Which metering device could NOT be used with a slightly overfed DX evaporator incorporating a suction line accumulator?

When analyzing the operation of a slightly overfed direct expansion (DX) evaporator that employs a suction line accumulator, it's important to consider the characteristics and functionalities of the different metering devices.

A thermostatic expansion valve (TXV) is designed to respond to the superheat of the refrigerant, adjusting the flow based on the actual thermal conditions within the system. In a scenario with an overfed evaporator, the TXV might struggle to regulate the refrigerant flow effectively because its operation relies on sensing the superheat to control the amount of refrigerant entering the evaporator. Since the system is overfed, it may not maintain the necessary superheat for proper operation, potentially leading to flooded conditions in the evaporator and affecting the TXV's performance.

Conversely, a hand expansion valve can be manually adjusted based on the operator's assessment of the system, and an automatic expansion valve works to maintain a constant pressure in the evaporator regardless of the flow. Both alternate options offer functionalities that could still accommodate an overfed scenario better than a TXV.

Consequently, the characteristics of the thermostatic expansion valve make it unsuitable for a slightly overfed DX evaporator with a suction line accumulator, explaining why it would not be a viable choice as