An air conditioner with refrigerant R-22 has a low-side pressure of 70 psig and a temperature of 55°F. According to the pressure-temperature chart, what is the state of the refrigerant?

To determine the state of the refrigerant R-22 at a low-side pressure of 70 psig and a temperature of 55°F, it's important to understand the relationship between pressure and temperature in refrigeration systems.

At 70 psig, according to the pressure-temperature chart for R-22, the corresponding saturation temperature is around 45°F. Therefore, if the refrigerant is at 55°F, it is above the saturation temperature. In this condition, the refrigerant is not in the saturated phase where liquid and vapor coexist, but rather in the superheated state. Superheating occurs when the refrigerant is heated above its boiling point (the saturation temperature) at a given pressure, which correlates to the fact that the refrigerant is fully vaporized and has absorbed additional heat.

In contrast to the other states, such as boiling (where the refrigerant transitions from liquid to vapor), saturated (where it exists as both liquid and vapor), and subcooled (where it is a liquid below the saturation temperature at a given pressure), the superheated state is distinct because it indicates that the refrigerant is fully vaporized and in a phase that can absorb more heat without increasing pressure. This is key for the efficiency of the refrigeration