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1、1,Shell and Tube Geometry,Shell and Tube Geometry,2,Shell and Tube Geometry,Contents,Standards Shell and head types Tubes: arrangement, type, selection Baffles: type, cut, orientation Clearances Fluid allocation,3,Shell and Tube Geometry,Standards,The mechanical design and construction of S&T exchan
2、gers is usually based on TEMA 7th Edition 1988. TEMA supplements the ASME Pressure Vessel code. TEMA provides 3 letter designation,4,Shell and Tube Geometry,Shell types,E-type shell should be used if possible but F shell gives pure counter-current flow with two tube passes (avoids very long exchange
3、rs) Note: longitudinal baffles are difficult to seal with the shell especially when reinserting the shell after maintenance,5,Shell and Tube Geometry,More shell types,Often only used for horizontal thermosyphon reboilers (with the shell-side flow upwards) Longitudinal baffle then more a distribution
4、 plate - may be perforated,6,Shell and Tube Geometry,J,X,K,Still more shell types,J & X give low shell side Dp Dividing J called I by HTFS,Divided flow,Cross flow,Kettle-type reboiler,7,Shell and Tube Geometry,Summary of shell types,E-type shells are standard G and H shells are normally only used fo
5、r horizontal thermosyphon reboilers J and X shells are used if allowable pressure drop can not be achieved in an E shell For services that need multiple shells and removable bundles, F shells should be considered as alternative K type is only used as a reboiler Note that TASC also handles “double-pi
6、pe” exchangers,8,Shell and Tube Geometry,Front and rear heads,Rear Head,Shell,Tube bundle,Front Head,BES,9,Shell and Tube Geometry,Front head types,A,B,Channel and removable cover,Bonnet (integral cover),A-type is standard for dirty tube side B-type for clean tube side duties. Use if possible since
7、cheap and simple.,10,Shell and Tube Geometry,More front head types,C,N,C-type with removable shell for hazardous tube-side fluids, heavy bundles or services that need frequent shell-side cleaning N-type for fixed for hazardous fluids on shell side,Channel integral with tube sheet,11,Shell and Tube G
8、eometry,Summary of front head selection,B type standard for clean tube side fluids A type standard for dirty tube side fluids Consider C type for Hazardous tubeside fluids Heavy tube bundles Frequent shellside cleaning Consider N type for fixed tubesheet exchangers with hazardous tubeside fluids Con
9、sider D type (or bonnet welded to tubesheet) for high pressure Consider conical for single tube pass (not actually a TEMA type),12,Shell and Tube Geometry,Rear head types,These fall into three general types fixed tube sheet (L, M, N) U-tube floating head (P, S, T, W) Use fixed tube sheet if T low*,
10、otherwise use other types to allow for differential thermal expansion You can use bellows in shell to allow for expansion but these are special items which have pressure limitations (max. 35 bar) *For preliminary scoping studies, take below 500C as being low,13,Shell and Tube Geometry,Fixed head typ
11、es,Give small shell-to-bundle clearance,14,Shell and Tube Geometry,Floating head types,T has simpler construction than S but gives large shell with large shell-to-bundle clearance,Split backing ring,15,Shell and Tube Geometry,P and W floating heads,Rarely used except on small units Note that you can
12、not have a pass partition plate in a W type thus limiting it to 2 (or 1) pass,16,Shell and Tube Geometry,Rear head selection,fixed tube sheet (L, M, N) - low shell-baffle clearance U-tube - simple design but difficult to clean - low shell-baffle clearance floating head (P, S, T, W) - S most common S
13、 gives higher shell-to-baffle clearance T gives highest shell-to-baffle clearance W limited to 2 (or 1) passes,U-tube,17,Shell and Tube Geometry,Shell-to-baffle clearance,18,Shell and Tube Geometry,Rear Head Selection,Fixed tubesheets (L, M, N) provided that no overstressing due to differential expa
14、nsion shellside does not need mechanical cleaning Fixed tubesheet with bellows provided that shellside fluid is not hazardous shellside pressure is below 35 bar (500 psi) shellside does not need mechanical cleaning U-Tube provided that tubeside will not need mechanical cleaning countercurrent flow i
15、s not required (unless F shell ok) Split backing Ring Floating Head (S type) P,T,W floating head,19,Shell and Tube Geometry,TEMA designation - example,BES,20,Shell and Tube Geometry,Shell diameter,For sizes up to 610 mm (24 in) normally use standard pipe sizes British / US standard sizes are 152, 20
16、3, 254, 305, 356, 406, 508 and 610 mm (6, 8, 10, 12, 14, 16, 18 and 24 in) nominal bore For sizes 356 mm (14 in) and above actual inside diameter is 19 mm (0.75 in) less 152 mm (6 in) minimum size for most process applications,21,Shell and Tube Geometry,Shell diameter (cont.),Larger shells made from rolled plate Size limited by drilling and machining capacity of manufacturer but can be up to 3000 mm (118 in) or more For rolled shells any diameter possible but most designers p
