Aspen Plus Reference Manual, Unit Operation Models

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Unit Operation Models

S T E A D Y S T A T E S I M U L A T I O N

10

AspenTech

7

Aspen

Plus

Version

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About the Unit Operation Models Reference Manual

For More Information... x Technical Support ...xi 1 Mixers and Splitters

Mixer ...1-2 Flowsheet Connectivity for Mixer...1-2 Specifying Mixer...1-3 FSplit...1-5 Flowsheet Connectivity for FSplit...1-5 Specifying FSplit ...1-6 SSplit...1-8 Flowsheet Connectivity for SSplit ...1-8 Specifying SSplit ...1-8 2 Separators

Flash2...2-2 Flowsheet Connectivity for Flash2...2-2 Specifying Flash2 ...2-3 Flash3...2-5 Flowsheet Connectivity for Flash3...2-5 Specifying Flash3 ...2-6 Decanter...2-8 Flowsheet Connectivity for Decanter ...2-8 Specifying Decanter ...2-9 Sep...2-12 Flowsheet Connectivity for Sep ...2-12 Specifying Sep ...2-13 Sep2 ...2-14 Flowsheet Connectivity for Sep2 ...2-14 Specifying Sep2...2-15 3 Heat Exchangers

Heater ...3-2 Flowsheet Connectivity for Heater...3-2 Specifying Heater ...3-3 HeatX ...3-5 Flowsheet Connectivity for HeatX...3-5

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Specifying Hetran ... 3-24 Aerotran ... 3-26 Flowsheet Connectivity for Aerotran ... 3-26 Specifying Aerotran ... 3-27 4 Columns

DSTWU ... 4-3 Flowsheet Connectivity for DSTWU ... 4-3 Specifying DSTWU... 4-4 Distl ... 4-6 Flowsheet Connectivity for Distl... 4-6 Specifying Distl ... 4-7 SCFrac... 4-8 Flowsheet Connectivity for SCFrac ... 4-8 Specifying SCFrac ... 4-9 RadFrac... 4-11 Flowsheet Connectivity for RadFrac ... 4-12 Specifying RadFrac... 4-13 Free-Water and Rigorous Three-Phase Calculations ... 4-20 Efficiencies ... 4-20 Algorithms... 4-22 Rating Mode... 4-23 Design Mode... 4-24 Reactive Distillation ... 4-25 Solution Strategies ... 4-25 Physical Properties... 4-28 Solids Handling ... 4-28 MultiFrac ... 4-30 Flowsheet Connectivity for MultiFrac ... 4-31 Specifying MultiFrac ... 4-33 Efficiencies ... 4-41 Algorithms... 4-42 Rating Mode... 4-42 Design Mode... 4-42 Column Convergence... 4-43 Physical Properties... 4-46 Free Water Handling... 4-46 Solids Handling ... 4-46 Sizing and Rating of Trays and Packings ... 4-47 PetroFrac... 4-48 Flowsheet Connectivity for PetroFrac... 4-49 Specifying PetroFrac... 4-51 Efficiencies ... 4-57

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Solids Handling ...4-61 Sizing and Rating of Trays and Packings ...4-61 RateFrac...4-62 Flowsheet Connectivity for RateFrac...4-63 The Rate-Based Modeling Concept...4-65 Specifying RateFrac ...4-66 Mass and Heat Transfer Correlations...4-77 References...4-85 Extract ...4-87 Flowsheet Connectivity for Extract...4-87 Specifying Extract ...4-88 5 Reactors

RStoic ...5-2 Flowsheet Connectivity for RStoic ...5-2 Specifying RStoic ...5-3 RYield...5-6 Flowsheet Connectivity for RYield...5-6 Specifying RYield ...5-7 REquil ...5-8 Flowsheet Connectivity for REquil...5-8 Specifying REquil ...5-9 RGibbs...5-10 Flowsheet Connectivity for RGibbs ...5-10 Specifying RGibbs ...5-11 References...5-15 RCSTR ...5-16 Flowsheet Connectivity for RCSTR...5-16 Specifying RCSTR ...5-17 RPlug...5-21 Flowsheet Connectivity for RPlug ...5-21 Specifying RPlug ...5-22 RBatch ...5-25 Flowsheet Connectivity for RBatch...5-25 Specifying RBatch ...5-26 6 Pressure Changers

Pump ...6-2 Flowsheet Connectivity for Pump ...6-2 Specifying Pump ...6-3 Compr...6-9

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Flowsheet Connectivity for Valve ... 6-20 Specifying Valve ... 6-20 References ... 6-29 Pipe... 6-30 Flowsheet Connectivity for Pipe ... 6-30 Specifying Pipe ... 6-31 Two-Phase Correlations ... 6-35 Closed-Form Methods... 6-39 References ... 6-40 Pipeline ... 6-42 Flowsheet Connectivity for Pipeline... 6-42 Specifying Pipeline ... 6-43 Two-Phase Correlations ... 6-47 Closed-Form Methods... 6-50 References ... 6-52 7 Manipulators Mult ... 7-2 Flowsheet Connectivity for Mult... 7-2 Specifying Mult... 7-3 Dupl ... 7-4 Flowsheet Connectivity for Dupl... 7-4 Specifying Dupl... 7-5 ClChng ... 7-6 Flowsheet Connectivity for ClChng... 7-6 Specifying ClChng... 7-6 8 Solids

Crystallizer ... 8-3 Flowsheet Connectivity for Crystallizer ... 8-3 Specifying Crystallizer ... 8-4 References ... 8-11 Crusher... 8-13 Flowsheet Connectivity for Crusher... 8-13 Specifying Crusher ... 8-14 References ... 8-18 Screen ... 8-19 Flowsheet Connectivity for Screen ... 8-19 Specifying Screen... 8-19 References ... 8-22 FabFl ... 8-23 Flowsheet Connectivity for FabFl... 8-23 Specifying FabFl... 8-23

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VScrub...8-36 Flowsheet Connectivity for VScrub ...8-36 Specifying VScrub ...8-37 References...8-39 ESP...8-40 Flowsheet Connectivity for ESP ...8-40 Specifying ESP ...8-41 References...8-44 HyCyc ...8-45 Flowsheet Connectivity for HyCyc...8-45 Specifying HyCyc ...8-46 References...8-51 CFuge ...8-52 Flowsheet Connectivity for CFuge ...8-52 Specifying CFuge...8-53 References...8-55 Filter ...8-56 Flowsheet Configuration for Filter...8-56 Specifying Filter ...8-56 References...8-59 SWash ...8-61 Flowsheet Connectivity for SWash...8-61 Specifying SWash ...8-62 CCD ...8-64 Flowsheet Connectivity for CCD ...8-64 Specifying CCD...8-65 9 User Models

User ...9-2 Flowsheet Connectivity for User ...9-2 Specifying User...9-3 User2 ...9-4 Flowsheet Connectivity for User2 ...9-4 Specifying User2...9-5 10 Pressure Relief

Pres-Relief...10-2 Specifying Pres-Relief ...10-2 Scenarios ...10-3 Compliance with Codes ...10-6 Stream and Vessel Compositions and Conditions ...10-6

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Stop Criteria ... 10-18 Solution Procedure for Dynamic Scenarios... 10-19 Flow Equations ... 10-20 Calculation and Convergence Methods ... 10-23 Vessel Insulation Credit Factor... 10-24 References ... 10-25 A Sizing and Rating for Trays and Packings

Single-Pass and Multi-Pass Trays...A-2 Modes of Operation for Trays ...A-8 Flooding Calculations for Trays...A-8 Bubble Cap Tray Layout ...A-9 Pressure Drop Calculations for Trays ...A-10 Foaming Calculations for Trays ...A-11 Packed Columns ...A-12 Packing Types and Packing Factors...A-12 Modes of Operation for Packing...A-12 Maximum Capacity Calculations for Packing ...A-13 Pressure Drop Calculations for Packing ...A-15 Liquid Holdup Calculations for Packing ...A-16 Pressure Profile Update ...A-17 Physical Property Data Requirements...A-17 References ...A-18 Index

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Models Reference Manual

Volume 1 of the ASPEN PLUS Reference Manuals, Unit Operation Models, includes detailed technical reference information for all ASPEN PLUS unit operation models and the Pres-Relief model. The information in this manual is also available in online help and prompts.

Models are grouped in chapters according to unit operation type. The reference information for each model includes a description of the model and its typical usage, a diagram of its flowsheet connectivity, a discussion of the specifications you must provide for the model, important equations and correlations, and other relevant information.

An overview of all ASPEN PLUS unit operation models, and general information about the steps and procedures in using them is in the ASPEN PLUS User Guide as well as in the online help and prompts in ASPEN PLUS.

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context-sensitive prompts. The help system contains both context-sensitive help and reference information. For more information about using ASPEN PLUS help, see the ASPEN PLUS User Guide, Chapter 3.

ASPEN PLUS Getting Started Building and Running a Process Model

This tutorial includes several hands-on sessions to familiarize you with

ASPEN PLUS. The guide takes you step-by-step to learn the full power and scope of ASPEN PLUS.

ASPEN PLUS User Guide The three-volume ASPEN PLUS User Guide

provides step-by-step procedures for developing and using an ASPEN PLUS process simulation model. The guide is task-oriented to help you accomplish the engineering work you need to do, using the powerful capabilities of

ASPEN PLUS.

ASPEN PLUS reference manual series ASPEN PLUS reference manuals

provide detailed technical reference information. These manuals include background information about the unit operation models and the physical properties methods and models available in ASPEN PLUS, tables of

ASPEN PLUS databank parameters, group contribution method functional groups, and a wide range of other reference information. The set comprises: • Unit Operation Models

• Physical Property Methods and Models • Physical Property Data

• User Models

• System Management • Summary File Toolkit

ASPEN PLUS application examples A suite of sample online ASPEN PLUS

simulations illustrating specific processes is delivered with ASPEN PLUS.

ASPEN PLUS Installation Guides These guides provide instructions on

platform and network installation of ASPEN PLUS. The set comprises: • ASPEN PLUS Installation Guide for Windows

• ASPEN PLUS Installation Guide for OpenVMS • ASPEN PLUS Installation Guide for UNIX

The ASPEN PLUS manuals are delivered in Adobe portable document format (PDF) on the ASPEN PLUS Documentation CD. You can also order printed manuals from AspenTech.

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Technical resources To obtain in-depth technical support information on the

Internet, visit the Technical Support homepage. Register at: http://www.aspentech.com/ts/

Approximately three days after registering, you will receive a confirmation e-mail and you will then be able to access this information.

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1 Mixers and Splitters

This chapter describes the unit operation models for mixing and splitting streams. The models are:

Model Description Purpose Use For Mixer Stream mixer Combines multiple streams

into one stream

Mixing tees. Stream mixing operations. Adding heat streams. Adding work streams FSplit Stream splitter Divides feed based on splits

specified for outlet streams

Stream splitters. Bleed valves SSplit Substream splitter Divides feed based on splits

specified for each substream

Stream splitters. Perfect fluid-solid separators

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Mixer

Stream Mixer

Use Mixer to combine streams into one stream. Mixer models mixing tees or other types of mixing operations.

Mixer combines material streams (or heat streams or work streams) into one stream. Select the Heat (Q) and Work (W) Mixer icons from the Model Library for heat and work streams respectively. A single Mixer block cannot mix streams of different types (material, heat, work).

Flowsheet Connectivity for Mixer

Material

Water (optional) Material

(2 or more)

Flowsheet for Mixing Material Streams

Material Streams

Inlet At least two material streams

Outlet One material stream

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Heat Heat

(2 or more)

Flowsheet for Adding Heat Streams

Heat Streams

Inlet At least two heat streams

Outlet One heat stream

Work Work

(2 or more)

Flowsheet for Adding Work Streams

Work Streams

Inlet At least two work streams

Outlet One work stream

Specifying Mixer

Use the Mixer Input Flash Options sheet to specify operating conditions. When mixing heat or work streams, Mixer does not require any specifications.

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When mixing material streams, you can specify either the outlet pressure or pressure drop. If you specify pressure drop, Mixer determines the minimum of the inlet stream pressures, and applies the pressure drop to the minimum inlet stream pressure to compute the outlet pressure. If you do not specify the outlet pressure or pressure drop, Mixer uses the minimum pressure from the inlet streams for the outlet pressure.

You can select the following valid phases:

Valid Phase Solids? Number of phases? Free Water? Phase?

Vapor-Only Yes or no 1 No V

Liquid-Only Yes or no 1 No L

Vapor-Liquid Yes or no 2 No 

Vapor-Liquid-Liquid Yes or no 3 No 

Liquid Free-Water † Yes or no 1 Yes 

Vapor-Liquid Free-Water † Yes or no 2 Yes 

Solid-Only Yes 1 No S

†

Check Use Free Water Calculations checkbox on the Setup Specifications Global sheet.

An optional water decant stream can be used when free-water calculations are performed.

Mixer performs an adiabatic calculation on the product to determine the outlet temperature, unless Mass Balance Only Calculations is specified on the Mixer BlockOptions SimulationOptions sheet or the Setup SimulationOptions

Calculations sheet.

Use the following forms to enter specifications and view results for Mixer: Use this form To do this

Input Enter operating conditions and flash convergence parameters

BlockOptions Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block

Results View Mixer simulation results

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FSplit

Stream Splitter

FSplit combines streams of the same type (material, heat, or work streams) and divides the resulting stream into two or more streams of the same type. All outlet streams have the same composition and conditions as the mixed inlet. Select the Heat (Q) and Work (W) FSplit icons from the Model Library for heat and work streams respectively. Use FSplit to model flow splitters, such as bleed valves. FSplit cannot split a stream into different types. For example, FSplit cannot split a material stream into a heat stream and a material stream.

To model a splitter where the amount of each substream sent to each outlet can differ, use an SSplit block. To model a splitter where the composition and properties of the output streams can differ, use a Sep block or a Sep2 block.

Flowsheet Connectivity for FSplit

Material (2 or more) Material

(any number)

Flowsheet for Splitting Material Streams

Material Streams

Inlet At least one material stream

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Heat (2 or more) Heat

(any number)

Flowsheet for Splitting Heat Streams

Heat Streams

Inlet At least one heat stream

Outlet At least two heat streams

Work (2 or more) Work

(any number)

Flowsheet for Splitting Work Streams

Work Streams

Inlet At least one work stream

Outlet At least two work streams

Specifying FSplit

To split material streams Give one of the following specifications for each

outlet stream except one:

• Fraction of the combined inlet flow • Mole flow rate

• Mass flow rate

• Standard liquid volume flow rate • Actual volume flow rate

• Fraction of the residue remaining after all other specifications are satisfied FSplit puts any remaining flow in the unspecified outlet stream to satisfy material balance. You can specify mole, mass, or standard liquid volume flow rate for one of the following:

• The entire stream

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To specify the flow rate of a component or group of components in an outlet stream, specify a group of key components and the total flow rate for the group (the sum of the component flow rates) on the Input Specifications sheet, and define the key components in the group on the Input KeyComponents sheet.

Outlet streams have the same composition as the mixed inlet stream. For this reason, when you specify the flow rate of a key component, the total flow rate of the outlet stream is greater than the flow rate you specify.

When FSplit has more than one inlet, you can do one of the following: • Enter the outlet pressure on the FSplit Input FlashOptions sheet

• Let the outlet pressure default to the minimum pressure of the inlet streams

To split heat streams or work streams Specify the fraction of the combined

inlet heat or work for each outlet stream except one. FSplit puts any remaining heat or work in the unspecified outlet stream to satisfy energy balance.

Use the following forms to enter specifications and view results for FSplit: Use this form To do this

Input Enter split specifications, flash conditions and calculation options, and key components associated with split specifications

Results View split fractions for outlet streams, and material and energy balance results

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SSplit

Substream Splitter

SSplit combines material streams and divides the resulting stream into two or more streams. Use SSplit to model a splitter where the split of each substream among the outlet streams can differ.

Substreams in the outlet streams have the same composition, temperature, and pressure as the corresponding substreams in the mixed inlet stream. Only the substream flow rates differ. To model a splitter in which the composition and properties of the substreams in the output streams can differ, use a Sep block or a Sep2 block.

Flowsheet Connectivity for SSplit

Material (2 or more) Material

(any number)

Material Streams

Outlet At least two material streams

Specifying SSplit

For each substream, specify one of the following for all but one outlet stream: • Fraction of the inlet substream

• Mole flow rate • Mass flow rate

• Standard liquid volume flow rate

SSplit puts any remaining flow for each substream in the unspecified stream. You cannot specify standard liquid volume flow rate when the substream is of type CISOLID, and mole and standard liquid volume flow rates when the substream is of type NC.

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You can specify mole or mass flow rate for one of the following: • The entire substream

• A subset of components in the substream

You can specify the flow rate of a component in a substream of an outlet stream. To do this, define a key component and specify the flow rate for the key component. Similarly, you can specify the flow rate for a group of components in a substream of an outlet stream. To do this, define a key group of components and specify the total flow rate for the group (the sum of the component flow rates).

Substreams in outlet streams have the same composition as the corresponding substream in the mixed inlet stream. For this reason, when you specify the flow rate of a key, the total flow rate of the substream in the outlet stream is greater than the flow rate you specify.

When SSplit has more than one inlet, you can do one of the following: • Enter the outlet pressure on the Input FlashOptions sheet.

• Let the outlet pressure default to the minimum pressure of the inlet streams. The composition, temperature, pressure, and other substream variables for all outlet streams have the same values as the mixed inlet. Only the substream flow rates differ.

Use the following forms to enter specifications and view results for SSplit: Use this form To do this

Input Enter split specifications, flash conditions, calculation options, and key components associated with split specifications

Results View split fractions of each substream in each outlet stream, and material and energy balance results

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2 Separators

This chapter describes the unit operation models for component separators, flash drums, and liquid-liquid separators. The models are:

Model Description Purpose Use For Flash2 Two-outlet flash Separates feed into two outlet

streams, using rigorous vapor-liquid or vapor-vapor-liquid-vapor-liquid equilibrium

Flash drums, evaporators, knock-out drums, single stage separators

Flash3 Three-outlet flash Separates feed into three outlet streams, using rigorous vapor-liquid-liquid equilibrium

Decanters, single-stage separators with two liquid phases

Decanter Liquid-liquid decanter Separates feed into two liquid outlet streams

Decanters, single-stage separators with two liquid phases and no vapor phase Sep Component separator Separates inlet stream

components into multiple outlet streams, based on specified flows or split frractions

Component separation operations, such as distillation and absorption, when the details of the separation are unknown or unimportant

Sep2 Two-outlet component separator

Separates inlet stream components into two outlet streams, based on specified flows, split fractions, or purities

Component separation operations, such as distillation and absorption, when the details of the separation are unknown or unimportant

You can generate heating or cooling curve tables for Flash2, Flash3, and Decanter models.

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Flash2

Two-Outlet Flash

Use Flash2 to model flashes, evaporators, knock-out drums, and other single-stage separators. Flash2 performs vapor-liquid or vapor-liquid-liquid equilibrium calculations. When you specify the outlet conditions, Flash2 determines the thermal and phase conditions of a mixture of one or more inlet streams.

Flowsheet Connectivity for Flash2

Vapor Liquid Water (optional) Heat (optional) Heat (optional) Material (any number)

Material Streams

Outlet One material stream for the vapor phase

One material stream for the liquid phase. (If three phases exist, the liquid outlet contains both liquid phases.)

One water decant stream (optional)

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Heat Streams

Inlet Any number of heat streams (optional)

Outlet One heat stream (optional)

If you give only one specification (temperature or pressure) on the Input Specifications Sheet, Flash2 uses the sum of the inlet heat streams as a duty specification. Otherwise, Flash2 uses the inlet heat stream only to calculate the net heat duty. The net heat duty is the sum of the inlet heat streams minus the actual (calculated) heat duty.

You can use an optional outlet heat stream for the net heat duty.

Specifying Flash2

Use the Input Specifications sheet for all required specifications and valid phases. For valid phases you can choose the following options:

You can choose the following

options Solids? Number of phases? Free Water?

Vapor-Liquid Yes or no 2 No

Vapor-Liquid-Liquid Yes or no 3 No

Vapor-Liquid-FreeWater Yes or no 2 Yes

Use the Input FlashOptions sheet to specify temperature and pressure estimates and flash convergence parameters.

Use the Input Entrainment sheet to specify liquid and solid entrainment in the vapor phase.

Use the Hcurves form to specify optional heating or cooling curves.

Use the following forms to enter specifications and view results for Flash2: Use this form To do this

Input Enter flash specifications, flash convergence parameters, and entrainment specifications Hcurves Specify heating or cooling curve tables and view tabular results

Block Options Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block

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Solids

All phases are in thermal equilibrium. Solids leave at the same temperature as the fluid phases.

Flash2 can simulate fluid phases with solids when the stream contains solid substreams or when you request electrolytes chemistry calculations.

Solid Substreams Materials in solid substreams do not participate in phase

equilibrium calculations.

Electrolyte Chemistry Calculations You can request these on the Properties

Specifications Global sheet or the BlockOptions Properties sheet. Solid salts participate in liquid-solid phase equilibrium and thermal equilibrium calculations. The salts are in the MIXED substream.

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Flash3

Three-Outlet Flash

Use Flash3 to model flashes, evaporators, knock-out drums, decanters, and other single-stage separators in which two liquid outlet streams are produced. Flash3 performs vapor-liquid-liquid equilibrium calculations. When you specify outlet conditions, Flash3 determines the thermal and phase conditions of a mixture of one or more inlet streams.

Flowsheet Connectivity for Flash3

Vapor 2nd Liquid 1st Liquid Heat (optional) Heat (optional) Material (any number)

Material Streams

Outlet One material stream for the vapor phase One material stream for the first liquid phase One material stream for the second liquid phase

You can specify liquid entrainment of each liquid phase in the vapor stream. You can also specify entrainment for each solid substream in the vapor and first liquid phase.

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Heat Streams

If you give only one specification on the Input Specifications Sheet (temperature or pressure), Flash3 uses the sum of the inlet heat streams as a duty

specification. Otherwise, Flash3 uses the inlet heat stream only to calculate the net heat duty. The net heat duty is the sum of the inlet heat streams minus the actual (calculated) heat duty.

Specifying Flash3

Use the Input Specifications sheet for all required specifications. Use the Input Entrainment sheet to specify solid entrainment. To specify optional heating or cooling curves, use the Hcurves form.

Use the following forms to enter specifications and view results for Flash3: Use this form To do this

Input Enter flash specifications, key components, flash convergence parameters, and entrainment specifications

Hcurves Specify heating or cooling curve tables and view tabular results

Results View Flash3 simulation results

Dynamic Specify parameters for dynamic simulations

Solids

Flash3 can simulate fluid phases with solids when the stream contains solid substreams, or when you request electrolyte chemistry calculations.

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Specifications Global sheet or on the Input BlockOptions Properties sheet. Solid salts do participate in liquid-solid phase equilibrium and thermal equilibrium calculations. You can only specify apparent component calculations (Select Simulation Approach=Apparent Components on the BlockOptions Properties sheet). The salts will not appear in the MIXED substream.

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Decanter

Liquid-Liquid Decanter

Decanter simulates decanters and other single stage separators without a vapor phase. Decanter can perform:

• Liquid-liquid equilibrium calculations • Liquid-free-water calculations

Use Decanter to model knock-out drums, decanters, and other single-stage separators without a vapor phase. When you specify outlet conditions, Decanter determines the thermal and phase conditions of a mixture of one or more inlet streams.

Decanter can calculate liquid-liquid distribution coefficients using: • An activity coefficient model

• An equation of state capable of representing two liquid phases • A user-specified Fortran subroutine

• A built-in correlation with user-specified coefficients

You can enter component separation efficiencies, assuming equilibrium stage is present.

Use Flash3 if you suspect any vapor phase formation.

Flowsheet Connectivity for Decanter

Heat (optional) Heat (optional) 1st Liquid 2nd Liquid Material (any number)

Material Streams

Outlet One material stream for the first liquid phase One material stream for the second liquid phase

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Heat Streams

If you specify only pressure on the Input Specifications sheet, Decanter uses the sum of the inlet heat streams as a duty specification. Otherwise, Decanter uses the inlet heat stream only to calculate the net heat duty. The net heat duty is the sum of the inlet heat streams minus the actual (calculated) heat duty.

Specifying Decanter

You can operate Decanter in one of the following ways: • Adiabatically

• With specified duty

• At a specified temperature

Use the Input Specifications sheet to enter: • Pressure

• Temperature or duty

Use the following forms to enter specifications and view results for Decanter: Use this form To do this

Input Specify operating conditions, key components, calculation options, valid phases, efficiency, and entrainment

Properties Specify and/or override property methods, KLL equation parameters, and/or user subroutine for phase split calculations

Results Display simulation results

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Defining the Second Liquid Phase

If two liquid phases are present at the decanter operating condition, Decanter treats the phase with higher density as the second phase, by default.

When only one liquid phase exists and you want to avoid ambiguities, you can override the default by:

• Specifying key components for identifying the second liquid phase on the Input Specifications sheet

• Optionally specifying the threshold key component mole fraction on the Input Specifications sheet

When Decanter treats the

Two liquid phases are present Phase with the higher mole fraction of key components as the second liquid phase One liquid phase is present Liquid phase as the first liquid phase, unless the mole fraction of key components exceeds

the threshold value

Methods for Calculating the Liquid-Liquid Distribution

Coefficients (KLL)

When calculating liquid-liquid distribution coefficients (KLL), by default Decanter uses the physical property method specified for the block on the Properties PhaseProperty sheet or BlockOptions Properties sheet.

On the Input CalculationOptions sheet, you can override the default by doing one of the following:

• Specify separate property methods for the two liquid phases using the Properties PhaseProperty sheet

• Use a built-in KLL correlation. Enter correlation coefficients on the Properties KLLCorrelation sheet.

• Use a Fortran subroutine that you specify on the Properties KLLSubroutine sheet

See ASPEN PLUS User Models for more information about writing Fortran subroutines.

Phase Splitting

Decanter has two methods for solving liquid-liquid phase split calculations: • Equating fugacities of two liquid phases

• Minimizing Gibbs free energy of the system

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If you select Minimizing Gibbs free energy of the system, the following must be thermodynamically consistent:

• Physical property models • Block property method

You cannot use the Minimizing Gibbs free energy of the system method when: You specify On this sheet

Separate property methods for the two liquid phases

Properties PhaseProperty The built-in correlation for liquid-liquid

distribution coefficient ( KLL) calculations

Input CalculationOptions A user subroutine for liquid-liquid distribution

coefficient (KLL) calculations

Input Calculation Options

Equating fugacities of two liquid phases is not restricted by physical property specifications. However, Decanter can calculate solutions that do not minimize Gibbs free energy.

Efficiency

Decanter outlet streams are normally at equilibrium. However, you can specify separation efficiencies on the Input Efficiency sheet to account for departure from equilibrium. If you select Liquid-FreeWater for Valid Phases on the Input

CalculationOptions sheet, you cannot specify separation efficiencies.

Solids Entrainment

If solids substreams are present, they do not participate in phase equilibrium calculations, but they do participate in enthalpy balance. You can use the Input Entrainment sheet to specify solids entrainment in the first liquid outlet stream. Decanter places any remaining solids in the second liquid outlet stream.

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Sep

Component Separator

Sep combines streams and separates the result into two or more streams according to splits specified for each component. When the details of the

separation are unknown or unimportant, but the splits for each component are known, you can use Sep in place of a rigorous separation model to save

computation time .

If the composition and conditions of all outlet streams of the block you are modeling are identical, you can use an FSplit block instead of Sep.

Flowsheet Connectivity for Sep

Heat (optional) Material (2 or more) Material (any number)

Material Streams

Outlet At least two material streams

Heat Streams

Inlet No inlet heat streams

Outlet One stream for the enthalpy difference between inlet and outlet material streams (optional)

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Specifying Sep

For each substream of each outlet stream except one, use the Sep Input

Specifications sheet to specify one of the following for each component present: • Fraction of the component in the corresponding inlet substream

• Mole flow rate of the component • Mass flow rate of the component

• Standard liquid volume flow rate of the component

Sep puts any remaining flow in the corresponding substream of the unspecified outlet stream.

Use the following forms to enter specifications and view results for Sep: Use this form To do this

Input Enter split specifications, flash specifications, and convergence parameters for the mixed inlet and each outlet stream

Results View Sep simulation results

Inlet Pressure

Use the Sep Input Feed Flash sheet to specify either the pressure drop or the pressure at the inlet. This is useful when Sep has more than one inlet stream. The inlet pressure defaults to the minimum inlet stream pressure.

Outlet Stream Conditions

Use the Sep Input Outlet Flash sheet to specify the conditions of the outlet streams. If you do not specify the conditions for a stream, Sep uses the inlet temperature and pressure.

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Sep2

Two-Outlet Component Separator

Sep2 separates inlet stream components into two outlet streams. Sep2 is similar to Sep, but offers a wider variety of specifications. Sep2 allows purity (mole-fraction) specifications for components.

You can use Sep2 in place of a rigorous separation model, such as distillation or absorption. Sep2 saves computation time when details of the separation are unknown or unimportant.

If the composition and conditions of all outlet streams of the block you are modeling are identical, you can use FSplit instead of Sep2.

Flowsheet Connectivity for Sep2

Material Material Heat (optional) Material (any number)

Material Streams

Outlet Two material streams

Heat Streams

Inlet No inlet heat streams

Outlet One stream for the enthalpy difference between inlet and outlet material streams (optional)

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Specifying Sep2

Use the Input Specifications sheet to specify stream and/or component fractions and flows. The number of specifications for each substream must equal the number of components in that substream.

You can enter these stream specifications:

• Fraction of the total inlet stream going to either outlet stream • Total mass flow rate of an outlet stream

• Total molar flow rate of an outlet stream (for substreams of type MIXED or CISOLID)

• Total standard liquid volume flow rate of an outlet stream (for substreams of type MIXED)

You can enter these component specifications:

• Fraction of a component in the feed going to either outlet stream • Mass flow rate of a component in an outlet stream

• Molar flow rate of a component in an outlet stream (for substreams of type MIXED or CISOLID)

• Standard liquid volume flow rate of a component in an outlet stream (for substreams of type MIXED)

• Mass fraction of a component in an outlet stream

• Mole fraction of a component in an outlet stream (for substreams of type MIXED or CISOLID)

Sep2 treats each substream separately. Do not: • Specify the total flow of both outlet streams

• Enter more than one flow or frac specification for each component

• Enter both a mole-frac and a mass-frac specification for a component in a stream

Use the following forms to enter specifications and view results for Sep2: Use this form To do this

Input Enter split specifications, flash specifications, and convergence parameters for the mixed inlet and each outlet stream

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Inlet Pressure

Use the Input Feed Flash sheet to specify either the pressure drop or pressure at the inlet. This information is useful when Sep2 has more than one inlet stream. The inlet pressure defaults to the minimum of the inlet stream pressures.

Outlet Stream Conditions

Use the Input Outlet Flash sheet to specify the conditions of the outlet streams. If you do not specify the conditions for a stream, Sep2 uses the inlet temperature and pressure.

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3 Heat Exchangers

This chapter describes the unit operation models for heat exchangers and heaters (and coolers), and for interfacing to the B-JAC heat exchanger programs. The models are:

Model Description Purpose Use For Heater Heater or cooler Determines thermal and phase

conditions of outlet stream

Heaters, coolers, condensers, and so on HeatX Two-stream heat exchanger Exchanges heat between two

streams

Two-stream heat exchangers. Rating shell and tube heat exchangers when geometry is known.

MHeatX Multistream heat exchanger Exchanges heat between any number of streams

Multiple hot and cold stream heat exchangers. Two-stream heat exchangers. LNG exchangers. Hetran Shell and tube heat

exchanger

Provides interface to the B-JAC Hetran shell and tube heat exchanger program

Shell and tube heat exchangers, including kettle reboilers Aerotran Air-cooled heat exchanger Provides interface to the

B-JAC Aerotran air-cooled heat exchanger program

Crossflow heat exchangers, including air coolers

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Heater

Heater/Cooler

You can use Heater to represent: • Heaters

• Coolers • Valves

• Pumps (whenever work-related results are not needed) • Compressors (whenever work-related results are not needed)

You also can use Heater to set the thermodynamic condition of a stream. When you specify the outlet conditions, Heater determines the thermal and phase conditions of a mixture with one or more inlet streams.

Flowsheet Connectivity for Heater

Heat (optional)

Material Material

(any number)

Heat

(optional) Water (optional)

Material Streams

Outlet One material stream

One water decant stream (optional)

Heat Streams

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If you give only one specification (temperature or pressure) on the Specifications sheet, Heater uses the sum of the inlet heat streams as a duty specification. Otherwise, Heater uses the inlet heat stream only to calculate the net heat duty. The net heat duty is the sum of the inlet heat streams minus the actual

(calculated) heat duty.

Specifying Heater

Use the Heater Input Specifications sheet for all required specifications and valid phases.

Dew point calculations are two- or three-phase flashes with a vapor fraction of unity.

Bubble point calculations are two- or three-phase flashes with a vapor fraction of zero.

Use the Heater Input FlashOptions sheet to specify temperature and pressure estimates and flash convergence parameters.

Use the Hcurves form to specify optional heating or cooling curves.

This model has no dynamic features. The pressure drop is fixed at the steady state value. The outlet flow is determined by the mass balance.

Use the following forms to enter specifications and view results for Heater. Use this form To do this

Input Enter operating conditions and flash convergence parameters Hcurves Specify heating or cooling curve tables and view tabular results

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Solids

Heater can simulate fluid phases with solids when the stream contains solid substreams or when you request electrolyte chemistry calculations.

All phases are in thermal equilibrium. Solids leave at the same temperature as fluid phases.

Specifications Global sheet or the Heater BlockOptions Properties sheet. Solid salts participate in liquid-solid phase equilibrium and thermal equilibrium calculations. The salts are in the MIXED substream.

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HeatX

Two-Stream Heat Exchanger

HeatX can model a wide variety of shell and tube heat exchanger types including: • Countercurrent and cocurrent

• Segmental baffle TEMA E, F, G, H, J, and X shells • Rod baffle TEMA E and F shells

• Bare and low-finned tubes

HeatX can perform a full zone analysis with heat transfer coefficient and pressure drop estimation for single- and two-phase streams. For rigorous heat transfer and pressure drop calculations, you must supply the exchanger geometry.

If exchanger geometry is unknown or unimportant, HeatX can perform simplified shortcut rating calculations. For example, you may want to perform only heat and material balance calculations.

HeatX has correlations to estimate sensible heat, nucleate boiling, and condensation film coefficients.

HeatX cannot:

• Perform design calculations

• Perform mechanical vibration analysis • Estimate fouling factors

Flowsheet Connectivity for HeatX

Cold Outlet Water (optional) Hot Outlet Water (optional) Hot Inlet Cold Inlet

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Material Streams

Inlet One hot inlet One cold inlet

Outlet One hot outlet One cold outlet

One water decant stream on the hot side (optional) One water decant stream on the cold side (optional)

Specifying HeatX

Consider these questions when specifying HeatX:

• Should rating calculations be simple (shortcut) or rigorous? • What specification should the block have?

• How should the log-mean temperature difference correction factor be calculated?

• How should the heat transfer coefficient be calculated? • How should the pressure drops be calculated?

• What equipment specifications and geometry information are available? The answers to these questions determine the amount of information required to complete the block input. You must provide one of the following specifications: • Heat exchanger area or geometry

• Exchanger heat duty

• Outlet temperature of the hot or cold stream

• Temperature approach at either end of the exchanger

• Degrees of superheating/subcooling for the hot or cold stream • Vapor fraction of the hot or cold stream

• Temperature change of the hot or cold stream

Use the following forms to enter specifications and view results for HeatX: Use this form To do this

Setup Specify shortcut or detailed calculations, flow direction, exchanger pressure drops, heat transfer coefficient calculation methods, and film coefficients

Options Specify different flash convergence parameters and valid phases for the hot and cold sides, HeatX convergence parameters, and block-specific report option

Geometry Specify the shell and tube configuration and indicate any tube fins, baffles, or nozzles

UserSubroutines Specify parameters for user-defined Fortran subroutines to calculate overall heat transfer coefficient, LMTD correction factor, tube-side liquid holdup, or tube-side pressure drop

Hot-Hcurves Specify hot stream heating or cooling curve tables and view tabular results

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Use this form To do this

Cold-Hcurves Specify cold stream heating or cooling curve tables and view tabular results BlockOptions Override global values for physical properties, simulation options, diagnostic message

levels, and report options for this block

Results View a summary of results, mass and energy balances, pressure drops, velocities, and zone analysis

Detailed Results View detailed shell and tube results, and information about tube fins, baffles, and nozzles

Dynamic Specify parameters for dynamic simulations

Shortcut Versus Rigorous Rating Calculations

HeatX has two rating modes: shortcut and rigorous. Use the Calculation Type field on the Setup Specifications sheet to specify shortcut or rigorous rating calculations.

In shortcut rating mode you can simulate a heat exchanger block with the minimum amount of required input. The shortcut calculation does not require exchanger configuration or geometry data.

For rigorous rating mode, you can use exchanger geometry to estimate: • Film coefficients

• Pressure drops

• Log-mean temperature difference correction factor

Rigorous rating mode provides more specification options for HeatX, but it also requires more input.

Rigorous rating mode provides defaults for many options. You can change the defaults to gain complete control over the calculations. The following table lists these options with valid values. The values are described in the following sections.

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Variable Calculation Method Available in Shortcut Mode Available in Rigorous Mode LMTD Correction Factor Constant Geometry User subroutine Default No No Yes Default Yes Heat Transfer Coefficient Constant value Phase-specific values Power law expression Film coefficients Exchanger geometry User subroutine Yes Default Yes No No No Yes Yes Yes Yes Default Yes Film Coefficient Constant value

Phase-specific values Power law expression Calculate from geometry

No No No No Yes Yes Yes Default Pressure Drop Outlet pressure

Calculate from geometry

Default No

Yes Default

Calculating the Log-Mean Temperature Difference

Correction Factor

The standard equation for a heat exchanger is:

Q

= ⋅ ⋅

U A LMTD

where LMTD is the log-mean temperature difference. This equation applies for exchangers with pure countercurrent flow.

The more general equation is:

Q= ⋅ ⋅ ⋅U A F LMTD

where the LMTD correction factor, F, accounts for deviation from countercurrent flow.

Use the LMTD Correction Factor field on the Setup Specifications sheet to enter the LMTD correction factor.

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In shortcut rating mode, the LMTD correction factor is constant. In rigorous rating mode, use the LMTD Correction Method field on the Setup Specifications sheet to specify how HeatX calculates the LMTD correction factor. You can choose from the following calculation options:

If LMTD Correction Method is Then

Constant The LMTD correction factor you enter is constant.

Geometry HeatX calculates the LMTD correction factor using the exchanger specification and stream properties

User subroutine You supply a user subroutine to calculate the LMTD correction factor.

Calculating the Heat Transfer Coefficient

To determine how the heat transfer coefficient is calculated, set the Calculation Method on the Setup U Methods sheet. You can use these options in shortcut or rigorous rating mode:

If Calculation Method is HeatX uses And you specify Constant value A constant value for the heat transfer coefficient The constant value Phase-specific values A different heat transfer coefficient for each heat transfer

zone of the exchanger, indexed by the phase for the hot and cold streams

A constant value for each zone Power law expression A power law expression for the heat transfer coefficient as

a function of one of the stream flow rates

Constants for the power law expression

In rigorous rating mode, three additional values are allowed: If Calculation Method is Then

Exchanger geometry HeatX calculates the heat transfer coefficient using exchanger geometry and stream properties to estimate film coefficients.

Film coefficients HeatX calculates the heat transfer coefficients using the film coefficients. You can use any option on the Setup Film Coefficients sheet to calculate the film coefficients. User subroutine You supply a user subroutine to calculate the heat transfer coefficient.

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Film Coefficients

HeatX does not calculate film coefficients in shortcut rating mode. In rigorous rating mode, if you use film coefficients or exchanger geometry for the heat transfer coefficient calculation method, HeatX calculates the heat transfer coefficient using:

1

1 U

=

h

_c

+

h

_h

Where:

h

_c = Cold stream film coefficient

h

_h = Hot stream film coefficient

To choose an option for calculating film coefficients, set the Calculation Method on the Setup Film Coefficients sheet. The following are available:

If Calculation Method is HeatX uses And you specify Constant value A constant value for the film coefficient A constant value to be

used throughout the exchanger Phase-specific values A different film coefficient for each heat

transfer zone (phase) of the exchanger, indexed by the phase of the stream

A constant value for each phase Power law expression A power law expression for the film coefficient

as a function of the stream flow rate

Constants for the power law expression Calculate from geometry The exchanger geometry and stream

properties to calculate the film coefficient

The hot stream and cold stream film coefficient calculation methods are

independent of each other. You can use any combination that is appropriate for your exchanger.

Pressure Drop Calculations

To enter exchanger pressure or pressure drop for the hot and cold sides, use the Outlet Pressure fields on the Setup Pressure Drop sheet. In shortcut rating mode the pressure drop is constant.

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In rigorous rating mode, you can choose how pressure drops are calculated by setting the pressure options on the Setup PressureDrop sheet. The following pressure drop options are available:

If Pressure Option is Then

Outlet Pressure You must enter the outlet pressure or pressure drop for the stream.

Calculate from geometry HeatX calculates the pressure drop using the exchanger geometry and stream properties

HeatX calls the Pipeline model to calculate tube-side pressure drop. You can set the correlations for pressure drop and liquid holdup that the Pipeline model uses on the Setup PressureDrop sheet.

Exchanger Configuration

Exchanger configuration refers to the overall patterns of flow in the heat exchanger. If you choose Calculate From Geometry for any of the heat transfer coefficients, film coefficients, or pressure drop calculation methods, you may be required to enter some information about the exchanger configuration on the Geometry Shell sheet. This sheet includes fields for:

• TEMA shell type (see the next figure, TEMA Shell Types) • Number of tube passes

• Exchanger orientation • Tubes in baffle window • Number of sealing strips

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Two Pass Shell with Longitudinal Baffle

One Pass Shell E Shell F Shell G Shell H Shell J Shell X Shell Split Flow

Double Split Flow

Divided Flow

Cross Flow

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The Geometry Shell sheet also contains two important dimensions for the shell: • Inside shell diameter

• Shell to bundle clearance

The next figure shows the shell dimensions.

Outer Tube Limit Shell to Bundle Clearance Shell Diameter

Shell Dimensions

Baffle Geometry

Calculation of shell-side film coefficient and pressure drop require information about the baffle geometry within the shell. Enter baffle geometry on the

Geometry Baffles sheet.

HeatX can calculate shell-side values for both segmental baffle shells and rod baffle shells. Other required information depends on the baffle type. For segmental baffles, required information includes:

• Baffle cut • Baffle spacing • Baffle clearances

For rod baffles, required information includes: • Ring dimensions

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The next two figures show the baffle dimensions. The Baffle Cut in the

Dimensions for Segmental Baffles figure is a fraction of the shell diameter. All clearances are diametric.

Baffle Cut

Tube Hole Shell to Baffle

Clearance

Dimensions for Segmental Baffles

Ring Outside Diameter

Ring Inside Diameter Rod Diameter

Dimensions for Rod Baffles

Tube Geometry

Calculation of the tube-side film coefficient and pressure drop require information about the geometry of the tubebank. HeatX also uses this

information to calculate the heat transfer coefficient from the film coefficients. Enter tube geometry on the Geometry Tubes sheet.

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You can select a heat exchanger with either bare or low-finned tubes. The sheet also includes fields for:

• Total number of tubes • Tube length

• Tube diameters • Tube layout

• Tube material of construction

The next two figures show tube layout patterns and fin dimensions.

Tube Pitch 30o Triangle 45o Tube Pitch Rotated Square 60o Tube Pitch Rotated Triangle 90o Tube Pitch Square Direction of Flow

Tube Layout Patterns

Outside Diameter Fin Thickness Root Mean Diameter Fin Height

Fin Dimensions

Nozzle Geometry

Calculations for pressure drop include the calculation of pressure drop in the exchanger nozzles. Enter nozzle geometry on the Geometry Nozzles sheet.

Model Correlations

HeatX uses open literature correlations for calculating film coefficients and pressure drops. The next four tables list the model correlations.

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Tube-side Heat Transfer Coefficient Correlations

Mechanism Flow Regime Correlation References Single-phase Laminar Turbulent Schlunder Gnielinski [1] [1] Boiling - vertical tubes Steiner/Taborek [2] Boiling - horizontal tubes Shah [3, 4] Condensation - vertical tubes Laminar

Laminar wavy Turbulent Shear-dominated Nusselt Kutateladze Labuntsov Rohsenow [5] [6] [7] [8] Condensation - horizontal tubes Annular

Stratifying

Rohsenow Jaster/Kosky method

[8] [9]

Shell-side Heat Transfer Coefficient Correlations

Mechanism Flow Regime Correlation References Single-phase segmental Bell-Delaware [10, 11]

Single-phase ROD Gentry [12]

Boiling Jensen [13]

Condensation - vertical Laminar Laminar wavy Turbulent Shear-dominated Nusselt Kutateladze Labuntsov Rohsenow [5] [6] [7] [8]

Condensation - horizontal Kern [9]

Tube-side Pressure Drop Correlations

Mechanism Correlation

Single-phase Darcy’s Law Two-phase See Chapter 6† †

See Pipeline, Two-Phase Correlations, for the correlations available for two-phase pressure drop in a pipe.

Shell-side Pressure Drop Correlations

Mechanism Correlation References

Single-phase segmental Bell-Delaware [10, 11]

Single-phase ROD Gentry [12]

Two-phase segmental Bell-Delaware method with Grant’s correction for two-phase flow

[10, 11], [14]

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Flash Specifications

Use the Options Flash Options sheet to enter flash specifications. If you want to perform

these calculations Solids? Set Valid Phases to Vapor phase Yes or no Vapor-only Liquid phase Yes or no Liquid-only 2-fluid flash phase Yes or no Vapor-Liquid 3-fluid flash phase Yes or no Vapor-Liquid-Liquid 3-fluid phase free-water flash Yes or no Vapor-Liquid-FreeWater

Solids only Yes Solid-only

Physical Properties

To override global or flowsheet section property specifications, use the

BlockOptions Properties sheet. You can use different physical property options for the hot side and cold side of the heat exchanger. If you supply only one set of property specifications, HeatX uses that set for both hot and cold side

calculations.

Solids

HeatX can simulate fluid phases with solids when the stream contains solid substreams, or when you request electrolyte chemistry calculations.

Specifications Global sheet or HeatX BlockOptions Properties sheet. Solid salts participate in liquid-solid phase equilibrium and thermal equilibrium

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References

1. Gnielinski, V., "Forced Convection in Ducts." In: Heat Exchanger Design Handbook. New York: Hemisphere Publishing Corporation, 1983.

2. Steiner, D. and Taborek, J., "Flow Boiling Heat Transfer in Vertical Tubes Correlated by an Asymptotic Model." In: Heat Transfer Engineering, 13(2):43-69, 1992.

3. Shah, M.M., "A New Correlation for Heat Transfer During Boiling Flow Through Pipes." In: ASHRAE Transactions, 82(2):66-86, 1976.

4. Shah, M.M., "Chart Correlation for Saturated Boiling Heat Transfer: Equations and Further Study." In: ASHRAE Transactions, 87(1):185-196, 1981.

5. Nusselt, W., "Surface Condensation of Water Vapor." Z. Ver. Dtsch, Ing., 60(27):541-546, 1916.

6. Kutateladze, S.S., Fundamentals of Heat Transfer. New York: Academic Press, 1963.

7. Labuntsov, D.A., "Heat Transfer in Film Condensation of Pure Steam on Vertical Surfaces and Horizontal Tubes." In: Teploenergetika, 4(7):72-80, 1957.

8. Rohsenow, W.M., Webber, J.H., and Ling, A.T., "Effect of Vapor Velocity on Laminar and Turbulent Film Condensation." In: Transactions of the ASME, 78:1637-1643, 1956.

9. Jaster, H. and Kosky, P.G., "Condensation Heat Transfer in a Mixed Flow Regime." In: International Journal of Heat and Mass Transfer, 19:95-99, 1976.

10. Taborek, J., "Shell-and-Tube Heat Exchangers: Single Phase Flow." In: Heat Exchanger Design Handbook. New York: Hemisphere Publishing

Corporation, 1983.

11. Bell, K.J., "Delaware Method for Shell Side Design." In: Kakac, S., Bergles, A.E., and Mayinger, F., editors, Heat Exchangers: Thermal-Hydraulic Fundamentals and Design. New York: Hemisphere Publishing Corp., 1981. 12. Gentry, C.C., "RODBaffle Heat Exchanger Technology." In: Chemical

Engineering Progress 86(7):48-57, July 1990.

13. Jensen, M.K. and Hsu, J.T., "A Parametric Study of Boiling Heat Transfer in a Tube Bundle." In: 1987 ASME-JSME Thermal Engineering Joint

Conference, pages 133-140, Honolulu, Hawaii, 1987.

14. Grant, I.D.R. and Chisholm, D., "Two-Phase Flow on the Shell Side of a Segmentally Baffled Shell-and-Tube Heat Exchanger." In: Journal of Heat Transfer, 101(1):38-42, 1979.

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MHeatX

Multistream Heat Exchanger

Use MHeatX to represent heat transfer between multiple hot and cold streams, such as in an LNG exchanger. You can also use MHeatX for two-stream heat exchangers. Free water can be decanted from any outlet stream. MHeatX ensures an overall energy balance but does not account for the exchanger geometry.

MHeatX can perform a detailed, rigorous internal zone analysis to determine the internal pinch points and heating and cooling curves for all streams in the heat exchanger. MHeatX can also calculate the overall UA for the exchanger and model heat leak to or from an exchanger.

MHeatX uses multiple Heater blocks and heat streams to enhance flowsheet convergence. ASPEN PLUS automatically sequences block and stream convergence unless you specify a sequence or tear stream.

Flowsheet Connectivity for MHeatX

Hot Inlets (any number) Hot Outlets Water (optional) Hot Outlets Water (optional) Water (optional) Cold Outlets Cold Inlets (any number)

Material Streams

Inlet At least one material stream on the hot side. At least one material stream on the cold side

Outlet One outlet stream for each inlet stream

One water decant stream for each outlet stream (optional) The inlet stream sides are non-contacting.

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Specifying MHeatX

You must give outlet specifications for each stream on one side of the heat exchanger. On the other side you can specify any of the outlet streams, but you must leave at least one unspecified stream.

Different streams can have different types of specifications. MHeatX assumes that all unspecified streams have the same outlet temperature. An overall energy balance determines the temperature of any unspecified stream(s).

You can use a different property method for each stream in MHeatX. Specify the property methods on the BlockOptions Properties sheet.

Use the following forms to enter specifications and view results for MHeatX: Use this form To do this

Input Specify operating conditions, flash convergence parameters, parameters for zone analysis, flash table, MHeatX convergence parameters, and block-specific report options

BlockOptions Override global values for physical properties, simulation options, diagnostic message levels and report options for this block

Results View stream results, exchanger results, zone profiles, stream profiles, flash profiles, and material and energy balance results

Zone Analysis

MHeatX can perform a detailed, rigorous internal zone analysis to determine: • Internal pinch points

• UA and LMTD of each zone • Total UA of the exchanger • Overall average LMTD

To obtain a zone analysis, specify Number of zones greater than 0 on the MHeatX Input Zone Analysis sheet. During zone analysis MHeatX can add:

• Stream entry points (if all feed streams are not at the same temperature) • Stream exit points (if all product streams are not at the same temperature) • Phase change points (if a phase change occurs internally)

MHeatX can also account for the nonlinearities of zone profiles by adding zones adaptively. MHeatX can perform zone analysis for both countercurrent and co-current heat exchangers.