1 Source of non-condensable gas in refrigeration system During the operation of refrigerator, non-condensable gas in the system mainly comes from the following aspects:
(1) Before commissioning or after overhaul, the air in the system was not completely pumped out when the refrigerant was filled.
(2) Inadvertent operation when adding lubricating oil and refrigerant will inevitably lead to a small amount of air entering the system.
(3) When the refrigeration device operates under the evaporation pressure below atmospheric pressure, the outside air may enter the system from imprecise places (such as the shaft seal of the compressor, the joint of the flange, the packing of the valve, etc.). ).
(4) Lubricating oil and refrigerant will decompose a little at high exhaust temperature, producing some other non-condensable gases.
When there is non-condensable gas in the refrigeration system, it can only exist in the condenser and the high-pressure accumulator due to the liquid sealing effect of the liquid outlet pipe of the high-pressure accumulator, and most of it is concentrated in the condenser. Because of these gases, the heat transfer of the condenser will be hindered, and the exhaust pressure and temperature of the compressor will increase, thus increasing power consumption, so these gases must be removed.
2. Structure and working principle of air separator In the refrigeration system, non-condensable gases such as air are actually mixed with refrigerant vapor. The air separator cools the mixed gas to near the evaporation temperature under the condensation pressure, so that most of the refrigerant vapor in the mixed gas is condensed into liquid, and non-condensable gases such as air are separated, so as to achieve the purpose of recovering the refrigerant in the mixed gas and reduce the pollution and waste of the refrigerant discharged with the non-condensable gas to the atmosphere.
The types and structures of air separators are different. There are two kinds of air separators in common use: one is vertical air separator, and the other is quadruple tube air separator.
Vertical air separator is widely used in ammonia refrigeration system at present, and its structure is shown in Figure 7-6. Its shell is made of seamless steel pipe, and a group of cooling coils is arranged in the shell with sealed ends, the lower end of which is communicated with the liquid inlet pipe and the upper end is connected with the air return pipe. The middle side surface and the upper side surface of the shell are respectively welded with a mixed gas inlet pipe connector and an exhaust pipe connector. When the mixed gas enters the shell, it exchanges heat with the surface of the coil, and the condensed refrigerant is led out from the lower head of the shell and connected with the liquid inlet pipe after passing through the throttle valve. The separated non-condensable gas enters the water storage barrel from the upper air hole. Thermowells are arranged at the top of the housing. The exterior of the whole air separator is insulated with heat insulation material. —
Compared with horizontal air separation equipment, vertical air separation equipment has the advantage of simple operation, and automatic operation can be realized after installing automatic control elements.
It is welded by four seamless steel pipes with different diameters. Its first interlayer (i.e. outermost interlayer) is communicated with the third interlayer, and its second interlayer is communicated with the fourth interlayer. The ammonia water from the reservoir is throttled by the throttle valve, then enters the inner pipe and then enters the second interlayer. The mixed gas from the accumulator and condenser enters the first interlayer and the third interlayer, and the low-temperature ammonia liquid is evaporated by absorbing the heat of the mixed gas through the heat transfer pipe wall, and the evaporated gas enters the ammonia liquid separator or low pressure through the return pipe. The mixed gas is cooled at higher condensation pressure and lower evaporation temperature, and the ammonia vapor in it is condensed into liquid, which flows to the bottom of the air separation tower, is throttled by the throttle valve and sent to the fourth interlayer of the air separation tower for use. . Non-condensable gases such as air are connected through a joint.
When the pipe is put into the water, you can judge whether the air in the system has been exhausted from the size and quantity of bubbles in the water ... When the air in the system has been almost exhausted, there will be no atmospheric bubbles in the water. —。
The quadruple pipe air separator is located in the horizontal plane, and the ammonia inlet end should be slightly higher, about 30-50 mm, when installed, so that the separated ammonia liquid can flow into the bypass pipe. See 6-5- 1 for its structure.
Selection of number and air separators For people who need air separators,
-when the cooling capacity of the lake is above 4 187000 [KJ/h], KP-
50 sets (Note: I Ching D; 2 19mm), less than 4 187000 [kj/h]
A KF-30 (diameter d; 108mm).