KR20140146598A - Chiller or heat pump with a falling film evaporator and horizontal oil separator - Google Patents

Abstract

The cooling circuit uses a vapor compression cycle and is available for air conditioning, cooling or heat pump purposes. The circuit includes a lubrication compressor, a descent membrane or a hybrid underfill evaporator and a condenser connected to an oil separator vessel remote from the compressor. The oil separator extends generally horizontally. The oil separator vessel is divided into a primary space and a secondary space by a filter pad configured to substantially remove entrained oil droplets of about 5 um or more from the refrigerant entering the oil separator vessel. The primary space is in fluid communication with the outlet of the compressor. The secondary space is in fluid communication with the inlet of the condenser. The circuit has an oil mixed flow discharge of the lubricating oil from the compressor at least about 2 mass percent for the refrigerant flow.

Description

TECHNICAL FIELD [0001] The present invention relates to a cooler or a heat pump having a lower evaporator and a horizontal oil separator,

The present invention includes a descent film evaporator or hybrid descalder film evaporators with lubrication compressors connected to separate oil separators and uses media to provide high cooling capacity (typically greater than about 100 kW) using evaporator compression cycles Cooling and air conditioning apparatus or a heat pump.

From the viewpoint of energy saving and reduction of emission of greenhouse gases, high equipment efficiency and low refrigerant charge are sought. In order to achieve these objectives, improvements have been made to all parts of the device: compressors, variable speed drives, optimized selection of refrigerants, oil separators, heat exchangers and the like. Most compressors require a certain amount of lubrication, which causes a certain amount of oil carry-over from the compressor to the refrigerant circuit. This oil incorporated into the refrigerant circuit must be returned to the compressor by a suitable oil return device in order to avoid other adverse effects such as degrading the performance of the heat exchanger. This is especially true for screw compressors: these machines require a particularly large amount of lubricant to ensure proper sealing of the gas between the rotors and to avoid the need for additional synchronous gears between the rotors do. Therefore, screw compressors require a container, generally referred to as an oil separator, between the compressor outlet and the inlet of the condenser. One challenge associated with cooling machinery and heat pumps is managing the oil in the cooling circuit. This requires careful combination between oil carryover, oil return device and heat exchanger technology.

In addition to separating oil from the exhaust gas, the vessel or oil separator or separator vessel generally has the function of an oil sump to the compressor. Separator vessels or oil separators may be based on several operating principles. The most common ones include:

Impact separation: The two-phase mixture of oil and gas is injected into the wall or end of the vessel to provide a first stage of separation.

- gravity separation: gas mixed with oil is allowed to move horizontally or vertically in the vessel; This allows large droplets of liquid oil to be deflected for sufficient time by gravity acting on the bottom of the vessel.

- Filter Pads Separation: The mixture is pressed to pass through closely spaced and / or finely woven filament mattresses or pads of wires (acting as a filter). In one embodiment, the filter pad will comprise a wire mesh. Depending on the use of such filter manufacturers, the filter pads are usually installed horizontally, so that the gas circulates upward. The filtration level of the filter pads is relatively coarse; Very fine droplets mixed in gas or mist can not be stopped, but droplets can be removed rather than gravity separation.

- Centrifugation: 2 - The phase oil and gas mixture is introduced tangentially to the cylindrical vessel. The swirling motion tends to eject the oil droplets onto the cylinder wall of the vessel, where the droplets combine and fall to the bottom of the vessel. Like gravity separation, centrifugation can remove the largest droplets of oil.

Adhesive Filters: The two-phase mixture of oil and gas forces the cartridge to act as a filter. The filter material is typically glass fiber. Filtration is much finer compared to the filter pads (see above). For example, the coalescing filters substantially prevent droplets with a diameter of 1 탆 or more from passing through the coalescing filter during the operation of the cooling circuit. In a typical embodiment, the coalescing filters

Allows about 1 to 10 PPM of oil droplets entrained in the refrigerant flow to exit the separator.

Several other principles are often implemented in a single splitter. For example, when a coalescing filter is used, they are typically arranged to complement a filter / separator that can incorporate one or more operating principles such as collision, gravity, centrifugation, and / or filter pad separation. In the design of oil separators, the challenge is to find the best compromise between price, size, ease of installation, pressure drop, reliability, and of course the efficiency of separation.

Typical designs of oil separators include:

- Horizontal design with coalescing filters. Figure 1 shows an example of such a well known design. The separation is initiated at the end of the vessel in collision, continues through the gravity separation section used as the oil sump, and is completed by the coalescing filters.

 - vertical cyclone design with a coalescing filter (not shown)

When properly implemented, these designs provide highly efficient oil separation due to the adhesion elements. So far, the coalescing filters have some drawbacks. These are relatively expensive. If the coalescing filters are not properly installed, some of the seals in the seals will not meet the operating specifications. If inspection and filter removal is required, additional flanges or access manholes are required, which increases the risk of refrigerant leakage. In addition, hydraulic safety testing of containers with internal coalescing filters presents the risk of damaging these filters, and has the difficulty of evacuating the containers and drying them properly after testing.

In the case of accidental high fluid flow rates, the performance of the coalescing filters may be lost and may be clogged and / or destroyed under the influence of increased fluid forces. Increased fluid flow is particularly problematic in heat pump applications using high-pressure halogenated refrigerants such as HFC's. Even when used in air conditioning applications, the coalescing filters need to be overdone when using high pressure HFC's such as R-410A or R-507. The use of high temperature heat pumps increases the problems associated with such applications. For such a hot heat pump, the evaporation temperature is generally higher than when using the same machinery and refrigerant in the corresponding air conditioning application due to the high temperature of the water or other medium to be cooled in the evaporator. For high temperature heat pumps, the water leaving the evaporator will typically be at least about 20 ° C and can reach 60 ° C or higher. The resulting high evaporation temperature substantially increases the density and therefore increases the flow rate of the refrigerant even when using relatively low pressure refrigerants such as R-134a or using low pressure refrigerants such as R-245a.

In heat pumps or coolers using compressors such as screw compressors, an oil separator with an extremely simple design that does not include coalescing filters is provided, while providing sufficient oil separation during operation.

With respect to a heat pump or cooler using a screw compressor, the present invention relates to the use of a descent film evaporator or hybrid descale film evaporators as disclosed, for example, in U.S. Patent No. 7,849,710, herein incorporated by reference. These evaporators provide an optimal technical compromise between optimal performance and reduced refrigerant emissions. In addition, the descent film evaporator or hybrid descaler evaporator performance is less sensitive to oil carryover than conventional flooded evaporators, allowing oil separators such as filter pads to be used without sacrificing evaporator performance.

For purposes of the present invention, the filter pads incorporate the following characteristics: droplets having a diameter of about 5 mu m or more are substantially prevented from passing through the filter pads during the operation of the cooling circuit. In one embodiment, the filter pads operate between about 50 to 100 PPM of oil entrained in the refrigerant flow exiting the separator. In another example of a filter pad, the void percentage of the filter pad ranges from about 97 to 99 percent. In another embodiment of the filter pad, the diameters of the filaments and / or wires range from about 0.15 mm to about 0.35 mm.

The present invention relates to a cooling circuit using a vapor compression cycle, which cooling circuit can be used for air conditioning, cooling or heat pump purposes. The circuit includes a lubrication compressor connected to an oil separator vessel remote from the compressor, a descent membrane or a hybrid underfill evaporator and a condenser. The oil separator extends generally horizontally. The oil separator vessel is divided into a primary space and a secondary space by a filter pad configured to substantially remove entrained oil droplets of about 5 mu m or more from the refrigerant entering the oil separator vessel. The primary space is in fluid communication with the outlet of the compressor. The secondary space is in fluid communication with the inlet of the condenser. The circuit has an oil mixed flow discharge from the compressor of at least about 2 mass percent by mass for the refrigerant flow.

The present invention provides an oil separator such as a filter pad, which is less susceptible to oil carryover than conventional flooded evaporators, and without sacrificing evaporator performance, the performance of the submerged membrane evaporator or hybrid submerged membrane evaporator.

1 shows a conventional oil separator.
2 shows a preferred embodiment of the oil separator of the present invention.
3 shows a preferred embodiment of the oil separator of the present invention.
4 shows a preferred embodiment of the oil separator of the present invention.
5 shows a preferred embodiment of the vapor compression apparatus of the present invention.
6 is a view showing a preferred embodiment of the vapor compression apparatus of the present invention.
7 shows a preferred embodiment of the oil separator of the present invention.
8 shows a preferred embodiment of the oil separator of the present invention.

Figure 2 shows a horizontal vessel 1 with a filter pad 2 which is connected to the horizontal vessel 1 in a longitudinal direction by means of two openings: one with an inlet 4 to accommodate the discharge from the compressor, Into a secondary space (5) having an outlet (6) communicating with an inlet of the vehicle space (3) and a condenser (not shown). In a preferred embodiment the inlet 4 receives the compressor discharge and the gas and oil mixture 15 entering the separator vessel 1 provides a collision separation at the end of the vessel 1 in the primary space 3 . In addition, a second filter pad 7 may be provided at or near the end 17 of the vessel 1 in order to limit the re-entrainment of the gas and liquid discharged from the compressor after the gas discharge collides with the end of the vessel .

In this arrangement, as shown in Fig. 2, the oil separated from the gas becomes able to move from the primary space 3 to the secondary space 5. In one embodiment, the filter pads 2 are installed across the entire cross-sectional area of the vessel 1 in the transverse direction relative to the longitudinal direction of the vessel 1. The liquid oil 19 is collected in the lower part of the container 1 and functions as an oil sump. As the filter pad 2 provides a very small resistance to the circulation of the liquid oil 19 between the primary space 3 and the secondary space 5 the level of the liquid oil 19 is essential in the two spaces . Since oil has an opportunity to be disadvantageous from bubbles and bubbles by the filter pads 2 while entering the secondary space 5 from the primary space 3, It is preferable to collect the liquid oil 19 to return to the compressor through the pipe 9. [ With this arrangement, evaporators 12 (see FIG. 5), such as submerged evaporators or hybrid submerged membrane evaporators, can be used for refrigerant flow, that is, about 2 < th > flow sum of refrigerant and lubricant, A circuit with oil-entrainment flow discharge of lubricating oil discharged from a compressor of mass percent or more can be received by the oil separator. In one embodiment, the oil separator is separate from the compressor.

In one arrangement, the filter pads 2 separating the respective primary and secondary spaces 3, 5 are generally planar and arranged vertically, that is perpendicular to the longitudinal axis of the vessel 1, As shown in FIG. In other arrangements, the filter pads 2 may be positioned not perpendicular to the vessel axis, as shown in Fig. This arrangement has the advantage of reducing the velocity of the gas flowing through the filter pad 2. As a result, the container of the present invention may have a smaller vessel diameter than the diameter of the vessel of the conventional configuration, and the gas flow rate through the filter pad 2 in the small diameter vessel of the present invention is larger than that of the filter Will be similar to the working gas flow rate through the pad 2. In one embodiment, the small diameter vessel of the present invention will operate at a gas flow rate through the filter pad 2, which will be less than the gas flow rate of a large conventional vessel. In another embodiment, the filter pads 2 may consist of two or more parts arranged in the shape of "V" as shown in Fig. 4, which is a plan view of the vessel, at an angle to each other. In another embodiment, portions 2a and 2b will have a length that is not equal to each other.

In other arrangements, two oil separation regions or spaces using the same principle can be integrated in a single vessel 1, and each region or space or secondary space 5 can be separated from the primary space 3, And about half the volume of oil. In this arrangement, there is one vessel 1 with two filter pads 2, and there are two possible options for the direction of flow. In one embodiment shown in Fig. 7, one primary space 3, generally located between the middle of the vessel 1 and between the two filter pads 2, and one located at each end of the vessel There is a secondary space 5 of the second embodiment. As shown, one common gas inlet 4 is generally located in the middle of the primary space 3, one outlet 6 is in each of the opposing secondary spaces 5, The spaces (5) are located at each end of the primary space (3). These two outlets 6 are connected to a condenser inlet (not shown). The interconnecting piping between the two outlets can be internal or external to the vessel (1). In another embodiment (see FIG. 8), the flow reverses: there is a primary space located at each end of the vessel 1, the end of the gas inlet 4 extending into each primary space 3 , One common secondary space 5 is located between the opposing primary spaces 3, and a common gas inlet 4 enters the secondary space 5. In this embodiment, the regions of the inlet 4 connected to the compressor outlet are divided into two pipes or two primary spaces, each of which extends into each of the parts (one on each end of the vessel 1). The interconnected conduits or portions of the inlet 4 may be arranged inside or outside the vessel. For example, in FIG. 8, there is one common inlet 4 extending into a bifurcated inner pipe 13 that distributes the gas to each end of the vessel 1.

In the alternative embodiment of Fig. 7, the two outlets 6 may be connected to form a single pipe extending into one condenser inlet. In an alternative arrangement, a condenser (not shown) may have two inlets, one at each end, and each of the two separator outlets 6 is connected to one of the condenser inlets .

Arrangements with two areas or spaces in a common container provide several advantages. As the flow provided to each area or space decreases as it is reduced by the two elements, the required cross-section of the vessel is also reduced. Therefore, despite the additional length, a reduction in diameter will enable the production of low cost containers. An additional advantage is that small diameter vessels will typically produce less noise because the potential for wall resonance in small diameter shells is small. Finally, increasing the length of the vessel does not cause packaging problems due to other device parts unless the length of the evaporator or vessel substantially exceeds the length of the heat exchangers such as the condenser and / or the evaporator.

As the oil separator vessel is arranged horizontally, this arrangement can be easily packaged with horizontal shell and tube heat exchangers, and horizontal screw compressor drive lines. In a possible arrangement as shown in FIG. 5, the discharge of the compressor 9 is directed downward to the separator vessel 1. In another embodiment, as shown in Figure 6, the effluent of the compressor 9 will be directed from one side of the compressor 9 to the oil separator vessel 1. In another example, the compressor discharge will be directed in the direction to the oil separator vessel (not shown) between the downward and lateral directions of the compressor. In this arrangement, the compressor drive line may be installed at least partially above the oil separator vessel. As shown in FIG. 5, the evaporator 12 is disposed over the condenser 11 and is arranged near the compressor drive line and the separator vessel. In another embodiment (not shown), the evaporator 12 and the condenser 11 may be located in different arrangements with respect to each other and / or with respect to the compressor drive line and the oil separator vessel. In another arrangement, the compressor suction is arranged in a vertical manner such that the compressor 9 is installed at the top of the evaporator 12 so that the compressor discharge from one side of the compressor is directed to the oil separator vessel 1, . In another embodiment (not shown), the compressor suction may extend from the side to the exterior, or in other embodiments, the compressor suction may extend between the vertical direction and the lateral direction relative to the oil separator vessel 1. In this arrangement, the compressor (9) may be installed at least partially above the evaporator (12). As shown in FIG. 6, the oil separator vessel 1 is located outside the compressor 9 in the lateral direction and at the top of the condenser 11. In other embodiments, different arrangements between the compressor, the oil separator vessel, the condenser and the evaporator will be used.

This use of filter pads is particularly preferred when using heat pumps using halogenated refrigerants of HFC's or HFO's and is particularly preferred when the evaporation temperature is significantly greater than the evaporator temperature associated with the air conditioning application (e.g., 5 ° C) . For such heat pumps, when using HFC refrigerant R-134a or possible equivalents, the evaporation temperature may rise from 30 ° C to about 40 ° C and may rise to a high temperature associated with low pressure refrigerants such as R-245fa .

In another embodiment, the refrigerants will include hydrocarbons such as R-290 or R-1270.

Claims (16)

A cooling circuit that is usable for air conditioning, cooling, or heat pump purposes and that utilizes a vapor compression cycle,
A lubricating compressor connected to a separate oil separator vessel, a descending membrane or a hybrid descending membrane evaporator and a condenser, said oil separator extending generally horizontally, said oil separator vessel having a diameter of at least about 5 microns The primary space being fluidly connected to the outlet of the compressor by a filter pad configured to substantially remove entrained oil droplets, the primary space being in fluid communication with an outlet of the compressor, Wherein the circuit has an oil mixed flow discharge from the compressor of at least about 2 weight percent for refrigerant flow. 2. The cooling circuit of claim 1 wherein the bottom of the oil separator vessel is used as an oil sump and the oil sump is in fluid communication with the oil supply orifices of the compressor. 2. The compressor of claim 1, wherein the compressor has a generally downwardly directed discharge port and an intake port for introducing from the side of the compressor, the compressor drive line being located at least partially above the oil separator, Wherein the cooling circuit is located above the condenser. The compressor of claim 1, wherein the compressor has a downwardly directed inlet and an outlet extending from a side of the compressor, the compressor being located at least partially above the evaporator, the oil separator being located at least partially above the condenser Features a cooling circuit. 2. The cooling circuit of claim 1, wherein the inlet of the oil evaporator is a branch, and the oil separator vessel is divided into three spaces by two filter pads. 6. The cooling circuit of claim 5, wherein the cooling flow branches. 6. The cooling circuit of claim 5, wherein the three spaces include two secondary spaces that are not adjacent to each other. 2. The cooling circuit of claim 1, wherein the filter pads are positioned perpendicular to the longitudinal axis of the oil separator vessel. 9. The cooling circuit of claim 8, wherein the filter pad comprises a second filter pad located at approximately mid-length of the longitudinal axis of the oil separator vessel and provided at one end of the oil separator vessel. 2. The cooling circuit of claim 1, wherein the filter pads are positioned not perpendicular to the longitudinal axis of the oil separator vessel. 11. The cooling circuit of claim 10, wherein the filter pads are comprised of two or more portions arranged at an angle relative to each other. 12. The cooling circuit of claim 11, wherein the two or more portions are of unequal length. 2. The cooling circuit of claim 1, wherein the filter pad allows about 50 to about 100 PPM of oil entrained in the refrigerant to flow from the oil separator vessel. The cooling circuit according to claim 1, which is used as a heat pump and uses a halogenated fluid as a refrigerant. 15. The cooling circuit of claim 14, wherein the halogenated fluid is HFC or HFO as a refrigerant. The cooling circuit according to claim 1, wherein the refrigerant is a hydrocarbon.

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