HVAC Refrigerant Cycle Basics — Flashcards

The HVAC refrigerant cycle is a continuous, closed-loop process that moves heat from an indoor space to the outdoors using four main components: the compressor, condenser, metering device, and evaporator. It works by changing the refrigerant between liquid and vapor states to absorb heat indoors and reject it outdoors. 

The Four Main Components & Process
Compressor (The Pump): The cycle starts here. It compresses low-pressure, cool vapor into high-pressure, hot vapor, raising its temperature.
Condenser (Heat Rejection): Hot vapor flows through the condenser coils, where a fan blows air over them. The refrigerant cools and condenses from a vapor into a high-pressure liquid, releasing heat outdoors.
Metering Device (Expansion): The high-pressure liquid passes through a small opening (expansion valve or capillary tube), which causes a dramatic drop in pressure and temperature, turning it into a cold mixture of liquid and vapor.
Evaporator (Heat Absorption): The cold liquid travels through the evaporator coils, absorbing heat from the indoor air (cooling it). The refrigerant evaporates back into a low-pressure vapor and returns to the compressor to restart the cycle. 

Key Components Summary
High-Pressure Side: Compressor to the metering device.
Low-Pressure Side: Metering device to the compressor.
Refrigerant: The fluid used to transfer heat, which changes state (liquid <--> vapor) to maximize heat transfer efficiency. 

This process continuously cools the air inside a building by transferring heat to the outdoors.