A Basic Guide to Aircraft Air Conditioning Systems

For a majority of passenger aircraft that feature turbine engines, cabin oxygen and heat is provided by engine bleed air. This pressurized air is extremely hot before entering the cabin, making it essential that it is cooled as necessary for comfort. While air conditioning is often considered a luxury in other settings, it is absolutely essential in many aircraft to ensure that the air supplied for breathing is treated for safety, quality, etc. In this blog, we will discuss the various parts that make up aircraft air conditioning systems, allowing you to have a better understanding of how cabins are supplied with breathable air.

Heat Exchangers

Heat exchangers are an essential element of any aircraft air conditioning system, acting as passive devices that transfer heat between two mediums, typically fluids. As fluids of two different temperatures move through a heat exchanger, heat will be transferred from the hotter fluid to the cooler one. Though simplistic, this process allows for efficient temperature control in a number of assemblies.

Air and Vapor Cycle Machines

Air cycle machines (ACMs) and vapor cycle machines (VCMs) are two common devices used for cooling bleed air supplied from an engine. Gasses naturally get hotter when compressed, while expanding gasses will cool as heat is transferred into surrounding air. With an ACM, high-pressure bleed air is further compressed before entering heat exchangers for cooling, and the highly compressed air is then sent through an expansion chamber where dramatic cooling occurs. As this rapid cooling may potentially cause issues like freezing, such assemblies regularly have water traps for safety.

With a VCM, refrigerants are used to increase cooling efficiency with such materials following a similar process to the air within ACMs, except the rapidly expanding refrigerants in a chamber absorb heat from passing cabin air instead of being supplied to the cabin. Once refrigerants have absorbed heat from passing cabin air, they are sent back to the compressor to initiate another cycle of cooling. Generally, ACMs are best used in larger aircraft with large amounts of bleed air, while VCMs are best for aircraft with limited engine bleed air.

Temperature Mixing Valves

To allow for more precise control over cabin air temperatures, temperature mixing valves are implemented. Generally, these valves will allow cooled air from an ACM or VCM to be mixed with hot bleed air as necessary to increase temperatures by a smaller degree. To make temperature control easy, most modern aircraft will have automatic temperature control systems and cabin air temperature sensors that manage valve control. In the case that these automatic systems ever face errors or issues, manual control will be provided as well. In larger aircraft models, all environmental heating and cooling systems, ranging from ACMs to mixing valves, are combined into a single package known as a “PACK.”

Conclusion

With a general understanding of the common elements of aircraft air conditioning systems, you can be more aware of their functionality and how to best carry out maintenance and replacement. Here on ASAP Parts Services, we can help you secure competitive pricing and rapid lead times on all the aircraft air conditioning system parts you require, including turbine components, mechanical compressor products, electrical motors, and much more. With our purchasing power and market expertise, we offer customers highly competitive pricing and rapid lead times for their benefit. Additionally, every part number we list is ready for purchase at any time, and you are encouraged to begin with the submission of an online quote request form so that you may receive a tailored solution from one of our team members for your comparisons. If you have any questions or concerns, please give us a call or email, and we would be happy to assist you however we can!