Vapor Compression Cycle
“How do most AC systems work?”
While absorption refrigeration systems are great for many applications, sometimes we just want a more traditional technology for our cooling needs. So how exactly do most AC systems actually work? Well, let’s use our engineering mindset to find out.
Let’s start with the basics. Our goal is to take heat from one space and transport it to another. One very common way to do this is to use a heat exchanger. But to ensure continuous cooling, we must ensure that we have a constant supply of fluid at a temperature we desire. To build this system, let’s start with four components: a compressor, a condenser, an expansion valve, and an evaporator. Then, let’s have a refrigerant enter the compressor at a low temperature in a gaseous state, and do work on it to increase its temperature and pressure. Then, let’s have it enter the condenser, where heat is transferred into a nearby medium. Afterwards, let’s run it through an expansion valve to cool it and release pressure while turning some of the gas into a liquid. Finally, let’s pull it through an evaporator, which is basically a heat exchanger that allows the cold fluid to absorb heat from the surrounding medium (and therefore cool it) and gasify it. Once the fluid leaves the evaporator, it enters the compressor and the process (known as the vapor compression cycle) will start again.