Pressure drop heat exchanger shells

The baffle cut determines the fluid velocity between the baffle and the shell wall, and the baffle spacing determines the parallel and cross-flow velocities that affect heat transfer and pressure drop. Often the shell side of an exchanger is subject to low-pressure drop limitations, and the baffle patterns must be arranged to meet these specified conditions and at the same time provide maximum effectiveness for heat transfer. The plate material used for these supports and baffles should not be too thin and is usually minimum thick-... 

When a fluid flows over a stationary or moving surface, the pressure of the fluid decreases along the length of the surface due to friction. This is commonly called the pressure drop of the system. Of particular interest are the pressure drops in pipes (tubes) and in heat exchanger shells. 

Whitley, D. L., Galculating Heat Exchanger Shell-Side Pressure Drop, Chem. Eng. Prog, V. 57, No. 9, p. 59 (1961). 

Fredheim, A.O. Thermal design of coil-wound LNG heat exchangers, shell-side heat transfer and pressure drop , Dr.ing. thesis, NTH, 1994... 

This problem can be calculated using i rpropriate software such as CC-Therm. When this done, the overall heat transfer coefficient is about 10% higher and the pressure drop for the shell side is nearly 20% lower. Thus, the computer solution also indicates that the proposed heat exchanger can handle the specified heat load. 

Acceptable Pressure Drop Range for Shell and Tube Heat Exchanger... 

THIS PROGRAM CALCULATES THE PRESSURE DROP FOR THE SHELL SIDE OF A DOUBLE PIPE HEAT EXCHANGER... 

Shellside Pressure Drop. Surprisingly little attention has been devoted in engineering literature to estimate two-phase pressure drop on the shell side of shell-and-tube heat exchangers [77, 78]. In engineering practice, the estimation of the two-phase flow pressure drop can be performed in some situations using modified single-phase flow correlations. This approach is, however, highly unreliable. 

All calculations are carried out at a window cut of 20%. This seems to be an optimum figure as it produces the maximum heat transfer coefficient at a given pressure drop for all tested heat exchangers. It is further assumed that TEMA standard clearances would exist between the tubes and baffles and between the shell inside diameter and baffle outside diameter. The various numbers in Figures 2-33a and b denote the fluids, pressure drops and exchanger dimensions given in Table 2-6. 

Conclusion Three 1-2 exchangers are more than adequate for heat transfer even though the pressure drop on the shell side is slightly higher than allowable which is tolerable. Fewer exchangers cannot fulfill the process requirement... 

The shape of the cooling and warming curves in coiled-tube heat exchangers is affected by the pressure drop in both the tube and shell sides of the heat exchanger. This is particularly important for two-phase flows of multicomponent systems. For example, an increase in pressure drop on the shell side causes boiling to occur at a higher temperature, while an increase in pressure drop on the tube side will cause condensation to occur at a lower temperature. The net result being both a decrease in the effective temperature difference between the two streams and a requirement for additional heat transfer area to compensate for these losses. 

Coiled-tube heat exchangers frequently have flow distribution problems that include (1) tube distribution (2) two-phase tube distribution and (3) two-phase shell distribution. Good flow distribution within the tubes can be obtained by designing the headers in such a way that their pressure drop is considerably less than that for the frictional pressure drop in the tubes. To obtain good shell-side distribution one must use symmetric bundles and separately introduce the vapor and liquid phases to the bundles. It is also advisable to arrange for downflow of the shell-side fluid. For two-phase annular flow, the vapor will flow mostly in the space between the tube layers while the liquid needs to be carefully distributed in the radial direction for proportionate vapor-liquid flow normal to each tube layer. To avoid convection on the shell side due to density gradients, it is normal practice to use sufficiently large pressure drops on the shell side. 

Frictiona.1 Pressure Drop. The frictional pressure drop inside a heat exchanger results when fluid particles move at different velocities because of the presence of stmctural walls such as tubes, shell, channels, etc. It is calculated from a weU-known expression of... 

There are many text books that describe the fundamental heat transfer relationships, but few discuss the complicated shell side characteristics. On the shell side of a shell and tube heat exchanger, the fluid flows across the outside of the tubes in complex patterns. Baffles are utilized to direct the fluid through the tube bundle and are designed and strategically placed to optimize heat transfer and minimize pressure drop. 

These curves provide a comparison of heat transfer rotes for plate heat exchangers and shell and tube equipment. The values given ore typical for pressure drops shown and ore based upon the thermal characteristics of the fluids. 

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