Neutrons

– Electrons

Heat Transfer

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Basic Model of a Neutral Atom.

• Electrons (-) orbiting nucleus of protons (+) and neutrons. Same number of electrons as protons; net charge = 0.

• Atomic number (number of protons) determines element.

• Mass number (protons + neutrons)

Heat Transfer

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Heat Transfer

Page 106: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Radioactivity

• If a nucleus is unstable for any reason, it will emit and absorb particles. There are many types of radiation and they are all pertinent to everyday life and health as well as nuclear physical applications.

Heat Transfer

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Ionization

Ionizing radiation is produced by unstable atoms.

Unstable atoms differ from stable atoms because

they have an excess of energy or mass or both.

Unstable atoms are said to be radioactive. In order

to reach stability, these atoms give off, or emit, the

excess energy or mass. These emissions are called

radiation.

Heat Transfer

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Heat Transfer

Page 109: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer

Page 110: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer

Page 111: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer

Page 112: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Types or Products of Ionizing

Radiation

or X-ray neutron

Heat Transfer

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Ionizing Radiation

alpha particle

beta particle

Radioactive Atom

X-ray

gamma ray

Heat Transfer

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• The electro-magnetic waves vary in their length and frequency along a very wide spectrum.

Heat Transfer

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Heat Transfer

Page 116: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer

Page 117: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer

Page 118: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Types of Radiation

• Radiation is classified into:

–Ionizing radiation

–Non-ionizing radiation

Heat Transfer

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Ionizing Versus Non-ionizing

Radiation Ionizing Radiation

– Higher energy electromagnetic waves (gamma) or

heavy particles (beta and alpha).

– High enough energy to pull electron from orbit.

Non-ionizing Radiation

– Lower energy electromagnetic waves.

– Not enough energy to pull electron from orbit, but

can excite the electron.

Heat Transfer

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Ionizing Radiation

• Definition:

“ It is a type of radiation that is able to disrupt atoms and molecules on which they pass through, giving rise to ions and free radicals”.

Heat Transfer

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Another Definition

Ionizing radiation A radiation is said to be ionizing when it has enough

energy to eject one or more electrons from the atoms or

molecules in the irradiated medium. This is the case of a

and b radiations, as well as of electromagnetic radiations

such as gamma radiations, X-rays and some ultra-violet

rays. Visible or infrared light are not, nor are microwaves

or radio waves.

Heat Transfer

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Primary Types of Ionizing

Radiation

Alpha particles

Beta particles

Gamma rays (or photons)

X-Rays (or photons)

Neutrons

Heat Transfer

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Alpha Particles: 2 neutrons and 2 protons

They travel short distances, have large mass

Only a hazard when inhaled

Types and Characteristics of Ionizing

Radiation

Alpha Particles

Heat Transfer

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• Alpha Particles (or Alpha Radiation): Helium nucleus (2 neutrons and 2 protons); +2 charge; heavy (4 AMU). Typical Energy = 4-8 MeV; Limited range (<10cm in air; 60µm in tissue); High LET (QF=20) causing heavy damage (4K-9K ion pairs/µm in tissue). Easily shielded (e.g., paper, skin) so an internal radiation hazard. Eventually lose too much energy to ionize; become He.

Heat Transfer

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Beta Particles

Beta Particles: Electrons or positrons having small mass and

variable energy. Electrons form when a neutron transforms

into a proton and an electron or:

Heat Transfer

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• Beta Particles: High speed electron ejected from nucleus; -1 charge, light 0.00055 AMU; Typical Energy = several KeV to 5 MeV; Range approx. 12'/MeV in air, a few mm in tissue; Low LET (QF=1) causing light damage (6-8 ion pairs/µm in tissue). Primarily an internal hazard, but high beta can be an external hazard to skin. In addition, the high speed electrons may lose energy in the form of X-rays when they quickly decelerate upon striking a heavy material. This is called Bremsstralung (or Breaking) Radiation. Aluminum and other light (<14)

materials are used for shielding.

Heat Transfer

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Heat Transfer

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Gamma Rays

Gamma Rays (or photons): Result when the

nucleus releases energy, usually after an alpha,

beta or positron transition

Heat Transfer

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X-Rays

X-Rays: Occur whenever an inner shell

orbital electron is removed and

rearrangement of the atomic electrons

results with the release of the elements

characteristic X-Ray energy

Heat Transfer

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• X- and Gamma Rays: X-rays are photons (Electromagnetic radiations) emitted from electron orbits. Gamma rays are photons emitted from the nucleus, often as part of radioactive decay. Gamma rays typically have higher energy (Mev's) than X-rays (KeV's), but both are unlimited.

Heat Transfer

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Neutrons

Neutrons: Have the same mass as

protons but are uncharged

Heat Transfer

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Heat Transfer

Page 133: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

Heat Transfer

Page 134: Heat and mass TransferHeat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature. • Cold objects in

QUANTIFICATION OF RADIATION

• A. Quantifying Radioactive Decay

• B. Quantifying Exposure and Dose

Heat Transfer

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A. Quantifying Radioactive Decay

Measurement of Activity in disintegrations per second (dps);

• 1 Becquerel (Bq) = 1 dps;

• 1 Curie (Ci) = 3.7 x 1010 dps;

• Activity of substances are expressed as activity per weight or volume (e.g., Bq/gm or Ci/l).

Heat Transfer

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B. Quantifying Exposure and Dose

• Exposure: Roentgen 1 Roentgen (R) = amount of X or gamma radiation that produces ionization resulting in 1 electrostatic unit of charge in 1 cm3 of dry air. Instruments often measure exposure rate in mR/hr.

• Absorbed Dose: rad (Roentgen absorbed dose) = absorption of

100 ergs of energy from any radiation in 1 gram of any material; 1 Gray (Gy) = 100 rads = 1 Joule/kg; Exposure to 1 Roentgen approximates 0.9 rad in air.

• Biologically Equivalent Dose: Rem (Roentgen equivalent man)

= dose in rads x QF, where QF = quality factor. 1 Sievert (Sv) = 100 rems.

Heat Transfer

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Half Life Calculation

Heat Transfer

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Ionizing Radiation at the Cellular

Level

Causes breaks in

one or both DNA

strands or;

Causes Free Radical

formation

Heat Transfer

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Exposure Limits

• OSHA Limits: Whole body limit = 1.25 rem/qtr or 5 rem (50 mSv) per year.

• Hands and feet limit = 18.75 rem/qtr.

• Skin of whole body limit = 7.5 rem/qtr.

• Total life accumulation = 5 x (N-18) rem where N = age. Can have 3 rem/qtr if total life accumulation not exceeded.

• Note: New recommendations reduce the 5 rem to 2 rem.

Heat Transfer

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External/Internal Exposure Limits for

Occupationally Exposed Individuals Annual Dose Limits

Adult (>18 yrs)

Minor (< 18 yrs)

Whole body*

5000 mrem/yr

500 mrem/yr

Lens of eye

15000 mrem/yr

1500 mrem/yr

Extremities

50000 mrem/yr

5000 mrem/yr

Skin

50000 mrem/yr

5000 mrem/yr

Organ

50000 mrem/yr

5000 mrem/yr

*Effective dose equivalent

Heat Transfer

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Community Emergency Radiation

Hazardous Waste Sites:

• Radiation above background (0.01-0.02 m rem/hr) signifies possible presence which must be monitored. Radiation above 2 m rem/hr indicates potential hazard. Evacuate site until controlled.

Heat Transfer

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Your Annual Exposure

Activity Typical Dose

Smoking 280 millirem/year

Radioactive materials use

in a UM lab <10 millirem/year

Dental x-ray 10 millirem per x-

ray

Chest x-ray 8 millirem per x-

ray

Drinking water 5 millirem/year

Cross country round trip by

air 5 millirem per trip

Coal Burning power plant 0.165

millirem/year Heat Transfer

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• HEALTH EFFECTS

• Generalizations: Biological effects are due to the ionization process that destroys the capacity for cell reproduction or division or causes cell mutation. A given total dose will cause more damage if received in a shorter time period. A fatal dose is (600 R)

• Acute Somatic Effects: Relatively immediate effects to a person acutely exposed. Severity depends on dose. Death usually results from damage to bone marrow or intestinal wall. Acute radio-dermatitis is common in radiotherapy; chronic cases occur mostly in industry.

Heat Transfer

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0-25 No observable effect.

25-50 Minor temporary blood changes.

50-100 Possible nausea and vomiting and

reduced WBC.

150-300 Increased severity of above and diarrhea,

malaise, loss of appetite.

300-500 Increased severity of above and

hemorrhaging, depilation. Death may

occur

> 500 Symptoms appear immediately, then

death has to occur.

ACUTE DOSE(RAD) EFFECT

Heat Transfer

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• Delayed Somatic Effects: Delayed effects to exposed person include: Cancer, leukemia, cataracts, life shortening from organ failure, and abortion. Probability of an effect is proportional to dose (no threshold). Severity is independent of dose. Doubling dose for cancer is approximately 10-100 rems.

• Genetic Effects: Genetic effects to off-spring of exposed persons are irreversible and nearly always harmful. Doubling dose for mutation rate is approximately 50-80 rems. (Spontaneous mutation rate is approx. 10-100 mutations per million population per generation.)

Heat Transfer

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• Critical Organs: Organs generally most susceptible to radiation damage include: Lymphocytes, bone marrow, gastro-intestinal, gonads, and other fast-growing cells. The central nervous system is relatively resistant. Many nuclides concentrate in certain organs rather than being uniformly distributed over the body, and the organs may be particularly sensitive to radiation damage, e.g., isotopes of iodine concentrate in the thyroid gland. These organs are considered "critical" for the specific nuclide.

Heat Transfer

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Non-ionizing Radiation

• Definition:

“ They are electromagnetic waves incapable of producing ions while passing through matter, due to their lower energy.”

Heat Transfer

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– All earth surface system components emit radiation---the sun and the earth are the components we are most interested in

– The sun emits radiation composed of high energy infrared radiation, visible light, and ultraviolet radiation collectively known as shortwave radiation (SW)

– The earth emits radiation composed of lower energy infrared radiation collectively known as long-wave radiation (LW)

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Path of incoming solar radiation

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Albedo: a measure of how well a surface

reflects insolation

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Examples on Non-ionizing

Radiation Sources

Visible light

Microwaves

Radios

Video Display Terminals

Power lines

Radiofrequency Diathermy (Physical

Therapy)

Lasers

MICROWAVE

GAMMA

ULTRA V VISIBLE

INFRARED

TV AM RF

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Other Manmade Sources of Non-Ionizing Radiation

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Effects

Radiofrequency Ranges (10 kHz to 300 GHz)

– Effects only possible at ten times the permissible exposure limit

– Heating of the body (thermal effect)

– Cataracts

– Some studies show effects of teratoginicity and carcinogenicity.

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RADIATION CONTROLS

• A. Basic Control Methods for External Radiation

Decrease Time

Increase Distance

Increase Shielding

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• Time: Minimize time of exposure to minimize total dose. Rotate employees to restrict individual dose.

• Distance: Maximize distance to source to maximize

attenuation in air. The effect of distance can be estimated from equations.

• Shielding: Minimize exposure by placing absorbing

shield between worker and source.

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B. Monitoring

• Personal Dosimeters: Normally they do not prevent exposures (no alarm), just record it. They can provide a record of accumulated exposure for an individual worker over extended periods of time (hours, days or weeks), and are small enough for measuring localized exposures Common types: Film badges; Thermoluminescence detectors (TLD); and pocket dosimeters.

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• Direct Reading Survey Meters and Counters: Useful in identifying source of exposures recorded by personal dosimeters, and in evaluating potential sources, such as surface or sample contamination, source leakage, inadequate decontamination procedures, background radiation.

Common types:

• Alpha Proportional or Scintillation counters

Beta, gamma Geiger-Mueller or Proportional counters X-ray, Gamma Ionization chambers Neutrons Proportional counters

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• Continuous Monitors: Continuous direct reading ionization detectors (same detectors as above) can provide read-out and/or alarm to monitor hazardous locations and alert workers to leakage, thereby preventing exposures.

• Long-Term Samplers: Used to measure average exposures over a longer time period. For example, charcoal canisters or electrets are set out for days to months to measure radon in basements (should be <4 pCi/L).

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Elements of Radiation Protection Program • Monitoring of exposures: Personal, area, and screening

measurements; Medical/biologic monitoring. • Task-Specific Procedures and Controls: Initial, periodic, and

post-maintenance or other non-scheduled events. Engineering (shielding) vs. PPE vs. administrative controls. Including management and employee commitment and authority to enforce procedures and controls.

• Emergency procedures: Response, "clean-up", post clean-up testing and spill control.

• Training and Hazard Communications including signs, warning lights, lockout/tagout, etc. Criteria for need, design, and information given.

• Material Handling: Receiving, inventory control, storage, and disposal.

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Thank You

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