Expansion Valves are mechanical devices used in refrigeration and air conditioning systems to regulate the flow of refrigerant into the evaporator. They maintain a controlled reduction in pressure and temperature of the refrigerant as it passes through, facilitating the phase change from liquid to vapor. This process enables efficient heat absorption from the surrounding environment, crucial for cooling applications. Expansion valves play a critical role in optimizing system performance by ensuring the proper amount of refrigerant is delivered to the evaporator, thereby maintaining desired temperatures and improving energy efficiency.