Refrigeration and Refrigerants

Rating Ref. Equipment

•  it takes 144 Btu of heat to melt a pound of ice at 32 F

•  this figure is used in the capacity rating of refrigeration equipment

Pressure and Temperature Relationship

•  the boiling point of water can be changed and controlled by controlling the vapor pressure above water

•  press./temp. relationship correlates the vapor pressure and boiling points of water and is the basis for controlling the systems temperatures

•  a refrigerant is a substance that can be changed readily to a vapor by boiling it then changing it to liquid by condensing it

•  the pressure and temp. will correspond when both liquid vapor are present under two conditions

1. when the change of state(latent heat)(boiling or condensing) is occurring
2. when the refrigerant is under equilibrium(no heat is added or removed)

•  when the pressure is consistent the liquid and the vapor have the same saturation temp.

•  when refrigerant is saturated, both liquid and vapor can exist simultaneously.

•  The saturation temp depends on the pressure of the liquid./vapor mixture. This pressure is called the saturation pressure( higher the sat. temp, higher the sat. pressure & lower to lower)

•  The pressure temp. chart is also referred to as a saturation chart because it contains saturation temps. For different sat. pressures.

•  Vapor pressure is read on the gauge manifold

•  Vapor pressure decreases when liquid/vapor mixture temp. decreases and as liquid./vapor increases in temp vapor pressure increases