After nearly two decades of rapid growth in the environmental testing equipment sector, significant advancements and upgrades have been made to equipment aesthetics, control systems, and refrigeration systems—most notably in the latter two areas. Today, we will focus specifically on a critical component within the refrigeration system: the throttling expansion valve.

In earlier generations of equipment, most single-compressor refrigeration systems utilized thermal expansion valves—primarily those manufactured by Danfoss and Emerson. In dual-stage cascade refrigeration systems, the primary stage employed a thermal expansion valve; however, because no dedicated thermal expansion valves were available to specifically match the refrigeration requirements of the secondary stage, the latter typically relied on a throttling method involving multiple sets of capillary tubes. During low-temperature operation, the refrigeration system would first lower the chamber temperature below the target value by utilizing the principle of heat absorption via capillary throttling and expansion; subsequently, a heating compensation mechanism would be employed to fine-tune the experimental temperature back up to the target value, thereby achieving precise temperature control. This configuration was the mainstream standard for early environmental testing equipment. Its most significant drawbacks included high energy consumption, a relatively complex refrigeration system architecture, lengthy commissioning cycles, and a high failure rate.

Beginning in 2018, Hailisi Company transitioned to the comprehensive use of electronic expansion valves. These valves feature real-time adjustable opening degrees, allowing for precise control over both the cooling rate and refrigeration capacity. When integrated with the "cold-end output" programming of a dedicated control system, this technology enables rapid, efficient, energy-saving, and highly precise refrigeration performance. Compared to traditional thermal expansion valves, this approach results in a more streamlined refrigeration system design. The ability to directly visualize and adjust the throttling aperture significantly shortens the equipment commissioning cycle; furthermore, by eliminating the need for numerous solenoid valves, the overall equipment failure rate is substantially reduced.

Of course, such system upgrades and iterations inevitably entail enhanced functionality within the control system and a corresponding increase in overall cost. However, when weighed against the advantages gained—particularly for users with demanding requirements—the investment is entirely worthwhile. This represents not only the progress of the era but also a necessary step in the continuous evolution and technological upgrading of the field.