As its name implies, refrigerant in the evaporator "evaporates". Upon entering the evaporator, the liquid refrigerant's temperature is between 40° and 50°F; and without changing its temperature; it absorbs heat as it changes state from a liquid to a vapor.
As refrigerant travels through the evaporator, it absorbs heat from the air. As it absorbs heat, it vaporizes. If the system operates according to design, the refrigerant will be 100% vapor as it nears the exit of the evaporator. Before leaving the evaporator, the vapor continues absorbing heat, becoming superheated.
The evaporator target temperature is progressively increased while maintaining a low enough temperature to prevent misting.
The evaporator functions by allowing the refrigerant to evaporate and expand in a controlled environment. As the liquid refrigerant enters the evaporator, it encounters low pressure, which causes it to vaporize and absorb heat from the surrounding air or medium that needs cooling.
The evaporator does the exact opposite of the condenser. Instead of turning the refrigerant from gas to liquid, it turns the refrigerant from liquid to gas (thus the name “evaporator”). Instead of expelling heat, it absorbs heat and turns the air cold around it. This is where the “conditioning” of the air occurs.
As its name implies, refrigerant in the evaporator "evaporates". Upon entering the evaporator, the liquid refrigerant's temperature is between 40° and 50°F; and without changing its temperature; it absorbs heat as it changes state from a liquid to a vapor.
Since refrigerant comes out of the evaporator as a superheated vapor, it will enter the compressor as a superheated vapor. The compressor's job is to increase the pressure of the refrigerant. Recall that as pressure increases, temperature increases. This is exactly what the compressor does.
Refrigerant evaporates (or boils, to be exact) at room temperatures. As refrigerant evaporates from a liquid into a frigid vaporous state, it readily absorbs heat energy. Refrigerant vapor pressurized to very high temperatures condenses from a hot gas back to a liquid, releasing its load of heat energy.
It depends on the refrigerant and evaporator pressure. In a freon 22 system if evaporator pressure is 68.5 psig the temperature of freon would be 40 deg F.
Since the temperature of the evaporator coils is extremely cold, the temperature of the incoming air will start to decrease as it's circulated through the coils. The coils are designed to absorb heat energy and transform the air in the system from a warm temperature to a cold temperature.
Since the kinetic energy of a molecule is proportional to its temperature, evaporation proceeds more quickly at higher temperatures. As the faster-moving molecules escape, the remaining molecules have lower average kinetic energy, and the temperature of the liquid decreases.
The evaporator works the opposite of the condenser, here refrigerant liquid is converted to gas, absorbing heat from the air in the compartment. When the liquid refrigerant reaches the evaporator its pressure has been reduced, dissipating its heat content and making it much cooler than the fan air flowing around it.
Theoretically the evaporator coil has a wet bulb temperature of 40F. Typical outlet temperature would be 14–20F above entering temperature depending on airflow. I typically shoot for about 16–18 but I live in a fairly neutral humidity.
Refrigerant can shift easily between liquid and gas states, which makes it ideal for ACs since it doesn't take significant amounts of energy to cause the phase shift. Refrigerant starts inside the compressor, where the reduction of volume turns it into a high pressure gas about 150°F.
Superheat is sensible heat transfer that provides very little useful cooling. This occurs because there is no change of state; only change of temperature.
Typical evaporator temperature range is from –40 °C (–40 °F) to –65 °C (–85 °F).
The departing temperature of the now liquid refrigerant is approximately 20°F as it enters the Evaporator Coil. The cold R410A Refrigerant travels through the Evaporator Coils and begins to cool the air of your home blowing across it. The coils produce approximately 55°F air.
In reality, however, the evaporation temperature is never constant through the evaporator. Inside an evaporator, the increased velocity of the liquid/gas refrigerant mixture will induce a pressure drop, which thus reduces the saturation temperature.
In this final step, the low-pressure liquid refrigerant flows into the evaporator, where it absorbs heat from the indoor air to evaporate and become a low-pressure gas. The gas flows back to the compressor where the cycle starts all over again.
After leaving the evaporator, the vaporized refrigerant flows through the compressor. In the compressor, the pressure of the vaporized refrigerant is raised to a point at which it can be condensed by some relatively warm fluid, e.g. water. The compressor removes the refrigerant vapor.
When a refrigerant evaporates, it changes from a liquid state to a gaseous state. During this process, the refrigerant absorbs heat from its surroundings, causing the temperature of the surroundings to decrease. This is the basic principle behind how refrigeration systems work.
Freon™ MP39 enters the condenser (point E) as a saturated vapor at 117 °F and exits the condenser (point F) as a saturated Page 4 Freon™ Refrigerants 4 liquid at 109 °F for a “temperature glide” of 8 °F. By comparison, CFC-12 begins condensing at 113 °F and remains at that temperature until condensation is complete.
Many refrigerants also have a consistent boiling point, whether they are natural refrigerants or synthetic refrigerants. But high-glide refrigerants do not boil at a consistent temperature. A high-glide refrigerant may start boiling at 18°F, but as it boils into a gas, the boiling point “glides” up to 28°F.
A ton of refrigeration is a rate of heat transfer, not an amount of heat. One ton is equal to the heat absorbed in melting 2,000 pounds (1 ton) of ice at 32°F in 24 hours (1 day). This equates to 12,000 Btu/hr or 12,000 Btuh.
The purge unit is located at the top of the condenser coils. The refrigerant is sucked into the purge unit from the top of the condenser. The refrigerant free from air and moisture is then sent to the evaporator through the expansion valve.