What is the Working Principle of Heat Pipe Heat Exchangers?

The working principle of a heat pipe heat exchanger is based on the process of heat transfer by phase change of the working fluid inside the heat pipe.

A heat pipe is usually a closed vacuum tube filled with an appropriate amount of working fluid.

When one end of the heat pipe (the hot end) is heated, the working fluid inside the pipe absorbs the heat and vaporises rapidly, resulting in vapour flowing to the other end (the cold end) under a slight pressure difference.

At the cold end, the steam is cold and release the latent heat of vaporisation and condensation into a liquid, the liquid depends on capillary force or gravity and other roles back to the hot end.

So the cycle repeats, through the vaporisation and condensation of the working liquid, heat is continuously transferred from the hot end to the cold end.

In industrial waste heat recovery, the hot end of the heat pipe heat exchanger is exposed to high-temperature exhaust gases, the heat of the exhaust gases vaporises the working fluid in the heat pipe, and the steam carries the heat to the cold end, which is usually connected to the medium that needs to be heated, such as cold air or cold water, where the steam condenses and releases the heat, thus realising the recycling of waste heat.

In the heat dissipation of electronic equipment, the hot end of the heat pipe is in contact with the heating element, absorbing heat to vaporise the work material, and the steam is condensed at the cold end to transfer the heat to the heat sink, and then the heat is emitted by means of a fan or other means.

This working principle makes the heat pipe heat exchanger has very high heat transfer efficiency and good isothermal performance.

Heat pipe heat exchanger has the following advantages and disadvantages:

Advantages:

Highly efficient heat transfer: the phase change heat transfer process inside the heat pipe can achieve very efficient heat transfer, heat transfer efficiency is much higher than traditional heat exchangers.

Good isothermal: the surface temperature distribution of the heat pipe is relatively uniform, which can effectively reduce thermal stress and thermal deformation, and improve the reliability and service life of the equipment.

Flexible structure: can be designed into various shapes and structures according to different application scenarios and space requirements.

Strong adaptability: able to work stably in harsh environments such as high temperature, low temperature and high pressure.

Adjustable heat flow density: by changing the number, length and working medium of heat pipes, etc., the heat flow density can be flexibly adjusted to meet different heat transfer requirements.

Easy to install: relatively small size and light weight, easier to install and maintain.

Disadvantages:

Higher cost: due to its relatively complex manufacturing process, and the need to use high-quality materials, so the cost is higher.

High sealing requirements: heat pipe is a sealed structure, the sealing technology requirements are strict, if the sealing problems, may lead to leakage of the working medium, affecting the heat transfer performance.

Limitation of working medium: different working medium is applicable to a limited range of temperatures, the selection of suitable working medium is sometimes limited.

Heat transfer temperature difference is small: in some cases, may not be able to adapt to the requirements of the larger heat transfer temperature difference.

Existence of heat transfer limit: when the density of heat flow exceeds a certain limit, the heat transfer performance of the heat pipe may decline.

Despite the disadvantages of the heat pipe heat exchanger, it still has irreplaceable advantages in many areas where heat transfer performance is required.