Regarding heat exchangers

In a floating-head heat exchanger, the tube sheets at both ends are not connected to the shell; the end that is not connected in this way is called the floating head. When the tubes are heated, the tube bundle together with the floating head can expand and contract freely along the axial direction, completely eliminating thermal stress. 　　The structure of the floating head end for a new type of floating head heat exchanger consists of a cylinder, an outer head side flange, a floating head tube sheet, hook rings, a floating head cover, an outer head cover with threaded holes, steel rings, etc. Its features are as follows: a concave or trapezoidal sealing surface is provided on the inner surface of the outer head side flange; holes are drilled near the outside of this sealing surface, and multiple screws are inserted into these holes or welded there, with them being evenly distributed. The use of hook rings and related components is eliminated at the floating head area. The sealing groove of the floating head tube sheet remains in its original concave shape, while another trapezoidal groove is created on the same end face, with the center of this groove being the center of the tube sheet and its radius being slightly larger than the outer diameter of the tube bundle. Moreover, the partition groove of the tube sheet is connected only to the trapezoidal groove, not to the concave groove ； Holes are drilled between the concave and trapezoidal grooves, and multiple screws are inserted or welded there in a uniform manner. The floating head flange features dual sealing through concave and trapezoidal protrusions; the stage separation plate is connected to the trapezoidal protrusion and is located on a wide-flanged face on the same end face. The concave and trapezoidal protrusions as well as the stage separation plate correspond respectively to the concave and trapezoidal grooves and the stage separation groove of the floating head tube sheet. This floating head flange is welded together with a rimless spherical head to form a floating head cover, its flange screw holes matching those of the floating head tube sheet’s screw holes or screws, which are then used to fasten and compress the concave and trapezoidal grooves sowie the stage separation groove of the floating head tube sheet along with their gaskets. If necessary, the thickness and diameter of the floating head tube sheet as well as the inner diameter of the cylinder can be increased, with corresponding adjustments made to the sizes of the related components ； An additional steel ring without external assistance is also provided; the inner diameter of this ring is larger than the outer diameter of the floating head tube sheet. One end of the steel ring is equipped with a flange that connects to the concave or trapezoidal sealing surface on the inner side of the flange of the outer cover, thereby achieving sealing, while the other end has a flange or some other structure that seals against the original concave groove in the floating head tube sheet, as well as the gasket or the outer surface thereof. 　　Features of the floating-head heat exchanger: In a floating-head heat exchanger, one end of the tube sheet is fixed between the shell and the tube box, while the other end of the tube sheet can move freely within the shell; this feature can be observed on-site. The thermal expansion of this heat exchanger shell and tube bundle is free, and the tube bundle can be removed to facilitate cleaning between and inside the tubes. Its disadvantages are a complex structure and high cost (20% higher than that of fixed tube sheets), as well as leaks at the floating head during operation, which are difficult to detect and repair. Floating-head heat exchangers are suitable for conditions where there is a large temperature difference between the shell and the tube bundle, or where the fluid flowing in the shell side tends to form scale. 　　Main features of fixed-tube-sheet heat exchangers: Fixed-tube-sheet heat exchangers are primarily composed of components such as a shell, tube sheet, tube bundle, and top cover (also known as head). Inside the circular shell, a parallel tube bundle is installed; the ends of the tube bundle are fixed to the tube sheets by welding or expansion fitting. The two tube sheets are welded directly to the outer tubes, and the cover equipped with the inlet or outlet pipes is connected to the flanges at both ends of the shell using bolts. It is characterized by a simple structure, the absence of shell-side sealing connections, the maximum number of tubes that can fit within the same shell inner diameter, minimal bypass flow in cases where baffles are present, and the ability to divide the tube side into any desired number of sections. Since the two tube sheets are supported by the tubes themselves, its tube sheets are the thinnest among various shell-and-tube heat exchangers, resulting in lower costs; for these reasons it is widely used. The disadvantages of this type of heat exchanger are: difficult cleaning of the shell side, and the presence of temperature difference stress. When the average temperature difference between the hot and cold fluids is large, or when there is a significant difference in the expansion coefficients of the shell and the heat transfer tubes, and the thermal stress exceeds the allowable stress of the material, expansion joints must be installed on the shell. Due to the strength limitations of these expansion joints, the pressure in the shell side cannot be too high. This type of heat exchanger is suitable for applications where the temperature difference between the two media is not large, or where the temperature difference is significant but the pressure in the shell side is low, and where the medium in the shell side is clean and not prone to scaling.

Take a look at the Final Fantasy summary post; it might be helpful: http://bbs.hcbbs.com/thread-380043-1-1.html