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What Is Ammonia Refrigeration Cycle?
Jan 16, 2018

Ammonia refrigeration cycle

The complete refrigeration system should include the refrigerant circulation system, the lubricating oil circulation system, the cooling water circulation system and the refrigerant circulation system.

High-pressure system can be divided into three parts: the compression part, the condensation part and the adjustment part.


1. Compression part

Compression part consists of compressor, suction exhaust pipe, two-stage system of the intercooler and other components. Single-stage compression when there is only one evaporating loop, the compression division is relatively simple to connect the suction, exhaust pipe and compressor.The valve used to cut off the connection between machine and system is usually two rows, and the bottom row is the suction and exhaust valve of the machine, and the upper row is added in the design time, which is convenient to replace the compressor and repair the one-way valve. It is necessary to set the reverse running device on the machine.

When there are two or more evaporating loop in refrigeration system, each loop cooling machine must first meet to their system, on this basis, it is should be considered in special cases can also take other evaporative cooling loop task


2.Two-stage compression

As mentioned before, two-stage compression is the two or more compressors (or a compressor high and low pressure cylinder) series operation, and then set the intercooler to reduce the high-pressure stage compressor suction gas temperature, thereby reducing the high-pressure stage compressor Exhaust temperature to improve the operating conditions.Some intercooler can also play the role of separating oil and cooling high-pressure liquid refrigerant. Two-level compression with a group of two-level and single two-level two types.

A two-stage compression system composed of two low-pressure compressor with a high pressure stage compressor and a double compression system. In order to improve the operation flexibility, one of the connecting pipes and the valve parts can be added to the exhaust pipe of one of the low-pressure compressor, which can be changed to a single-stage compressor. The motor should be able to meet the requirements of high power.

Single-machine two-stage compression is a compressor which combines high pressure cylinder and low pressure cylinder. It is called single machine two-stage compressor. Double - stage compression can be achieved with a single - machine dual - stage machine. The low pressure cylinder is sucked into the intermediate cooler by pressure to the middle pressure, and then compressed by the high-pressure cylinder to the condensing pressure to the exhaust pipe.

Group of two-stage, standalone two-stage compression have different features, among them with group of two-stage selection with combinations of ideal theoretical displacement ratio, close to the optimum condition, making it the actual working condition and can be changed to single-stage operation, scheduling flexibility. The single-machine two-stage machine has advantages in initial investment, machine occupation area, unit power cooling capacity and operation management, and its coordination flexibility can only be considered between two different evaporation circuits.


3. Integrated system

There are both single stage compression, and two stage compression refrigeration system is very common in the actual cooling device, the machine, pipeline configuration scheme, in addition to meet the needs of each loop, also can consider to each other between different evaporation circuit switching and flexible application.

Reverse running device Settings: operation is the exchange through the compressor suction, exhaust pipe, high pressure system of refrigerant gas input low voltage system, the high pressure system into vacuum state, to use in maintenance, etc. Since the device is not commonly used, the whole cooling system is set up, preferably on a single stage.

Condensing part

Condensing part is composed of oil separator, condenser, liquid reservoir and related valve parts and pipelines.

The high-pressure superheated steam from the compressor enters the oil separator through the exhaust pipe, and the separated ammonia gas enters the condenser to be cooled by the cooling medium, and the ammonia liquor is then drained into the reservoir. This part of pipeline configuration is related to the type of equipment such as condenser and oil separator. But no matter what the configuration, it is necessary to ensure that the refrigerant gas condenses into liquid and circulates smoothly in the system.


1. Oil separator configuration

According to the type of oil separator are the following types


a) Configuration of filler oil separator. The packing oil separator USES filtration to separate the oil droplets, the separation effect is better, but the resistance is larger. Its pipeline configuration is simple, but different manufacturers produce different structure, and pay attention to the position of air outlet.

b) Configuration of the washing oil separator. The washing oil separator is a special equipment for ammonia system. It maintains a certain liquid level at the bottom, mainly using ammonia solution washing and cooling to separate the oil droplets. Therefore, the lower part of the oil separator is provided with a liquid supply interface, which is connected with the liquid pipe under the condenser to ensure the supply of the oil separator.

c) Configuration of centrifugal oil separator. Centrifugal oil separators use the centrifugal force of the flow in the spiral flow to separate the oil droplets and apply to large machines.

When the system has several oil separators, it should be connected in parallel, and pay attention to the uniformity of air intake. The oil separating the oil separator is usually put into the oil collector through the discharge pipe.


2. Condenser configuration

Ammonia refrigeration cycle commonly used vertical, horizontal and evaporative condenser, the condenser tube interface, in addition to the air inlet, a liquid, considering the safety and economic operation and other factors, the actual pressure increased, object completely, put oil, such as interface, the interface and the corresponding equipment should be properly connected.


3. Dispenser configuration

In the refrigeration system, the refrigeration system is often under variable load, and the condensate is difficult to control directly through the throttle valve. When the evaporation capacity is less than the condensation amount, a certain amount of liquid will be stored in the condenser, which occupies a certain amount of condensation area. When the evaporation capacity is greater than the condensation rate, there will be high pressure gas entering the evaporator and the refrigeration system will be disordered. Therefore, it is necessary to set the reservoir after the condenser. The main function of the reservoir is to store condensate, adjust and balance the demand relationship between heat load and refrigerant. The liquid seal between the high and low pressure system of the refrigeration device is used to prevent the high pressure gas from entering the supply pipe. It can hold the liquid of the condenser, prevent the condensate from taking up the condensation area and increase the condensing pressure; Store refrigerant during equipment maintenance.


4. Air separator configuration

The air separator is used to remove the non-condensable gases (mainly air) in the refrigeration system. There are three types of horizontal bushing, vertical coil and automatic air separator in China. The first two pipes are configured with connection requirements:

a) The supply pipe can be connected from the high pressure liquid pipe near the main regulating station or the air separator, and as the cold source of the air separator after throttling.

b) The return air pipe shall be connected to the back airway of the evaporating loop with low evaporative temperature, stable cooling condition and regular work, and shall not be connected directly with the suction pipe to avoid the wet travel during the liquid supply.

c) The mixed gas pipe shall be connected with the liquid receiver and condenser. Because of the liquid seal of the liquid reservoir, the non-condensable gas that enters the refrigeration system accumulates in the condenser and the receiver. Therefore, the mixing pipe should be taken from the two devices to the air separator. Some vertical condensers have upper and lower air connections. This is because under certain pressure, the temperature is low in the air, the vertical condenser works, the temperature near the outlet is the lowest, so the air is suitable. When you stop working, you can release air from the upper outlet.

d) The air pipe is connected to the water.

e) For the treatment of the condensed liquid, the horizontal is the internal circulation, and the vertical can be used by the air separator for circulation, and the high difference can be used to enter the reservoir.



5. Oil collector configuration

In ammonia refrigeration system, the lubricating oil is unfavorable to the heat transfer equipment such as condenser and evaporator. In order to reduce the influence of oil on heat transfer equipment, any equipment that has the potential to accumulate oil has an oil discharge interface and is connected to the oil collector through the discharge pipe. Decompression of the upper oil trap tube is used to reduce the pressure in the oil trap, make oil gasification ammonia liquid under low pressure in the absorption of ammonia mixture and make the oil separation, ammonia, ammonia was siphoned off, oil remaining in the oil trap and then released. The larger refrigeration system can set up two oil collectors to separate the high and low voltage equipment separately.



Adjustment part


The adjustment part mainly refers to the setting of the general adjustment station. In the refrigeration system, the valve that can control the distribution of high pressure liquid is concentrated, and then a few display instruments constitute the total control station. The structure type of the total control station varies with the supply of liquid and compression series.

a) Single stage compression master station.


Single-stage compressed total control station, the direct expansion supply is often set on the regulating station, thereby controlling, throttling and reducing pressure; The liquid pump and gravity feed are generally used in the low pressure circulation bucket and ammonia liquid separator, the float ball valve or automatic feed liquid is used, and no throttle valve is installed on the control station, and the stop valve is controlled. In order to maintain the convenience, the valve can be installed before and after the regular maintenance of the throttle valve. But with that comes the increase in the number of valves, the increase in resistance and the complexity of the system, so it should be properly set.


b) Two-stage compression master station.

The total control station is divided into high and low temperature, and the intermediate bridge valve is used to communicate with each other. The high temperature part of the liquid source is high pressure liquid storage device, ammonia station, etc. For high evaporative temperature supply, intermediate coolant supply and serpentine coil supply, etc. The low temperature part of the liquid source is the intermediate cooler, the serpentine tube supercooled liquid, the drain barrel drainage, etc. Go to the low evaporation temperature supply.


For simpler refrigeration systems, there is also no general regulation station.


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