How to choose the right heat exchanger?

We usually use four types of heat exchangers to control heat: shell and tube heat exchangers, plate heat exchangers, tube heat exchangers, and fin heat exchangers. The theory behind heat exchangers is based on solid, liquid or gaseous media, applying heat transfer, conduction, convection, and radiation.

Specifically, the medium and temperature affect the choice of a heat exchanger. One factor that is often overlooked is whether a noise is likely to occur. For example, if you have an open-loop ground source heat pump, you will not want to use a plate heat exchanger, but prefer to use the coaxial cable model, which has high speed and low head conditions and is not easy to produce noise. When we have to choose which type of heat exchanger to use for the refrigerant to water heat exchanger, we need to consider this design. Many products on the market will use the COAX model or copper model. Traditionally, we use the COAX model for high speed and low head, but we want to reduce the size, weight and cost to make the product more competitive. We finally chose a unique shell-and-tube design that is less prone to wrinkles and close to zero degrees in temperature, which allows us to extract higher water temperatures than most other types of heat exchangers.

Shell and tube heat exchangers are often used in remote columns, boilers, evaporators, and other heavy-duty high-temperature high-pressure chemical processes. Shell and tube exchangers can withstand very high temperatures even at 1000 degrees Celsius. Shell-and-tube heat exchangers are more expensive than other types of heat exchangers and may require larger space. Due to its simple operation, the tube and shell-type are easy to control and run.

Plate heat exchangers are widely used in the cooling systems of automobiles and refrigeration systems. Plate heat exchangers are only suitable for low temperature and low-pressure processes, not exceeding 200 degrees Celsius and 20 bar. Plate heat exchangers are inexpensive and easy to install. The total heat transfer coefficient is high.

Tubular exchangers are commonly used in casing pipes, which means that hot fluid is injected into the inner tube and cold fluid is injected into the space between the inner and outer tubes. Tubular heat exchangers are used in automotive radiators, refrigeration systems, and heating systems. Current and countercurrent can be easily controlled through the tube. It is also often used for cooling, heating and pasteurization applications in the food and beverage industry. The combination of straight tubes and bellows heat exchangers can achieve the best efficiency and maximum output.

The fin tube heat exchanger is mainly used for air heating in the drying system and is the main equipment in the hot air device. The heat medium used by the radiator can be steam or hot water, or heat conduction oil. The working pressure of the steam generally does not exceed 0.8Mpa The temperature of the hot air is below 150 ℃.

When we consider whether to use a plate heat exchanger or a tubular heat exchanger, we need to focus on the following issues:

1. Is it necessary to deal with high-temperature shell-and-tube heat exchangers more efficiently, because there are more chances of leakage in PHE than shell-and-tube heat exchangers, because we use gaskets between each plate, so it becomes a weaker part?

2. Whether high pressure: The pressure drop in -PHA is very high, so we must apply high pressure at the entrance, but there are too many joints, easy to leak. The pressure drop is small and the chance of leakage is minimal.

3. The minimum increment T required for the heat transfer between the cold and hot fluids of the shell and tube heat exchanger is 3 to 5 degrees Celsius, while for PHE, it is only 1 degree Celsius. The plate heat exchanger uses more countercurrent than crossflow, so it can achieve a lower approach temperature difference, high-temperature change, and higher efficiency.

4. Compared with the shell and tube heat exchanger, the area required by PHA is less, and we can increase or decrease the area of PHA as needed

Each heat exchanger has its application and limitations. However, in both cases where it can be used, it is recommended to use a plate heat exchanger (PHE) because of its high heat transfer efficiency, the mechanism is that a larger fluid has a larger contact area (plate area) and more Thin channels (that is, the fluid area/volume ratio increases, so heat transfer increases. For example, the heat capacity of PHE is five times that of the bulb, and PHE can be 90% smaller than the equivalent bulb HEX.

When working in a liquid-cooled environment, you may have two choices: shell or plate heat exchanger. Shell-and-tube and plate heat exchangers work on the same principle, exchanging heat through the heat conduction between the two fluids, but their structural methods are quite different. Only by fully understanding the

advantages and disadvantages of these designs can you choose the right heat

exchanger for you.

Shell and tube heat exchanger

Shell and tube heat exchanger structure is simple and effective, by the large cylindrical shell (or) within a bunch of small tubes, his works originated from the steam boiler. The design of this kind of heat exchanger is simple and flexible.

Requiring regular maintenance and maintenance, for example, shell-and-tube heat exchangers are widely used in Marine environments because of most shell-and-tube designs are easily disassembled.

The advantage of shell and tube heat exchanger;

Design smaller, effectively reduce the cost

Easy to maintain

Use O — ring seal to reduce maintenance cost

Provide a better solution to water coolant or other liquids may jam in confined

spaces.

A better installation configuration can be provided

It is an ideal choice for mining, hydraulic power, water cooling and swimming pool heating work environment.

Plate exchanger

Although the principle of the plate heat exchanger is very similar to that of shell and tube heat exchanger, the structure is quite different. Rather than using a tube plate heat exchanger using several layers of flat stacked together, to form a series of liquid flows through the channel. They are generally more compact and sometimes less costly than shells, but the design is not as flexible as shells. However, their all-stainless steel construction makes them ideal for applications such as food processing and drug production.

Advantages of the plate heat exchanger;

More compact design

Where stainless steel is required, low-cost configurations are available

Meet the requirements for higher working pressure

Adapt to higher temperature requirements

Very suitable for application in the small district heating and cooling drinks,

food, and drug production and low oil cooling load cases.

Because of its ease of maintenance and compatibility with seawater coolant, shell and tube heat exchangers remain the preferred choice for many engineers. If a plate heat exchanger with seawater is to be used, its plate packaging must have a plate gasket made of titanium, so the cost is higher.