Heat Exchangers
Transcript of Heat Exchangers
Saturday, April 8, 2023Saturday, April 8, 2023 11
Heat ExchangersHeat Exchangers
B K KumbharB K Kumbhar
Saturday, April 8, 2023Saturday, April 8, 2023 22
Presentation pointsPresentation points
Importance & ClassificationImportance & Classification Types of Heat Exchangers in Dairy & Food Types of Heat Exchangers in Dairy & Food
IndustryIndustry Selection of Heat ExchangersSelection of Heat Exchangers Indirect Contact Type Heat Indirect Contact Type Heat Direct Contact Type Heat Direct Contact Type Heat
Saturday, April 8, 2023Saturday, April 8, 2023 33
Heat ExchangerHeat Exchanger Heating and/or cooling of the process streams during Heating and/or cooling of the process streams during
processing processing Heat transfer between two fluids through a separating wall Heat transfer between two fluids through a separating wall
or by direct contact with each otheror by direct contact with each other Classification based onClassification based on
Degree of heat transfer surface compactness Degree of heat transfer surface compactness Construction features Construction features
Flow arrangementsFlow arrangementsNumber of fluids Number of fluids Heat transfer mechanismsHeat transfer mechanisms
Saturday, April 8, 2023Saturday, April 8, 2023 44
In Dairy and Food IndustriesIn Dairy and Food Industries
Direct ContactDirect Contact
Steam InjectionSteam Injection
Steam infusionSteam infusion
Indirect ContactIndirect Contact
TubularTubular
PlatePlate
Jacketed KettleJacketed Kettle
Saturday, April 8, 2023Saturday, April 8, 2023 55
Selection of Heat ExchangersSelection of Heat Exchangers
Flow Rate of Both the Fluids Flow Rate of Both the Fluids Heat SensitivityHeat Sensitivity Terminal TemperaturesTerminal Temperatures Types of Fluids Types of Fluids Properties of Both FluidsProperties of Both Fluids Flow ArrangementFlow Arrangement Operating Pressure and TemperatureOperating Pressure and Temperature Pressure DropPressure Drop
Contd
Saturday, April 8, 2023Saturday, April 8, 2023 66
Selection of Heat Exchangers ----contdSelection of Heat Exchangers ----contd
Heat Recovery Heat Recovery FoulingFouling Ease of Inspection, Cleaning, Repair & Ease of Inspection, Cleaning, Repair &
MaintenanceMaintenance Materials of ConstructionMaterials of Construction Cost of Heat ExchangerCost of Heat Exchanger
Saturday, April 8, 2023Saturday, April 8, 2023 77
Flow Rate of Both the FluidsFlow Rate of Both the Fluids
SizeSizeLengthLengthWidthWidthHeightHeightWeightWeight
Site RequirementSite RequirementLifting and Servicing capabilitiesLifting and Servicing capabilitiesInventory ConsiderationsInventory Considerations
Sizing of the Heat ExchangerSizing of the Heat ExchangerMinimum Pressure DropMinimum Pressure DropFlow RatioFlow Ratio
Saturday, April 8, 2023Saturday, April 8, 2023 88
Heat SensitivityHeat Sensitivity
Low Hold-up VolumeLow Hold-up Volume Low Residence TimeLow Residence Time Low Surface Temperature Low Surface Temperature
RequirementsRequirements Good Flow DistributionGood Flow Distribution High Heat Transfer CoefficientHigh Heat Transfer Coefficient Small Channel VolumeSmall Channel Volume
Saturday, April 8, 2023Saturday, April 8, 2023 99
Terminal TemperaturesTerminal Temperatures Performance of Heat Exchanger depends on terminal Performance of Heat Exchanger depends on terminal
temperaturestemperatures
Heat Transfer Units (HTU) defined asHeat Transfer Units (HTU) defined asRatio ofRatio of
* Temperature of one fluid* Temperature of one fluid * Mean temperature difference between the fluids * Mean temperature difference between the fluids
Plate heat exchanger > Tubular Heat Exchanger Plate heat exchanger > Tubular Heat Exchanger Up to 4 HTU in case of Plate heat exchanger Up to 4 HTU in case of Plate heat exchanger
Saturday, April 8, 2023Saturday, April 8, 2023 1010
Types of FluidsTypes of Fluids
LiquidsLiquids GasesGases
Tubular heat exchanger suitable for condensable Tubular heat exchanger suitable for condensable gases (steam)gases (steam)
Plate heat exchanger suitable for liquids with less Plate heat exchanger suitable for liquids with less than 50000 cPthan 50000 cP
Saturday, April 8, 2023Saturday, April 8, 2023 1111
Properties of Both FluidsProperties of Both Fluids
Heat Transfer CalculationsHeat Transfer Calculations Pumping CalculationsPumping Calculations
ViscosityViscosityLow viscosity- Low viscosity- Plate heat exchanger Plate heat exchanger
High viscosity- High viscosity- Scraped surface heat exchanger Scraped surface heat exchanger Thermal conductivityThermal conductivity DensityDensity Specific heatSpecific heat Thermal diffusivityThermal diffusivity
Saturday, April 8, 2023Saturday, April 8, 2023 1212
Flow ArrangementFlow Arrangement
ConcurrentConcurrent – – Flow in same directionFlow in same direction Thermodynamically poorThermodynamically poor High thermal stresses since large temperature difference at inletHigh thermal stresses since large temperature difference at inlet Heat sensitive materialsHeat sensitive materials
Counter currentCounter current- - flow opposite to each otherflow opposite to each other Thermodynamically superiorThermodynamically superior Minimum thermal stressesMinimum thermal stresses Maximum heat recoveryMaximum heat recovery Least heat transfer area Least heat transfer area
Cross flowCross flow- - Flow perpendicular to each otherFlow perpendicular to each other In between the aboveIn between the above Design of headers require less spaceDesign of headers require less space Space is important Space is important
Saturday, April 8, 2023Saturday, April 8, 2023 1313
Saturday, April 8, 2023Saturday, April 8, 2023 1414
Operating Pressure and TemperatureOperating Pressure and TemperatureMechanical DesignMechanical Design Operating PressureOperating Pressure Operating TemperatureOperating Temperature
Problems of high operating temperature and pressureProblems of high operating temperature and pressure VibrationVibration FatigueFatigue Thermal stresses, etc.Thermal stresses, etc.
Plate heat exchanger free from such problems however plate Plate heat exchanger free from such problems however plate thickness and gasket material limit its applicationthickness and gasket material limit its application
Saturday, April 8, 2023Saturday, April 8, 2023 1515
Maximum Operating ConditionsMaximum Operating Conditions
Heat ExchangerHeat Exchanger T, T, 00CC P, kg/cm²P, kg/cm² Q, l/hQ, l/h
Plate heat exchangerPlate heat exchanger 260260 21 21 50,00,0050,00,00 Double pipeDouble pipe 540540 70 70 no limitno limit Shell and tubeShell and tube 540540 105105 no limitno limit Scraped surfaceScraped surface 250 250 35 35 27,0027,00 KettleKettle 260260 5 5 - -
Saturday, April 8, 2023Saturday, April 8, 2023 1616
Pressure DropPressure Drop
Important forImportant for Pumping CostPumping Cost - - proportional to pressure dropproportional to pressure drop
Heat Transfer RateHeat Transfer Rate - - proportional to pressure dropproportional to pressure drop
Specific pressure drop defined asSpecific pressure drop defined as Pressure drop per unit HTUPressure drop per unit HTU Used to compare the performance of different heat exchangersUsed to compare the performance of different heat exchangers
Saturday, April 8, 2023Saturday, April 8, 2023 1717
Heat RecoveryHeat Recovery
Conservation of energy- very important Conservation of energy- very important Recovery of heat from used/waste process streamsRecovery of heat from used/waste process streams
Less than 50% in tubular heat exchangersLess than 50% in tubular heat exchangers Up to 95% in plate heat exchangerUp to 95% in plate heat exchanger
Saturday, April 8, 2023Saturday, April 8, 2023 1818
FoulingFoulingDeposition of solid material-Deposition of solid material- poor conductor of heat poor conductor of heat
* * Decreases heat transferDecreases heat transfer* Decreases flow rate* Decreases flow rate* Lead to corrosion* Lead to corrosion* Loss of valuable materials* Loss of valuable materials* Affects the design and size of the unit* Affects the design and size of the unit* Affects the production runs * Affects the production runs
Factors affecting foulingFactors affecting fouling Velocity- Velocity- High velocity less foulingHigh velocity less fouling
* Shearing force* Shearing force * Turbulence* Turbulence* Laminar layer thickness* Laminar layer thickness * Residence time* Residence time
Surface temperatureSurface temperature – important for heat sensitive liquids – important for heat sensitive liquids
- small temperature difference required- small temperature difference required Bulk fluid temperatureBulk fluid temperature – more fouling in less bulk temperature – more fouling in less bulk temperature
CompositionComposition
Saturday, April 8, 2023Saturday, April 8, 2023 1919
Ease of Inspection, Cleaning, Repair & MaintenanceEase of Inspection, Cleaning, Repair & Maintenance
Requirement Requirement PHE PHE DPDP STST SS SS Kettle Kettle Inspection for foulingInspection for fouling Product side Product side a a b b a a a a a a Media side Media side a a b b b/d b/d d d c/dc/d
Inspection for leakageInspection for leakage Product side Product side a a b/c b/c b/d d b/d d c/d c/d Media side Media side a a a a a b a b aa
Inspection for corrosionInspection for corrosion Product side Product side a a a/b a/b a/d a/d a a a a Media side Media side a a b/d b/d a/dc a/dc c c b/cb/c
a: Very good b: Acceptable c: Poor d: Impossible a: Very good b: Acceptable c: Poor d: Impossible PHE- Plate heat exchanger DP- double pipe ST- shell and tube SS- scraped PHE- Plate heat exchanger DP- double pipe ST- shell and tube SS- scraped
surface surface
Saturday, April 8, 2023Saturday, April 8, 2023 2020
Ease of Inspection, Cleaning, Repair & Maintenance Ease of Inspection, Cleaning, Repair & Maintenance ------contd------contd
Chemical cleaningChemical cleaning Product side Product side a a a a b/c a b/c a a a Media side Media side a a a a a a a a aa
Manual cleaningManual cleaning Product side Product side a a b b a a a a a a Media side Media side a a c/d c/d a/d a/d d d c/dc/d
Extension Extension a a b/d b/d d d d d dd
Repair Repair a a b/c b/c b b a a aa
Saturday, April 8, 2023Saturday, April 8, 2023 2121
Materials of ConstructionMaterials of ConstructionMaterial of construction depends onMaterial of construction depends on Properties of the fluids such as heat sensitivity, fouling, corrosivity, Properties of the fluids such as heat sensitivity, fouling, corrosivity, Operating temperature and pressureOperating temperature and pressure Welding easeWelding ease AvailabilityAvailability Conformance to all applicable laws, codes and insurance Conformance to all applicable laws, codes and insurance
requirementsrequirements CostCost
MaterialsMaterialsStainless steelStainless steel Carbon steelCarbon steel GraphiteGraphiteAluminumAluminum TitaniumTitanium HastalloyHastalloy
GasketsGasketsNitryl rubberNitryl rubber Butyl rubberButyl rubberTeflonTeflon Compressed asbestos fibersCompressed asbestos fibers
Saturday, April 8, 2023Saturday, April 8, 2023 2222
Cost of Heat ExchangerCost of Heat Exchanger
Optimization based on cost considerationOptimization based on cost consideration Consider all above factorsConsider all above factors
Saturday, April 8, 2023Saturday, April 8, 2023 2323
Indirect Contact Type Heat ExchangersIndirect Contact Type Heat Exchangers
Plate heat exchangerPlate heat exchanger Tubular heat exchangersTubular heat exchangers
Double pipe heat exchangerDouble pipe heat exchanger Scraped surface heat exchanger (SSHE)Scraped surface heat exchanger (SSHE) Spiral tube heat exchangerSpiral tube heat exchanger Shell and tube heat exchangerShell and tube heat exchanger
Jacketed kettleJacketed kettle
Saturday, April 8, 2023Saturday, April 8, 2023 2424
Plate Heat ExchangerPlate Heat Exchanger Consists of rectangular thin corrugated plates Consists of rectangular thin corrugated plates
stacked in a frame.stacked in a frame. Plates pressed against each other between the Plates pressed against each other between the
stationary frame plate and movable pressure plate stationary frame plate and movable pressure plate with compression bolt to form narrow flow with compression bolt to form narrow flow channels.channels.
Hot and cold streams flow in alternate channels.Hot and cold streams flow in alternate channels. Corner openings termed as portsCorner openings termed as ports
Flow portFlow port Transfer portTransfer port
Fluid flow may be diagonal or verticalFluid flow may be diagonal or vertical
Saturday, April 8, 2023Saturday, April 8, 2023 2525
Plate Heat ExchangersPlate Heat Exchangers ConstructionConstruction PortsPorts CorrugationsCorrugations Flow arrangementsFlow arrangements AdvantagesAdvantages LimitationsLimitations
Saturday, April 8, 2023Saturday, April 8, 2023 2626
Parts of Plate heat exchangerParts of Plate heat exchanger Thin corrugated platesThin corrugated plates Stationary frame plateStationary frame plate Movable pressure plateMovable pressure plate Plate carrying barPlate carrying bar Plate guide barPlate guide bar Compression boltCompression bolt Connecting plateConnecting plate GasketGasket Inlet and outlet nozzles for each streamInlet and outlet nozzles for each stream
Saturday, April 8, 2023Saturday, April 8, 2023 2727
Plate Heat ExchangerPlate Heat Exchanger
Movable pressure plate
Connecting plate
Stationary frame platePlate carrying bar
Plate carrying bar
Hot water in
Hot water out
Milk out
Milk in
Compression nut & bolt
Saturday, April 8, 2023Saturday, April 8, 2023 2828
Saturday, April 8, 2023Saturday, April 8, 2023 2929
Flow Path in Plate Heat ExchangerFlow Path in Plate Heat Exchanger
Hot Water in Hot Water out
Milk inMilk Out
First pass
Second passFour pass of milk
Two pass of hot water
Saturday, April 8, 2023Saturday, April 8, 2023 3030
GasketsGaskets Prevent leakage of liquidsPrevent leakage of liquids Eliminate possibility of mixingEliminate possibility of mixing
Criteria for gasket materialsCriteria for gasket materials Thermal stabilityThermal stability Resistance to assuming permanent deformationResistance to assuming permanent deformation Good ageing characteristicsGood ageing characteristics Low compression setLow compression set Selection depends on the chemical composition of the Selection depends on the chemical composition of the
process streams and operating temperature.process streams and operating temperature.
Saturday, April 8, 2023Saturday, April 8, 2023 3131
Type of PortsType of Ports
Flow PortFlow Port Transfer PortTransfer Port
Saturday, April 8, 2023Saturday, April 8, 2023 3232
CorrugationsCorrugations Inducing turbulence in the process streamInducing turbulence in the process stream Providing reinforcementProviding reinforcement Plate support points to maintain interplate Plate support points to maintain interplate
separation and increasing heat transfer surface separation and increasing heat transfer surface area.area.
PatternsPatterns Trough typeTrough type Chevron or herringbone typeChevron or herringbone type
Saturday, April 8, 2023Saturday, April 8, 2023 3333
Flow arrangementFlow arrangement Series – low flow rates and large temp. changeSeries – low flow rates and large temp. change Looped – large flow rates and small Looped – large flow rates and small
temperature changetemperature change Complex – intermediate cases of flow and Complex – intermediate cases of flow and
temperature changetemperature change
Looped flow
Series Flow
Looped flow
Series Flow
Looped flow
Series Flow
Looped flow
Series Flow
Saturday, April 8, 2023Saturday, April 8, 2023 3434
Series flowSeries flow
Looped flow
Series Flow
Looped flow
Series Flow
Saturday, April 8, 2023Saturday, April 8, 2023 3535
Looped Flow PatternLooped Flow Pattern
Looped flow
Series Flow
Looped flow
Series Flow
Saturday, April 8, 2023Saturday, April 8, 2023 3636
Parts of a PlateParts of a Plate
Flow portTransfer port
Gasket
Flow portTransfer port
Corrugations
Flow distribution triangles
Gasket
Saturday, April 8, 2023Saturday, April 8, 2023 3737
Herringbone (Chevron type, 3D)Herringbone (Chevron type, 3D)
Saturday, April 8, 2023Saturday, April 8, 2023 3838
Flow patternFlow pattern
Looped flow
Series Flow
Saturday, April 8, 2023Saturday, April 8, 2023 3939
Overall heat transfer coefficient higherOverall heat transfer coefficient higher Effective mean temp difference usually higherEffective mean temp difference usually higher Less costLess cost Occupies less floor and head space – low hold-up Occupies less floor and head space – low hold-up
volume gives quicker start up and faster response to volume gives quicker start up and faster response to control function changes.control function changes.
Less massive foundationLess massive foundation Less foulingLess fouling Disassembled easilyDisassembled easily Variety of ways for assemblingVariety of ways for assembling Multiple duties like heating, cooling, regeneration etc.Multiple duties like heating, cooling, regeneration etc. Intermixing prevented by double gasket.Intermixing prevented by double gasket. Over 90 % heat recovery.Over 90 % heat recovery.
ADVANTAGESADVANTAGES
Saturday, April 8, 2023Saturday, April 8, 2023 4040
LimitationsLimitations
Cannot withstand operating pressures much in Cannot withstand operating pressures much in excess of 21 kg/cmexcess of 21 kg/cm22 (300 psi) (300 psi)
Gaskets should be elastomeric. So, maximum Gaskets should be elastomeric. So, maximum operating temp. usually limited to 260operating temp. usually limited to 26000C.C.
For mild steel construction, plate heat For mild steel construction, plate heat exchangers are costlier.exchangers are costlier.
Moderate pressure loss required to produce Moderate pressure loss required to produce economic designs to handle large quantities of economic designs to handle large quantities of low density fluids such as vapors and gases.low density fluids such as vapors and gases.
Saturday, April 8, 2023Saturday, April 8, 2023 4141
Tubular Heat ExchangersTubular Heat Exchangers
Double/triple pipeDouble/triple pipe Shell and tubeShell and tube Spiral tubeSpiral tube Scraped surface heat exchangers (SSHE)Scraped surface heat exchangers (SSHE)
• Common factor among former three is that tube of Common factor among former three is that tube of relatively smaller diameter housed in shell.relatively smaller diameter housed in shell.
• SSHE is basically large double pipe heat SSHE is basically large double pipe heat exchanger with scraper inside the inner tube exchanger with scraper inside the inner tube
Saturday, April 8, 2023Saturday, April 8, 2023 4242
Double Pipe Heat ExchangersDouble Pipe Heat Exchangers Simplest Type of Heat ExchangerSimplest Type of Heat Exchanger Pair of single lengths of pipe Pair of single lengths of pipe smaller diameter pipe -within another pipe smaller diameter pipe -within another pipe from a number of lengths arranged in a vertical row from a number of lengths arranged in a vertical row Welding of the outer jacket to the inner pipe is done Welding of the outer jacket to the inner pipe is done
oror A packed stuffing box -permit differential A packed stuffing box -permit differential
movement - removal of inner pipe for cleaning or movement - removal of inner pipe for cleaning or maintenance purpose. maintenance purpose.
5-10 cm pipe size shells5-10 cm pipe size shells 1.9-6.35 cm inner tubes 1.9-6.35 cm inner tubes
Saturday, April 8, 2023Saturday, April 8, 2023 4343
Application of Double Pipe HEApplication of Double Pipe HE
Can be used for liquid-liquid or steam/gas-Can be used for liquid-liquid or steam/gas-liquid duties with high liquid duties with high μμ
Suitable for low flow rates Suitable for low flow rates high temp. ranges high temp. ranges withstand high pressurewithstand high pressure Difficult to inspect for fouling or leakage.Difficult to inspect for fouling or leakage.
Saturday, April 8, 2023Saturday, April 8, 2023 4444
Low flow rates Low flow rates High temperature range High temperature range High pressure because of small diameter pipes High pressure because of small diameter pipes Space requirement - high as compared to plate Space requirement - high as compared to plate
heat exchangerheat exchanger Ceiling or wall mounted thereby taking up no floor Ceiling or wall mounted thereby taking up no floor
space. space. Flow distribution is no problemFlow distribution is no problem In-place-cleaning - very easilyIn-place-cleaning - very easily
Most difficult to inspect for fouling orMost difficult to inspect for fouling or leakage. leakage.
Saturday, April 8, 2023Saturday, April 8, 2023 4545
Repair - not difficult Repair - not difficult very close temperature approaches- true very close temperature approaches- true
counter current flow counter current flow Sometimes three tubes - concentrically - triple Sometimes three tubes - concentrically - triple
pipe heat exchangerpipe heat exchanger annuals between the innermost and annuals between the innermost and
intermediate tubes intermediate tubes concurrently or counter currently concurrently or counter currently to preheat the liquid food material before to preheat the liquid food material before
evaporation or spray drying evaporation or spray drying
Saturday, April 8, 2023Saturday, April 8, 2023 4646
Space requirement normally highSpace requirement normally high No problem in flow distribution and in-place No problem in flow distribution and in-place
cleaning, repair no problem.cleaning, repair no problem. Three tubes mounted concentrically to form triple Three tubes mounted concentrically to form triple
pipe heat exchanger.pipe heat exchanger. Velocity in heater is high and excellent heat Velocity in heater is high and excellent heat
transfer rates possible.transfer rates possible. In double pipe type, heat recovery or regeneration In double pipe type, heat recovery or regeneration
not possible, while the triple tube arrangement not possible, while the triple tube arrangement makes possible the use of efficient and compact makes possible the use of efficient and compact regenerative hook-up.regenerative hook-up.
Typical application – dairy and food industryTypical application – dairy and food industry To preheat the liquid food material before evaporation or To preheat the liquid food material before evaporation or
spray drying.spray drying.
Saturday, April 8, 2023Saturday, April 8, 2023 4747
Saturday, April 8, 2023Saturday, April 8, 2023 4848
Scraped surface heat exchanger (SSHE)Scraped surface heat exchanger (SSHE)
Also called votator or swept surface heat Also called votator or swept surface heat exchanger.exchanger.
Two concentric scraper fitted cylinders with two Two concentric scraper fitted cylinders with two or more scraper blades.or more scraper blades.
Outer cylinder covered with insulating materialOuter cylinder covered with insulating material Stainless steel sheet used to cover the insulation to Stainless steel sheet used to cover the insulation to
protect from mechanical damage.protect from mechanical damage. Inner cylinder made of SS or MS lined with Inner cylinder made of SS or MS lined with
chrome-nickel plating.chrome-nickel plating.
Saturday, April 8, 2023Saturday, April 8, 2023 4949
Scraped Surface Heat ExchangerScraped Surface Heat Exchanger
Saturday, April 8, 2023Saturday, April 8, 2023 5050
Scraped Surface Heat ExchangerScraped Surface Heat Exchanger
Saturday, April 8, 2023Saturday, April 8, 2023 5151
Scraped Surface Heat ExchangerScraped Surface Heat Exchanger Fixed-clearance scrapersFixed-clearance scrapers
small clearance between the blades and the heat transfer small clearance between the blades and the heat transfer surface highly abrasive products such as sugar/fat surface highly abrasive products such as sugar/fat
mixturesmixtures Variable-clearance scraper- floating bladesVariable-clearance scraper- floating blades
• Forced toward the wall by, springs, centrifugal force, and hydrodynamic Forced toward the wall by, springs, centrifugal force, and hydrodynamic action of the fluid scrape, sweep, or cut the product film -minimum fouling action of the fluid scrape, sweep, or cut the product film -minimum fouling and burn on takes place and burn on takes place
Heat transfer rate increases Heat transfer rate increases mechanically-induced turbulence, film removal, product mixingmechanically-induced turbulence, film removal, product mixing HTC compare very well with those of plate heat exchangerHTC compare very well with those of plate heat exchanger
Product velocity at the heat transfer surface Product velocity at the heat transfer surface speed of the scraper, number of rows of blades. It does speed of the scraper, number of rows of blades. It does not not depend on the product flow ratedepend on the product flow rate
The product requires whipping and aerating - ice-cream The product requires whipping and aerating - ice-cream freezers - beatersfreezers - beaters
Saturday, April 8, 2023Saturday, April 8, 2023 5252
OperationsOperations
Liquid-full operationLiquid-full operation
filled completely with liquid productfilled completely with liquid product
sensible heat transfersensible heat transfer Thin-film operationThin-film operation
does not run full does not run full
phase changephase change
Saturday, April 8, 2023Saturday, April 8, 2023 5353
Diameters 7.5-25 cms Diameters 7.5-25 cms And lengths 120-180 cms And lengths 120-180 cms Viscosity up to 100000 cp Viscosity up to 100000 cp Solids contents upto 75 per centSolids contents upto 75 per cent Temperatures -180 to 30 C Temperatures -180 to 30 C
Saturday, April 8, 2023Saturday, April 8, 2023 5454
Ice cream, condensed milk, baby foods, etc. Or for Ice cream, condensed milk, baby foods, etc. Or for pasteurization or sterilizationpasteurization or sterilization
Space requirement Space requirement -high or low depending upon the type of unit. -high or low depending upon the type of unit.
Vertical installation Vertical installation -less floor area- difficult to inspect for cleaning-less floor area- difficult to inspect for cleaning
Horizontal installationHorizontal installation needs double unit size for removal of rotor shaft if floor mounted -easy needs double unit size for removal of rotor shaft if floor mounted -easy
to lower down for inspection. to lower down for inspection.
. .
Saturday, April 8, 2023Saturday, April 8, 2023 5555
Costliest among all heat exchangers Costliest among all heat exchangers Moving parts, seals and blades -proper Moving parts, seals and blades -proper
maintenance maintenance Lubrication -manufacturers instructions. Lubrication -manufacturers instructions. Blades - sharpened as they get worn. Blades - sharpened as they get worn.
Saturday, April 8, 2023Saturday, April 8, 2023 5656
ScrapersScrapers• Scrape the film continuously.Scrape the film continuously.• More heat transfer rate.More heat transfer rate.• Minimum fouling and burningMinimum fouling and burning
Fixed clearance scrapersFixed clearance scrapers Used for highly abrasive products (sugar/fat Used for highly abrasive products (sugar/fat
mixtures)mixtures) Variable clearance scrapersVariable clearance scrapers
Floating blades forced towards wall by springs, Floating blades forced towards wall by springs, centrifugal force, hydrodynamic action of the centrifugal force, hydrodynamic action of the fluid or combination of these factorsfluid or combination of these factors..
Saturday, April 8, 2023Saturday, April 8, 2023 5757
SSHE can be used for two modes of operationsSSHE can be used for two modes of operations Liquid-full operationLiquid-full operation
Vessel completely filled with productVessel completely filled with product Almost always sensible heat transferAlmost always sensible heat transfer
Thin-film operationThin-film operation Does not run full, but liquid flows in a thin film down Does not run full, but liquid flows in a thin film down
the vessel devicethe vessel device Sensible + latent heat transferSensible + latent heat transfer
Saturday, April 8, 2023Saturday, April 8, 2023 5858
Spiral tube heat exchangerSpiral tube heat exchanger One or more spirally wound tubesOne or more spirally wound tubes Heat transfer higherHeat transfer higher Turbulence induced is more due to higher velocityTurbulence induced is more due to higher velocity Natural scrubbing of the tubeNatural scrubbing of the tube Production cycle extended for a longer time.Production cycle extended for a longer time. Fewer cleaning cycles required.Fewer cleaning cycles required. Large amount of space accommodated.Large amount of space accommodated. Used for aseptic production of liquid and semi-Used for aseptic production of liquid and semi-
solid food productssolid food products @ 75 – 15000 lit/hr@ 75 – 15000 lit/hr
Saturday, April 8, 2023Saturday, April 8, 2023 5959
• Diameters 7.5 to 25 cm, lengths 120 to 180 cmDiameters 7.5 to 25 cm, lengths 120 to 180 cm• Continuous heating or freezing (Continuous heating or freezing (μμ = 1,00,000 cP = 1,00,000 cP
and solid content up to 75 %)and solid content up to 75 %)• Temperature range 180Temperature range 18000 to -30 to -3000CC• Manufacturing of ice cream, condensed milk, baby Manufacturing of ice cream, condensed milk, baby
foods etc.foods etc.• Space requirement high or low depending upon Space requirement high or low depending upon
type of unittype of unit• Costliest among all othersCostliest among all others
Saturday, April 8, 2023Saturday, April 8, 2023 6060
Considerable amount of surface can be Considerable amount of surface can be accommodated in a given space by spiraling. accommodated in a given space by spiraling. Thermal expansion -not a problemThermal expansion -not a problem
Cleaning of the outer surface of the tube is Cleaning of the outer surface of the tube is difficult. difficult.
Used for aseptic production of liquid and semi-Used for aseptic production of liquid and semi-solid food productssolid food products
Saturday, April 8, 2023Saturday, April 8, 2023 6161
Spiral Tube Heat ExchangerSpiral Tube Heat Exchanger
Saturday, April 8, 2023Saturday, April 8, 2023 6262
Shell and Tube Heat ExchangersShell and Tube Heat ExchangersRound tubes housed in a cylindrical shell Round tubes housed in a cylindrical shell One fluid flows inside the tube while the other fluid flows One fluid flows inside the tube while the other fluid flows
across and along the tubesacross and along the tubes Major components- Major components-
Tubes Tubes ShellShell BafflesBaffles Tube sheetsTube sheets Pass divider Pass divider Channel coverChannel cover Tube side and shell side nozzles Tube side and shell side nozzles
The tubes The tubes Arranged on a square pitch- easily cleanedArranged on a square pitch- easily cleaned Triangular pitch pattern -more number of tubesTriangular pitch pattern -more number of tubes
Saturday, April 8, 2023Saturday, April 8, 2023 6363
Shell and tube heat exchangersShell and tube heat exchangers Tubes arranged on square or triangular pitch patternTubes arranged on square or triangular pitch pattern
Square pattern – easy cleaningSquare pattern – easy cleaning Triangular pattern – more no. of tubes to a given shell Triangular pattern – more no. of tubes to a given shell
diameterdiameter.. Material – usually low carbon steel, low alloy steel. Material – usually low carbon steel, low alloy steel.
SS, Cu etc.SS, Cu etc. BafflesBaffles
Support tubes, prevent vibration and guide shell side Support tubes, prevent vibration and guide shell side fluid back and forthfluid back and forth
Increase in velocity, turbulences, degree of mixing Increase in velocity, turbulences, degree of mixing and high heat transfer coefficient.and high heat transfer coefficient.
Saturday, April 8, 2023Saturday, April 8, 2023 6464
Shell and tube heat exchanger -widely used in process Shell and tube heat exchanger -widely used in process industries - relatively easy construction -wide range of industries - relatively easy construction -wide range of duties-mechanically rugged -withstand normal shop duties-mechanically rugged -withstand normal shop fabrication stresses, shipping and field erection stresses fabrication stresses, shipping and field erection stresses and normal operating conditionsand normal operating conditions
Can be reasonably easily cleanedCan be reasonably easily cleaned Gaskets and tubes, which are most subject to failure, can Gaskets and tubes, which are most subject to failure, can
be replaced easilybe replaced easily Low solids content and viscosities normally less than Low solids content and viscosities normally less than
10000 cps10000 cps Often used for non-food processing steps such as chilling Often used for non-food processing steps such as chilling
the brine for refrigeration or as hot water heatersthe brine for refrigeration or as hot water heaters Tubular evaporators - shell and tube heat exchanger Tubular evaporators - shell and tube heat exchanger
Saturday, April 8, 2023Saturday, April 8, 2023 6565
Shell and Tube Heat ExchangerShell and Tube Heat Exchanger
Saturday, April 8, 2023Saturday, April 8, 2023 6666
Saturday, April 8, 2023Saturday, April 8, 2023 6767
ShellShell Roundness of the shell -important for inserting and Roundness of the shell -important for inserting and
fixing the baffles of maximum diameter impingement fixing the baffles of maximum diameter impingement baffle -below the shell-side inlet nozzle- prevent the baffle -below the shell-side inlet nozzle- prevent the impact of fluid on the tubes, which may lead to erosion, impact of fluid on the tubes, which may lead to erosion, cavitation, and/or vibration of tubes cavitation, and/or vibration of tubes
Tube bundle- tubes, tube sheets and baffles from the Tube bundle- tubes, tube sheets and baffles from the shell for inspection and cleaningshell for inspection and cleaning
Tube-side channels and nozzles control - tube-side fluid Tube-side channels and nozzles control - tube-side fluid into and out of the tubes into and out of the tubes
Channel cover -round plate fitted to the channel flanges Channel cover -round plate fitted to the channel flanges - removed for tube inspection - removed for tube inspection
Saturday, April 8, 2023Saturday, April 8, 2023 6868
BafflesBafflesTo support the tubes in proper position during assembly and To support the tubes in proper position during assembly and
operation operation To prevent vibration of the tubes caused by flow induced To prevent vibration of the tubes caused by flow induced
eddies eddies To guide the shell side fluid back and forth across the tube To guide the shell side fluid back and forth across the tube
field field Increase in velocity, turbulences, degree of mixing and heat Increase in velocity, turbulences, degree of mixing and heat
transfer coefficient transfer coefficient Types of BafflesTypes of Baffles Transverse baffles are placed along the length of tubesTransverse baffles are placed along the length of tubes Longitudinal bafflesLongitudinal bafflesMinimum spacing between baffles -one-fifth of the shell diameterMinimum spacing between baffles -one-fifth of the shell diameter
Saturday, April 8, 2023Saturday, April 8, 2023 6969
A pass divider A pass divider Plate fitted into one or both the channel Plate fitted into one or both the channel Pass dividers - fitted tightly to prevent the leakage of Pass dividers - fitted tightly to prevent the leakage of
fluid from one pass to anotherfluid from one pass to another Tube side passes – may be moreTube side passes – may be more
Shell side passes – restricted to one- twoShell side passes – restricted to one- two Sometimes more than two.Sometimes more than two.
Saturday, April 8, 2023Saturday, April 8, 2023 7070
Fluid choiceFluid choice
Fouling and corrosion characteristics of the fluid, Fouling and corrosion characteristics of the fluid, permissible pressure drop across the heat permissible pressure drop across the heat exchanger, constructional cost, etc. exchanger, constructional cost, etc.
Corrosive and more susceptible for fouling fluids - Corrosive and more susceptible for fouling fluids - tubes tubes
In shell-side fluid -more pressure drop In shell-side fluid -more pressure drop
Saturday, April 8, 2023Saturday, April 8, 2023 7171
Types of baffles:Types of baffles:• TransverseTransverse• LongitudinalLongitudinal Minimum spacing between baffles 1/5 th of shell Minimum spacing between baffles 1/5 th of shell
diameter, but not less than 5 cm.diameter, but not less than 5 cm.
Choice of fluid depends on:Choice of fluid depends on: Fouling and corrosion characteristicsFouling and corrosion characteristics Permissible pressure dropPermissible pressure drop Constructional cost etc.Constructional cost etc. Corrosive and fouling producing fluids in tubesCorrosive and fouling producing fluids in tubes
Saturday, April 8, 2023Saturday, April 8, 2023 7272
Jacketed KettleJacketed Kettle Semispherical container and a jacket Semispherical container and a jacket cylindrical container with jacket - jacketed vat. cylindrical container with jacket - jacketed vat. The steam or hot water may be used as a heating mediumThe steam or hot water may be used as a heating medium Hot water- spray- more efficient- rapidly moving thin filmHot water- spray- more efficient- rapidly moving thin film Flooded into the heating/cooling medium passageFlooded into the heating/cooling medium passage 40 percent saving in heating time by spray method 40 percent saving in heating time by spray method
agitator or scraper- uniform heating and increase rate of heat agitator or scraper- uniform heating and increase rate of heat transfertransfer
small capacity plant small capacity plant production of small quantities of material in large capacity plantsproduction of small quantities of material in large capacity plants not efficient as compared to other types of heat exchangersnot efficient as compared to other types of heat exchangers the initial cost of the exchanger is low. the initial cost of the exchanger is low. Operation and maintenance are easyOperation and maintenance are easy No skilled worker is needed. No skilled worker is needed. energy consumption of the heat exchanger is moreenergy consumption of the heat exchanger is more
Saturday, April 8, 2023Saturday, April 8, 2023 7373
JACKETED KETTLEJACKETED KETTLE
Spray or flooded typeSpray or flooded type 40 % saving in heating time in spray40 % saving in heating time in spray Agitator for uniform heatingAgitator for uniform heating Scraper when concentration of liquid doneScraper when concentration of liquid done Operation and maintenance easier.Operation and maintenance easier. Not efficient as compared to othersNot efficient as compared to others Initial cost is lowInitial cost is low Volume /heat transfer area highVolume /heat transfer area high Area/volume lowArea/volume low
Saturday, April 8, 2023Saturday, April 8, 2023 7474
Agitator or scraper- uniform heating and increase rate of Agitator or scraper- uniform heating and increase rate of heat transferheat transfer
Cylindrical container with jacket - jacketed vat. Cylindrical container with jacket - jacketed vat. Small capacity plant Small capacity plant Production of small quantities of material in large capacity Production of small quantities of material in large capacity
plantsplants Not efficient as compared to other types of heat exchangersNot efficient as compared to other types of heat exchangers The initial cost of the exchanger is lowThe initial cost of the exchanger is low Operation and maintenance are easyOperation and maintenance are easy Energy consumption of the heat exchanger is moreEnergy consumption of the heat exchanger is more
Saturday, April 8, 2023Saturday, April 8, 2023 7575
DIRECT CONTACT TYPE HEAT DIRECT CONTACT TYPE HEAT EXCHANGERSEXCHANGERS
Steam injectionSteam injection Steam into process fluidSteam into process fluid
Steam infusionSteam infusion Process fluid spread into vessel with steam Process fluid spread into vessel with steam
atmosphereatmosphere Employed in dairy industry for UHT processingEmployed in dairy industry for UHT processing Temp. rises very rapidly to 135-150Temp. rises very rapidly to 135-15000C.C. Heat transfer mainly due to condensation of Heat transfer mainly due to condensation of
steam resulting in 10 % dilution of the product.steam resulting in 10 % dilution of the product.
Saturday, April 8, 2023Saturday, April 8, 2023 7676
Advantages of Direct contact HEAdvantages of Direct contact HE
Very rapid heating and coolingVery rapid heating and cooling Less scaling permits longer production runsLess scaling permits longer production runs Low oxygen content of final productLow oxygen content of final product
Saturday, April 8, 2023Saturday, April 8, 2023 7777
Limitations/disadvantages of Direct Contact Limitations/disadvantages of Direct Contact HEHE
Direct heating more complexDirect heating more complex RequiresRequires
more plant components, more plant components, additional controls and additional controls and high quality steam (culinary steam)high quality steam (culinary steam)
Relatively expensive in Relatively expensive in initial and initial and operating costoperating cost
No regenerative heating above the temperature at No regenerative heating above the temperature at which steam is mixedwhich steam is mixed
Saturday, April 8, 2023Saturday, April 8, 2023 7878
Direct Contact TypeDirect Contact Type Steam injection - steam -suitable nozzle -liquidSteam injection - steam -suitable nozzle -liquid Steam infusion heat exchangers - spread into a Steam infusion heat exchangers - spread into a
vessel with steam atmospherevessel with steam atmosphere Raises the temperature very rapidly to 135 - 150. Raises the temperature very rapidly to 135 - 150. Heat transfer - condensation of steam Heat transfer - condensation of steam 10% dilution of the product10% dilution of the product Vacuum chamber- evaporatively cooled and the Vacuum chamber- evaporatively cooled and the
condensed water is flushed off. Adjustment of the condensed water is flushed off. Adjustment of the vacuum - necessary removal of water and vacuum - necessary removal of water and simultaneously controls the dry matter content of simultaneously controls the dry matter content of the final produce. the final produce.
Saturday, April 8, 2023Saturday, April 8, 2023 7979
Advantages of Direct Contact HEAdvantages of Direct Contact HE
Very rapid heating and cooling and consequently a low total temperature load on the product.
Less scaling in the equipment as compared to indirect heating which also permits longer production runs because of less frequent cleaning cycles.
Low oxygen content of the final product. Expansion cooling does not only remove water but also dissolved air (02) resulting in an oxygen content of the final product (milk) of about or less than 0.1 ppm.
Saturday, April 8, 2023Saturday, April 8, 2023 8080
It is not possible to use regenerative heating It is not possible to use regenerative heating above the temperature at which steam is above the temperature at which steam is mixed with the product. mixed with the product.
Saturday, April 8, 2023Saturday, April 8, 2023 8181
Steam Injection SystemSteam Injection System
Injection requires steam pressures higher Injection requires steam pressures higher than those of the product in the infuser.than those of the product in the infuser.
Saturday, April 8, 2023Saturday, April 8, 2023 8282
Steam Infusion SystemSteam Infusion System
With infuser, any pool of product in the With infuser, any pool of product in the bottom of heating vessel contributes much bottom of heating vessel contributes much of the holding period needed for sterilizing of the holding period needed for sterilizing effect. effect.
Very close control of product level at this Very close control of product level at this point is necessary if the process is not to be point is necessary if the process is not to be variablevariable
Saturday, April 8, 2023Saturday, April 8, 2023 8383
Temperature-Time Profile in Temperature-Time Profile in UHT ProcessUHT Process
Saturday, April 8, 2023Saturday, April 8, 2023 8484
Temperature-Time ProfileTemperature-Time Profile