On the previous page, we learned what heat does to an object when it is gained or released.Heat gains or losses result in changes in temperature, changes in state or the performance of work. Heat is a transfer of energy. When gained or lost by an object, there will be corresponding energy changes within that object.
Process design of heat exchanger.1.NPTEL – Chemical Engineering – Chemical Engineering Design - IIJoint initiative of IITs and IISc – Funded by MHRD Page 1 of 41Module #1PROCESS DESIGN OF HEAT EXCHANGER: TYPES OF HEAT EXCHANGER,PROCESS DESIGN OF SHELL AND TUBE HEAT EXCHANGER, CONDENSER ANDREBOILERS1. PROCESS DESIGN OF SHELL AND TUBE EXCHANGER FOR SINGLEPHASE HEAT TRANSFER1.1. Classification of heat exchangers1.2. Thermal design considerations1.2.1. Tube pitch, tube-layout and tube-count1.2.4. Tube passes1.2.5.
Tube sheet1.2.6. Fouling Considerations1.2.8. Selection of fluids for tube and the shell side1.3. Process (thermal) design procedure1.4.
Design problem2. PROCESS DESIGN OF SHELL AND TUBE EXCHANGER FOR TWOPHASE HEAT TRANSFER2.1.
Types of condensers2.1.2. Condenser design2.1.2.1. Mean temperature difference2.1.2.2. Calculation of heat transfer co-efficient duringcondensation2.1.2.3. Pressure drop calculation2.1.3. De-superheating and sub-cooling2.2. Classification of reboilers2.2.2.
Design of Kettle reboiler.NPTEL – Chemical Engineering – Chemical Engineering Design - IIJoint initiative of IITs and IISc – Funded by MHRD Page 2 of 41Lecture 1: Heat Exchangers Classifications1. PROCESS DESIGN OF SHELL AND TUBEEXCHANGER FOR SINGLE PHASE HEATTRANSFER1.1. Classification of heat exchangersTransfer of heat from one fluid to another is an important operation for most of thechemical industries.
The most common application of heat transfer is in designing of heattransfer equipment for exchanging heat from one fluid to another fluid. Such devices forefficient transfer of heat are generally called Heat Exchanger.
Heat exchangers arenormally classified depending on the transfer process occurring in them. Generalclassification of heat exchangers is shown in the Figure 1.1.Amongst of all type of exchangers, shell and tube exchangers are most commonly usedheat exchange equipment. The common types of shell and tube exchangers are:Fixed tube-sheet exchanger (non-removable tube bundle): The simplest and cheapesttype of shell and tube exchanger is with fixed tube sheet design. In this type ofexchangers the tube sheet is welded to the shell and no relative movement between theshell and tube bundle is possible (Figure 1.2).Removable tube bundle: Tube bundle may be removed for ease of cleaning andreplacement.
Removable tube bundle exchangers further can be categorized in floating-head and U-tube exchanger. Floating-head exchanger: It consists of a stationery tube sheet which isclamped with the shell flange. At the opposite end of the bundle, the tubesmay expand into a freely riding floating-head or floating tube sheet. Afloating head cover is bolted to the tube sheet and the entire bundle can beremoved for cleaning and inspection of the interior. This type of exchangeris shown in Figure 1.3. U-tube exchanger: This type of exchangers consists of tubes which are bentin the form of a „U‟ and rolled back into the tube sheet shown in the Figure1.4. This means that it will omit some tubes at the centre of the tube bundle.NPTEL – Chemical Engineering – Chemical Engineering Design - IIJoint initiative of IITs and IISc – Funded by MHRD Page 3 of 41depending on the tube arrangement.
The tubes can expand freely towardsthe „U‟ bend end.The different operational and constructional advantages and limitations depending onapplications of shell and tube exchangers are summarized in Table 1.1. TEMA (USA)and IS: 4503-1967 (India) standards provide the guidelines for the mechanical design ofunfired shell and tube heat exchangers. As shown in the Table 1.1, TEMA 3-digit codesspecify the types of front-end, shell, and rear-end of shell and tube exchangers.NPTEL – Chemical Engineering – Chemical Engineering Design - IIJoint initiative of IITs and IISc – Funded by MHRD Page 4 of 41Figure 1.1. Classification of heat exchangers depending on their applications.RecuperativeRegenerativeRotaryregeneratorFixed-matrixregeneratorIndirectcontact-typeDirectcontact-typeDisk typeDrum typeTubularPlateExtendedsurfaceDouble pipeSpiral tubeShell & tubeFinned tubeFinned plateGasketed plateSpiral plateLamellaRemovable bundleFloating headFixed tubesheetU-tubeHeatExchangerHeat exchanger may have singeor two phase flow on each sideFlowParallel CounterCross.NPTEL – Chemical Engineering – Chemical Engineering Design - IIJoint initiative of IITs and IISc – Funded by MHRD Page 5 of 41Table 1.1. Features of shell and tube type exchangers.Shell andTubeExchangersTypicalTEMA codeAdvantages LimitationsFixed tubesheetBEM, AEM,NENProvides maximum heattransfer area for a givenshell and tube diameter.Provides for single andmultiple tube passes toassure proper velocity.Less costly thanremovable bundle designs.Shell side / out side of the tubes areinaccessible for mechanical cleaning.No provision to allow for differential thermalexpansion developed between the tube andthe shell side.
This can be taken care byproviding expansion joint on the shell side.Floating-headAEW, BEW,BEP, AEP,AES, BESFloating tube sheet allowsfor differential thermalexpansion between theshell and the tube bundle.Both the tube bundle andthe shell side can beinspected and cleanedmechanically.To provide the floating-head cover it isnecessary to bolt it to the tube sheet.