heat transfer

1. APPLICATION OF HEAT
TRANSFER IN BIOPROCESS
A.SHEIK ABDULLA
M.SORNAMALYA
M.THASLEEMA PARVEEN
3RD YEAR B.TECH(BIOTECH)
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2. HEAT TRANSFER
 In Bioprocessing, heat exchange/transfer occurs between the
fluids.
 Equipment is provided to allow transfer of heat while
preventing the fluids to contact with each other.
 Heat is transferred through a solid metal wall.
 Sufficient area is provided so that heat is transferred.
 Heat transfer is facilitated by aeration and turbulent flow of the
fluids.
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3. EQUIPMENT USED FOR HEAT
EXCHANGE IN BIOREACTORS
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4. TYPES OF HEAT EXCHANGER
 Double-pipe heat exchanger
 Shell and tube heat exchanger
 Plate –fin heat exchanger
single-pass shell and tube heat exchanger
double tube-pass heat exchanger
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5. DOUBLE-PIPE HEAT EXCHANGER
 It consists of two metal pipes , one inside the other.
 One fluid flows through the inner tube while the other fluid
flows in the annular space between the pipe walls.
 Due to this the hot fluid becomes cold and cold fluid becomes
warmer.
 It can be operated with counter current or co-current flow of
fluids.
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DOUBLE PIPE HEAT EXCHANGER
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FLOW ARRANGEMENTS
counter current
Fluid flows in opposite direction
co-current flow
Fluids flow in same direction
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SHELL-&-TUBE HEAT EXCHANGER
SINGLE-PASS SHELL-AND-TUBE HEAT
EXCHANGER
 It is used for all type of fluids.
 It occupies large surface area.
 The heat transfer system is in two sections :a tube bundle and a
shell or cavity.
 Where one fluid flows into the shell and other flows into the
tube.
 The shell and tube fluids pass through the length of the
equipment only once.
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SINGLE-PASS SHELL-AND-TUBE
HEAT EXCHANGER
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DOUBLE TUBE-PASS HEAT
EXCHANGER
 The flow of tube and shell fluids are countercurrent for one
tube pass and cocurrent for other.
 Due to the action of baffles cross flow of shell fluid normal to
the tubes.
 Temperature cross occurs where the temperature of the hot
fluids equals to the temperature of the cold fluid .
 This can be avoided by increasing the number of shell pass.
 So, heat exchangers with multiple shell-pass can be used.
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DOUBLE TUBE-PASS HEAT
EXCHANGER
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TEMPERATURE CHANGES IN
EXCHANGER
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PLATE-FIN HEAT EXCHANGER
 It uses plates and finned chambers to transfer heat between
fluids.
 It is made of layers of corrugated sheets separated by flat metal
plates.
 It has relatively high heat transfer surface area to volume ratio.
 Separate hot and cold fluid streams flow through alternating
layers of the heat exchanger.
 They are enclosed at the edges by side bars.
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14. PLATE-FIN HEAT
EXCHANGER
FLOW ARRANGEMENTS
 This allows for the two
fluids to result in cross
flow, counter flow and
cross-counter flow
 It can work in perfect
countercurrent
arrangement.
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MECHANISM OF HEAT TRANSFER
Conduction:-
By Fourier’s law, the rate of heat conduction is
Ǭ = – kA (dT/dy)
Where,
Ǭ - rate of heat transfer
k - thermal conductivity
A - surface area perpendicular to direction of heat flow
(dT/dy) - temperature gradient
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Steady state Conduction:-
From conduction,
Ǭdy = – kAdT
by integration,
Ǭʃdy = – kAʃdT
Ǭy = – kAT
In case of boundary condition T=T1 at y=0
Ǭ = ( kA/y) (T1 –T)
Ǭ at steady state is same at all point y including y=B and T=T2
Ǭ = (kA/B) ΔT
(kA/B) can be written as (1/RW)
RW = B/kA
RW = thermal resistance to heat transfer
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EFFECT OF THICKNESS ON SURFACE
AREA FOR HEAT TRANSFER
 In cylindrical geometry, the hot fluid is flowing inside a pipe
while cold fluid flows outside.
 Because of inside diameter is smaller than outside diameter,
the surface area for heat transfer between the fluid and the wall
are different from two fluids.
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 40% to 50% of energy are stored s a carbon source and which
gets converted into ATP remaining are released as a heat.
 Heat is directly related to growth for actively growing cells.
 Heat generated can be calculated using the heat of combustion
of the substrate and of cellular material.
ΔΗs /YX/S = ΔΗc +(1/YH ) - 1
Where,
ΔΗs – heat of combustion of the substrate
YX/S - substrate yield coefficient
ΔΗc - heat of combustion of the cells
(1/YH )- metabolic heat evolved /g of cell mass produced
HEAT GENERATION BY
MICROBIAL GROWTH
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ENTHALPHY BALANCE FOR MICROBIAL
UTILIZATION OF SUBSTRATE
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From eqn 1,
YH = YX/S /(ΔΗs - YX/S ΔΗc )
 ΔΗs andΔΗc can be determined from the combustion of
substrate and cells
 The degree of oxidation of the substrate has a strong effect on
heat released.
 The total heat evolution in a batch fermentation is
QGR = VL µnet X(1/YH ) (QGR ≈ 0.12QO2 )
Where,
VL – liquid volume
X – cell concentration
 That metabolic heat released during the fermentation can be
removed by the heat exchanger.
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REFERENCES
 Bioprocess engineering principle: Pauline M. Doran
 Bioprocess engineering basic concepts: Michael L. Shuler and
Fikret Kargi
 https://en.wikipedia.org/wiki/Plate_fin_heat_exchanger
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