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Noise, vibration, and … harshness?
December 04, 2023
NVH (noise, vibration, and harshness) is an increasingly important design metric for many commercial products—from vacuum cleaners and dishwashers, to lawnmowers and chain saws, to cars, trucks, and aircraft. Consumers demand a product that performs well but with low "observables." The first two qualities are measureable. A sound power meter can...
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Industry Interest in Electric Heaters Continues to Heat Up
November 06, 2023
Process electric heaters are an intriguing alternative to fuel burning heaters like the shell-and-tube exchangers commonly used in industrial plant settings. Electric heating elements, rather than heated fluid in tubes, provide constant heat flux. Electric heaters can thus control duty more precisely and produce higher heat fluxes than steam condensers. Since...
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TechTip: Modeling Process Electric Heaters in Xist
October 05, 2023
Xist® 9.1 introduced electric heater functionality. This webinar describes the basic modeling approach for electric heaters and the inputs and outputs for the electric service types. It also covers the current limitations of the model and forecasts potential improvements in Xist. A case study demonstrates how users can build and evaluate an electric...
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TT-32 Condensation of two liquid phases in steam/hydrocarbon applications
September 06, 2023
Component: Xist Applicable to: All supported versions (Version 8.2 and Version 9.x) Date posted: 6 September 2023 During condensation of a steam/hydrocarbon mixture, the condensate can form two immiscible liquids (also known as two liquid phases). These phases can exist only in equilibrium with the vapor phase at a single point (the...
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TT-31 Beware of flow obstructions in inlet and outlet regions
February 14, 2023
Component: Xist, Xvib Applicable to: All supported versions (Version 8.2 and Version 9.x) Date posted: 14 February 2023 Flow obstructions in the inlet and outlet regions can invalidate the Xist bundle entrance and exit velocities and thus impact the rho-V2 calculations. The Xist vibration analysis for shell and bundle entrance and exit...
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S-SS-3-30 Predictions of Single-phase Flow in TEMA F-shell Heat Exchanger: CFD vs. Xist
December 21, 2022
This report compares computational fluid dynamics (CFD) and Xist predictions of single-phase performance in a TEMA F-shell heat exchanger with a sealed longitudinal baffle. In the initial comparison, CFD underpredicted both duty (16% less) and pressure drop (over 50% less). We then represented an F shell in Xist using two E-shell...
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BK1-18 A Parametric Study of Entrainment Using CFD Simulations
November 10, 2022
Accurate prediction of kettle entrainment is crucial for sizing kettles effectively, reducing equipment cost, and increasing column efficiency. Operating experience has informed the development of simple sizing rules. Two-phase CFD models can compute the amount of entrainment directly from the governing equations of motion. Two computational approaches are demonstrated: one uses...
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Getting Started: Building Your First Case in Xist
June 22, 2022
Are you ready to build your first case in Xist®? This webinar provides an overview of the program's user interface and basic functionality then demonstrates the specification of an exchanger design in Xist using the information in a TEMA Spec Sheet. View this webinar for a step-by-step specification of a new Xist case including process conditions, physical...
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BT-43 Liquid Film Breakdown in Tubeside Falling Film Evaporators
May 19, 2021
This report provides an overview of several mechanisms for the breakdown of falling film. Available literature and HTRI data enable confirmation of the minimum wetting flow rate calculation used in Xist 8.2 and the development of two correlations for determining Reynolds numbers for the Marangoni breakdown, one for the subcooled zone...
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CS-22 Enhanced Methods in Xist 8 for Gravity-controlled Shellside Condensation
June 22, 2020
This report documents the revised methods in Xist 8 for predicting the gravity-controlled condensate heat transfer coefficient on horizontal tube bundles. Reformulation of the relevant equations using the local condensate Reynolds number on an element of the tube bundle facilitates exploitation of the Xist 3D incremental structure more effectively than was...
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Baffle design dictates ideal flow
June 11, 2020
Ashley Simmons, Engineer, Technical Support Each heat exchanger has unique requirements due to process constraints, site limitations, or cost concerns. The fundamentals of good design apply to every variety of exchanger. The primary goal of every designer is to optimize exchanger design for the most effective heat transfer possible. One of...
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TT-29 Kettle vaporizers and the modified three-point heat release curve
February 17, 2020
Component: Xist Applicable to: All supported versions (versions 7.3 through 8.1) Date posted: 17 February 2020 Kettle design promotes shellside recirculation in the tube bundle, making kettles ideal for vaporizing pure or nearly pure fluids. In vaporizers, liquid recirculates within the bundle, and vapor separates from liquid droplets in the volume...
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TechTip: Challenges in Modeling Kettle Vaporizers
January 16, 2020
Modeling kettle vaporizers presents multiple challenges, including entrainment and circulation issues. As part of the kettle Circulation Boiling Model (CBM), Xist® modifies the heat release curve (program calculated or user specified) to create a unique kettle three-point heat release curve to determine the temperature profile within the bundle. This webinar focuses on when...
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TT-28 Specifying disk-and-doughnut baffles in Xist
December 04, 2019
Component: Xist Applicable to: All supported versions (Versions 8.2 and 9) Date posted: 5 December 2019 (updated 26 October 2023) Disk-and-doughnut baffles are an alternative to conventional segmental baffles. Figure 1 illustrates a generic disk-and-doughnut baffle configuration. In many industrial units, tubes are present only in the overlap region between the...
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CS-21 Xist Thermal Predictions of Horizontal Shellside Condensation with Subcooling
October 10, 2018
HTRI collected data in a horizontal E-shell exchanger with vertical-cut baffles, obtaining varying degrees of subcooling at the exchanger outlet for water, n-pentane, p-xylene, and a binary mixture of n-pentane/p-xylene. Liquid level measurements along the length of the exchanger confirmed the presence of shellside flooding. Xist predicted the heat transfer area...
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Measuring sound...with a phone?
July 12, 2018
Kevin J. Farrell, Principal Engineer, Computational Simulation & Validation Sound propagates as pressure fluctuates in fluids; measuring sound means converting these fluctuations into electrical signals with a transducer. A sound level meter—a pressure transducer attached to a voltmeter—has often been used to record noise levels around a heat exchanger experiencing acoustic...
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TechTip: Tube Layout Design and Customization
August 24, 2017
This webinar discusses the tube layout options in Xchanger Suite® 7. Specifically, we will discuss the different features of the view and edit mode; describe a recommended workflow for Xist®, and review output drawings. Updated for Xchanger Suite 7.3.1....
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STG-21 Computational Simulation of Fluid Flow, Heat Transfer, and Temperature-induced Mechanical Stress in a Shell-and-tube Heat Exchanger
July 21, 2017
We completed a multiphysics computational simulation of a shell-and-tube exchanger, where simultaneous fluid flow and heat transfer of both fluid streams occurred. Temperature-induced mechanical stress also acted on the solid structures. A weak coupling of a finite-volume CFD Navier-Stokes model with a finite-element computational solid mechanics model underlies the multiphysics simulation....
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TT-25 Modeling anti-vibration support plates in Xist
May 04, 2017
Component: Xist Applicable to: All supported versions (versions 7.3 and 8) Date posted: 4 May 2017 With high crossflow velocities and long tube spans, bundle entrance and exit regions can be susceptible to tube vibration. Anti-vibration support plates1 can be effective in these regions and can reduce tube vibration potential. At...
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TT-24 Modeling U-bend supports in Xist
May 04, 2017
Component: Xist Applicable to: All supported versions (versions 7.3 and 8) Date posted: 4 May 2017 Long unsupported spans in the U-bend region of U-tube exchangers can result in excessive vibration. When the nozzle is at or after the U-bend, the Runtime Messages and the Vibration Analysis report in Xist...
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TT-17 Tubecount assumptions in Xist
January 26, 2017
Component: Xist Applicable to: All supported versions (Versions 7.3 and 8) Date posted: 25 March 2015 To calculate tubecount, Xist uses different methods based on input selections: Rigorous vs. non-rigorous tubecount If rigorous tubecount is specified on the Tube Geometry panel, Xist generates a tube layout drawing starting at the center...
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TT-9 Specify double-segmental baffles in Xist
January 26, 2017
Component: Xist Applicable to: All supported versions (Versions 7.3 and 8) Date posted: 19 August 2009 Double-segmental baffles are TEMA baffles that split the flow along the length of a bundle. The baffle pattern diverts flow with alternating center baffles and wing baffles as shown in Figure 1. Figure 1. Double-segmental...
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TT-1 Beware of large height under nozzle with parallel-cut baffles
January 26, 2017
Component: Xist Applicable to: All supported versions (versions 7.3 and 8) Date posted: 4 January 2008 In cases with parallel-cut baffles, when the height under nozzle lowers the top of a tube bundle below the baffle cut, the accuracy of Xist results is reduced. In such cases, a bundle bypass path...
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TechTip: Momentum Recovery in Tubeside Vacuum Condensers
February 01, 2017
Traditionally, for tubeside vacuum condensers, designers attempt to ensure that the velocity profile through the exchanger decelerates from the inlet nozzle to the outlet nozzle. Momentum recovery occurs with a reducing velocity profile throughout an exchanger. If correlations do not account for momentum recovery in the inlet and outlet header of...
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Is My Design OK? Lessons Learned: Falling Film Evaporators
February 01, 2017
The purpose of this webinar is to discuss industry experience with vertical tubeside falling film evaporators, including specified applications and design principles for configuration. In this webinar, we identify potential design problems in keeping tube walls wet and discuss HTRI’s current methods in addressing these concerns within Xist®....
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Beyond the Basics: Interpreting Common Xist Warning Messages
February 01, 2017
This webinar describes the different types of error messages that Xist® can generate. We focus on several important messages that are sometimes misunderstood or overlooked due to their frequency. These messages include warnings about a low B-stream, fluid property extrapolation, and fluidelastic instability. We describe their origins and the impact on...
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TechTip: Vibration Analysis in U-bends
January 16, 2017
As heat exchanger design continues to evolve toward larger units with ever-increasing flowrates, the importance of tube vibration analysis has never been more important. However, u-tube designs can be particularly problematic. This webinar will discuss Xist® assumptions with U-bends and when Xvib® should be used for an accurate vibration analysis...
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Beyond the Basics: Understanding the Simple vs. Detailed Piping Option in Xist
January 16, 2017
Xist® includes two options for specifying piping geometries: simple (default) and detailed. The simple piping option requires fewer inputs but relies on several default assumptions which may not conform to the intended piping configuration. In contrast, the detailed piping option requires users to specify each piping element (e.g., straight pipe runs,...
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Research Update: Boiling on Enhanced Surfaces
January 16, 2017
This webinar reviews improvements in boiling heat transfer through the use of passive surface enhancements. Commercial tubes enhanced with porous coatings or mechanically with integral structure provide a larger surface area for heat transfer and nucleation site density when compared with plain tubes. Boiling heat transfer enhancement for clean fluids increases...
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S-SS-3-29: CFD Simulations of Diabatic Shellside Viscous Flows
January 16, 2017
For shellside diabatic flows of highly viscous fluids, Xist can predict inconsistent pressure drops and heat transfer coefficients. HTRI examined the transition between forced and natural convection in single-segmental and double-segmental exchangers with Alta-Vis oil and an asphalt blend as test fluids. Comparisons were made between experimental data, open literature, computational...
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TechTip: Kettle Entrainment Prediction
January 16, 2017
After discussing an overview of kettle reboilers and the fundamentals of entrainment, this webinar reviews Xist® input and output as well as design considerations that affect kettle entrainment. By working through an example case, this webinar teaches that accurate prediction of liquid entrainment is crucial for some applications, that liquid carryover...
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TechTip: How Xist Estimates External Pressure Requirements for Pipes and Tubes
January 16, 2017
This webinar will investigate how Xist® uses ASME code design methods to determine the external pressure requirements for cylinders. Using three cases, we will discuss how to determine thickness for specified temperature and pressure how to determine the maximum external pressure for a specified thickness external pressure limitations as compared to...
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TechTip: Self-venting Nozzles in Condensers
January 16, 2017
Self-venting nozzles are often desired in partial or complete condensers. HTRI recommends sizing these nozzles for gravity condensate flow to produce weir-type flow. Xist® can help users size self-venting nozzles properly with warning or informative messages; however, certain criteria must be met for the software to complete the necessary calculations. Xist uses...
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S-SS-3-28 Optimal Application of Shellside Sealing Devices
January 16, 2017
This report documents two approaches to analyze the performance of different sealing devices. The first approach examines an exchanger with a fixed sealing device count and varied baffle spacing. The second approach considers an exchanger with fixed shellside geometry but different sealing device types and arrangements. Comparisons are made between experimental...
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Research Update: Maldistribution in Shellside Laminar Viscous Flow
January 16, 2017
Xist® can predict unexpected performances of shellside viscous fluids in laminar regimes, where thermal maldistribution is present. The heat transfer of viscous flows across vertical baffles is analyzed by CFD to determine impact of such non-uniformity. Maldistribution can be monitored using a viscosity-independent Richardson number. The Richardson relates the impact of...
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Research Update: Sealing Device Application
January 16, 2017
During this webinar, we discuss the basics of sealing devices, including common practices and design guidelines. Further, we review the basic flow resistance equation for sealing strips used in Xist® Version 7 and compare the measured performances of HTRI research-scale heat exchanger using sealing strips to CFD and Xist predictions....
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Is My Design OK? Design Guidance for Impingement Rods
January 16, 2017
This webinar discusses the background of impingement rods used in heat exchanger design, identifies HTRI recommendations for the use of impingement rods (and their design), and describes current HTRI research in this field....
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Beyond the Basics: Understanding the Xist Vibration Report
January 16, 2017
Avoiding flow-induced vibration problems in shell-and-tube exchangers is an important task best accomplished at the design stage. Xist® completes a screening analysis using mechanistic-based methods that have been validated with real cases and data. Because there are two types of vibration (tube and acoustic) and several excitation mechanisms, careful examination of...
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TechTip: Service Type Defaults in Xist
January 16, 2017
Xist® service types are improved and expanded in Xchanger Suite® 7. During this webinar, we will discuss and demonstrate the default values provided for thermosiphon reboiler and reflux condenser service types....
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S-SS-3-25 Analysis of NTIW shellside performance using CFD and Xist
January 16, 2017
Using computational fluid dynamics (CFD) and Xist, HTRI simulated three configurations of no-tubes-in-window (NTIW) bundles in shell-and-tube heat exchangers. Our analysis of the trends in pressure drop and heat transfer underscores the importance of window friction and window momentum losses, even without tubes in this region, as well as the existence...
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Research Update: Analysis of NTIW Shellside Performance using CFD and Xist
January 16, 2017
This webinar will discuss Xist® and CFD predictions of three NTIW exchanger configurations – 2 baffle, 4 baffles, and 6 baffles. The discussion will focus on the contributions of crossflow and longitudinal flow on heat transfer, which is due to varied baffle spacing for the same baffle cut. During the webinar,...
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TechTip: Tube Spans in the Xist Vibration Report
January 16, 2017
Xist® automatically generates a vibration analysis report for all cases. The software selects tube spans for analysis based on a range of factors, including TEMA shell type, baffle type and baffle orientation. While users are generally familiar with the structure of the vibration report for TEMA E shells, the methods applied to...
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TechTip: Modeling DX Evaporators
January 16, 2017
This webinar provides an overview of DX evaporators and how to model them in Xist® and Xace®, including what has changed in Xchanger Suite® 7....
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Is My Design OK? Designing with Dummy Tubes
January 16, 2017
Dummy tube use is commonly overlooked and underspecified in tubular heat exchanger design. This webinar provides definitions of dummy tube types, explains why and when they are needed, and, using specific design examples, explores their use in Xist® Version 7....
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Is My Design OK? Selecting Finned-Tube Bundles
January 16, 2017
Are you using Xchanger Suite® to model finned-tube bundles? This webinar provides an overview of finned tubes and the various types of finned tubes that Xchanger Suite models. In addition to guidance on when to select each type, the session highlights important, high-level mechanical design aspects of finned tubes....
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Is My Design OK? Evaluating the Potential for Acoustic Vibration
January 16, 2017
Intense sound and vibration can be produced by gas flow through a heat exchanger array of tubes. Typically, the oscillating pressure corresponds to a transverse standing wave across the heat exchanger shell that is perpendicular to the crossflow and the tube axes. The sound is attributed to flow-induced pressure pulsations that...
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TechTip: Skin Temperature Computation in Xist
January 16, 2017
Skin temperature is an important variable in heat exchanger design because it may influence both fouling and corrosion. Xist® output reports list various skin, wall, and tube metal temperatures, but these data need to be interpreted correctly. In this webinar, we explain the influence of skin temperature on heat exchanger reliability, review...
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Is My Design OK? Floating Head Design and Effects on Tube Layout
January 16, 2017
This webinar will discuss the reasons for using floating heads, the differences between the four types (S, T, P, and W), and the effects of diameter and length on floating head design. As we describe design considerations for each type, we will provide tips and rules-of-thumb for achieving optimal, practical designs....
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S-ST-1-14 CFD Study of Single-Phase Laminar Mixed Convection in Inclined Tubes
January 16, 2017
To gain insight into the thermal-hydraulic phenomena associated with mixed convection in internal flows, we used computational fluid dynamics (CFD) to conduct a parametric study of single-phase laminar liquid flows in inclined tubes with isothermal, uniform wall temperatures (UWT). Both heating and cooling processes were simulated to isolate the effects of...
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TechTip: Modeling Horizontal Thermosiphon Oil Coolers
January 16, 2017
Thermosiphons are used in distillation columns, solar water heaters, refrigeration, and many other applications. This webinar focuses on one type: cooling screw compressor oil using a thermosiphon. It also includes a discussion of design and operation guidance available in open literature. The session ends with a demonstration of how Xist® models horizontal...
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S-SS-3-22 Stream Analysis in a Single-Segmentally Baffled Exchanger: CFD vs. Xist
January 16, 2017
HTRI conducted computational fluid dynamics (CFD) simulations to investigate leakage and bypass stream behavior under various flow regimes in an industrial-scale heat exchanger with single-segmental baffles. To cover a wide range of Reynolds numbers, the simulations tested single-phase water and Alta-Vis oil. Both concentric and eccentric configurations of the exchanger’s tube-to-baffle...
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Is My Design OK? Thermosiphon Modeling in Xist
January 16, 2017
To help you better use Xist® to model thermosiphon reboilers, this webinar begins with an overview of thermosiphon reboiler operations. Next, we discuss design rules-of-thumb and Xist input guidelines, including reboiler inputs and piping. The webinar concludes with helpful hints for interpreting results by focusing on troubleshooting error messages....
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TechTip: Improvements in Specifying EMbaffles
January 16, 2017
HTRI continues to improve EMbaffle® implementation in Xist®. In this webinar specifically geared toward the use of EMbaffles in Xist, we describe the technology, discuss how to specify EMbaffle in Xist, and explain the EMbaffle-related improvements in Service Pack 3. We conclude the webinar by demonstrating input options for E- and F-shells...
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TechTip: Modeling Flooded Evaporators
January 16, 2017
This webinar describes modeling flooded evaporators using Xist®. It reviews HTRI shellside boiling methods and discusses the similarities and differences for modeling kettles, x-shells, and flooded evaporators in Xist®. We use an ammonia chiller case to demonstrate a performance comparison of these three models....
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Is My Design OK? Baffled by Heat Exchanger Design
January 16, 2017
This webinar examines different types of baffles (TEMA and non-TEMA) and demonstrates how different baffles affect heat exchanger performance. Further, we discuss some rules-of-thumb for proper design with respect to baffle cut, spacing, and orientation. Finally, we will provide a summary of the performance characteristics of the different baffle types, to...
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S-SS-3-21 Disk-and-Doughnut Baffled Heat Exchangers: CFD Simulations and Methods
January 16, 2017
Disk-and-doughnut baffled heat exchangers can generate more heat transfer with less pressure drop than conventional segmental exchangers in certain industrial applications. Unfortunately, little information is available on these units in service. This report introduces new methods for analyzing and rating a disk-and-doughnut baffled heat exchanger. Using three-dimensional computational fluid dynamics (CFD)...
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BK1-12 Three-Dimensional CFD Simulations of Kettle Reboilers
January 16, 2017
Three-dimensional computational fluid dynamics (CFD) simulations of experimental kettle reboiler slices from the literature, as well as from the HTRI kettle reboiler, allow examination of fluid flow behavior on a fine spatial scale—significantly beyond the resolution of available experimental measurements. Interestingly, our simulations of kettle slices yield recirculation ratios that agree...
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STV-16 Calculating Fluidelastic Instability of U-Tubes Near Inlet Nozzles
January 16, 2017
The challenges of a rules-based vibration screening in Xist® have often led to excessive conservatism for U-tubes positioned near the inlet nozzle. In this study, we simulated shellside diabatic flow over the U-bend portion of the bundle for a number of nozzle locations using computational fluid dynamics (CFD). Using the simulation...
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S-SS-3-18 CFD Simulations of Single-Phase Turbulent Shellside Flow
January 16, 2017
High fidelity, tube-by-tube computational fluid dynamics (CFD) simulations of the turbulent, multistream shellside flow within a 9-crosspass, 591-mm diameter, 2276-mm long E shell were completed at four flow rates. The shellside water flow was heated by a full bundle at a uniform tube wall temperature. Computational results for duty and pressure...
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STV-15 Select Crossflow Velocity Distributions for Analyzing Tube Vibration Potential
January 16, 2017
Both the value and distribution of velocity along each span are important for proper assessment of tube vibration potential. Because of the disparity in spatial resolution between the small-scale finite element structural model of Xvib® and the larger scale incrementation scheme of Xist®, engineering judgment is required to populate the important...
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S-SS-3-17 Heat Transfer and Pressure Drop Methods for Square One Baffles
January 16, 2017
TRICO Metal Products, Inc. manufactures Square One™ baffles, a strip baffle or egg crate tube support technology for square pitch layouts. This report documents heat transfer and pressure drop methods for shellside flow using Square One baffles. Based on the existing Xist® window flow model, the methods have been adjusted for...
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