shell and tube heat exhangerPPT学习教案

1、会计学1shell and tube heat exhanger第1页/共31页第2页/共31页designs/materials第3页/共31页ShellTubesBaffle第4页/共31页Baffle Type and GeometryBaffles support the tubes for structural rigidity, thus prevent tube vibration and saggingThey also divert the flow across the tube bundle to obtain a higher heat transfer coeffic

2、ientBaffles can be transverse or longitudinalTransverse baffles are plate type or rod typePlate bafflessingle and double segmental most commonbaffle spacing is critical (optimum between 0.4 and 0.6 of the shell diameter)triple and no-tubes-in-window segmental baffles for low pressure drop applicatio

3、ns第5页/共31页Figure 8.8 Plate Baffle Types第6页/共31页Figure 8.8 Plate Baffle Types (continued)第7页/共31页第8页/共31页Inlet support bafflesDouble-segmental bafflesNo tubes in the window - with intermediate support bafflesTubesWindows with no tubesIntermediate baffles第9页/共31页第10页/共31页ShellFront endstationary head

4、typeRear endhead type第11页/共31页BChannel and removable coverBonnet (integral cover)A第12页/共31页BND第13页/共31页Basic ComponentsShell TypesFront and rear head types and shell types are standardized by TEMA, identified by alphabetic characters (Fig. 8.2)E-shell is the most commoncheap and simple configuration

5、one-shell pass and one- or multiple-tubepassesif one-tube pass, nominal counterflow is achievedmost common for single-phase shell fluid applicationsF-shell used when there are two tube passes and pure counterflow is desiredlongitudinal baffle results in two-shell passesunits in series, each shell pa

6、ss represents one unithigher pressure drop than that for E-shell第14页/共31页Shell Types (continued)J-shell has divided flowfor low pressure drop applicationsnormally, single nozzle for shell-fluid at tubecenter, two nozzles near tube endswhen used for condensing the shell fluid, two inlets for shell-si

7、de vapor and one central outlet for condensate (figure)X-shell has cross flowcentral shell-fluid entry and exitno baffles are usedvery low pressure dropused for vacuum condensers and low-pressure gasesG-shell and H-shell are single- and double-split flowDivided Flow第15页/共31页Shell Types (continued)G-

8、shell and H-shell are single- and double-split flowG-shell has a horizontal baffle with endsremoved, central shell-fluid entry and exitH-shell is similar, but with two baffles,and two nozzles at the entry and exit第16页/共31页Tube Bundle Types (rear head types)Main objectives in design are to accommodat

9、e thermal expansion and allow easy cleaning (or to provide the least expensive construction)U-tube configuration (Fig. 8.4)allows independent expansion of tubes and shell (unlimited thermal expansion)only one tube sheet is needed (least expensive construction)tube-side cannot be mechanically cleaned

10、even number of tube passesindividual tubes cannot be replaced (except those in the outer row)第17页/共31页第18页/共31页Tube Bundle Types (continued)Fixed tube sheet configuration (Fig. 8.5)allows mechanical cleaning of inside of tubes but not outside because shell is welded to the tube sheetslow-costlimited

11、 thermal expansionindividual tubes replaceablePull-through floating head (Fig. 8.6)allows the tube sheet to float move with thermal expansionthe tube bundle can be removed easily for cleaning suitable for heavily fouling applications第19页/共31页Figure 8.2TEMAs Standard Shell, Front-end and Rear-end Typ

12、es第20页/共31页第21页/共31页第22页/共31页第23页/共31页第24页/共31页第25页/共31页第26页/共31页Tubes and Tube PassesA large number of tube passes are used to increase fluid velocity and heat transfer coefficient, and to minimize foulingTube wall thickness is standardized in terms of the Birmingham Wire Gauge (BWG) of the tube (T

13、ables 8.1 & 8.2)Small tube diameters for larger area/volume ratios, but limited for in-tube cleaningLarger tube diameters suitable for condensers and boilersFins used on the outside of tubes when low heat transfer coefficient fluid is present on the shell-sideLonger tubes fewer tubes, fewer holes drilled, smaller shell diameter, lower cost. However