Double tube heat exchanger

The double tube heat exchanger is one of the most well-known types of heat exchangers. As such, they are usually heating devices that can be used to transfer heat (thermal energy) from one material flow to another. The following explains which applications the heat exchangers are used in, how they are constructed and what advantages and disadvantages they have.

Double tube heat exchanger advantages and disadvantages

By using heat exchangers, waste heat is used sensibly and hot liquids can be cooled easily. As a result, energy and heating costs fall and efficiency increases. Among the heat exchangers, double tube heat exchangers occupy a special place because they are comparatively cheap to buy. At the same time, they take up a relatively large amount of space.

Benefits:

• Simple construction
• Inexpensive
• Possibility of transferring high pressures
• Easy cleaning and maintenance

Disadvantages:

• Large design/space requirement
• Medium efficiency

The construction of double tube heat exchangers

Double tube heat exchangers score with a relatively simple design, which is why they are comparatively inexpensive. They have two tubes arranged coaxially (on the same axis). In some models, these are ribbed inside and out, which has the advantage that the heat-transferring surface is expanded.

Between the inner and outer tube - and thus between the fluid streams that flow through the tubes during operation - there is a partition that serves as a transfer surface. The ends of the outer tubes are connected to one another and thus form a flow channel.

How well the heat can be conducted through the tube walls depends primarily on the wall thickness and its material. Steel, copper, aluminium, brass or copper-nickel are used to build the devices - i.e. materials that have good thermal conductivity.

Double tube heat exchanger function

Basically, the function of a heat exchanger is to transfer the thermal energy or the high temperature level of a medium to one with a lower temperature level.

Double tube heat exchangers have a power range from 1 kW to 35 kW and reach temperatures of up to 200 degrees Celsius. The inner and outer tubes of double tube heat exchangers are arranged coaxially. While a heat-transferring medium or fluid is guided through the annular gap between the inner and outer tube, the other flows through the inner tube. The media flow in direct current or countercurrent to each other.

Double tube heat exchangers belong to the group of indirect heat exchangers, more precisely the recuperators. As such, two media flow through them at the same time and transmit the heat indirectly, for example through a partition wall that is permeable to the medium. A typical recuperator are classic radiators that transfer the heat from the heating water to the room air via their walls.

Double tube heat exchangers are designed for liquid media. While the first fluid flows in the inner tubes, the second flows in the gap between the inner and outer tubes. The exchange of heat occurs through the tube wall and indirectly. This means that the hot medium transfers the heat to the separating tube wall. From there it is then passed on to the cold medium - without any delay.

Areas of application

Double tube heat exchangers can be used in numerous industries to increase the overall efficiency of systems and processes. The areas of application are diverse, so that double tube heat exchangers are used, among other things, in the food industry, heating technology, waste water use and in combined heat and power plants.

What types of heat exchangers are there?

A distinction is made between heat exchangers according to the technology of heat transfer. There are double tube, rotary, finned tube, spiral, fin, plate, shell and tube and heat tube heat exchangers.

How is a heat exchanger calculated?

The calculation and design of heat exchangers ensures that their components achieve the right performance for the respective properties of the medium. The precise calculation allows, for example, the size of the heat exchanger surfaces to be optimally adapted to media parameters such as flow and temperatures.

Basically, you first need the required power for the heat exchanger calculation. This depends on the medium used in each case as well as on the mass flow and the planned spread.

Values and properties such as the durability of the material, the inlet and outlet temperatures of the medium at the heat exchanger and the so-called degreeness, i.e. the difference between the temperatures at the heat exchanger, are also decisive. In addition, the calculation depends on the design and operating principle of the heat exchanger and the operating principle as well as the direction of flow. No matter how large the heat transfer surface is, the devices always perform better when the liquids or gases flow past each other in opposite directions (countercurrent principle).

Nowadays, numerous manufacturers offer easy-to-use calculation tools. These specify the categories for the required basic data, so that the calculation of the heat exchanger is easy.

What is a double tube heat exchanger?

Double tube heat exchangers have two liquid media flowing through at the same time. The first fluid flows through the inner tubes, the second flows through the gap between the inner and outer tubes. The tube wall serves to exchange heat between the hotter and the colder fluid. There is no time delay.

Where can i buy a double tube heat exchanger?

The use of a custom-made heat exchanger makes sense for many applications. Individual double tube heat exchangers are available from PURPLAN, the experts for plant engineering. We are happy to make our many years of experience and excellent know-how available to our customers. You too can benefit from excellent advice, reliable support and fast national and international delivery times! Feel free to contact us.