CLIAMS:
1. An oil separator for separating and recovering oil from a refrigerant gas containing oil, said oil separator comprising:
a housing;
a separator of a predetermined thickness, dividing the housing in upper section and lower section, said upper section has an inlet for compressed gas containing oil formed in the upper section of the housing, said upper section reduces velocity of the compressed gas containing oil for effecting primary oil separation and said separator comprises a demister for increasing contact surface area for carrying out secondary oil separation; and
an outlet of compressed gas extending from top of the housing below the separator to the lower section of the housing;
wherein compressed gas travels towards gravity direction from upper section to bottom sections through the separator with minimum pressure drop.

2. The oil separator as claimed in claim 1 wherein a filter pocket is adapted on the outlet for compressed gas.

3. The oil separator as claimed in claim 1 wherein the upper section of the housing comprises at least one deflector plate for reducing the velocity of the compressed gas.

4. The oil separator as claimed in claim 1, wherein the inlet port is adapted tangential to the upper section for creating cyclic flow to reduce the velocity of the compressed gas.

5. The oil separator as claimed in claim 1, wherein the lower section comprises an oil reservoir having at least one outlet for oil.

6. The oil separator as claimed in claim 1 or 5, wherein the lower section comprises an oil guard plate separating the outlet of compressed gas from the oil reservoir for avoiding oil turbulence.

7. The oil separator as claimed in claim 1, wherein the predetermined thickness of the separator is 1/3th to1/4th of height of the oil separator.

8. The oil separator as claimed in claim 1, wherein the upper section is 1/5th to 1/4th of height of the oil separator.

9. The oil separator as claimed in claim 1, wherein the lower section is 2/5th to 1/2th of height of the oil separator.

10. The oil separator as claimed in claim 1, wherein the demister comprises a plurality of demister pads.
,TagSPECI:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]

OIL SEPARATOR;

BLUE STAR LIMITED A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS KASTURI BUILDINGS, MOHAN T. ADVANI CHOWK, JAMSHETJI TATA ROAD, MUMBAI – 400 020, MAHARASHTRA, INDIA

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INVENTION
The present invention relates to oil separators used for separation of oil from the mixture of oil and gas in the form of mist. In particular, this invention relates to the oil separator used in refrigeration systems including single or multi air conditioners.

BACKGROUND OF THE INVENTION
Generally, refrigeration systems are used to cool or heat the interiors of houses, restaurants or office buildings. The refrigerant system comprises a compressor for compressing the refrigerant. The compressor is one of moving parts of the refrigerant system. For this reason, a large amount of oil is injected into the compressor to prevent wear of parts of the compressor due to friction between the parts of the compressor, partially cool heat generated when the refrigerant is compressed in the compressor, disperse fatigue of metal parts of the compressor, and prevent leakage of the compressed refrigerant through formation of oil film at a sealing line of the compressor. When the refrigerant is compressed in the compressor, however, the oil injected into the compressor is mixed with the refrigerant. As a result, the compressed refrigerant is discharged out of the compressor together with the oil injected into the compressor. If refrigerant containing oil flows through the refrigerant flow channel, the oil may be accumulated in some parts of the refrigerant flow channel, and therefore, the refrigerant cannot smoothly flow. Furthermore, the amount of oil in the compressor is decreased, and therefore, performance of the compressor is deteriorated thereby affecting the life of the compressor. Further, it is observed that oil carrying maximum takes place in variable speed or capacity compressors than that of in the conventional compressors. Therefore, an oil separator for separating and recovering oil from the compressed gas is installed in the refrigeration system or in the compressor.
In traditional oil separation methods, it includes introducing of compressed gas so as to flow along the circumferential direction from a side surface of a cylindrical housing, and there is produced rotating flow of the compressed gas along an inner wall surface of the housing. By the resulting centrifugation effect, the lubricating liquid component is gathered on the inner wall surface of the housing for separation from the gaseous component. However, the separation of the lubricating liquid is less. Further, demister are disposed in the path of the gas However, it results in pressure drop.
Moreover, in the oil separator which utilizes the centrifugation effect, it is necessary to enlarge the vertical length of the housing in order to enhance the separation efficiency. As a result, not only the cost of the lubricating liquid separator itself increases, but also there arises the problem of space.

SUMMARY OF THE INVETION
Accordingly, the present invention provides an oil separator for separating and recovering oil from compressed gas containing oil, said oil separator comprising a housing, a separator of a predetermined thickness which divides the housing in upper section and lower section. An inlet is formed in the said upper section of the housing for compressed gas containing oil and an outlet for compressed gas extends from top of the housing below the separator to the lower section of the housing. The upper section reduces velocity of the compressed refrigerant gas containing oil for effecting primary oil separation and the separator comprises a plurality of demister pads for increasing contact surface area for carrying out secondary oil separation. According to the present invention, compressed gas travels towards gravity direction from upper section to bottom sections through the separator with minimum pressure drop.
According to an embodiment of the present invention, a filter pocket is adapted on the outlet of compressed gas.
According to the present invention, the upper section of the housing comprises at least one deflector plate for reducing the velocity of the compressed gas. Alternatively, the inlet port can be adapted tangential to the upper section for creating cyclic flow to reduce the velocity of the compressed gas.
According to an embodiment of the present invention, the lower section comprises an oil reservoir and an oil guard plate for separating outlet of compressed gas from the oil reservoir for avoiding oil turbulence.
According to the present invention, the predetermined thickness of the separator is 1/3th to1/4th of height of the oil separator.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS:
The features, aspects and other advantages of the present invention will become better understood when the following description is read with reference to the accompanying drawings, wherein:
Figure 1 shows a basic refrigeration system with an oil separator of the present invention;
Figure 2 shows a cross sectional view of an oil separator according to an embodiment of the present invention; and
Figure 3 shows a partial sectional perspective view of the oil separator as shown in Figure 2.

DETAILED DESCRIPTION OF THE INVENTION WITH THE ACCOPANYING DRAWINGS:
In general, the present invention provides an oil separator for separating and recovering oil from a refrigerant gas containing oil principally comprising a separator that divides housing of the oil separator in upper section and lower section. The oil separation takes in two place wherein primary oil separation takes place in upper section due to reduce in velocity of compressed gas in the upper section and the secondary oil separation takes place on demister provided in the separator. The oil separator is configured to separate oil from the refrigerant with minimum pressure drop and maximum oil separation.
For the purposes of disclosure, a refrigeration or chiller system (100) is shown in Figure 1 including two compressors (10) connected on its high pressure outlet side to a condenser (20) through an oil separator (50) embodying the invention to be described herein below. Typically, it is known that the compressor (10) particularly variable speed compressors requires a large amount of lubricating and cooling oil in operation, and such oil is entrained in the hot compressed refrigerant during compressing process forming an oil-gas mixture which is then discharged on the compressor high side through conduit (12) to the oil separator (50). The compressors (10) are in fluid communication with the oil separator (50) through an oil return conduit (15) from oil separator (50) through which oil is returned to and maintained in the compressor (10) at a preselected level by a conventional oil level regulator (not shown) or the like. The condenser (20) is connected with the oil separator (50) through a refrigerant gas conduit (14) from the oil separator (50). The hot compressed refrigerant gas (and a minor, acceptable amount of entrained oil) passes through conduit (14) to condenser (20) where it is cooled and condensed into a high pressure liquid phase. The condenser (20) connects through conduit (16) to an evaporator (40) or like heat exchanger through an expansion valve (30). Refrigerant liquid is caused to expand and absorb heat to provide refrigeration by exchanging heat between the expanding liquid refrigerant and a chilled liquid in the chiller system whereas in a typical commercial refrigeration system the expanding refrigerant absorbs heat from a circulating airflow that cools a space or product zone. In either case the refrigerant liquid absorbs latent heat and changes to a gaseous phase, and is returned to the compressor (20) on its low side through suction conduit (18) to complete the refrigeration cycle.
Referring Figures 2 and 3 shows the oil separator (50) according to preferred embodiment of the present invention for separating oil from refrigerant gas containing oil or mist of the oil and refrigerant. The oil separator (50) comprises a vertical housing (52) of generally cylindrical shape. A separator (54) divides the housing (52) in upper section (52A) and lower section (52B).
According to the present invention, the separator (54) comprises a demister (55) adapted between the two screen plates (54A, 54B). The separator has a substantial-thickness that provides substantial contact surface for incoming oil-laden refrigerant and being arranged to accumulate and recover oil in liquid form without re-entrainment back into the refrigerant discharge vapor.
According to the present invention, the pressure drop across the oil separator depends upon the thickness of the separator and the type of the demister used. Advantageously, the demister is formed by plurality of demister pads to increase contact surface. Accordingly, the preferable thickness of the separator is 1/3th to1/4th of height of the oil separator. According the upper section is 1/5th to 1/4th of height of the oil separator and the lower section is 2/5th to 1/2th of height of the oil separator
An inlet port (51) is formed near top of the upper section (52A) for compressed gas containing oil. The upper section (52A) is formed to reduce velocity of the compressed gas containing oil for effecting primary oil separation and demister plate of the separator carries out secondary oil separation.
As shown in Figure 1 and 2, a refrigerant vapor outlet or an outlet for compressed gas (56) extends from upper section (52A) of the housing (52) below the separator (54) to the lower section of the housing. Preferably, the outlet of compressed gas (56) extends along the central axis from the top of the oil separator (50). Alternatively, the refrigerant vapor outlet can be extended from side of the oil separator. The oil-gas mixture enters the upper section (52A) at a high velocity, velocity of the mixture reduces in the upper section effecting primary oil separation and as the refrigerant vapor outlet (56) is below the separator (54) in the lower section (52B) of the housing (52), the compressed gas moves downward and oil particles formed in the primary separation comes into contact with the demisters (55) provided in the oil separator (50) leading secondary oil separation. Thus, oil particles accumulate on and over the demister (55) and build up in liquid form to drain downwardly by gravity in an oil reservoir (58) provided in the lower section (52B) of the oil separator (50) as well as the compressed gas also forced the separated oil that travels gravity direction from upper section (52A) to lower section (52B) through the separator (54) towards refrigerant vapor outlet (56).
As shown in Figures 2 and 3, the upper section (52A) of the housing (52) comprises a deflector plates (53) for reducing the velocity of the compressed gas according to the preferable embodiment of the invention. Alternatively, the inlet port (51) can be adapted tangential to the upper section of the housing alone or in combination with the deflector plate for creating cyclic flow to reduce the velocity of the compressed gas.
The oil reservoir (58) has at least one outlet for oil. In Figures 2 and 3, the oil reservoir (58) has three oil outlets (58A, 58B,58C). As shown in Figure 2 and 3, an oil guard plate (57) is provided in the lower section (52B) for separating the refrigerant vapour outlet (56) from the oil reservoir (58) for avoiding oil turbulence. Further, a filter pocket (59) is adapted on the refrigerant vapour outlet (56) for ensuring contamination free refrigerant out from the oil separator (50). Advantageously, the filter pocket is a tapered filer pocket.
The oil separator of the present invention is compact and requires less space. Further, the pressure drop across the oil separator is less and also substantial amount of oil recovery about or more than 93% takes place in the oil separator. Furthermore, pressure drop across the oil separator of the present invention is very low and about 1 psi. The oil separator can use in for multiple compressor system ensuring substantially contamination free refrigerant out from oil separator leading less oil make-up required for system due to improved oil separation efficiency which also results in reducing oil recovery cycles of the indoor oil unit in multi air conditioner system. Since major oil is recovered at oil separator itself, risk of oil trapping in installation piping, bends and obstacles of the refrigeration system reduces substantially.

Example 1:
The oil separator of the present invention was tested in a variable refrigerant flow system as shown in Figure 1. The thickness of the separator in the tested oil separator was 1/3rd of the height (150 mm) of the oil separator. The test data is shown as below in Table No. 1. A sight glass was provided on the Oil separator to observe the oil level in the oil separator. Initially, oil level in the oil separator was zero. After start up of the compressor, the time taken (180 sec) for recovery was noted for oil volume of 100 cc level. Oil discharge rate of the compressor was provided by compressor manufactures. By using oil reserving volume and oil discharge rate, the efficiency was calculated. According to the test data, the oil separation ratio was 93% and pressure drop across the separator was 1 psi when the compressor was running at a very high speed wherein possibility of maximum oil carry over is high. In lower speeds, oil recovery percentage observed higher than 93%. For measuring the pressure drop across the oil separator, pressure gauges were connected at inlet and refrigerant vapour outlet of the oil separator for observing pressure drop across the separator. Observed pressure drop was 1 psi.

Table No. 1
A] EFFICIENCY CALCULATION
Oil carryout rate through compressor = 386.7 CC/m
Accordingly, oil carry out volume of the compressor at high speed was 386.7/60*180=1160 cc

Height of oil recovered in oil Reservoir of the Oil separator at High speed of the compressor = 100 mm
Diameter of Oil Reservoir = 117 mm
Accordingly, volume of oil recovered=100*117^2*3.14/4/1000 =1074.6 cc

Oil reserving time till 100 mm height was 180 sec

Then oil separation ratio=1,074.6/1,160= 93%

B] PRESSURE DROP CALCULATION
Gauge pressure inlet of oil separator observed was 420 psig
Gauge pressure outlet of oil separator observed was 419 psig
Accordingly Pressure drop across oil separator = 420-419 = 1 psig

The present invention is in providing oil separator having a separator and outlet of compressed gas below the separator for providing more surface contact area and effective separation oil from the compressed gas with minimum pressure drop. Though a thickness of the separator is mentioned, a person skilled in the art can easily understand that it will not limit the invention to the said thickness as it also depends upon the type of demister used. While the present invention has been described herein with respect to the various exemplary embodiments, it will be apparent to one of the ordinary skill in the art that many modifications, improvements and sub combinations of the various embodiments, adaptations and variations can be made to the invention without departing from the spirit and the scope thereof as claimed in the following claims: