What in a refrigeration system determines the low-side pressure?

In a refrigeration system, the low-side pressure is primarily determined by the temperature of the refrigerant. The refrigeration cycle operates based on the principles of thermodynamics, where the pressure and temperature of the refrigerant are closely related. As the refrigerant evaporates in the evaporator coil, it absorbs heat from the environment, which leads to a phase change from liquid to vapor and results in a corresponding low pressure.

When we consider the relationship between pressure and temperature, we can reference the refrigerant's specific pressure-temperature chart, which describes how, at a given temperature, the refrigerant will exhibit a specific pressure. Therefore, if the low-side temperature decreases, the low-side pressure will also decline. Conversely, if the temperature increases, so will the pressure. This direct correspondence emphasizes the critical role that the refrigerant temperature plays in establishing and maintaining low-side pressure in the system.

The options that refer to the amount of liquid in the system, compressor speed, and type of refrigerant may influence performance and operation but do not directly set the low-side pressure in the way that temperature does. These factors can contribute to the operational efficiency of the refrigeration cycle, but they are secondary compared to the primary and fundamental role of temperature in determining pressure.