To better comprehend the many types of heat exchangers, it is necessary to first understand what they are.
Heat exchangers are machines that transfer heat between two or more fluids having differing temperatures, such as liquids, vapors, or gases. The heat transfer process might be gas to gas, liquid to gas, or liquid to liquid, depending on the kind of heat exchanger used. The fluids are exchanged through a solid separator, which prevents direct contact.
The type of heat exchanger and the materials used in its construction determine a fluid’s suitability and compatibility with it. Most fluids, including oil, water, and even seawater, are suitable for standard heat exchangers. Other materials, such as stainless steel and titanium, are required for some corrosive fluids, such as chlorinated saltwater, refrigerants, and acids.
Other features, such as construction materials, components, and parts, as well as a distinct heat transfer method, will help to identify and classify different types of heat exchangers. These features also aid us in determining which one is better suited to specific applications in a variety of sectors and for general use. Almost all heat exchangers operate on the same principles.
Alaqua is a heat exchanger equipment supplier and other processing equipment in the United States, including evaporators, crystallizers, distillation, and solvent recovery systems.
Types of Heat Exchangers
The flow arrangement and kind of construction are generally used to categorize these devices. Heat exchangers with hot and cold fluids flowing in the same, opposing, or perpendicular directions are the most basic. Parallel-flow, Counter-flow, and Cross-flow heat exchangers are made up of two concentric pipes with differing diameters.
Parallel-flow Arrangements: Hot and cold fluids enter at the same end of a parallel-flow heat exchanger, move in the same direction, and exit at the same end.
Counter-flow Arrangements: Unlike parallel-flow heat exchangers, fluids enter at opposing ends, travel in opposite directions, and exit at opposite ends in counter-flow heat exchangers.
Cross-flow Arrangements: Fluids can flow in perpendicular directions, which is referred to as a cross-flow arrangement. Finned and unfinned tubular are the two major types. Both fluids are unmixed in a finned tubular heat exchanger, and the one between the fins is directed in a direction transverse to the tube flow direction. Heat can be exchanged in all directions and the fluid can mix in an unfinned exchanger.
It is discovered that a counter-flow heat exchanger transfers more heat than a parallel flow heat exchanger when we compare these two types of heat exchangers. Furthermore, the temperature profiles of the two heat exchangers reveal two significant drawbacks in the parallel-flow design:
- Thermal strains are caused by a considerable temperature differential between the two ends.
- The temperature of the cold fluid exiting the heat exchanger never exceeds the temperature of the hot fluid at its lowest point.
When two fluids must be brought to approximately the same temperature, however, a parallel-flow heat exchanger is useful.
Heat exchangers’ heat transfer surfaces come in a variety of configurations. Heat exchangers are classified as Double pipe heat exchangers, Shell and tube heat exchangers, or Plate heat exchangers depending on the heat transfer surface.
Double Pipe Heat Exchangers: Double pipe heat exchangers are one of the most cost-effective heat exchangers in terms of design and maintenance, making them an excellent choice for small businesses. In these heat exchangers, one fluid moves within the tube while the other moves outside. Although this type of heat exchanger is easy to build and maintain, their poor efficiency, along with the enormous amount of space they take up on big scales, has led contemporary businesses to choose more efficient heat exchangers such as shell and tube.
Shell and Tube Heat Exchangers: Shell and tube heat exchangers are the most popular and widely used heat exchangers in the industry, with a variety of structural variations. The number of shell and tube passes in a shell-and-tube heat exchanger is divided into two categories. High-pressure applications generally require shell and tube heat exchangers with pressures more than 30 bar and temperatures greater than 260°C. High pressures may be handled by shell and tube heat exchangers because of their form. The primary fluid travels via these tubes in this form of the exchanger, which has some tiny bore pipes placed between two tube plates. The secondary fluid flows through the shell and over the surface of the tubes as the tube bundle is enclosed in a shell. As a steam generator, this design is common in nuclear engineering. To enhance the quantity of heat transmitted and electricity generated, the heat exchange surface is increased. Tubes are used to enhance the surface area in this design.
Plate Heat Exchangers: The heat is transferred between two fluids using metal plates in this sort of exchanger. This type of arrangement is used in heat exchangers that employ air or gas, as well as low-velocity fluid flow. An internal combustion engine uses this type of heat exchanger, with engine coolant passing through radiator coils as air passes through the coils, cooling the coolant while heating the incoming air. When stacked-plate heat exchangers are compared to shell and tube heat exchangers, the stacked-plate design is generally smaller and less expensive. Another contrast is that plate exchangers often serve low to medium pressure fluids, whereas shell and tube exchangers typically serve medium to high pressures.
Scraped Surface Heat Exchangers: Heat transmission to viscous or sticky materials is required in several applications. Due to the scraping blades that prevent products from settling on the inner surfaces, scraped surface heat exchangers are the greatest option for providing effective heat transmission in such applications. The scraped surface tube’s product enters a cylinder at the bottom. In a cylinder enclosing the product channel, heating or cooling fluids travel in a counter-current flow. Blades inside the product channel remove the product from the channel wall to ensure that the product receives consistent heat transmission. The scraping blades come in a range of materials to accommodate various processing needs, and they’re intended for gentle product handling to prevent compromising product quality and uniformity. Surface exchangers with scraped surfaces can be placed vertically or horizontally. An electric motor spins a rotor with scraping blades on the inside. Rotors turn and the product moves through the heat exchanger in the same direction to avoid product damage, with the product entering at the bottom and exiting at the top. The inside surface of the heating surface has been polished to a high gloss.
Dimple Plate/Plate Coil Heat Exchanger: Dimple plate/plate coil technology is the greatest answer for situations when one of the fluids isn’t moving while having a significantly smaller market share than the other two groups. It can also be used in retrofit applications, such as waste heat recovery if the original designs did not allow for it. When refrigeration or heating would be too expensive, this is a great alternative for passively heating or cooling a storage tank (such as a bright beer tank or a dairy tank). The concept is simple: two steel sheets are spot-welded together and then inflated to produce fluid-flow channels. Dimple plate/plate coil technology may be adapted to any application because of its simplicity and low-cost materials. Tank jackets for beer and dairy tanks are the most common use, although dimple plate pieces can also be trimmed to fit within a tank and buried in the stored liquid for effective heat transmission. Dimple plate/plate coil heat exchangers combine the greatest features of both types of heat exchangers: they are inexpensive, adaptable, and small, yet they can resist extremely high pressures and temperatures owing to their design and materials. It can also be tacked on as a last-minute addition to a variety of industrial processes, most notably to reduce energy costs or comply with environmental requirements.
Air Cooled Heat Exchangers: Air cooled heat exchangers are widely utilized in automobiles and other mobile applications where there is no fixed cool water source. A fan or the airflow created by the vehicle’s movement produces cool air.
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