What component is primarily responsible for regulating refrigerant flow in an HVAC system?

The component that is primarily responsible for regulating refrigerant flow in an HVAC system is the expansion valve. The expansion valve plays a crucial role in controlling the refrigerant's pressure and flow rate before it enters the evaporator coil. By doing this, it ensures that the refrigerant expands properly and allows for efficient heat absorption within the evaporator. This regulation is vital for the overall efficiency and capacity of the refrigeration cycle, as it directly impacts the system's ability to provide adequate cooling.

In an HVAC system, the thermostat is primarily responsible for detecting temperature and maintaining the desired temperature setting, rather than regulating refrigerant flow itself. The compressor works to circulate the refrigerant throughout the system but does not specifically manage its flow. The evaporator coil serves to absorb heat from the surrounding environment but does not have direct control over how much refrigerant enters it. Therefore, the expansion valve is the correct component for this specific function within the refrigeration cycle.