Fixed Tube Sheet Heat Exchangers
Fixed Tube Sheet Heat Exchangers Overview : –
A Fixed Tube Sheet Heat Exchanges is the most common type of heat exchanger in all Industries. Mostly used in higher-pressure and Higher Temperature applications.
Fixed tube Sheet heat exchangers are the one that are very much used in process chemical industries and refinery services, as there is absolutely no chance for intermixing of fluids. This type of heat exchanger is employed where even slightest intermixing of fluids cannot be tolerated.
A fixed-tubesheet heat exchanger has straight tubes that are secured at both ends to tube sheets welded to the shell. The construction may have removable channel covers , bonnet-type channel covers , or integral tube sheets. The principal advantage of the fixedtubesheet construction is its low cost because of its simple construction. In fact, the fixed tube sheet is the least expensive construction type, as long as no expansion joints required.
Features of Fixed Tube Sheet Heat Exchangers : –
The Fixed Tube sheet design consists of two stationary tube sheets attached to the shell. The bundle of straight tubes is connected between the tube sheets and contain baffles to direct the flow around the tubes in order to generate the required heat transfer. A head assembly is attached to each tube sheet.
The U-tube design consists of straight length tubes bent into a U-shape with both ends terminating at the tube sheet. The tube bundle is fitted with supports or flow baffles. The tube sheet/tube bundle is placed in the shell and bolted between the head flange and body flange. A head assembly is required to direct the fluid into and out of the tube bundle. This configuration allows for the entire tube bundle to be removable.
Maintenance of Fixed Tube Sheet Heat Exchangers : –
Other advantages are that the tubes can be cleaned mechanically after removal of the channel cover or bonnet, and that leakage of the shell side fluid is minimized since there are no fanged joints’ disadvantage of this design is that since the bundle is fixed to the shell and cannot be removed, the outsides of the tubes cannot be cleaned mechanically.
However, if a satisfactory chemical clean-ing program can be employed, fixed-tubesheet construction may be selected for fouling services on the shellside.In the event of a large differential temperature between the tubes and the shell, thetubesheets will be unable to absorb the differential stress, thereby making it necessary to incorporate an expansion joint. This takes away the advantage of low cost to a significant extent.