In a sealed refrigeration system, which two properties tend to rise and fall together?

• A. Humidity and Temperature
• B. Pressure and Temperature
• C. Volume and Humidity
• D. Density and Temperature

Answer: (B)

In a sealed refrigeration system, the refrigerant is confined with essentially fixed volume and mass, so adding heat raises the refrigerant’s temperature. As temperature increases, the molecules move more vigorously and collide more, which raises the pressure inside the closed container. When heat is removed, both temperature and pressure fall together. Humidity isn’t a primary factor for the refrigerant in a sealed system, and volume is fixed, so it doesn’t rise with temperature. Density tends to decrease when temperature rises (at constant volume), so it doesn’t rise in step with temperature. The two properties that move up and down together are pressure and temperature.