ES2613413T3 - Cooling distributor for a heat exchanger - Google Patents

Abstract

An evaporator (22) for a vapor compression circuit and comprising a distributor (12), the distributor (12) comprising: an elongated body (50A, 50B) that can be placed inside the evaporator (22) adjacent to a side wall (42) of the same; an inlet portion (56A) that can be placed near an inlet port (38) of the evaporator (22) to receive a flow of refrigerant; first and second distal ends (58A, 58B) extending along a length of the evaporator (22); discharge holes (60A, 60B) positioned along a length of the elongated body (50A, 50B); and a channel (49) having a cross-sectional area extending from the first distal end (58A) to the second distal end (58B), where the channel (49) is defined by the elongated body (50A, 50B) and the side wall (42) of the evaporator (22), characterized in that the elongated body (50A, 50B) comprises: first and second side surfaces to include the discharge holes (60A, 60B); a lower edge (52A, 52B) disposed along each side surface to contact the side wall (42) of the evaporator (22); and an upper edge along which the first and second side surfaces are joined, and where the discharge holes (60A, 60B) comprise elongated openings, of decreasing section, having an increasing area extending from near the inlet portion (56A) to near the first and second distal ends (58A, 58B), respectively, where the discharge holes (60A, 60B) are configured to be bounded by the lower edge (52A, 52B) of the elongated body and the side wall (42) of the evaporator (22).

Description

DESCRIPTION

Refrigeration distributor for a heat exchanger 5 BACKGROUND

Typical refrigeration and air conditioning systems depend on steam compression cycles to transfer heat from one place to another in order to cool or heat an enclosed space. Such steam compression cycles comprise a compressor, a condenser, an expansion device and an evaporator connected to form a closed cycle circuit. In "chiller" systems, the steam compression circuit is used to facilitate the cooling of multiple spaces within a building. Each component of the system is connected by a pipe section that conducts a working fluid, such as a cooling coolant, through a circuit. The compressor controls the flow of cooling refrigerant through the circuit to adjust the amount of temperature control that takes place in the space. The condenser and evaporator comprise heat exchangers 15 to add and subtract heat from the cooling refrigerant. The compressors depend on mechanical means, such as double screws, alternative or spiral pistons, to compress and expel the refrigerant at a higher pressure to push the fluid through the system. From the compressor, the heated and pressurized refrigerant is directed to the condenser where the refrigerant cools and condenses before reaching the expansion device. The expansion device converts the refrigerant into biphasic refrigerant comprising both liquid and gaseous components. The evaporator then vaporizes the cooled refrigerant before it is returned to the compressor to continue the steam compression process.

In cooling systems, the evaporator is used to service the "cooler" heat exchanger that circulates a refrigerant fluid such as a refrigerant, or water, to cool the plurality of spaces within the building. Often, the evaporator is of a shell and tube construction to facilitate the large flow rates necessary for the cooling systems. In such a construction, the cooling refrigerant flows through the housing to interact with a bundle of heat exchange tubes. The heat exchange tubes circulate the refrigerant fluid from the refrigerator heat exchanger through the housing whereby the cooling refrigerant extracts heat from the refrigerant fluid to supply refrigerant fluid at a lower temperature to the refrigerator heat exchanger 30. In this way, the efficiency of the cooler and the cooling systems are affected by the exchange of heat between the two-phase refrigerant that enters the housing and the cooling fluid entering the tubes.

A particular problem related to vapor exchange evaporators arises from the biphasic nature of the refrigerant flowing through the heat exchange tubes. Typically, the biphasic refrigerant enters the housing through a single inlet located about half a width of the housing. As the gaseous and liquid refrigerant enters the housing, the liquid refrigerant sits in a pool at the bottom of the housing, while the gaseous refrigerant rises through the liquid refrigerant until it causes a cavity or bubble in the liquid pool . As such, a vacuum is created that prevents the liquid refrigerant from exchanging heat with the heat exchange tubes, thereby interfering with the vaporization process and the efficiency of the evaporator.

Therefore, refrigerant distributors are used to disperse the two-phase refrigerant through the housing so that the liquid refrigerant reaches a greater surface area of the heat exchange tubes. In addition, having the gas refrigerant dispersed uniformly within the housing encourages convection boiling 45 in the liquid pool from the tubes. However, difficulties arise in implementing and manufacturing conventional distributors. For example, distributors often produce a large pressure coffee through the distributor, which reduces the pressure available to circulate the refrigerant through the steam compression circuit. Such pressure coffees are particularly problematic for steam compression circuits that use economizers. In addition, such distributors often comprise intricate assemblies that add 50 production time and cost to the manufacture of the evaporator. Therefore, there is a need for an improved distributor that overcomes these and other problems.

JP2002-81699A describes an evaporator having the characteristics of the preamble of claim 1.

55

SUMMARY

In accordance with the invention, an evaporator is provided as set forth in claim 1.

Also according to the present invention, there is provided a method for distributing biphasic refrigerant as set forth in claim 5.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a steam compression system that includes an evaporator having a distributor of the present invention.

Fig. 2 shows a schematic front view of a shell and tube heat exchanger that has a distributor of the present invention.

Fig. 3 shows a perspective sectional view of an evaporator having a distributor of the present invention.

Fig. 4 shows a front view of a first embodiment of a distributor of the present invention in which the refrigerant is released along discharge holes that have an increasing cross-sectional area along a length of the distributor.

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Fig. 5 shows a front view of an alternative distributor that is outside the scope of claim 1, in which the refrigerant is released along successive discharge orifices having increasing heights.

Fig. 6 shows a front view of another alternative distributor that is outside the scope of claim 1, 20 in which the refrigerant is released along successive discharge holes having increasing widths.

DETAILED DESCRIPTION

Fig. 1 shows a diagram of the steam compression system (10) that includes the distributor (12) of the present invention. The steam compression system (10) includes the discharge pipe (14A), the suction pipe (14B), the condenser pipe (14C), the evaporator pipe (14D), the compressor (16), the condenser (18), the expansion device (20) and the evaporator (22): The compressor (16), the condenser (18), the expansion device (20) and the evaporator (22) are connected in a series circuit which uses a conduit that includes the compressor discharge pipe (14A), the compressor suction pipe (14B), the condenser pipe (14C) 30 and the evaporator pipe (14D). The steam compression system (10) also includes other components such as the economizer (24) and the oil distribution system (26). In one embodiment, the steam compression system (10) comprises a water-cooled "cooler" system that is used to provide cooling to a plurality of spaces, such as within a building. The condenser (18) and the evaporator (22) comprise heat exchangers in which cooling coolant is circulated to exchange heat with fluids 35 traveling through bundles of tubes (28) and (30), respectively. The condenser (18) includes manifolds (32A) and (32B) that conduct water from a cooling tower through the tube bundle (28). The water tower cools the water used to transfer heat from the cooling system. The evaporator (22) also includes manifolds (34A) and (34B) that conduct a refrigerant fluid, such as water, refrigerant or a mixture, from a "cooler" heat exchanger through the tube bundle (30). The refrigerator heat exchanger serves one or more heat exchangers used to cool the plurality of spaces.

In the embodiment shown, the steam compression system (10) comprises the rotary screw compressor (16) that compresses a refrigerant, such as R-122 or R-134a, to provide high pressure heated refrigerant to the condenser (18) through the discharge line (14A). In other embodiments, the compressor (16) includes other mechanical means for compressing a working fluid, such as alternative pistons or orbiting spirals. For any mechanical compression means, the compressor (16) is provided with an oil source from the oil distribution system (26) to provide cooling and lubrication to the compressor (16). The oil is mixed with the refrigerant inside the compressor (16) and both are supplied to the condenser (18) through the discharge line (14A). The oil is filtered from the refrigerant inside the condenser (18) through an oil separator 50 (36) that collects and returns the oil to the compressor (16) with the distribution system (26). Using cooling water from the cooling tower provided through the manifold (32B), the refrigerant cools and condenses into a saturated liquid that has a slightly lower temperature at a high pressure inside the condenser (18), rejecting the heat to water inside the tube bundle (28).

55 From the condenser (18), the refrigerant is conducted through the condenser pipe (14C) to the expansion device (20) whereby the refrigerant undergoes an instant evaporation process at reduced pressure and temperature and is converted into a biphasic refrigerant comprising liquid and gas phase refrigerant. The gaseous refrigerant is vented back to the compressor (16), such as through the economizer (24). Under the pressure of the compressor (16), the two-phase refrigerant continues through the evaporator pipe (14D) to 60 the evaporator (22) in the inlet port (38). In order to improve the efficiency of the steam compression system (10), particularly the heat transfer efficiency of the evaporator (22), the distributor (12) is provided in the evaporator (22). The distributor (12) is placed inside the evaporator (22) to receive the

two-phase refrigerant produced by the expansion device (20). The distributor (12) prevents the accumulation of refrigerant in the vapor phase near the inlet hole (38) so that more surface area of the tube bundle (30) is available to contact the liquid phase refrigerant by increasing the heat transfer between the cooling refrigerant and the cooling fluid from the manifold (34B). The relative warmth of the refrigerant fluid 5 from the "cooler" heat exchanger provided by the manifold (34B) vaporizes the cooling refrigerant in a saturated vapor phase refrigerant. Under the suction of the compressor (16), the refrigerant leaves the evaporator (22) through the outlet orifice 40 and returns to the compressor (16) through the suction pipe (14B). As such, the steam compression system (10) operates using perfectly known thermodynamic principles to transfer heat from the evaporator (22) to the condenser (18)

10

Fig. 2 shows a schematic front view of the shell and tube evaporator (22) that the distributor (12) has in accordance with the present invention. The evaporator (22) also includes the tube bundle (30), the manifolds (34A) and (34B), the inlet hole (38), the outlet hole (40) and the housing (42). The housing (42) comprises a flooded type evaporator in which a cylindrical body wraps the tube bundle (30) and a pool of liquid refrigerant. The sides of the housing (42) are covered by manifolds (34A) and (34B) to form a pressure vessel within which the refrigerant flows to the flood housing (42) and substantially submerges the tube bundle (30) into the liquid coolant pool. The tubes of the tube bundle (30) extend through the housing (42) between the manifolds (34A) and (34B). The inlet opening (38) is placed near a lower part of the housing (42) and the outlet opening (40) is placed near an upper part of the housing (42). In the illustrated embodiment, the distributor (12) is placed at the bottom of the housing (42) opposite the inlet hole (38).

The refrigerant that flows through the steam compression system (10) is partially vaporized or throttled in the expansion device (20) (fig. 1) and directed into the evaporator (22) through the inlet port (38) ) as a two-phase refrigerant, indicated by solid arrows in fig. 2. Simultaneously, the heated refrigerant from the refrigerator heat exchanger is circulated through the tube bundle (30) using the manifold (34B), as indicated by the arrows outlined in fig. 2. The heated refrigerant enters some of the tubes through the inlet (44) in the manifold (34B), flows through the tube bundle (30) and into the manifold (34A) so that the heated refrigerant gives the turn and is directed back to the manifold (34B) through 30 other tubes to exit the evaporator (22) through the outlet (46). In other embodiments, the heated refrigerant enters the evaporator (22) through the manifold (34B), flows through all the tubes in the tube bundle (30), and leaves the evaporator (22) through the manifold (34A). The tube bundle (30) comprises a plurality of individual tubes between which the two-phase refrigerant passes. The relative heat from the heated refrigerant fluid boils and vaporizes the liquid component of the two-phase refrigerant refrigerant by free boiling and heat transfer by convection so that the vapor refrigerant leaves the evaporator (22) through the outlet (40).

Typically, the incoming gaseous refrigerant comprises approximately 15% to approximately 20% by mass of the biphasic refrigerant, which is equal to approximately 91% to approximately 95% by volume. Generally, the mayone or all of the liquid refrigerant is vaporized by the tubes (30) so that the entire volume of the incoming two-phase refrigerant leaves the evaporator (22) as a gas phase refrigerant. In particular, the gaseous refrigerant has a tendency to accumulate above the inlet port (38), forming a vapor barrier and preventing the liquid refrigerant from coming into contact with the tubes of the tube bundle (30). The gaseous refrigerant forms a dry bubble around the tubes preventing boiling heat transfer. In order to increase the liquid contact with the tube bundle (30) and the efficiency of the evaporator 45 (22), the distributor (12) is placed at the bottom of the housing (42). The distributor (12) prevents the formation of large vapor bubbles by dispersing the refrigerant in the gas phase into smaller bubbles flowing through the evaporator (22).

Fig. 3 shows a perspective sectional view of the evaporator (22) showing the housing (42) and the distributor 50 (12) of the present invention. The housing (42) comprises a cylindrical body into which the two-phase refrigerant is received by the inlet port (38) and the gaseous refrigerant is discharged by the outlet port (40). The manifolds (34A) and (34B) (fig. 2) connect to the housing (42) by the ends of the open side of the housing (42). The distributor (12) is connected to an inner surface of the housing (42) so that the distributor (12) covers the inlet hole (38). In the embodiment shown, the inlet port (38) is placed near the centers of the evaporator (22) and the distributor (12), but in other embodiments the inlet hole (38) may be placed closer to one end. of the evaporator (22). The distributor (12) comprises an elongated body that forms a structure similar to a cuvette or similar to a tube that is opened by a part of its outer penimeter along an entire segment of its length. As such, the distributor (12) cooperates with the housing (42) to form the channel (49) defined between the housing (42), which defines a bottom wall of the channel, and the distributor (12), which forms the parts 60 of remaining wall of the channel. Thus, the channel (49) defines a generally uniform cross-sectional area that extends substantially along the entire length of the elongated body of the distributor (12). The profile of the transverse section of the elongated body of the distributor (12) can define various profiles, such as rectangular,

square, semicircular or V-shaped.

In the embodiment of the invention shown in fig. 3, the distributor (12) comprises an elongated V-shaped body. The V-shaped body includes the first side (50A), the second side (50B), the first lower edge (52A), the 5 second lower edge (52B) and the upper edge (54). The first side (50A) and the second side (50B), which are joined along the upper edge (54), include inlet parts (56A) and (56B), distal ends (58A) to (58D), and discharge holes (60A) to (60D). In one embodiment, the distributor (12) is manufactured from a single flat piece of steel having a penimeter that includes the bottom edges (52A) and (52B), the inlet parts (56A) and (56B) and the distal ends (58A) to (58D). Then discharge holes (60A) - (60D) of the distributor (12) are cut in the 10 penimeter of the flat piece. Cutting the discharge holes (60A) - (60D) at the bottom edges (52A) and (52B) prevents erosion of the fluid in the tube bundle (30) and simplifies the production of the distributor (12). The flat piece is then folded or folded to form the upper edge (54) and to give the distributor (12) a V-shaped profile. In one embodiment, the angle between the first side (50A) and the second side (50B ) is approximately 120 degrees. In other embodiments, the distributor (12) is formed from a piece of standard iron angle that already includes the fold. In one embodiment, the input parts (56A) and (56B) and the distal ends (58A) - (58D) are welded to the housing (42) to form the channel (49) between the housing (42) and the distributor (12). In other embodiments, other fixing or joining means may be used. Thus, the distributor (12) can be easily manufactured from standard material with few necessary manufacturing steps, which helps speed up production time and reduce production costs.

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Referring to fig. 3, the cross section of the channel (49) is defined by an arcuate lower part of an inner side wall of the housing (42) and an opposite angular part of the distributor (12). Thus, the channel (49) extends substantially uniformly along the length of the distributor (12). The input parts (56A) and (56B) are positioned opposite the entrance hole (38). The mass flow of the two-phase refrigerant entering 25 in the inlet port (38) impacts the inlet parts (56A) and (56B) of the first side (50A) and the second side (50B) to be divided into two coolant streams flowing outward along the length of the distributor (12) towards the distal ends (58A) - (58D) thereof through the channel (49). The refrigerant is prevented from migrating upwards towards the outlet orifice (40) by the first and second sides (50A) - (50B). The distributor (12) includes discharge holes (60A) - (60D) to disperse the biphasic refrigerant in a controlled manner within the housing (42) so that a greater quantity of liquid phase refrigerant will impact the tube bundle ( 30) compared to the absence of the distributor (12). Thus, heat transfer by convection is promoted to facilitate evaporation of the liquid phase refrigerant. In addition, the discharge ports (60A) - (60D) are shaped to produce a minimum amount of pressure in the refrigerant as it passes through the distributor (12) so that pressure is maintained to drive the refrigerant through the system of steam compression 35 and for controlling the expansion device (20). In particular, the discharge orifices (60A) - (60D) are shaped to produce equal mass flow rates of the two-phase refrigerant in successive positions along the first and second sides (50A) - (50B). The distal ends of the V-shaped body between the first side (50A) and the second side (50B) are also open to allow the two-phase refrigerant to escape from inside the channel (49).

40

In the embodiment shown, the discharge holes (60A) - (60D) comprise cradle-shaped vents that are placed along the bottom edges (52A) and (52B). For example, the first hole (60A) extends along the bottom edge (52A). The first hole (60A) begins at the inlet part (56) and extends towards the distal end (58A), extending more and more into the lower edge (52A) and the first side (50A) to form a vent in crib shape. The ramp and the travel of the cradles are selected, together with the size of the cross-sectional area of the flow channel (49) inside the distributor (12), so that they release equal amounts of the biphasic refrigerant in different positions along from the distributor (12). The specific geometry of the discharge orifices is selected using mathematical or numerical analysis of the flow of two-phase fluid to model the flow of refrigerant through the channel (49) and the discharge orifices (60A) - (60D). For the purpose of simplification, the discussion of the benefits of the present invention can be appreciated with reference to the equations of conservation of mass and amount of movement and fluid flow in steady state.

The volumetric flow rate Q of a fluid entering a channel is determined by the area Ai of the channel inlet multiplied by the speed Vi of the fluid at the inlet, as shown in Equation (1). The volumetric flow rate of a fluid entering the channel must be equal to the volumetric flow rate of the fluid leaving the channel through an output area A2 and with output speed V2, as also shown in Equation (1).

Q = AlVl = A2V2 (m3 / s) Equation (1)

60 Thus, the volumetric flow rate of the two-phase refrigerant entering the channel (49) through the inlet port (38) is equal to the total amount of refrigerant leaving the channel (49) through the discharge holes (60A ) - (60DB) and

the open ends of the channel (49).

The mass flow rate m of a fluid is determined by the density of the fluid p multiplied by the flow rate

volumetric Q of the fluid, as shown by Equation (2). In addition, the mass flow rate m of the fluid can be determined based on the pressure losses between two points of the flow path, Pi and P2, and the area of the flow path A2, as also shown in Equation (2), where K represents a constant based on friction and other factors.

m = pQ = pA 2 V2 = KA ^ / 2p (P1 - P2) (kg / s)

Equation (2)

10

It can be seen that the mass flow rate depends on the speed of the fluid and the area through which it is flowing at any given point. Thus, the mass flow rate of a refrigerant through a discharge orifice depends on the area of the discharge orifice and the velocity of the refrigerant through the orifice. Alternatively, the mass flow rate through the discharge orifice depends on the area of the discharge orifice and the pressures on either side of the orifice. 15 Thus, the mass flow rate of a refrigerant through a discharge orifice depends on the pressure in the channel (49) and the pressure in the housing (42), as well as the area of the discharge orifice and the channel (49) .

As is known from Bernoulli's equation and the loss of charge due to viscosity, the speed and pressure of a fluid flowing through a channel decreases along the length of that channel due to friction and other considerations. Thus, for example, by manipulating the size of the discharge orifice (60A) and knowing the refrigerant velocity profile through the channel (49), the distributor (12) of the present invention produces a mass flow rate that is emitted from a part of the discharge orifice (60A) near the inlet part (56A) that is equal to or almost equal to a mass flow that is emitted from a part of the discharge orifice (60A) near the distal end (58B) to produce a flow more uniform biphasic refrigerant across the width of the housing (42). Thus, discharge holes can be produced having various geometries along the length of the distributor (12) to achieve a more uniform distribution of refrigerant within the evaporator (22).

Fig. 4 shows a front view of the first embodiment of the distributor (12) of the present invention shown in figs. 2 and 3, in which the refrigerant is released along discharge ports (60A) and (60B). The distributor 30 (12) includes the first side (50A), the lower edge (52A), the upper edge (54), the inlet part (56A), the distal ends (58A) and (58B), the holes discharge (60A) and (60B) and mounting posts (62A) and (62B). The mounting posts (62A) and (62B) are configured to be received inside holes or coupling holes inside the housing (42) so that the bottom edge (52A) along the inlet part (56A) and the distal ends (58A) and (58B) come into contact with the inner surface of the housing (42). Posts (62A) 35 and (62B) are then secured to the housing (42) using a welding procedure or some other procedure. In other embodiments, posts (62A) and (62B) comprise appendages that are connected to the bottom edge (52A). The second side (50B) of the distributor (12) includes components and features similar to the first side (50A), including discharge holes and mounting posts. As such, in the embodiment shown in fig. 4, the distributor (12) includes fourth mounting posts and four cradle-shaped discharge holes.

40

The mass flow mi of refrigerant enters the distributor (12) at pressure Pi and speed Vi near the inlet part (56A) and is divided into two branches m2 and m3 that contain half the mass flow of the amount that enters by the entrance hole (38) (fig. 3). The two m2 and m3 branches of two-phase refrigerant continue to the distal ends (58A) and (58B), losing refrigerant through the discharge holes (60A) and (60B). The pressure Pi and the pressure P ’inside the housing (42) are determined by the operating conditions of the steam compression system (10) and the loss of pressure through the distributor (12). Pressure Pi is generally greater than pressure P ’since there must be some pressure differential across the distributor (12) to allow flow through the distributor (12). The discharge orifices (60A) and (60B) are shaped to produce a uniform mass flow along the width w of each discharge orifice by varying the pressure differential between the pressure within the distributor (12) near the various positions along each discharge hole and P '. For example, at point X near the inlet part (56A), the refrigerant has the velocity V4 at the pressure P4 and the area of the discharge orifice (60A) near that point has a given area. The pressure P4 is lower than the pressure Pi since some loss of load occurs between the inlet port (38) and the discharge port (60A). As the refrigerant flows through the distributor (12) along the discharge hole (60A), such as up to point 55 Y, the pressure and the refrigerant speed continue to decrease to the pressure P5 and the speed V5. Thus, Pi> P4> P5> P ’, and Vi> V4> V5, as expected from a flow channel that has an almost constant cross-sectional area. In order to maintain the same mass flow along the length of the distributor (12), the area of the discharge orifice (60A) varies so that the area of the discharge orifice (60A) near the point Y is greater than

the area of the discharge hole (60A) near point X.

As illustrated by Equation (2), in order to maintain a constant mass flow rate for a flow of a fluid having a decreasing velocity, the area must increase. As Equation (2) also illustrates, in order to maintain a constant mass flow rate for a fluid flow that has a decreasing pressure differential, the area must increase. The sizes of the discharge orifice (60A), defined by the height h and the width w, and the size of the channel defined by the distributor (12) and the housing (42), are selected so that the mass flow rates in various

points along the discharge hole (60A), such as m4 and m5 at points Xe Y are equal. The mass flow

Total output from the discharge holes (60A) and (60D) (fig. 3) is equal to m2. In one embodiment of the invention, the length of the distributor (12) can be sized so that the mass flows in the openings of the distributor (12) near the distal ends (58A) and (58b) are zero or almost and the pressures theref are approximately equal to the pressure P '. The size of the discharge holes is also selected to produce the smallest pressure coffees possible through the discharge holes. Generally, the discharge orifice (60A) has the area of the increasing cross section along a length of the distributor (12) that extends from the inlet part (56A) to the distal end (58A). In other words, the height h of the discharge orifice (60A) increases along the width w, from the inlet part (56A) to the distal ends (58A).

Mathematical and numerical modeling can be used to analyze the mass flow of the refrigerant at any point along the length of the discharge holes to determine the distribution of the refrigerant along the length of the discharge holes. Modeling can also be used to determine and verify other considerations. For example, modeling can be used to ensure that the channel geometry (49) and the discharge holes are selected to produce a minimum loss of pressure through the distributor (12). In addition, the distributor geometry (12) is selected to avoid problems related to the speed of the sound. In a high speed refrigerant flow through a channel, the refrigerant speed is limited by the speed of the sound and the area of the channel. The distributor (12) of the present invention is sized to avoid problems with the speed of sound by dimensioning the channel (49) to be large enough so that the refrigerant flowing to the distal ends (58A) and (58B) is below the speed of sound.

30 The following equations demonstrate the modeling strategy to determine the two-phase flow through a distributor.

35

dPa

1 r 2

-fPa ^ a

dLa

D

dPb

12

-pb

dLb

D

dma = PaVt

d (Aa - Ac) dL

■ dL „

• d (A - A) 1T

dmb = PbVb ----- n ^ dLb

dLb

40

The boundary conditions for pressure balance and mass flow are:

APa = APb

Four. Five

ma + mb = m

That is to say,

L

image 1

Lb

image2

ma, e + mb, e +

The • Lb •

| Jma + | dmb

= m

5 Where,

ma, e = P a, e ^ a, eAc

mb, e = Pb, eVb, eAc

10 f Darcy's friction coefficient using the two-phase Martinelly model

Aa, A Open flow area in each section

A Distributor cross section area

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D Hydraulic diameter of the cross section of the distributor

e Sub-index indicating the end of the distributor

20 The length of one half of the distributor from the inlet part to the distal part

Lb Length of one half of the distributor from the inlet part to the distal part

These equations illustrate, among other things, that the flow entering the distributor is equal to the flow leaving the distributor through the discharge orifices. The flow is determined, among other things, by integrating the pressure differential along the length of each discharge orifice. Thus, the mathematical and numerical modeling can be used to determine the cross-sectional area of the channel (49) within the distributor (12) and the shape of the discharge orifices (60A) - (60D) so that the mass flow discharged at successive points along the width of the distributor (12) are equal. Using the discharge channels, (60A) - (60D), the distributor (12) of the present invention achieves a true uniform distribution of mass flow of refrigerant through the width of each discharge hole. In other distributors, a series of discharge orifices are used to produce successive distributions of biphasic refrigerant having the same mass flow rate, as shown in figs. 5 and 6

35 Fig. 5 shows a front view of an alternative distributor (12) outside the scope of claim 1 in which the refrigerant is released along successive and discrete discharge holes having increasing opening heights. Fig. 6, which is also outside the scope of claim 1, is analyzed simultaneously with fig. 5, shows a front view of an additional distributor in which the refrigerant is released along successive discharge holes that have increasing opening widths. The distributors of figs. 5 and 6 are manufactured from similar procedures and materials. However, instead of shaping the bottom edge (52A) to form the discharge holes, the discharge holes are cut at the sides (50A) and (50B) (fig. 3), as with a cutting process by To be. As such, the distributor (12) comprises a rectangular piece of steel that is bent to provide an upper edge (54), and the lower edges (52A) and (52B) (fig. 3) come into contact with the inner surface of the housing (42) along its entire length. In the embodiments of figs. 45 5 and 6, the cradle-shaped discharge holes (60A) and (60B) have been replaced by a pair of quadrangular discharge holes. For example, the first side (50A) of the distributor (12) includes the discharge holes (64A) - (64D). The second side (50B) of the distributor (12) also includes four quadrangular discharge holes so that, in the embodiment shown, the distributor (12) includes eight discharge holes. However, in other embodiments other numbers of discharge holes may be used.

The distributors (12) shown in figs. 5 and 6 work similarly to that of the distributor (12) of fig. Four.

However, instead of producing a continuous release of biphasic refrigerant along the length of the distributor, intermittent bursts of refrigerant are released at discrete points along the distributor, with a

greater number of holes that produce a more uniform mass distribution. The mass flow mi of refrigerant entering the distributor (12) at a pressure Pi and a velocity Vi near the inlet part (56A) and is divided into two branches m2 and m3 each containing half the mass flow of the amount that enters through the hole of

entry (38). The velocity of the mass flow m2 decreases as it travels through the discharge orifice (64A) and (64B) towards the distal end (58A), losing pressure along the path due to loss of load. In order to produce a uniform mass distribution from each discharge hole, the areas of the discharge holes increase as the series of discharge holes extends towards the distal end (58A).

10

In fig. 5, the discharge opening (64A) comprises a rectangle having height hi and width wi, and the discharge opening (64B) comprises a rectangle having height h2 and width W2. The widths wi and W2 are the same, but the height h2 is greater than the height hi so that the discharge opening (64B) has an area greater than the discharge opening (64B). In fig. 6, the discharge opening (64A) comprises a rectangle having height hi and width wi, 15 and the discharge opening (64B) comprises a rectangle having height h2 and width W2. The width wi is greater than the width w2, and the height hi is equal to the height h2 so that the discharge orifice (64B) has an area greater than the discharge orifice (64B). The discharge holes (64A) and (64B) are bounded by inner edges inside the side (50A). In addition, in other embodiments, discharge holes of other shapes, such as circular ones, can be used. In another embodiment, a triangular hole having a shape similar to the cradle-shaped discharge holes of fig. 4 may be incorporated into the perimeter of the distributor (i2) to produce a more uniform distribution of the refrigerant. The pressure difference between P ’and the pressure in the discharge orifice (64A) is greater

that the pressure difference between P ’and the pressure in the discharge orifice (64B). As such, m4y mass flows

m5 are the same.

The distributor (i2) of the present invention produces homogeneous distribution of two-phase refrigerant within an evaporator to optimize the evaporation of liquid phase refrigerant. The distributor (i2) is produced from a single, single-piece body that can be manufactured from a single flat piece of standard steel material, or from a standard piece of iron angle. The distributor (i2) includes discharge holes that produce equal mass flows of refrigerant in various positions along the width of the distributor (i2). In an alternative arrangement, the discharge holes comprise cradle-shaped grooves that release a continuum of refrigerant to produce a true uniform distribution. In an alternative arrangement, the discharge holes comprise successively larger windows in the distributor (i2) that release discrete and equal mass flows of refrigerant. Computer and numerical modeling can be used to optimize flow, minimize pressure losses and to account for the speed of sound. The geometry of the distributor 35 (i2) and the discharge holes can be easily enlarged or reduced for use in evaporators having different capacities.

Although the present invention has been described with reference to preferred embodiments of the invention, those skilled in the art will recognize that changes in form and detail can be made without departing from the scope of the claims.

Claims (5)

An evaporator (22) for a steam compression circuit and comprising a distributor (12), the distributor comprising (12): an elongated body (50A, 50B) that can be placed inside the evaporator (22) adjacent to a side wall (42) thereof; an inlet part (56A) that can be placed near an inlet port (38) of the evaporator (22) to receive a flow of refrigerant; a first and a second distal ends (58A, 58B) extending along a length of the evaporator (22); 15 discharge holes (60A, 60B) placed along an elongated body length (50A, 50B); Y a channel (49) having a cross-sectional area that extends from the first distal end (58A) to the second distal end (58B), where the channel (49) is defined by the elongated body (50A, 50B) and the side wall (42) of the evaporator (22), twenty characterized in that the elongated body (50A, 50B) comprises: first and second side surfaces to include the discharge holes (60A, 60B); 25 a bottom edge (52A, 52B) disposed along each side surface to come into contact with the side wall (42) of the evaporator (22); Y an upper edge along which the first and second lateral surfaces are joined, 30 and because the discharge holes (60A, 60B) comprise elongated openings, of decreasing section, which have a growing area that extends from near the inlet part (56A) to near the first and second distal ends (58A, 58B), respectively, where the discharge holes (60A, 60B) are configured to be bounded by the lower edge (52A, 52B) of the elongated body and the side wall (42) of the evaporator (22). The distributor (12) of claim 1, wherein the channel (49) has a V-shaped cross section so that the channel (49) has a substantially constant cross-sectional area. 3. The distributor (12) of claim 1, wherein the discharge holes (60A, 60B) are configured to discharge an equal amount of refrigerant mass at various positions along the elongated body. 40 4. The distributor (12) of claim 3, wherein the cross-section of the channel (49) is configured to produce a decrease in the speed of the refrigerant flowing from the inlet part (56) to the first and second distal ends (58A , 58B), and the size of the discharge holes (60A, 60B) is configured to produce decreasing pressure differentials along the elongated body from the inlet part (56) to the 45 first and second distal ends (58A, 58B). 5. A method for distributing biphasic refrigerant in an evaporator (22) using a distributor (12), the procedure comprising: 50 introduce refrigerant into an evaporator (22); channel the refrigerant into opposite legs of a distributor (12), the legs having substantially constant cross-sectional areas; 55 Unpack the refrigerant from the channel (49) inside the evaporator through discharge holes (60A, 60B) placed along leg lengths, the discharge holes having increasing areas that extend along the leg lengths. 6. The method of claim 5, wherein the step of disbursing the refrigerant further comprises continuously releasing refrigerant having uniform mass flow along lengths of the orifices of discharge (60A, 60B).