1. Tubular heat exchanger
Principle
Each segment of the coating is called a “single pass”. The inner tube (heat transfer tube) of the pass is connected by U-shaped elbow tubes, while the outer tube is connected in rows with short tubes and fixed on the bracket. Heat is transferred from one fluid to another through the inner tube wall. Typically, hot fluid (Fluid A) is introduced through the upper section and cold fluid (Fluid B) is introduced through the lower section. Both ends of the outer tube of the shell are connected to the inner tube by welding or flanges. The inner tube and U-shaped elbow tube are connected by flanges, making cleaning easier and increasing or decreasing heat transfer tubes. The effective length of each heat transfer tube is 4 to 7 meters. The heat transfer area of this heat exchanger can reach up to 18 square meters, making it suitable for small-scale heat exchange.
Advantage:
It has a simple structure and can withstand high pressure, making it suitable for various applications. Furthermore, the heat transfer area can be easily adjusted to meet different needs.
Disadvantages:
There are numerous joints between pipes that are prone to leaks. Additionally, it takes up a significant amount of space and requires a substantial amount of metal per unit of heat transfer surface.
2. Floating head heat exchanger
Principle
The structure of a floating head heat exchanger consists of a cylinder, an outer head cover side flange, a floating head tube plate, a hook ring, a floating head cover, an outer head cover, holes for screws, a steel ring and more. The velcro floating head design is shown in the attached illustration.
Advantage:
When there is a temperature difference between the heat exchange tube and the shell, the shell or the heat exchange tube will not inhibit each other and will not create temperature difference stress. The tube bundle can be removed from the box to facilitate cleaning inside and between the tubes.
Disadvantages:
The structure is complex, resulting in a large amount of materials and costs. If the seal between the floating head cover and the floating tube plate is not tight, it may cause internal leakage, leading to the two media mixing.
3. Immersed coil heat exchange
Principle
This type of heat exchanger forms metal tubes into various shapes suitable for the container and dips them into the liquid inside the container.
Advantage:
It has a simple structure and can withstand high pressure, and can also be made of corrosion-resistant materials.
Disadvantages:
The degree of turbulence of the liquid in the container is low and the heat transfer coefficient on the outside of the tube is small. To improve the heat transfer coefficient, a stirrer can be installed in the container.
4. Plate heat exchanger
Principle
The Plate Heat Exchanger is an ideal equipment for carrying out heat exchange between liquids and between a liquid and a vapor. It is a highly efficient heat exchanger made up of a series of corrugated metal sheets.
The structural principle of the Plate Heat Exchanger consists of multiple corrugated sheets pressed together at a fixed interval, sealed with gaskets and held in place by frames and compression bolts. The four corners of the plates and joints form the fluid distribution and collection tubes. Cold and hot fluids are separated and flow through flow channels on both sides of each plate, where heat exchange across the plates occurs.
5. Compensation ring heat exchanger
Principle
The heat exchanger consists of a baffle, a compensation ring and a heat release nozzle. When the fluid exchanges heat at high temperature, the compensation ring eliminates the thermal stress caused by the large temperature difference between the shell and the tube bundle, which results from different thermal expansion rates.
6. Plate fin heat exchanger
Principle
The finned plate heat exchanger is an efficient, compact and lightweight heat transfer device. In the past, its high manufacturing cost limited its use to a few industries, such as aerospace, electronics, and atomic energy. However, it has been gradually adopted in the petrochemical and other industrial sectors. There are several structural forms of finned plate heat exchangers, but the basic elements remain the same: two thin parallel metal plates with corrugated or molded metal fins added between them to seal the sides, forming a basic heat exchange unit.
Advantage:
- High heat transfer efficiency and good temperature control.
- The fins are thin, compact and small.
- The fins have a heat transfer surface and support function and have high strength.
Disadvantages:
- The flow passage is narrow, easy to be blocked and difficult to clean.
- The diaphragm and fins are very thin, so it is necessary that the medium does not corrode the aluminum. If it corrodes, it will cause internal leakage, which is difficult to repair.
- The complex structure makes the project more difficult.
7. Jacket heat exchanger
Principle
A jacket is installed on the outer wall of the container, creating a space between the jacket and the container that serves as a path for heating or cooling the medium. However, the heat transfer surface is limited by the container wall, resulting in a low heat transfer coefficient. To improve the coefficient and ensure uniform heating of the liquid in the container, a stirrer can be installed. Additionally, spiral baffles or other turbulence enhancing measures can be fitted into the jacket when cooling water or non-phase changing heating agents are introduced, further increasing the heat transfer coefficient on one side of the jacket.
Advantage:
Simple structure and convenient processing.
Disadvantages:
Small heat transfer area and low heat transfer efficiency.
8. U-tube heat exchanger
Principle
The U-shaped tubular heat exchanger is composed of heat exchange tubes bent into a U-shape, with both ends fixed to the same tube plate. The casing and heat exchange tubes are separate, allowing the tube bundle to expand and contract freely without generating temperature difference stress. This heat exchanger has a simple structure, with just a tubular plate and no floating head. The tube bundle can be easily extracted and installed for cleaning, making it convenient to use.
However, the U-shape of the tubes with different radii of curvature means that only the outermost heat exchange tube can be replaced if it is damaged, while the others must be blocked. Furthermore, the gap in the center of the tube bundle caused by the limited bending radius of the heat exchange tubes may result in short circuit of the fluid, affecting the heat transfer performance.
Feature
The advantages of a U-shaped tubular heat exchanger include:
- The tube bundle can float freely without the worry of temperature difference stress, making it suitable for high temperature difference scenarios;
- It has a simple structure with fewer flanges and possible leakage points, as it has only one tubular plate;
- The tube bundle can be easily cleaned by pulling out the core;
- However, due to the minimum bending radius of U-shaped tubes, the splitting distance is greater and therefore there are fewer tubes;
- High flow rates in pipelines can lead to severe erosion of the U-shaped elbow section, reducing the life of the exchanger.
- Cleaning the inside of U-shaped tubes can be difficult, so the internal environment must be clean and not subject to scale.
Advantage:
The structure is simple, with only one tubular plate, fewer sealing surfaces, ensuring reliable operation and low cost. The tube bundle can be easily removed for convenient cleaning between tubes.
Disadvantages:
The tube is difficult to clean;
Due to the requirement of a certain bending radius, the utilization rate of the tubular plate is low;
The spacing between the innermost tubes of the tube bundle is large, causing the potential for short circuits on the shell side;
If the inner tube breaks, it cannot be replaced and must be blocked, leading to a high scrap rate.
9. Tubular heat exchanger
Principle
The tubular heat exchanger is currently the type of heat exchanger most used in the chemical industry and in alcohol production. It consists of components such as housing, tube plate, heat exchange tubes, head and baffle. The materials used can be made from common carbon steel, red copper or stainless steel.
In the heat exchange process, a fluid enters through a connecting tube in the head, flows through the tubes, and exits through the outlet tube at the opposite end of the head, known as the tube side.
Meanwhile, another fluid enters through a connecting tube in the shell and exits through another connecting tube, known as the shell side in a tubular heat exchanger.
10. Spiral plate heat exchanger
Principle
Spiral plate heat exchanger is a new, efficient and stable heat exchange equipment that can work well together with multiple units. It has high heat transfer efficiency and strong operation reliability, with low resistance.
However, the spiral plate heat exchanger requires high-quality welding and may be difficult to repair. Furthermore, due to its heavy weight and low rigidity, extra care must be taken during transportation and installation.
11. Spray heat exchanger
Principle
This type of heat exchanger involves fixing heat exchange tubes in rows on a steel frame. The hot fluid flows inside the tubes, while the cooling water is evenly distributed by the spray device above. It is also known as a spray cooler.
The heat transfer coefficient outside the tube is significantly higher than that of an immersion-type heat exchanger due to the presence of a high-turbulence liquid film layer outside the tube. In addition, these heat exchangers are often placed in areas with air circulation, and the evaporation of the cooling water also removes some of the heat, which helps to lower the temperature of the cooling water and increases the driving force of heat transfer. .
Therefore, the spray-type heat exchanger has greatly improved heat transfer effect compared with the immersion-type heat exchangers.
12. Heat pipe heat exchanger
Principle
Heat pipes are a type of heat transfer component with high thermal conductivity. They transfer heat through evaporation and condensation of the working medium in a fully enclosed vacuum enclosure.
They have many advantages such as high thermal conductivity, good isothermal behavior, ability to change the heat transfer area on both the hot and cold side, long-distance heat transfer, temperature control and much more.
However, the disadvantage is low oxidation and high temperature resistance. This can be solved by installing a ceramic heat exchanger in the front, which solves the problem of high temperature resistance and corrosion resistance.
Currently, heat pipes are widely used in industries such as metallurgy, chemical, petroleum refining, boilers, ceramics, transportation, light textiles, machinery and others. As a means of recovering waste heat and utilizing thermal energy in the process, heat pipes have demonstrated notable economic benefits.
