Which expansion device is generally not used in small refrigeration systems?

The hand expansion valve is generally not used in small refrigeration systems because it does not offer the precise control needed for such applications. Small refrigeration systems typically require reliable and continuous operation with minimal manual intervention. The hand expansion valve, which is manually operated, does not provide the automatic adjustment necessary to maintain optimal performance based on varying load conditions.

In contrast, devices like the thermostatic expansion valve, electronic expansion valve, and capillary tube are designed for better performance in smaller systems. The thermostatic expansion valve automatically adjusts based on the evaporator temperature, ensuring efficient operation. Electronic expansion valves offer fine control and rapid response to load changes, making them suitable for modern systems. Capillary tubes are simple and passive devices that provide a fixed flow of refrigerant, making them appropriate for small, low-cost applications where precision isn't as critical.

Thus, the hand expansion valve is less practical for the needs of small refrigeration systems, which prioritize efficiency and automatic control.