1 Dehydrator Cycle

2011-01-21T21:25:25Z

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Dryer Cycle

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Drier removes water and non-condensable gases. This indicates any water leak in the refrigerant (see # 6 in Fig. 8-11).

This system contains refrigerant condensing coil and Commerce, the water drain valve, purging valve, pressure gauge, float valve refrigerant and refrigerant.

Desiccant-line fence constantly raises the refrigerant vapor and contaminants, if any, from the condenser. Vapor condenses into liquid desiccant condensing coil. Water, if present, disconnects, and floats on the surface of the liquid refrigerant. The water level can be observed through the sight glass.

Water can be withdrawn manually on water drain valve. Air. and other non-condensable gases collect in the top of the desiccant condensation chamber. Drier gage indicates the presence of air or other gases through the increase in pressure. These gases can be manually out through the purge valve.

Float valve maintains the refrigerant fluid level and pressure required for refrigerant condensing action. Purified refrigerant is returned to the refrigerator dryer float chamber.

Lubrication Cycle

2011-01-21T21:25:05Z

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Lubrication Cycle

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Oil pump and oil reservoir contained in unishell. Oil is pumped through the oil filter-cooler, which removes heat and particles. Part of the oil enters the compressor motor-end bearings and seals. The remaining oil serves to lubricate the compressor transmission, compressor thrust and radial bearings and seals. Oil is returned to the tank to complete the cycle.

Oil Pressure Failure Control

2011-01-21T16:00:49Z

The list goes on. If you develop something that requires electric actuator to the valve, check the characteristics of the electromagnetic valve.

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Oil circulation

2010-09-08T11:41:59Z

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Circulation oils

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Leaving the compressor, the discharge line should be led down where possible. It will allow to avoid accumulation of oil or pressure liquid refrigerant in the compressor during idle periods. Where capacitor above the compressor, you must have a sufficient rate in the line from the compressor, or oil separator to ensure that oil is carried forward. The check valve can be installed as a guarantee to prevent oil flowing back. Horizontal lines should downward slope in the direction of flow. Traces of oil, which come in the condenser will settle on the surface cooling and drop to the bottom in the form of liquid or dissolve in the condensed refrigerant. In any case, these two fluids will then pass to the expansion valve and the evaporator. Here, the refrigerant vapour changes, but most of the oil will remain as a liquid, containing dissolved refrigerant. Slight traces of oil, as low vapour pressure with suction gas. It is necessary to limit the accumulation of liquid oil in the evaporator, as it will accumulate quickly, reducing heat transfer and violations.

With ammonia, oil falls to the bottom and does not go into solution with the refrigerant.{loadposition banner2} Ammonia condensers, receivers and flooded evaporators can be distinguished by the provision of oil drain pots and connections in the bottom point. Automatic drainage and oil return will depend on the different densities of small and very rarely installed. Removal of oil from the collection of pots and low point drains periodic manual function and as part of regular maintenance. Some of the ammonia systems are designed for oil return through the maintenance of the gas velocity, for example, direct and a liquid expansion overfeed evaporators. Halocarbons all fairly mixed with oil to prevent the possibility of separate drainage and in any case they are rarely used with flooded evaporators.

The most common way of getting oil from the evaporator, compressor, to keep it in motion, providing a continuous velocity of the fluid in all parts of the schema using direct expansion evaporator. This dynamic method of treatment is a decisive factor in the design of almost all freon evaporators.

The critical section of the chain, where no liquid refrigerant to help move oil, i.e. evaporator and suction back to the compressor. Suction pipe must have a slope down compressor, but do not allow liquids to flooding of the compressor. Minimum gas velocities of about 3.5 m/s required. Where the compressor, evaporator below vertical sections provide sufficient speed analyser, as a rule, not less than 7 m/s you want to drop of oil will be back dry gaseous refrigerant in the compressor. On Fig. 11.1 shows piping arrangements that can be used to transport oil.

In some situations, liquid separator (see Chapter 9) is used to prevent large volumes of oil and/or refrigerant from suddenly compressor at start or immediately after thawing, for example. This system behavior is called ingress of liquid refrigerant compressors invariably designed to handle this to some extent.

With some small refrigeration circuits that can operate on the reduction of gas consumption for capacity controlled, it may not be possible to maintain a minimum rate for oil transportation back to the compressor, and it will settle in the chain. This is especially true with variable speed compressors, where many low speed allowed. Reversing the refrigerant type circuits (i.e. cooling/heat pumps)are another example. Measures should be aimed at improving or reverse gas flow periodically move, this oil....

Oil separators

2010-09-08T11:41:39Z

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Oil separators

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During the compression stroke piston machine, the gas becomes hotter and a little oil on the wall of the cylinder will be held, with the discharge of gas. Some oil carry-over will occur with all types of compressors lubrication, and in small stand-alone systems, he quickly finds his way back to the compressor. Start after a long period of inactivity can lead to a large number remainder of the oil within a short period of time in connection with the foam at the mouth. Larger and more complex systems with remote evaporators oil it is desirable to match the separation of oil in the discharge line in order to reduce rolling into the system (see Fig. 5.5).

Hot gas injection spiral of falling lose most of the oil on the surface under the action of centrifugal force. Some 95-98% of oil are accumulated can be separated from the hot gas and sink to the bottom and can be returned to the crankcase. The oil return line is controlled by a float valve, or he can talk. In any case, the account device must be backed up by a solenoid valve to provide tight shut-off at a stop of the compressor, because as a separator at discharge pressure and oil in the crankcase of the compressor suction pressure.

Completion of the work under high pressure in the gas separator, it will be cool, and some will condense into a liquid for the dilution of the oil remaining in the bottom.{loadposition banner2} When the compressor restarts, this diluted oil will pass into the sump. In order to limit this dilution, heater, usually installed in the base of the separator in large installations.

Oil-injected screw compressors invariably have oil separators and these handles continuous oil carry-over from the fuel process. They often built into the compressor Assembly, especially with semi-hermetic air conditioning types. Recycling ago injection ports and bearings constantly. For low-temperature screw compressors oil is commonly cooled in the recycling process. For installations that can be very sensitive to oil accumulations, in two phases : oil separator can be installed and up to 99.7% of the accumulated oil can be removed. However, effective separation process, small quantities of oil will be carried forward in the design of the system must accommodate oil circulation.....

Moisture and air contamination

2010-09-08T11:41:21Z

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Moisture and air pollution

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In the past, the main problem of humidity of ice formation in critical areas such as expansion valves, but it also caused corrosion and damage to the motor windings. Lubricants play an important role in determining the impact of pollutants on the cooling system. Oil should remain as clean as it is, when he entered the compressor (unlike a car engine, that quickly contaminated by fuel, water, atmospheric carbon dioxide and dust). The state of the oil in the compressor, so the direct link to the physical and chemical purity of the system. Lubricating oil should be stored in tightly closed containers, excluding atmospheric moisture. Oil from ammonia systems is not re-used, if it can be properly filtered and stored in a dry place. Overheating or short circuit occurred in the coil hermetic or semi-hermetic reciprocating compressor engine will produce pollutants, including halogen acids. Eye goggles and rubber gloves when working with such a suspect oil. If it is shown that the acid, the oil must be removed and carefully disposed of and the system is thoroughly cleaned.

Moisture reacts with POE lubricants and this leads to the emergence of organic acids.{loadposition banner2} They are much weaker than halogen acids and should be considered when the level of acidity is measured using an acid test kit. However, any failure of POE is undesirable and it is recommended that the level of moisture content below 50 ppm in POE systems. Because the checkpoint have a high affinity moisture is very important to preserve the effects of oil atmospheric air to an absolute minimum. Moisture can not be fully resolved with the help of vacuum procedures and, therefore, the corresponding filter driers are always recommended. Figure 5.4 shows a typical expected moisture content of deviations in the process of installation and commssioning. Compressor, which was previously charged with PoE was due primarily to complete devices, such as the compressor is installed on the territory of the observing correct and evacuation procedures seals and, finally, with the subsequent control of moisture content is reduced to 50 ppm by land.

Proper evacuation will remove the contents of the air to the minimum possible. Oxidation and other high-temperature chemical reactions are more likely to cause damage in the presence of moisture. When the system changes from CFC or HCFC, HFC refrigerants, oil, as a rule, should be amended to POE. Original equipment manufacturers and the recommendations should seek to convert.....

Requirements and characteristics

2010-09-08T11:41:02Z

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Requirements and specifications

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Oil properties, consider the behavior of the system, namely the return of oil from the compressor system, and its influence on the process of heat transfer in the evaporator and condenser. Part of the compressor designer's task is to provide lubrication for fitness, compressors and systems.

I n the working environment of lubricant is always a mixture of oil and refrigerant and therefore in its composition and properties are regulated solubility characteristics of pressure and temperature dependent. CFCs, HCFCs and ammonia refrigerant/mineral oil combinations, backed by years of experience; their properties are well known. Compressor designers used a combination of viscosity and excellent boundary lubrication (slippery) properties of chlorine-containing refrigerants to good effect in the design of the moving parts. With the advent of HFC refrigerants, it is necessary to move from mineral oils, synthetic oils, in order to ensure compatibility with the refrigerant and, consequently, adequate oil return from the system.{loadposition banner2} POE oils were selected for most applications, depending on their properties, the cost and availability. The CPT made of organic acids and alcohols, which together produce esters and water. The formulation of ether is determined acid structure. As its name implies, POE is a mixture of esters derived from a mixture of acids.

The behavior of lubricating oil in the refrigerant circuit and physical interaction with the refrigerant itself are the dominant factors in the development of schemes in General and evaporators, in particular. It should be noted that the solubility of ammonia in most lubricants is very low.

The degree of solubility of refrigerant in oil is desirable because the viscosity of the mixture in the evaporator reduced, allowing it to become more mobile, and that AIDS transport back to the compressor. The most important property for compressor operation is the viscosity solution for lubrication of bearings. As the low pressure varies with temperature in the evaporator, the refrigerant concentration changes, and this in turn affects the viscosity. Typical behavior for Halocarbon refrigerants is shown in Fig. 5.2 .

At low pressure of 1 bar, relevant evaporation, say, from -40C a small amount of refrigerant dissolved and it has little effect on the viscosity. Higher evaporation pressure, say, 6 bar, corresponding to 10C oil absorbs 10% of the refrigerant, which effectively reduces the viscosity of that half of the base oil and the carrying capacity is reduced. These effects are studied using the viscosity / temperature/pressure chart, the format of which is shown in Fig. 5.3. This scheme is just intended to illustrate the General form of the characteristic and is based on the refrigerant R134a and PoE. Specific data can be found in the ASHRAE Refrigeration links.

When liquid lubricants and liquid refrigerants are mixed together and helped to solve, homogeneous mixtures can be generated. In this case, the pair, as they say, is mixed with water prevailing pressure and temperature. In addition, two separate steps, forms, one of which is oil solution of other refrigerant-rich solution. In most cases heavier refrigerant-rich solution is below. This will cause problems on systems where the compressor in a cool place condenses and refrigerant in the Carter during shutdown. "When you start, oil pump, as a rule, would make a very low viscosity refrigerant-rich mixture. The crankcase heaters and pumping cycles are used to avoid this problem. This is not the case, ammonia, and is, as a rule, are not mixed with lubricants, except for small quantities and oil tend to accumulate at the bottom of evaporators, where it can be removed.

The desired properties for lubrication can be summarized as follows. Many characteristics that affect the refrigerant and therefore oil property cannot be considered in isolation.

Adequate lubrication viscosity at high temperatures and high pressures in bearings and quite useful for sliding contacts.
Resistance to chemical reaction or decay occurs in the conditions which will be faced. As a rule, high temperature and pressure in the discharge of compression. Oxidation resistance is measured point of ignition.
The lubricant must be moisture and contamination-free as possible.
Lubrication must be compatible with the materials used in the system. Special points of non-metallic flexible rubber and plastic parts, such as seals. The boiler can be used with ammonia.
Viscosity of liquid at low temperatures, the parties must be low enough for adequate oil return.
Solids should not be precipitated. Mineral oil may sometimes wax residue at low temperature; identified with the floc the time of testing.
High electric resistance it is necessary for enclosed motors.
Foaming characteristics should be considered.
Availability, at an acceptable cost is significant.

To comment on the above, it should be noted that the characteristics of the grease in a real working environment can be tested only on real experience and/or tests. This is a tribute to the engineering effort compressor builders and installers systems that the transition to HFC refrigerants and polyester oils was very smooth and hassle-free process. Chemical stability shall be adequate in the presence of moisture and air, although the aim is always to exclude these contaminants from the system. Traces however, currently in practice, and this is discussed below. Excessive foaming not desirable when it is due to the rapid release of refrigerant in the compressor starts and crankcase pressure reduces the fact that it tends to lead to loss of oil in the system. Some foaming during normal operation and can help the distribution of oil in the compressor and reduce noise.....

Oil in refrigerant circuits

2010-09-08T11:40:34Z

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Oil in the refrigeration circuit

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The main objective of the oil for lubrication of the compressor; in addition, sealing and cooling for the oil-filled types. Oil specified by the manufacturer of the compressor should be used whenever possible. Various mineral and synthetic base oils such as Rice. 5.1 gives some indication of their suitability for this type of refrigerant. A blank indicates that the type of oil, as a rule, are not suitable. It should be emphasized that oil types shown, each of which is a family of products that can be used to reduce viscosity, and you must use the class or family of products. For example, polyester (POE) oils are specified as suitable for hydrocarbons, but a higher viscosity class, as a rule, demand for hydrocarbon raw materials in comparison with that used for HFCs. In addition, specific additives to improve lubricants or act as inhibitors may be present in branded products, and, therefore, compressor manufacturer should be consulted in regard to the modification of oil for a particular compressor.

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