Which type of expansion valve is rarely utilized in refrigeration systems?

The hand-operated expansion valve is rarely utilized in refrigeration systems primarily due to its manual nature, which can lead to inconsistent performance and control. These valves require manual adjustment to regulate refrigerant flow, making them unsuitable for modern refrigeration applications that demand consistent temperature control and efficiency. Most refrigeration systems benefit from automatic or electronically controlled valves, which can adjust to varying load conditions in real-time.

In contrast, thermostatic expansion valves and electronic expansion valves offer automated control, improving system efficiency and responsiveness to changes in cooling demand. Capped expansion valves, while less common, may still find specific applications but are not suited for general use in modern thermostatic systems like the other two options. The manual operation of hand-operated expansion valves makes them impractical for the dynamic requirements of most refrigeration systems, leading to their rare application in the field.