What is the potential issue when using a constant pressure expansion valve instead of a thermostatic expansion valve under various loads?

Using a constant pressure expansion valve in place of a thermostatic expansion valve can lead to improper refrigerant flow to the evaporator under varying load conditions. A significant potential issue is that the constant pressure valve does not adjust the refrigerant flow based on the actual cooling demand of the system.

In scenarios where the cooling load decreases, the constant pressure valve may continue to allow the same amount of refrigerant to enter the evaporator as it would under higher load conditions. This can lead to an oversupply of refrigerant, resulting in liquid refrigerant not evaporating properly, which can cause a flood of liquid refrigerant back to the compressor. Conversely, if the load increases and the valve doesn't provide enough refrigerant, it can lead to starvation of the evaporator, preventing it from absorbing the necessary heat. Therefore, the fluctuating demands of the cooling load can create a situation where the evaporator cannot effectively exchange heat, leading to inefficiencies and potential damage.

This is contrasted with the performance of a thermostatic expansion valve, which actively monitors the evaporator's temperature and adjusts the refrigerant flow as needed to match the cooling load, thus maintaining optimal performance.