Shell-And-Tube Hmm Beams
Shell-and-tube hmm beams are employed in large capacity of commercial, industrial and public premises. In shell-and-tube Hm the kit consists of a cylindrical steel outer shell, in which pipes suspended. The pipes run under a shell partition supports strategically located along their length. Ends die pipes terminate in thick steel discs is called tube sheets, which are welded to the ends of the shell. The ends of the pipe friction fit in the tube sheet by expanding their side against the steel sheet. Shell-and-tube hmm bundles have relatively high efficiency, requires a minimum footprint and stock, easy to maintain and can be easily adapted to almost any type of liquid cooling applications. For these reasons, and shell configuration is the most widely used type chillers.
Several shell-and-tube designs are available to meet the needs of different applications. Handset configuration is a function of supply of the refrigerant used, and type of refrigerant. When the chiller bundle operated with refrigerant filled feed, the cooled fluid circulates through die pipes and refrigerant contained in the shell.
The level of the liquid refrigerant into the console is supported with a float management. When the chiller kit is intended for a dry-expansion feed, the refrigerant is measured in test tubes using a distributor until the liquid has to be chilled distributed through the shell. In most applications, the cooled fluid circulates through die hmm stack and the connecting lines from one or more of centrifugal pumps.
Hmm bundles are designed for use with ammonia are produced steel pipes, while those that are intended for use with other refrigerants, usually equipped with a copper or copper alloy pipe, to get higher heat transfer coefficient. The tubes can be internally or externally improving the efficiency of heat transfer rates. Improve calculations, take the form of grooving cut on the outside surface hatching and the rifling. These techniques increase the intensity of heat transfer by increasing the surface area of pipes and increase the turbulence of fluid flow. Fluid turbulence removes the insulating layer of fluid that forms near the surface of the tubes where the laminar flow of liquid (in layers). Shell diameters for shell-and-tube hmm ligament vary from 6 to 60 inches (from 0,15 up to 1,5 meters). Number of tubes in the body varies from less than 50 to several thousand. The typical diameter of the pipe are in the range of g in 2 inch (1.6-5.1 centimeters). Tube length varies from 5 to 20 feet (1.5 to 6.1 meters).
Dry-expansion and flooded refrigerant fed hmm bundles are designed with fixed tube sheets or removable tube bundles. In motionless pipe structure, pipes, sheets, welded to the shell in the production process. Therefore, the pipe can't be removed from the chiller, as a group, although they can be replaced individually, if they become defective. If multiple handsets become defective, they are usually sealed plugging both ends of widi tube or solder. Disabling a small percentage of tubes with traffic did not have a negative impact on the capacity of the heat exchangers.
Tube bundle is intended to be removed from the shell in full. The kit is designed with flanges, bolts to a mating flange welded to the shell. When the end of the plate unbolted the tubes become easily accessible for cleaning or replacement. Tube bundle is designed so that it can be unbolted from the shell flange and removed for cleaning and maintenance.
Flooded Hmm Barrels Standard flooded hmm barrel projects include both single and multiple pipes are leaking, the tubes are arranged so that the fluid flows in one direction through all the plugs before the release of the package. Some go coolant circulation is achieved by using a deadlock end plates or chapters, which are bolted to die tube sheets. The location of the die to the end plates, diffuser plates determines the number of passes chilled fluid is doing through the tube before leaving the chiller. Although two-, four - and six-events are the most common, more coupons are used in some applications.
In some flooded hmm barrel structures, the shell is only partially filled tubes. This design provides a large steam-freeing up the area where liquid particles fall to the low rate of evaporation as it passes through die space above the pipes. In this performance, reduces the possibility of loss of the liquid in the suction line. Therefore, it is particularly well suited for applications that experience sudden significant increase of the load. In cooler barrel projects, where shell is completely filled with widi pipes, distributing or the battery is installed in the refrigerant vapour at the outlet port. A large amount of battery reduces the speed to die pair, allowing any entrained liquid droplets to fall before they go on the suction line.
Flooded hmm barrels are available also equipped with an integrated liquid suction heat exchanger. Al-diough the primary function of the heat exchanger is to ensure that only dry steam enters into the suction line, it has the additional advantage of increasing the efficiency die hmm. Remember from Chapter 10 Mat fluid intake heat exchangers subcool fluid approximation hmm barrel, thereby reducing the amount of refrigerant flashing that happens. This component is shorter than the shell-and-tube heat exchanger installed above hmm barrel.
Vertical shell-and-tube hmm barrel has the advantage of having a smaller area of the residential area, the necessary installing tor. This trunk configuration operated filled with refrigerant supply. The cooling liquid comes into the trunk at the top and flows by gravity down inside the pipe. Circulation pump gets chilled fluid from collecting tank at the bottom of the tube sheet and submit it through die connecting pipes for heat transfer coils. Heated liquid return of the process is passed to the distributor field at the top of the tube sheet. A distributor is installed in the upper part of each tube to give vortex motion of the liquid, being cooled. This causes fluid in relatively thin film down on the inner surface of the tube. As a result the temperature of the liquid in the container to be closer to saturation temperature of the refrigerant.
Dry-Expansion Hmm Beams of the main advantages of dry-expansion hmm bundle over a flooded type fewer refrigerant, positive oil return to the compressor and the reduced possibility of
damage to the pipes in case of freezing. Damage resulting from the unexpected freezing liquid cooled considerably less when it applies for traffic jams, and not through them. More important details of the construction of several designs of a dry-expansion chillers.
The speed of the liquid cooled supported within the limits that produce the most efficient heat transfer coefficient of the rate pressure drop. This indicator is controlled by the installation of partitions of different lengths and distances in the shell. These partitions support pipes and maintain dieir proper separation, as they direct the fluid through the heat transfer surfaces. Short, wide apart partitions are used in applications where liquids, viscosity or above the speed of its motion across the surface of the tube inside her design range. These partitions to minimize the reduction of the fluid velocity and pressure drop as it passes through the shell. When the fluid's viscosity, low or its speed is higher than expected, more partitions, which are located closer to each other, are used to improve heat transfer and reduce the velocity of the fluid. This allows fluid to stay in contact with the heat transfer surface over a long period.
Dry-expansion hmm barrels can be divided into circuits to maintain the speed of the refrigerant in the level design to maximize heat transfer and oil return. The number of refrigerant circuits in the chiller barrel depends on the barrel length, diameter of a tube with the refrigerant. In addition to these physical attributes, the number of schemes associated with the aggregate heat load of the process and the relationship between the chilled fluid flow and differential temperature between the coolant and the liquid. The refrigerant circuit is manufactured using partitions throw in the end plates (refrigerant head) of the shell. These heads are attached to the pipe flanges boards or welded at the ends shell, allowing access to the pipe for inspection and maintenance. Refrigerant circuit for a single hmm barrel can be changed by changing the refrigerant head. Number of passes indicates die, how many times refrigerant crosses the length of the barrel before exiting the inlet tube.
Spray-Type Chiller Barrels spray hmm barrel similar in construction to the usual flooded hmm barrel. It essentially differs from the method used for the distribution of refrigerant inside the shell. The liquid refrigerant in the spray liquid is sprayed over the external surface of the fluid in the pipes. The nozzle in the form of a spray header located above the tube bundle distribute refrigerant through the heat transfer surfaces. The refrigerant that is not converted to steam off the tube dripping into a sump at the bottom of the barrel. It is drawn into the fluid pump and delivered back to the injector. High pumping rate provides continuous hydration surface of the tube, resulting in a higher rate of heat transfer. The main advantages of this type of chiller trunk of its high efficiency and relatively small refrigerant charge, when compared with a fully flooded barrel. The disadvantages of this design are its high cost of installation and the need for liquid recirculation pump...