What Is A Heat Pipe Air Preheater?

What Is A Heat Pipe Air Preheater

A heat pipe air preheater is an air-to-air heat exchange device that utilizes the waste heat from boiler exhaust to preheat combustion air. It is primarily used in industrial boiler systems and drying processes.

The core component of a heat pipe air preheater is the heat pipe, a sealed tube evacuated to a high vacuum and filled with a small amount of working fluid (such as water, acetone, or thermal conductivity). The tube wall is lined with a capillary porous material (the wick). Its operation is divided into three zones:

Evaporation section (hot end): This section is located in the flue gas duct. As the high-temperature flue gas flows through the evaporation section, heat is transferred through the tube wall to the working fluid within the tube, causing it to rapidly evaporate and absorb a large amount of latent heat of vaporization.

Transfer section: Due to the significant vapor pressure difference between the evaporation section and the condensation section, the steam instantly flows to the other end of the tube (the condensation section). This process is extremely fast and highly efficient in heat transfer.

Condensation section (cold end): This section is located in the air duct. Steam flowing from the evaporator section encounters the cooler tube walls, releasing its latent heat of vaporization and condensing into liquid. This released heat then heats the cold air flowing through it. The condensed liquid fluid, driven by capillary action within the tube core, automatically flows back to the evaporator section, completing the cycle.

The widespread use of heat pipe air preheaters stems from the numerous advantages offered by their unique design:

Ultra-High Heat Transfer Efficiency:

Heat pipes utilize the phase change (evaporation and condensation) of the fluid to transfer heat, resulting in a heat transfer capacity several orders of magnitude higher than that of conventional heat exchange tubes that rely solely on metal heat conduction.

Perfect Airtightness, Zero Leakage:

The flue gas and air channels are completely separated by the heat pipe's central partition. Flue gas and air are prevented from mixing under any circumstances. This completely eliminates the inherent air leakage problem of rotary air preheaters, ensuring boiler efficiency and avoiding increased induced draft fan load. Excellent corrosion and dust accumulation resistance:

By adjusting the heat transfer area ratio between the evaporator and condenser sections of the heat pipe (i.e., the "fin ratio"), the heat pipe wall temperature can be effectively controlled to avoid the acid dew point, significantly reducing low-temperature acid corrosion on the flue gas side.

Optimized flow rate design and smooth fin surfaces reduce dust accumulation.

Excellent controllability and safety:

Each heat pipe is an independent heat transfer element. If a single or a small number of heat pipes are damaged by corrosion or wear, they will only fail, without causing mixing (leakage) of the two media. The system can continue to operate until scheduled maintenance, providing high safety.

Easy maintenance:

Compact and modular design. If replacement is necessary, damaged heat pipes can be removed individually without disassembling the entire heat exchanger, significantly reducing maintenance costs and downtime.