What is liquid migration?

A key principle underlying the concept of liquid migration is that migration forms an intrinsic part of wider social transformations within origin and destination countries in Europe.

What is liquid migration HVAC?

Refrigerant migration is defined as refrigerant, either liquid or vapor, traveling to the compressor's suction line or crankcase during the off cycle. During the off cycle, or especially during a long shutdown, refrigerant will want to travel, or migrate, to a place where the pressure is the lowest.

How do you prevent liquid migration?

The only sure solution to avoiding migration is to get rid of all the refrigerant in the evaporator, suction line, and crankcase before the off cycle. This can be accomplished by an automatic pumpdown system. In such a system, a thermostat controlling box temperature is wired in series with a liquid line solenoid.

What causes oil migration?

Hydrocarbons migrate from a position of higher potential energy to one of lower potential energy. The spatial location of these energy differences defines the expected migration path. There are many sources for this energy that causes oil and gas migration.

What prevents liquid from entering the compressor?

SUCTION LINE ACCUMULATORS. Suction line accumulators are designed to protect the compressor when refrigerant flooding and/or migration do occur. They should be installed between the evaporator and the compressor on the suction line, usually as close to the compressor as possible.

HVAC 075 crankcase heater, intro to refrigerant migration

What happens if liquid enters compressor?

In reciprocating compressors, when a large volume of liquid appears inside the cylinder, and the piston cannot expel it through the discharge valve during the short duration when it is open, it leads to excessive pressure buildup inside the cylinder.

Why does liquid damage a compressor?

A compressor is designed to pump refrigerant in its vapor form, but if liquid refrigerant returns to the Compressor and passes through the suction valve, it may bend or break the suction valve.

Why is oil return so important to a refrigeration system?

Oil helps to lubricate compressor bearings and other moving parts in the system. It is important to note that once oil travels through the entire refrigeration unit, it returns to the compressor, as it is vital to the proper functioning of it.

Is there oil in a refrigeration system?

Where the refrigerant is essential for the cooling properties of a refrigeration system, the refrigeration oil is crucial for the correct functioning of the compressor. Lubricants for refrigeration compressors reduce friction, prevent wear and act as a seal between the high and low pressure sides.

Which refrigerants must be recovered before opening?

All CFCs and HCFCs must be recovered before opening a system for service or disposing of appliances. Cylinder & Appliance Disposal: Before disposing of any appliance containing a CFC or HCFC refrigerant, the refrigerant must be recovered.

How do you stop a compressor Floodback?

Refrigerant migration to the crankcase may also result in liquid slugging during start-up. Although refrigerant migration and floodback can be prevented by adding a suction accumulator to the system, accumulators may also flood in a severe flooding condition.

How frequently must reusable containers for refrigerants that are under high pressure?

Correct answer is D: 5 years. Reusable refrigerant containers that are normally under any pressure above 15 psig, must be hydrostatically tested and date stamped every 5 years.

How do you stop liquid slugging?

The single best device to protect the compressor from slugging and floodback is the suction line accumulator. Accumulators are most often found on low temperature systems, but all refrigeration systems can benefit from this relatively low-cost protective device.

What causes liquid slugging?

Slugging can result in broken valves, broken head gaskets, broken connecting rods, and other major compressor damage. Refrigerant-cooled semi-hermetic compressors will often draw liquid from the suction line through hot motor windings in the motor barrel, which will assist in vaporizing any liquid.

What causes foamy refrigerant?

In general, foaming occurs when the oil-refrigerant mixture is exposed to a sudden pressure drop, as is the case in starting up a reciprocating compressor 1. The foaming oil may be sucked into a cylinder, which causes liquid compression and valve failure.

What are the 3 types of oils in refrigerant?

What is purging in refrigeration?

Whether a system uses ammonia or a freon refrigerant, he heat transfer efficiency will greatly improve when the unwanted noncondensable gas (or air), is removed. The process of removing the colorless, odorless air is called purging. This purging process has become increasingly automatic over time.

Is refrigerant gas or liquid?

The refrigerant, a chemical compound that changes easily from liquid to a gas. When the refrigerant is pushed into the compressor, it is a low pressure gas.

What happens when oil is mixed with refrigerant?

One of the basic characteristics of a refrigerant-oil mixture in a sealed system is the fact that refrigerant is attracted by the oil and will vaporize and migrate through the system to the compressor, even though no measurable pressure difference exists to cause the movement.

What is floc point of oil?

Floc Point – the temperature at which wax will separate from the oil. Above this temperature, the wax will remain in the solution. Pour Point – the temperature at which the oil begins to pour.

Which oil is used in refrigerator compressor?

Polyol ester (POE): this refrigeration oil is the most common type of synthetic lubricant being used with HFC refrigerants, like R134a. these refrigeration oils have a good thermal and chemical stability.

What is the difference between slugging and flooding?

What is the difference between flooding and slugging? Flooding is a little liquid refrigerant reaching the compressor; slugging is a lot of liquid refrigerant reaching the compressor all at once.

What is the difference between a pump and a compressor?

A pump is a device that expends energy to raise, transport, or compress fluids—liquids and gases. The term pump is generally used for liquid-handling or hand-operated devices, while the term compressor is used when the pressure of a gas is increased in a motor-driven machine.

What is the difference between compressor and turbine?

Turbine is the device in which fluid expands. During the expansion work will be done by the fluid to drive, for example, electric generation. In this case, power output occurs. Compressor is the device which is used to compress the fluid and increase its pressure.