S&T HEAT EXCHANGERS, Part I: Configuration, TEMA; Tube
S&T HEAT EXCHANGERS, Part I:Configuration, TEMA; Tube thk,Tubesheet and Flat CoversSTUDY NOTESInstructor: Javier ulting.com
TrainingProjectsConnecting DotsTable of contentsIntroduction . 41.2.3.4.5.6.Terminology . 81.1)Fluids . 81.2)Pressure . 81.3)Temperature. 91.4)External loads. 101.5)Other definitions . 11Shell and tube heat exchangers . 122.1)Parts of heat exchangers . 132.2)Types of heat exchangers . 152.3)Main components . 172.4)TEMA heat exchanger selection . 20Design codes . 213.1)TEMA code (Tubular Exchangers Manufacturers Association) . 223.2)HEI Standard (Heat Exchange Institute) . 253.3)API 660–American Petroleum Institute . 273.4)ASME VIII Div.1 Code, UHX part . 283.5)ASME VIII Div.1 Code, pressure parts . 293.6)Scope and precedence . 33Material Selection . 354.1)Corrosion . 364.2)Corrosion types . 374.3)Corrosion allowance . 404.4)Essential properties of materials . 424.5)Technical-economical selection . 464.6)Product forms. 474.7)Material designation . 484.8)Recommended good practices . 50Shell and tube heat exchangers arrangement . 545.1)Tube pattern . 545.2)Tube side number of passes . 585.3)Shell side number of passes . 59Tube bundle design . 62SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 2
TrainingProjectsConnecting Dots7.8.6.1)Tubesheet . 636.2)Tube bundle assembly . 696.3)Transverse baffles . 716.4)Longitudinal baffle . 746.5)Tubes . 766.6)Tube – tubesheet joint . 786.7)Floating head . 826.8)Impingement plate . 856.9)Pulling devices. 87Design of external elements . 887.1)Main parts . 887.2)Flat covers . 94Bibliography . 97SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 3
TrainingProjectsConnecting DotsIntroductionThere are many different applications that are covered by each type of heatexchanger, but in general, they are used to recover heat between two fluidstreams in a particular process plant.The term heat exchanger encompasses all devices used to transferenergy from one fluid to another. Some examples of this group are:radiators, water heaters, refrigeration batteries, evaporators, steamgenerators, etc.ClassificationThe more general classification that can be done for heat exchangersisaccording to the type of heat transfer method between the fluids.Following this criterion, heat exchangers are divided into two groups:Direct contact heat exchangers, also known as mix exchangers, aredevices where both fluids undergo a complete physical mixture.SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 4
TrainingProjectsConnecting DotsAmong others, cooling towers and mix condensers belong to the directcontact heat exchangers group.On the other hand, devices in which heat transfer takes place through aflat or cylindrical surface are called indirect contact exchangers. Thereis a barrier that physically separates the two fluid flows, thus there being nopossibility of direct contact or contamination between such fluids, except incase of damage of the separation barrier.Examples of this type of heat exchanger areshell and tube exchangers,double tube exchangers and plate heat exchangers.On the other hand, according to their type of construction, exchangers areclassified as:In multi-tubular or shell and tube heat exchangers, it is usual to combinethe above classification to anotherbased on the number of times eachparticle of the fluidtravels the entire exchanger length, a process called a“pass”.In addition to their type of construction, tubular exchangers are oftenclassified based on the relative directionflow of both fluids. Thus, thereare parallel and cross flow heat exchangers, according to the direction ofthe streams inside the exchanger.Additionally, tubular exchangers having same direction and sense arecalled co-current. When the flow circulates in opposite direction, theheat exchanger is operating in counter counter.Parallel flow heat exchangers mostly used in industrial plants are, amongothers: plate and frame, double tube, shell and tube and hair pin.SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 5
TrainingProjectsConnecting DotsSHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 6
TrainingProjectsConnecting DotsDesignTo design a shell and tube heat exchanger it is mandatory to have theinputs indicated in the data sheet of the equipment. The data sheet isnothing more than a compilation of information obtained during thethermal study of the process in which the exchanger is included. With thisinformation can then be determined the mechanical elements that will bedesigned individually.The design methods of the parts that could be included in a shell and tubeheat exchanger will be described in the following chapters of this document.However, not every element described herein will be involved in the design ofevery shell and tube heat exchanger. Elements should be selected according tothe needs and requirements specified in the data sheet. For example, thismeans that a TEMA heat exchanger type "NEN" will not require a floating heador torispherical head, elements that are also described in this document for thecases which do required them.In general, for the calculation and design of the different components ofheat exchangers, in this document the criteria set by TEMA code isfollowed, sometimes ASME code suggested design methods and less oftenHEI minimum requirements. This criterion is adopted in order to cover thewidest range of possible applications, since TEMA is the more used code.SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 7
TrainingProjectsConnecting Dots1.Terminology1.1)1.1.1)FluidsTube sideThe fluid flowing inside the tubes (that belong to the tube bundle) iscalled the tube side of a shell and tube heat exchanger.1.1.2)Shell sideOn the contrary, the fluid flowing inside the shell is called the shell sideof a shell and tube heat exchanger.1.2)1.2.1)PressureInternal PressureThe difference between the operation (Po) and design pressure (Pd) is asafety margin. This margin exists because sometimes it is difficult to establishoperation conditions with certainty. If we need to design but only haveoperating pressure, a workaround could be as follows:If Po 300 psi Pd 1.1. Po.If Po 300 psi Pd Po 30 psiWhere Pd is the design pressure, and Po is the operating pressure.When determining the design pressure (Pd), the hydrostatic head(pressure of the fluid column) should be considered, especially in verticalcylindrical vessels.SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 8
TrainingProjectsConnecting Dots1.2.2)External pressureIf under operating conditions the equipment gets depressurized oroperates under vacuum, at that moment the atmospheric pressure isacting outside the pressure vessel.At sea level, atmospheric pressure is 1 atm. According to the location (heightabove sea level) at which the equipment is to be installed, we should see theatmospheric pressure declining. To simplify the calculations, and always on thesafe side, usually 1 atm external pressure is taken without considering theheight above sea level.Steam out or blanketingWhen performing a steam out operation (used to clean the vessel) using highor medium steam pressure, steam can condense due to a temperature changeand produce vacuum. Depending on the temperature of the steam used, it isadvisable to calculate the equipment under external pressure due to vacuum.1.2.3)Maximum allowable working pressure (MAWP)MAWP is the maximum continuous working pressure that the vessel couldoperate, assuring that the equipment will not deform plastically.Is MAWP the same as the design pressure? The answer is NO. Adoptedthicknesses usually exceed the required thickness by calculation. This excessis what generates the pressure to jump up to the MAWP.The MAWP is a consequence of over-thickness due to: commercial thicknesses,margin of safety and manufacturing methods.When dealing with shell and tube heat exchangers, it is important tomention that many of the parts of this equipmentface the effect of pressure,temperature or corrosion from both the tube side and the shell side. Sincedesign conditions may be different for the tube side and for the shell side,the most critical condition should be always specified.1.2.4)Test pressure (Pt)The test pressure is commonly known as hydrostatic test pressure. Thistest is carried out once the heat exchanger manufacturing process iscompleted. This test consists in filling the equipment with water while it issubjected to pressure as indicated by the ASME code (to be discussedlater).1.3)1.3.1)TemperatureMinimum temperatureIt is the minimum temperature at which membrane stress occurs due to anenvironmental or process condition. The client or process department mustprovide this information. If this information is not available and there are noSHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 9
TrainingProjectsConnecting Dotsprocess requirements, we look for the historical minimum temperature of thesite.1.3.2)Minimum design metal temperature (MDMT)MDMT is the minimum temperature that our material is able to resistagainst a brittle fracture. It is a property of the material.1.3.3)Operating temperature (To)It is the shell and tube heat exchanger temperature, considering normaloperating conditions.1.3.4)Design temperature (Td)It is the temperature to be used in the design of the heat exchanger. Same aswith the design pressure, this value is defined by the thermal design. When onlythe operating temperature is known, it could be estimated as follows: For fluids operating above 0ºC, the design temperature should be thegreater of the following expressions:oTo x 1,1oTo 15 º Co65º CFor fluids operating at a temperature of 0º C or lower, it should besimultaneously specified the minimum and maximum expectedtemperature, the latter being not less than 65º C for the shell side. Thisconsideration is made in order to consider the hot air flow during thedrying operation, after the hydrostatic test.1.4)1.4.1)External loadsWind, snow and earthquakeThese external conditions are imposed according to the place of installation ofthe equipment. Ideally, a detailed study of the legislation of the place shall becarried out; misreading values represent a lot of man-hour rework.To analyze combined actions is essential to review the requirements of theclient.1.4.2)Cyclic loadingIf a pressure vessel has a requirement of cyclical service, the equipment shouldmeet the requirements of fatigue analysis of Div.2. Does this mean that theentire pressure vessel should be designed according to the Div.2? NO. Thevessel can be design according to Div.1, but must also meet the requirementsfor fatigue analysis according Div.2.SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 10
TrainingProjectsConnecting DotsAn alternative to the fatigue analysis according to the provisions of Part 5 Div.2is FEA. This latter method is being used more and more nowadays.1.5)1.5.1)Other definitionsDesign stress (S)It is the maximum stress value that a material, that forms part of a shelland tube heat exchanger, can undergo in normal operation. Its value isbased on 25% of the final tensile strength of the material.1.5.2)Joint efficiency (E)Joint efficiency can be defined as the reliability that you can obtain fromwelded joint. This coefficient can be values smaller than 1, and it can besaid that the joint efficiency is a way of reducing the allowable stress ofthe material. Therefore, the joint efficiency depends on the level of nondestructive examination (NDE) and the category and type of the weld we usefor joining two pieces of equipment.SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 11
TrainingProjectsConnecting Dots2.Shell and tube heat exchangersA heat exchanger is a device in which two fluids, one through the tubeside and the other through the shell side, circulating at differenttemperature conditions, exchange heat through the walls of the tubes,without direct contact between them.There are different types of shell and tube exchanger, one of the most usedclassifications is shown below:The most widely used shell and tube heat exchangers in industrialprocesses are horizontal and pressurized circulation. Therefore, this type ofheat exchanger will be studied in later chapters.Horizontal shell and tube heat exchangers can take several configurations.Different alternatives, geometries and configurations are described in thefollowing chapters.SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 12
TrainingProjectsConnecting Dots2.1)Parts of heat exchangersThe name given to each of the components of a shell and tube heat exchanger isprovided in the figures shown below.Then four figures presented below correspond to the most frequently used shelland tube heat exchangers. Schemes refer to different positions, which are listedin the reference table shown after the exchanger figures.SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 13
TrainingProjectsConnecting Dots1. Stationary head with flat cover20. Sliding flange2. Stationary head with elliptical cover21. Floating head flat cover3. Flange of stationary head22. Floating head shell4. Flat cover of stationary head23. Gasket box5. Stationary head inlet nozzle24. Gasket6. Fixed tubesheet25. Box counter flange7. Tubes26. Sealing ring8. Shell27. Tie rods and spacers9. Shell head28. Transverse baffles10. Shell flange mating tubesheet29. Impingement plate11. Shell flange mating shell head30. Longitudinal baffle12. Shell inlet nozzle31. Partition pass plate13. Shell head flange32. Shell flange mating shell head14. Expansion joint33. Shell head flange mating shell15. Floating tubesheet34. Instrumentation nozzle16. Floating tubesheet head35. Saddles or supports17. Floating tubesheet flange36. Lifting device18. Floating tubesheet counter flange37. Support brackets19. Floating tubesheet backing ringSHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 14
TrainingProjectsConnecting Dots2.2)2.2.1)Types of heat exchangersFixed tubesheetThis kind of exchanger features two fixed plates at both ends of thetube bundle.Advantages: its fabrication is the most economical of all types, minimizingjacketed gaskets, thereby reducing potential leakage.Disadvantages: the shell and outside of the tubes of the bundle cannot bemechanically cleaned or physically inspected. For significant temperaturegradients, it presents structural problems, caused by differentialthermal expansion between the shell and the tube bundle2.2.2)U tubeIn this case, there is only one tubesheet anchoring all tubes that are Ushaped. Thus, the fluid returns to the stationary head.Advantages: this kind of exchanger can handle high pressure andtemperature fluids in the tube side. Another positive aspect is its ability tofreely absorb thermal expansions at low cost.Disadvantages: it is difficult to mechanically clean the internal part of thetubes. Moreover, the number of passes in the tube side is limited.SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 15
TrainingProjectsConnecting Dots2.2.3)Floating tubesheetThese exchangers are a mixture of the two presented above. Althoughthetubes are not U-shaped, the fluid returns to the stationary head due tothe floating head that is design at the end of the tube bundle.Advantages: this configuration is the best option for inspection,maintenance and repair.It eliminates differential thermal expansion effectsbetween the tube bundle and the shell, as a result of the free movement of thefloating head.Disadvantages: the manufacturing cost is the highest of all configurations.Due to the numerous jacketed gaskets present, it is not the best option fortoxic or hazardous processes.SHELL & TUBE HEAT EXCHANGERS, PART I – Instructor: Javier TirentiPage 16
TrainingProjectsConnecting Dots2.3)2.3.1)Main componentsShellThe shell is a cylindrical body constructed from one or more pieces,obtained from a rolled plate or a seamless tube, containing the tubebundle. The fluid bathing the tubes and the tube bundle circulates insidethe shell. It is one of the most important parts of a shell and tube heatexchanger, especially from the structural point of view.2.3.2)Tube bundleThe tube bundle is a component formed mainly by tubes and baffles. Thisbundle is located inside de shell, following the same alignment. Thefunction of the tubes is to transfer heat between the two present fluids. Thebaffles support the tubes, create turbulence and direct the fluid flowi
heat exchangers, in this document the criteria set by TEMA code is followed, sometimes ASME code suggested design methods and less often HEI minimum requirements. This criterion is adopted in order to cover the widest range of possible applications, since TEMA is the more used code.File Size: 1MB
This standard applies to Liquid to Liquid Heat Exchangers as defined in Section 3, which includes the following types of heat exchangers: 2.1.1 Plate heat exchangers 2.1.2 Shell-and-tube heat exchangers 2.1.3 Shell-and-coil heat exchangers 2.1.4 Shell-and-U-Tube heat exchangers 2.2 Exclusions. This standa
The two basic types of heat exchangers are compact and conventional heat exchangers. The ratio of the heat transfer surface area of a heat exchanger to its volume is called the area density β. A heat exchanger with β 700 m2/m3 is classified as a Compact heat exchanger (CHEs) and if β 700 m2/m3 then they are the Conventional heat exchangers.
OF HEAT EXCHANGERS Bureau of Energy Efficiency 55 4.1 Introduction Heat exchangers are equipment that transfer heat from one medium to another. The proper design, operation and maintenance of heat exchangers will make the process energy efficient and minimize energy losses. Heat exchanger performance can deteriorate with time, off
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API Heat Transfer (Suzhou) Co. Ltd. Air Cooled Aluminum Heat Exchangers Shell & Tube Heat Exchangers Plate Heat Exchangers 156 Qingqiu Street, 3rd District Suzhou Industrial Park Suzhou, Jiangsu 215126 China (86)512-88168000 Fax: (86)512-88168003 API Heat Transfer, Inc. 2777 Walden Avenue Buffalo, New York 14225 (716) 684-6700 www .
Brazed Plate Heat Exchangers 2 Smaller, lighter, stronger and more efficient. Lowara Brazed Plate Heat Exchangers are ideal for residential and light commercial hydronic systems because they provide maximum heat dissipation from a compact, lightweight heat exchanger. Unlike conventional shell and tube heat exchangers, our units can be used
media involved in the heat exchange (standard). FUNKE is a leader in the development and production of quality heat exchangers with a heat transfer area of up to 2 400 m². The range of products comprises shell-and-tube heat exchangers, bolted and brazed plate heat exchangers as well as oil / air cooling units and electrical oil pre-heaters.
Applications of heat exchangers present two distinct categories of design problems (Sarkomaa 1994): 1. Design and optimization of mass-produced heat exchangers, e.g. automobile radiators, heat exchangers of HVAC equipment, oil cooling heat exchangers for machinery, etc. 2. Design and optimization of
