Design and Specification of Packinox Heat Exchangers

1. Table of Contents

1. Table of Contents 1

2. Purpose 1

3. General 1

4. Exchanger Codes and Standards 2

5. Exchanger Sizing and Economics 2

5.1 Heat Utilization 2

5.2 Economic Analysis – Combined Feed – Effluent Heat Exchangers (CFE’s) 2

5.3 Computer Programs 3

6. General Considerations 3

6.1 Process Information 4

6.2 Mechanical Considerations 4

7. Preparation of the 416 Specification 4

7.1 Process Section 4

7.2 Mechanical Section 6

Table 1 - Hot Side and Cold Side Design Pressure and Temperature 7

7.3 Notes 8

Table 2 - Design Parameters 11

8. Other Considerations 12

Figure 1 - Typical Packinox Welded Plate Heat Exchanger 14

Appendix I 15

2. Purpose

This procedure provides Inflection Point Engineering practice and guidelines for the design and specification of Packinox welded plate heat exchangers.

3. General

Packinox welded plate heat exchangers are used in a limited number of applications. They may be used for combined feed versus effluent exchangers in such processes as Platforming, Pacol, various aromatics units, and a limited number of other applications. These exchangers become advantageous over shell & tube exchangers when the required surface area is greater than 10,000 square feet or if the hot end approach temperature difference is less than 75°F (42°C). A Packinox welded plate heat exchanger consists of a bundle of heat transfer plates, a pressure containment vessel and pipes and expansion bellows to connect the plate bundle to the pressure vessel (See Figure 1).

A Packinox welded plate heat exchanger has the advantage of being more efficient and more compact than shell and tube exchangers. They are smaller in size and can attain lower approach temperature differences than tubular heat exchangers. A single Packinox exchanger can in most cases perform the same as two or more vertical tubular exchangers. The smaller size and reduced weight will generally mean lower cost.

Reference Procedure for Inflection Point Engineering practice and guidelines for the administrative aspect of preparing heat exchanger specifications.

4. Exchanger Codes and Standards

Design all welded plate type heat exchangers to the ASME Code Section VIII, Division 1.

5. Exchanger Sizing and Economics

Consider the following points to establish the size of a Packinox exchanger during the process design:

5.1 Heat Utilization

The Design Engineer needs to consider how to utilize the heat in a process stream most efficiently. For example, in a reactor feed-effluent system consisting of a heat exchanger and a fired heater, the split of duty between the two pieces of equipment is a design variable. The greater the duty of the exchanger, the smaller the duty of the heater and vice versa. There is a constant operating cost for burning fuel in the heater but only a one-time capital cost for the exchanger. Therefore, the split of duty is an economic optimization. This economic optimization must take into account the value of energy versus capital, exchanger size limitations, pinch point limitations, cost impact on the fired heater and other downstream exchangers, optimization of process variables, and operational flexibility for the process unit.

5.2 Economic Analysis – Combined Feed – Effluent Heat Exchangers (CFE’s)

An economic analysis is used to determine the duty split between the heat exchanger and the fired heater. Select several outlet temperature values around a target hot end approach temperature difference for the heat exchanger. Use about a 10ºF (5.6°C) increment when selecting alternative values. Estimate the equipment cost of the heat exchanger. The Packinox CFE is sized using the PASHA software provided by Packinox (see section 5.3 for more information). For comparison, a tubular vertical combined feed exchanger may be sized using HTRI software. Obtain the operating cost of the fuel in the fired heater (typically provided in the BEDQ).

Obtain the rate of return or payback period that the Customer wants to use for the evaluation of capital expenditures. Determine the optimum size of the heat exchanger by selecting the largest heat exchanger that can be justified within the Customer’s capital expenditure criteria. The increased capital cost of incrementally larger Packinox CFEs is offset by lower operating costs of reduced fired heater fuel consumption. The payback period will increase as increasing amounts of exchanger surface area are required to achieve additional fuel savings. If there are alternate operating cases such as alternate feeds, SOR, EOR, or turndown, the optimum design must be re-rated with the alternate conditions to ensure sufficient thermal (surface area) and hydraulic (pressure drop) performance. Also, the Packinox entrainment factor, which is the criteria for proper lift of liquid feed with the recycle gas up the plate bundle (calculated by the PASHA computer program), must be satisfied for all operating cases. Packinox recommends an absolute minimum entrainment factor of 1.0; higher limits may be used depending on the process and the potential for other operating conditions that may not be evaluated. All cases with lower recycle gas flows should be checked to determine if they are limiting for liquid lift, and these cases should then be specified on the 416 project specification if necessary.

The optimum Packinox size depends on the relative costs of fuel versus exchanger surface area. These values sometimes favor very large heat exchangers with relatively small temperature approaches. There are minimum temperature pinches and MTDs that must also be respected when determining the exchanger size. See section 7.3.i for more details. Typically, MTDs lower than 45 °F are not specified. For process contingency and safety, there are minimum required sizes for charge heater duties which must be considered so that the process remains in a controllable regime.

Typically, the economic analysis is performed by an Exchanger Specialist who is experienced in the design and optimization of welded plate heat exchangers in combined feed – effluent services. This analysis is done based on information provided by the Process Engineer. Consult with an Exchanger Specialist for more information regarding the economic evaluation process.

5.3 Computer Programs

The sizing and cost estimating of the Packinox welded plate heat exchanger is done in conjunction with Packinox using their computer program PASHA. This software will estimate the size and cost of a Packinox welded plate heat exchanger for use in an economic analysis.

This software is provided to Inflection Point Engineering under a non-disclosure agreement between Inflection Point Engineering and Packinox.

The design details of any Packinox design (surface area, plate quantity, plate dimensions, coefficients, etc.) MUST NOT BE DISCLOSED OUTSIDE OF Inflection Point Engineering.

6. General Considerations

Consider the following items when specifying a Packinox combined feed – effluent heat exchanger:

6.1 Process Information

Typically, the high pressure stream is used to pressure the vessel. There is not the same concern of fluid flow side selection as there is in tubular exchangers, as both fluids are in the plate bundle.

The process information requirements are similar to those required for a typical 401 (Shell & Tube Heat Exchanger) specification. The main difference is that the cold fluid may be a combination of two separate streams, a liquid feed stream and a recycle gas stream. List selected information for each stream (such as flow rate, molecular weight and density) individually for use in sizing of the liquid and vapor distributors. In addition, list the mixed streams physical properties.

Typically, the hot end approach temperature difference for a Packinox CFE is about 60°F (33°C) for Platforming units and 65-75°F (36-42°C) for Isomar and Tatoray units.

6.2 Mechanical Considerations

The sole manufacturer of these exchangers is Alfa Laval. Alfa Laval governs the mechanical design of this type of exchanger. This exchanger is basically a welded bundle of stainless steel heat transfer plates. The exchanger uses very large plates compared to a plate and frame type exchanger due to Alfa Laval’s unique manufacturing method of explosion forming the plates rather than pressing them. The plate bundle is contained within a pressure vessel to minimize the pressure differences in and around the plate bundle. The plate bundle only has to be designed to contain the differential pressure between the streams since the cold fluid gas stream (typically recycle gas) is used to pressurize the pressure vessel.

A strainer is normally located upstream of the exchanger on the liquid feed side to prevent plugging of the liquid distributor. Therefore, an 806 Project Specification for Strainers is also required. It is also recommended that the liquid feed piping between the strainer and the Packinox CFE be stainless steel to prevent pipe scale from plugging the liquid feed distributors. This is especially important when the piping length exceeds 10 meters.

7. Preparation of the 416 Specification

The preparation of the 416 Specification uses Tools and .

7.1 Process Section

Import the process and equipment data into the specification in the identical manner as it is for a 401 Specification. The data includes 10 points for generation of physical properties and for calculation of a heat release curve. The heat release curve is almost always non-linear in nature. Individual inlet stream data for the Feed (liquid stream) and the Recycle Gas (vapor stream) must be shown on the Specification. Ensure that the correct streams have been loaded into ABEand connect them to the appropriate linksets in the spec tool bridge (TZ-416-02) to automatically transfer them into the specification.

It is necessary to evaluate all operating cases to determine the design case for the exchanger. The design case requires that the thermally and hydraulically governing operating cases be identified. The thermally governing case is the case that requires the greatest heat transfer surface area. This often is not the case with the largest duty. Similarly, the hydraulically governing case is the case that will cause the largest pressure drop. It is often not the case with the largest mass flow rate, as pressure drop also depends on density, viscosity, and the vapor mass fraction of the stream.

A given Packinox design can only accommodate a finite range of combined feed inlet vapor fractions, and the cold liquid lift must be considered for each operating case. The more dissimilar the operating cases in flow and/or pressure, the more difficult to find a single Packinox design which accommodates all cases. All operating cases should be considered and provided to the exchanger specialist when determining the required performance of the Packinox as described in Section 5.2.

As necessary, multiple cases may be shown on the 416 Specification to cover limiting thermal, hydraulic, and liquid lift cases that must be respected by the vendor. These cases are usually identified during the economic analysis described in Section 5.2.

Once the optimum design for the governing case has been selected (see Section 5.2), the simulation must be updated for all cases to reflect the result of the economic analysis. Appendix I details the procedure for updating the simulation conditions for Isomar and Tatoray unit. A similar procedure may be followed for other technologies. Consult the process design manual or technology specialist for any modifications needed.

The hot and cold side pressure drops specified should be consistent with the exchanger sizing completed for the economic analysis. Depending on the process technology, there may be standard pressure drop values for the hot and cold sides that are used to maintain consistency with the Yield Estimate and other process work. For all Platforming Unit CFE, the standard pressures drops shown in Table 2 should always be specified so that the Specification is consistent with the Yield Estimate. For the non-hydraulically governing case, consult the exchanger specialist for the applicable pressure drops and manually input these values into hydraulics.

7.2 Mechanical Section

The mechanical section of the specification is small. Provide the hot and cold side mechanical design temperatures and pressures using the same criteria as for shell and tube type heat exchangers. This information is used by Packinox to determine the proper grading of the pressure vessel material from the hot to cold end of the exchanger. The hot and cold side design pressures and temperatures are typically set by the following criteria depending upon the process:

Table 1 - Hot Side and Cold Side Design Pressure and Temperature

Process	Hot side Design Press.	Cold side Design Press.	Hot side Design Temp.	Cold side Design Temp
Platforming	Plat. Design Manual Based On Accumulated Hydraulic Case	Plat. Design Manual Based On Accumulated Hydraulic Case	Reactor Design Temperature
Tatoray	Accumulated Hydraulic Case	Accumulated Hydraulic Case	Reactor Design Temperature	IPE-TM-100-02
Isomar	Accumulated Hydraulic Case	Accumulated Hydraulic Case	Reactor Design Temperature	IPE-TM-100-02
Pacol	Accumulated Hydraulic Case	Accumulated Hydraulic Case	IPE-TM-100-02	IPE-TM-100-02

Some process units have regeneration temperatures that are higher than the design temperature of the exchanger (Isomar CFE). For these cases, the regeneration design temperatures and pressure must also be specified in addition to the normal design temperatures and pressures.

As introduced briefly above and described in more detail in Sections 7.3 g and h, the Packinox pressure vessel design is graded from the hot end to the cold end of the vertical heat exchanger. It is important to define the terms “hot end”, “cold end”, “hot side” and “cold side” when referring to the specification and design of a Packinox CFE. The “hot end” is the top end of the vertical exchanger, where the “hot side” inlet and the “cold side” outlet nozzles are located. The “cold end” is at the bottom end of the vertical exchanger, where the “cold side” inlet and the “hot side” outlet nozzles are located. The “hot side” and the “cold side” refer to the two “sides” containing the process streams passing through the heat exchanger, which are transferring heat from the hot fluid to the cold fluid.

Provide the operating pressures and allowable pressure drops for both streams. See section 7.3.i for more information on typical allowable pressure drops.

The hot fouling factor and the cold fouling factor are typically specified as 0.002 ft2-hr-°F/Btu (0.0004 m²-hr-°C/kcal), which is consistent with tubular exchangers. The fouling factor for a plate type exchanger is lower than for a shell and tube type exchanger. The higher shear stresses on particles in a plate bundle result in lower fouling factor values compared to a tubular exchanger in the same service. Packinox may adjust the fouling factors accordingly.

7.3 Notes

Some decisions need to be made for the Notes section of the 416 Specification. The basis for these notes is as follows:

a. The Packinox plate bundle has a limited ability to resist deforming under internal pressure. Therefore, a Packinox CFE is specified as a differential pressure design. It is normally designed such that the pressure vessel side of the exchanger is at a higher pressure than the plate bundle side so that the differential pressure is compressive on the plate bundle. The allowable difference in pressure between the vessel side and the bundle internal pressure depends on a number of parameters including the gap between the plates, the thickness of the plates, the plate material of construction, and the operating temperature. For most applications the typical plate design would allow a maximum pressure difference of 250 psi (17.6 kg/cm²) at 120°F (49°C). This allowable differential pressure would decrease to 160 psi (11.2 kg/cm²) at 1000°F (538°C) and about 110 psi (7.7 kg/cm²) at 1100°F (593°C). In some common cases where dissimilar plate gaps are required to improve the cold side inlet velocity, the maximum differential pressure decreases to approximately 115 psi (8.1 kg/cm²) at 1000°F (538°C) and 80 psi (5.6 kg/cm²) at 1100°F (593°C).

Under no circumstances (unless appropriate mechanical design requirements are specified as described below for certain regeneration cases) should an anticipated startup, shutdown, relieving, cleaning, or maintenance scenarios (evacuation/depressuring) result in a higher pressure on the hot side than on the cold side.

The bundle design differential pressure between the feed and effluent sides is the maximum of the following three values:

• The accumulated pressure at the recycle compressor discharge minus the accumulated pressure at the recycle compressor suction.

• 1.15 times the rated P across the recycle compressor.

• A minimum value of

• 40 psi (2.8 kg/cm²) for Pacol Packinox CFE
• 70 psi (4.9 kg/cm²) for all other Packinox CFE

The situation changes when a regeneration case exists in certain process units. During certain regenerations the pressure on the plate bundle side is higher than the shell side pressure. For this case, also specify an internal differential pressure so that additional structural bracing can be provided. Typically, without reinforcement, the maximum internal differential pressure that can be withstood by the plate bundle is 0 psi (0 kg/cm²). When required, it is common to use a 15 psi (1.05 kg/cm²) maximum internal bundle pressure differential for regeneration cases.

b. Both sides of the exchanger are normally designed for full vacuum conditions. Typically the vacuum design temperature is the same as the value specified for the reactors. These are standard values, which are summarized in Table 2. Due to the differential pressure design of the bundle, the pressure vessel side of the bundle should only be allowed to encounter vacuum conditions simultaneously with the bundle side.

c. Liquid feed distribution is done by the use of spray bar distributors upstream of the welded plate bundle. The vendor determines the number of spray bars required. Typically two (2) spray bars are used, except for small exchangers where a single spray bar may be used. The normal pressure drop in the liquid distributor (spray bars) is 15 psi (1.05 kg/cm²), and is listed separately from the hot and cold side pressure drops. This distributor pressure drop and the feed strainer pressure drop should be included in hydraulics. For revamp evaluations where there is an existing Packinox CFE, the pressure drop of the liquid distributor and the recycle gas distributor should be checked to confirm that they are within the amounts available in the hydraulic calculations. See an Exchanger Specialist for revamp evaluations of existing Packinox CFE.

d. The sum of the pressure drops on both process sides together is typically controlling rather than the pressure drop on each side individually. The distribution of process pressure drop between the hot and cold sides is frequently redistributed by Packinox to optimize the CFE design. The Packinox 416 specification has a note stating that redistribution may not be done without written approval from Inflection Point Engineering. Often this request is granted after review by the process or project engineer.

e. Normally size vent and drain nozzles as NPS 2 for vessels up to or equal to 15 feet diameter (4.5 m) and NPS 3 for vessels from 15 feet (4.5 m) to 20 feet (6.0 m) in diameter. This is the default information in the BEDQ, and should be checked for specific Customer requirements, such as a volume-based criterion. It is rare to have a Packinox CFE with a vessel diameter exceeding 15 feet.

The diameter of the vessel manway at the top of the vessel should be sufficient for replacing the hot end expansion bellows, and shall respect the minimum manway size specified in the BEDQ. Similarly, the recycle gas inlet nozzle must be large enough to replace the cold end expansion bellows, and the contractor shall provide a transition piece between the incoming piping and the nozzle so the piping can easily be disconnected and the nozzle can be used as manway.

f. The bundle plates are typically made of type 321 or 304 stainless steel.

g. The pressure vessel is normally specified as graded construction. The hot and cold end design temperatures are typically set by the following criteria depending upon the process. Typically, the hot end design temperature is the same as the hot side design temperature. For Platforming Units: Set the hot end design temperature equal to the design temperature of the Reactor. The cold end design temperature is equal to 550°F (288°C). This temperature was derived from the ASME code (allowable stresses).

For Tatoray, Isomar and Pacol Units: Set the hot end design temperature equal to the design temperature of the Reactor for the Tatoray and Isomar Units. Design the hot end design temperature per IPE-TM-100-02 for the Pacol Units. The cold end design temperature is equal to 550°F (288°C) for Isomar and Pacol Units. The cold end design temperature is equal to 500°F (260°C) for Tatoray Units.

h. The material for the pressurized vessel is typically 1¼Cr - ½Mo steel. If necessary for very low minimum design metal temperatures (MDMT) 2¼Cr - ½Mo steel is used. Both materials are listed in a typical specification with a reference to Inflection Point Engineering Standard Specification 3-12. Packinox will determine the materials of construction based on ASME pressure vessel code and economics.

Normally the vessel is specified as graded construction. That is, the hot end of the vessel would be alloy while the cold end would be killed carbon steel. The breakpoint operating temperature for where the material change takes place is a function of hydrogen partial pressure and material (Nelson Curve). When the partial pressure of hydrogen is equal to or less than 200 psia the breakpoint operating temperature between low alloy and killed carbon steel is 525°F (274°C). For hydrogen partial pressures greater than 200 psia the breakpoint operating temperature between low alloy and killed carbon steel is 475°F (246°C). Based on this criterion, typically specify the Platforming, Isomar and Pacol Units with a breakpoint operating temperature of 525°F (274°C) and Tatoray Unit with a breakpoint operating temperature of 475°F (246°C).

Similarly, the hot end and cold end flange classes are also based on the graded design of the pressure vessel. Consequently, the flange class specifications in Packinox CFE are different from typical heat exchanger specifications that show “hot side” and “cold side” flanges. The Packinox CFE “hot end” flange classes are based on the hot end design temperature and metallurgy, while the “cold end” flange classes are based on the cold end design temperature and metallurgy. Flange class breaks across the exchanger are acceptable. Any additional design conditions such as regeneration design temperatures and pressure shall also be checked while determining the flange classes. The vessel design pressure (cold side design pressure) is used for all flange class calculations.

The flange class of the liquid feed inlet nozzle should also consider the metallurgy of the liquid feed lines. Typically these lines are specified as stainless steel. At higher pressures, such as in Tatoray Units, the stainless steel metallurgy may require a higher flange class than the cold end Packinox vessel metallurgy.

i. Many of the design parameters are dependent on the service the exchanger is used in. The following table summarizes these process-related criteria. For applications in other processes, contact a Heat Exchanger Specialist.

Table 2 - Design Parameters

	Process Unit	Process Unit	Process Unit	Process Unit
Parameter	Platforming	Isomar	Pacol	Tatoray
Minimum Pinch Temperature (*)	New: 14F (7.8°C) Revamp: 10F (5.6°C)	New: 14F (7.8°C) Revamp: 10F (5.6°C)	18F (10°C)	New: 14F (7.8°C) Revamp: 10F (5.6°C)
Minimum Mean Temperature Difference (MTD)	---	---	60°F	---
Pressure Drop (Hot/Cold Side)	7.5 psi / 5 psi	7.5 psi / 7.5 psi	5 psi / 3 psi	7.5 psi / 5 psi
Alloy vs. KCS breakpoint operating temperature	If H2 PP<=200 psi: 525°F (274°C) If H2 PP>200 psi: 475°F (246°C)	If H2 PP<=200 psi: 525°F (274°C) If H2 PP>200 psi: 475°F (246°C)	If H2 PP<=200 psi: 525°F (274°C) If H2 PP>200 psi: 475°F (246°C)	If H2 PP<=200 psi: 525°F (274°C) If H2 PP>200 psi: 475°F (246°C)
Cold End Design Temperature	550F (288°C)	550F (288°C)	550F (288°C)	550F (288°C)
Hot End Design Temperature	Reactor Design Temperature	Reactor Design Temperature	IPE-TM-100-02	Reactor Design Temperature
Vacuum Design Temperature	750F (400°C)	350F (177 °C)	300F (149°C)	750F (400°C)

Notes: (*) Confirm using the PASHA computer program.

8. Other Considerations

8.1 For a revamp of a fixed bed Platforming unit, verify that the EDI - Operating Philosophy is completed. This document guides the end-user in avoiding certain risks of internal differential pressure situations that may occur during regeneration due to caustic circulation downstream of the CFE. For a grass roots fixed bed Platforming Unit, consult with the Technology Specialist. If there is a regeneration case for an Isomar Unit, then consult with the Technology Specialist for proper documentation.

8.2 Since early 2001 Packinox no longer provides bundle designs with lateral water injection due to concerns about proper injection location and concerns about thermal shocks and thermal inertia at the injection manifold. Water injection is used to wash ammonium chloride salts from the reactor effluent side of the exchanger, which is commonly required for NHT Units. A practical method for injecting sufficient wash water upstream of the Packinox has not been established. Until water washing and corresponding corrosion concerns can be resolved, Packinox CFE’s are not recommended for NHT Units.

8.3 It is important to avoid specifying Packinox CFE in units that have potential for fouling the CFE.

In general, feed side fouling can result from feed contamination, overuse or misuse of a corrosion inhibitor in an upstream process, or from processing feed from non-blanketed intermediate storage. For example, high rates of inhibitor injection, coupled with an inhibitor that is not highly hydrocarbon-soluble, result in the inhibitor passing through the NHT stripper and entering the Platforming unit. Feed from a non-blanketed intermediate storage or oxygen contamination of the feed is another cause of fouling, with the resultant peroxide gums depositing on the feed side of the exchanger plates.

The reactor effluent side can observe a build up of ammonium chloride salts if there is an excursion of nitrogen in the naphtha feed or in the unit. Eliminating the nitrogen will eliminate the salts fouling. A properly performed in-situ water wash can effectively remove the salts and restore the performance of the exchanger.

8.4 During regeneration, to avoid potential corrosion of the stainless steel plates, it is critical to prevent the temperature within the CFE from dropping below the dew point temperature. Therefore, it is important to NOT cool the recycle gas after it is compressed.

8.5 It has been observed that a shutdown of the reactor loop that is long enough to let the fired heaters cool (2 hours or more), but short enough that the reactors and CFE remain hot (less than a couple of days, depends on the unit size), can at the restart of recycle gas flow cause rapid removal of heat from the reactors and CFE. This thermal transient may cause damage to the welded plate bundle, resulting in cross-leakage from the feed stream to the effluent stream. This has been observed in at least one Platforming unit where there was significant heater area. Platforming units have a low flow low firing restart procedure that addresses this possibility.

8.6 Packinox has several procedures that form their Operating Manual. A very useful section is “Installation (SAIEXWA0002)”, which provides vendor recommendations for exchanger protection, surrounding equipment, instrumentation, and alarms. Please see an Exchanger Specialist to obtain the latest version of the Packinox Operating Manual.

Figure 1 - Typical Packinox Welded Plate Heat Exchanger

Appendix I

OVERVIEW OF CFE PROCESS DESIGN PROCEDURE- TATORAY/ ISOMAR

PROCESS ENGINEERING TASKS

• Prepare HWB for ALL cases
• Use Unisim template and Data Workbook (DWB) as the starting point.
• Use the Default LMTD specification for the CFE.
• Packinox CFE is assumed as the basis. Consult with Specialist for VCFE application.

• Share Results with Heat Exchanger Specialists
• Create a separate sub-folder “CFE Evaluation” in your Process Work/ Studies folder. Use this folder exclusively for sharing files for CFE study.
• Copy Unisim flowsheet files for all feed cases. Be sure to include SOR and EOR.
• Place copies of ALL files to be evaluated in CFE Evaluation folder.
• Send an email with a link to the CFE Evaluation folder to the Heat Exchanger Specialists. Be sure to include the Fuel Gas cost and Payback Period information for the project BEDQ (if known).
• If process revisions are made, replace outdated files in the CFE Evaluation folder and repeat Step 2.

• Incorporate CFE Study results into Unisim for the GOVERNING case as determined by the Heat Exchanger Specialist
• Update the LMTD specification with the study result for the GOVERNING case.

• Unisim calculated duty and terminal temperatures may not match CFE study exactly.
• User may attempt to reconcile values by adjusting the number of intervals (50, 100, etc.).
• Heat duty should be within +/- 1%. Pinch temperatures should be within +/- 0.5°F.
• Contact Heat Exchanger Specialist if above criteria cannot be met.
• MTD specification must match CFE study as specified.

• Incorporate CFE Study into Unisim- NON-GOVERNING case
• Obtain the GOVERNING case UA value from the exchanger object in Unisim.
• Calculate the NON-GOVERNING case UA, where:

UA = UAgov * (F/Fgov)0.65

UAgov is the GOVERNING case UA Value from Unisim

F is the mass flow rate to the CFE.

Fgov is the GOVERNING case mass flow rate to the CFE

• Change the CFE specification to UA
• Enter the calculated UA value from Step 4b.

• Unisim calculated duty and terminal temperatures for the NON-GOVERNING case will not match the CFE Study for the GOVERNING case.
• Leave the LMTD calculation intervals unchanged from the GOVERNING case.
• If the pinch T for the NON-GOVERNING case determined by the above procedure is <10°F, then the UA for the NON-GOVERNING case shall be adjusted (decreased) to achieve 10°F.

• Repeat Step 4 for additional Feed cases.

• Confirm Results
• Confirm HWB results for Design Case are consistent with CFE Study.
• Fill out CFE summary table in DWB for internal PFD review meeting for all cases.

EXAMPLE:

Case	GOVERNING- STUDY	GOVERINING- UNISIM	OTHER CASES- UNISIM
Duty
LMTD
Pinch T
COLD SIDE	COLD SIDE	COLD SIDE	COLD SIDE
Total Mass Flow
Recycle Gas Mass Flow
Recycle Gas MW
H2:HC
Inlet T
Outlet T
Inlet P
Outlet P
HOT SIDE	HOT SIDE	HOT SIDE	HOT SIDE
Total Mass Flow
Inlet T
Outlet T
Inlet P
Outlet P

• Re-confirm prior to start of Project phase.
• If CFE operating conditions have changed the CFE design must be re-confirmed with the Heat Exchanger Specialists.