EP3865791A1

EP3865791A1 - A method for controlling a liquid refrigerant level in a condenser, a condenser arrangement and use of a condenser arrangement

Info

Publication number: EP3865791A1
Application number: EP20157414.2A
Authority: EP
Inventors: Olav AABO; Simon Stubkier
Original assignee: Johnson Controls Denmark ApS
Current assignee: Johnson Controls Denmark ApS
Priority date: 2020-02-14
Filing date: 2020-02-14
Publication date: 2021-08-18

Abstract

Disclosed is a condenser arrangement (1) comprising a condenser (2) including a refrigerant conduit (3) and a coolant conduit (4), wherein the refrigerant conduit (3) and the coolant conduit (4) are separated by a wall (5) through which a refrigerant (16, 17) flowing through the refrigerant conduit (3) and a coolant (18) flowing through the coolant conduit (4) may exchange heat to condense at least a part of the refrigerant (16, 17). The condenser arrangement (1) also comprises a buffer tank (6) and a liquid conductor (7) arranged to form liquid communication between a buffer liquid outlet (8) of the refrigerant conduit (3) and a buffer liquid inlet (9) of the buffer tank (6), wherein the buffer liquid outlet (8) is arranged at a bottom (10) of the condenser (2). Further, the condenser arrangement (1) comprises a gas conductor (11) arranged to form fluid communication between a gaseous refrigerant outlet (12) of the refrigerant conduit (3) and a buffer gas inlet (13) of the buffer tank (6), wherein the buffer gas inlet (13) is arranged at a closed upper part (14) of the buffer tank (6), wherein the gaseous refrigerant outlet (12) is arranged at a desired liquid refrigerant level (15) in the condenser (2), and wherein the condenser arrangement (1) further is arranged to cool gaseous refrigerant (16) in the buffer tank (6) to a temperature below the condensation temperature of the refrigerant (16, 17).

A method for controlling a liquid refrigerant level in a condenser (2) and use of a condenser arrangement (1) is also disclosed.

Description

Field of the invention

The invention relates to a condenser arrangement for controlling a liquid refrigerant level in a condenser. The invention also relates to a method for controlling a liquid refrigerant level in a condenser and use of a condenser arrangement.

Background of the invention

A condenser is a device used to condense a gaseous refrigerant into a liquid state through cooling. The condenser relies on the efficient heat transfer that occurs during phase changes, i.e. during the condensation of a refrigerant vapor into liquid refrigerant by heat exchange with a secondary fluid - often called a coolant.
The refrigerant vapor enters the condenser at a temperature above that of the coolant. As the vapor cools, it reaches the saturation temperature, condenses into liquid refrigerant and releases large quantities of latent heat. As this process occurs along the flow path inside the condenser, the quantity of vapor decreases and the quantity of liquid increases and at the outlet of the condenser, only liquid remains. If the condenser is used in a closed cooling circuit or in a heat pump circuit the condensed refrigerant will typically continue from the condenser to an expansion valve, an evaporator, a compressor and then back into the condenser. However, in cooling circuits and heat pumps the load may vary e.g. due to usage, ambient temperature (e.g. if heat exchange with the surroundings takes place) or other and the gaseous/liquid ratio in the system may change. It is therefore advantageous if the system comprises some sort of buffer system to hold any excess liquid refrigerant. Such a buffer tank is typically placed under the condenser so that gravity pulls the liquid refrigerant down into the tank from which liquid refrigerant can be drawn near the bottom of the tank.
Another solution is presented in the German patent DE 3822184 C1 in which a condenser is provided with a siphon device for keeping a constant fluid level in a condensation accumulation space below the condenser. But this design also requires that the accumulation space is placed below the condenser and that the siphon device is located at or below the condensation accumulation space.
An object of the invention is therefore to provide for an advantageous technique for controlling a liquid refrigerant level in a condenser.

The invention

The invention provides for a condenser arrangement comprising a condenser including a refrigerant conduit and a coolant conduit, wherein the refrigerant conduit and the coolant conduit are separated by a wall through which a refrigerant flowing through the refrigerant conduit and a coolant flowing through the coolant conduit may exchange heat to condense at least a part of the refrigerant. The condenser arrangement also comprises a buffer tank and a liquid conductor arranged to form liquid communication between a buffer liquid outlet of the refrigerant conduit and a buffer liquid inlet of the buffer tank, wherein the buffer liquid outlet is arranged at a bottom of the condenser. Further, the condenser arrangement comprises a gas conductor arranged to form fluid communication between a gaseous refrigerant outlet of the refrigerant conduit and a buffer gas inlet of the buffer tank, wherein the buffer gas inlet is arranged at a closed upper part of the buffer tank, wherein the gaseous refrigerant outlet is arranged at a desired liquid refrigerant level in the condenser, and wherein the condenser arrangement further is arranged to cool gaseous refrigerant in the buffer tank to a temperature below the condensation temperature of the refrigerant.
Leading the excess liquid refrigerant to a buffer tank, in which gaseous refrigerant is cooled to a temperature below the condensation temperature of the refrigerant, is advantageous in that the liquid refrigerant hereby is sucked up into the buffer tank enabling that the buffer tank be located independent from the condenser - i.e. the buffer tank can be placed next to or even above the condenser - enabling a more efficient system design. And by arranging a gas conductor so that is connects the condenser with a closed upper part of the buffer tank, it is ensured that as long the as the gaseous refrigerant outlet of the gas conductor is above the liquid level in the condenser, the gas conductor will equalise the pressure in the condenser and the buffer tank and once the liquid level in the condenser rises and covers the gaseous refrigerant outlet, the cooling of the gaseous refrigerant in the buffer tank will condense at least some of the gaseous refrigerant and thereby reduce the pressure and suck liquid refrigerant up into the buffer tank through the liquid conductor until the gas conductor again is above the liquid level in the condenser. In this way the liquid level in the condenser is maintained at the gaseous refrigerant outlet in the condenser.
It should be noted, that the condensation temperature of the refrigerant obviously is dependent of the pressure in the system, and that the condensation temperature referred to here obviously is the condensation temperature of the refrigerant at the specific pressure in the condenser arrangement - more specifically the pressure in the condenser of the condenser arrangement.
In an aspect of the invention, at least an upper part of the buffer tank is formed as a cul-de-sac.
Forming the buffer tank as a dead end is advantageous in that it increases the efficiency of the cooling process in the buffer tank.
In an aspect of the invention, the condenser arrangement further comprises a liquid refrigerant outlet through which liquid refrigerant leaves the condenser arrangement and wherein the liquid refrigerant outlet is arranged in the liquid conductor or below a vertical middle of the buffer tank.
Arranging the liquid refrigerant outlet in the liquid conductor or below the vertical middle of the buffer tank is advantageous in that the risk of the flow of liquid from the condenser and out of the outlet will heat up the cooled liquid and gas in the buffer tank is hereby reduced - thus, increasing the efficiency of the condenser arrangement by reducing the need for cooling in the buffer tank.
In an aspect of the invention, the condenser arrangement further comprises liquid refrigerant chicane means arranged to alter the flow direction of the liquid refrigerant before it leaves the condenser arrangement through the liquid refrigerant outlet.
Forcing the flow of liquid refrigerant past a chicane before it leaves the condenser arrangement is advantageous in that at least some heavier fluids - such as oil - is thereby flung out of the refrigerant flow to enable separation of the heavier fluids from the liquid refrigerant.
It should be noted that in this context the term "chicane means" should be understood as any kind of chicane suited for altering the flow direction of the liquid refrigerant, such as any kind of sharp flow turns, flow obstacles, plates or other that could induce a centrifugal force in the liquid refrigerant.
In an aspect of the invention, the buffer tank and/or the liquid conductor comprises a collection hollow.
Providing the buffer tank and/or the liquid conductor with a collection hollow is advantageous in that such a hollow enables heavier fluid to settle in the hollow in which they are concentrated and can easily be removed from the condenser arrangement. These fluids are thereby prevented from leaving the condenser arrangement and additional oil separators and the like can thereby be omitted.
In an aspect of the invention, the collection hollow is arranged at or after the liquid refrigerant outlet.
The liquid refrigerant flows more or less constantly from the condenser and out of the outlet. Thus, it is advantageous to arrange the collection hollow at or after the liquid refrigerant outlet it that this is where the liquid is most calm and the chance of heavier fluids settling in the hollow is the highest.
In an aspect of the invention, the condenser arrangement is arranged to cool gaseous refrigerant in the buffer tank to a temperature below the condensation temperature of the refrigerant by means of cooling means.
Providing cooling means ensures a faster and more efficient cooling of the gaseous refrigerant.
It should be noted that in this context the term "cooling means" should be understood as any kind of cooler - passive or active - suited for cooling gaseous refrigerant in the buffer tank to a temperature below the condensation temperature of the refrigerant - such as an active flow of coolant or another cooling medium in or on the buffer tank, the ambient medium surrounding the buffer tank, an integrated refrigerator, addition of subcooled fluid or gas or other or any combination thereof.
In an aspect of the invention, the cooling means comprises an ambient medium arranged to enclose at least a part of the buffer tank.
The condensation temperature of most suited refrigerants is above 30 degrees Celsius and it is therefore advantageous to simply form the cooling means as a surrounding flow of water e.g. in a stream, the sea, in a basin or other, by the surrounding ground if the buffer tank was buried below ground surface, by the surrounding air - if the buffer tank was placed in an environment where the air temperature never (or almost never) will exceed the condensation temperature of the refrigerant - or other since such passive cooling means are readily available, relatively failsafe and inexpensive.
In an aspect of the invention, the cooling means comprises active cooling means in or on the buffer tank.
Providing the buffer tank with active cooling means is advantageous in that by actively cooling the content of the buffer tank a more precise and efficient control of the condenser arrangement can be achieved.
It should be noted that in this context the term "active cooling means" should be understood as any kind of active cooler suited for actively cooling gaseous refrigerant in the buffer tank to a temperature below the condensation temperature of the refrigerant - such as a pump or a fan actively generating a flow of coolant or another cooling medium in or on the buffer tank, a valve controlling the flow rate of coolant or another cooling medium or on the buffer tank in, a refrigeration system arranged to cool in or on the buffer tank or other or any combination thereof.
In an aspect of the invention, the active cooling means comprises a pump arranged to establish an actively driven flow of buffer coolant in or on the buffer tank.
Providing a pump that will circulate or supply a buffer coolant to cool the buffer tank is advantageous in that more efficient and/or precise cooling hereby can be achieved.
In an aspect of the invention, the active cooling means comprises a coolant conductor arranged for guiding coolant in or on the buffer tank and between the condenser and the buffer tank.
Very cold coolant is readily available in the coolant supply to the condenser and it is therefore advantageous to cool the buffer tank by means of the condenser coolant.
In an aspect of the invention, the active cooling means comprises an expansion valve.
An expansion valve will reduce the pressure in the coolant or another cooling medium in or on the buffer tank thereby increasing the cooling effect.
In an aspect of the invention, the gaseous refrigerant outlet comprises displacement means by means of which the position of the gaseous refrigerant outlet can be displaced vertically.
The position of the gaseous refrigerant outlet defines the level of the liquid refrigerant in the condenser and providing displacement means is a simple and efficient way of adjusting the liquid level in the condenser by adjusting the vertical position of the gaseous refrigerant outlet.
It should be noted that in this context the term "displacement means" should be understood as any kind of displacer suited for vertically displacing the gaseous refrigerant outlet in the condenser. Thus, the term comprises any kind of adjustable clamping arrangement, threaded connections, wedge-based connections or other or any combination thereof.
In an aspect of the invention, the condensation temperature of the refrigerant is between 0 and 150 degrees Celsius, preferably between 15 and 120 degrees Celsius, and most preferred between 25 and 95 degrees Celsius.
If the condensation temperature of the refrigerant is too low or too high it will require more energy to ensure the phase change in the condenser and/or the refrigerant will become more difficult to handle. Thus, the present temperature ranges presents an advantageous relationship between efficiency and safety.
In an aspect of the invention, the minimum cross-sectional area of the liquid conductor is at least three times bigger than the minimum cross-sectional area of the gas conductor.
If the cross-sectional area of the gas conductor is too big, in relation to the cross-sectional area of the liquid conductor, too much liquid refrigerant will be sucked into the buffer tank through the gas conductor when the gaseous refrigerant outlet is covered by liquid refrigerant in the condenser, which will reduce the suction effect of the buffer tank in that the liquid refrigerant entering through the gas conductor will at least to some extend counteract the cooling of the content of the buffer tank. Thus, by making the liquid conductor at least four times bigger than the gas conductor this problem is alleviated to a degree where it does substantially not affect the efficiently of the condenser arrangement.
The invention also provides for a method for controlling a liquid refrigerant level in a condenser, the method comprising the steps of:

guiding a flow of gaseous refrigerant into a condenser,
condensing the gaseous refrigerant to form liquid refrigerant in the condenser by heat exchange with a flow of coolant being guided through the condenser by means of a coolant conduit thereby cooling the gaseous refrigerant in the condenser,
arranging a liquid conductor between the condenser and a buffer tank and guiding the liquid refrigerant out of the condenser by means of the liquid conductor, wherein the liquid conductor is arranged at a bottom of the condenser,
arranging a gas conductor at a desired liquid refrigerant level in the condenser to enable fluid communication between the condenser and a closed upper part of the buffer tank,
cooling the content of the closed upper part of the buffer tank to a temperature below the condensation temperature of the refrigerant.

Cooling the content of the closed upper part of the buffer tank to a temperature below the condensation temperature of the refrigerant is advantageous, in that this will condense any gaseous refrigerant trapped at the closed upper part of the buffer tank, which in turn will reduce the pressure in the buffer tank and create a suction effect that will suck liquid refrigerant into the buffer tank as long as the gas conductor is arranged below the liquid refrigerant level in the condenser. As soon as the gas conductor is above the liquid refrigerant level in the condenser the underpressure in the buffer tank is equalized whereby a fixed level of liquid refrigerant in the condenser is ensured at the mouth of the gas conductor in the condenser. And because of the suction effect created in the buffer tank by the cooling, it is ensured that the buffer tank can be arranged anywhere under, next to or even above the condenser thus providing more freedom to create a space efficient design.
In an aspect of the invention, the content of the closed upper part of the buffer tank is cooled by heat exchanging with the ambient medium surrounding the buffer tank.
Cooling at least the upper part of the buffer tank by means of heat exchange with a "cold" ambient medium - such as the surrounding air - is a simple, failsafe and inexpensive way of cooling the content of the buffer tank.
In an aspect of the invention, the method further comprises the step of locating at least the upper part of the buffer tank in an ambient medium having temperature below the condensation temperature of the refrigerant.
Placing at least the upper part of the buffer tank in a "cold" ambient medium - such as the surrounding air - is a simple, failsafe and inexpensive way of cooling the content of the buffer tank.
In an aspect of the invention, the method further comprises the step of cooling the content of the closed upper part of the buffer tank to a temperature below the condensation temperature of the refrigerant by means of the coolant.
Cooling the content of the closed upper part of the buffer tank by means of the coolant is advantageous in that enables a more controllable and efficient cooling process.
In an aspect of the invention, the method further comprises the step of cooling the content of the closed upper part of the buffer tank to a temperature below the condensation temperature of the refrigerant by actively cooling the content by means of dedicated cooling means.
Cooling the content of the closed upper part of the buffer tank by means of dedicated cooling means is advantageous in that enables a more controllable and efficient cooling process.
In an aspect of the invention, the method further comprises the step of guiding the liquid refrigerant out of the condenser arrangement through a liquid refrigerant outlet arranged in the liquid conductor or below a vertical middle of the buffer tank.
Arranging the liquid refrigerant outlet in the liquid conductor or below the vertical middle of the buffer tank is advantageous in that the risk of the flow of liquid from the condenser and out of the outlet will heat up the cooled liquid and gas in the buffer tank is hereby reduced - thus, increasing the efficiency of the condenser arrangement by reducing the need for cooling in the buffer tank.
In an aspect of the invention, the method further comprises the step of changing the flow direction of the liquid refrigerant before guiding the liquid refrigerant out of the condenser arrangement.
Changing the flow direction of the liquid refrigerant before guiding the liquid refrigerant out of the condenser arrangement is advantageous in that at least some heavier fluids - such as oil - is thereby flung out of the refrigerant flow to enable separation of the heavier fluids from the liquid refrigerant.
In an aspect of the invention, the flow direction is changed by guiding the liquid refrigerant around liquid refrigerant chicane means.
Forcing the flow of liquid refrigerant past a chicane before it leaves the condenser arrangement is advantageous in that at least some heavier fluids - such as oil - is thereby flung out of the refrigerant flow to enable separation of the heavier fluids from the liquid refrigerant.
In an aspect of the invention, the method further comprises the step of arranging a collection hollow at or after the liquid refrigerant outlet as seen in the flow direction of the liquid refrigerant during normal use.
The liquid refrigerant flows more or less constantly from the condenser and out of the outlet. Thus, it is advantageous to arrange the collection hollow at or after the liquid refrigerant outlet it that this is where the liquid is most calm and the chance of heavier fluids settling in the hollow is the highest.
In an aspect of the invention, the method is performed on a condenser arrangement according to any of the previously discussed condenser arrangements.
Hereby is achieved an advantageous embodiment of the invention.
Further, the invention provides for use of a condenser arrangement according to any of the previously discussed condenser arrangements for controlling a liquid refrigerant level in a condenser forming part of a closed cooling circuit.
In closed cooling circuits it is particularly important to control the liquid refrigerant level in the condenser to maintain the efficiency of the cooling circuit and it is therefore particularly advantageous to apply the present invention to a closed cooling circuit.

Figures

An embodiment of the invention will be described, by way of non-limiting example, in the following with reference to the figures in which:

fig. 1: illustrates a condenser arrangement where the buffer tank is cooled by an ambient medium, as seen from the side,
fig. 2: illustrates a condenser arrangement comprising active cooling means with coolant from the condenser, as seen from the side,
fig. 3: illustrates a condenser arrangement comprising active cooling means with circulating buffer coolant, as seen from the side,
fig. 4: illustrates a condenser arrangement comprising displacement means, as seen from the side, and
fig. 5: illustrates an embodiment of a closed cooling circuit.

Detailed description

Fig. 1 illustrates a condenser arrangement 1 where the buffer tank 6 is cooled by an ambient medium 24, as seen from the side.
In this embodiment the condenser arrangement 1 comprises a condenser 2 in the form of a plate heat exchanger. In this embodiment the plate heat exchanger is composed of many thin, slightly separated plates forming walls 5 having a very large surface area and small fluid flow passages 3, 4 for heat transfer. However, in another embodiment the condenser 2 could also or instead comprise a shell and plate heat exchanger - where a fully welded plate pack is placed inside shell, a shell and tube heat exchanger - where a series of tubes is placed inside a shell or the condenser 1 could comprise another type of heat exchanger.
In this embodiment the condenser 2 comprises two separate flow paths 3, 4 separated by walls 5 formed by the plate stack - i.e. a refrigerant conduit 3 and a coolant conduit 4 - which are separated by the walls 5 in the plate heat exchanger, so that a refrigerant 16, 17 flowing through the refrigerant conduit 3 may exchange heat with a coolant 18 flowing through the coolant conduit 4 to enable that the refrigerant 16, 17 condenses while it passes through the condenser 1.In fig. 1 the coolant flow is indicated by the dotted lines and the refrigerant flow is indicated by the solid lines. However, it is obvious to the skilled person that the flow parts through the condenser can be arranged in several other ways dependent on the specific use, the specific condenser design and other.
In this embodiment the condenser 2 is provided with a refrigerant inlet 32 through which the gaseous refrigerant 16 enters the condenser 2. The condenser 2 is also provided with a coolant inlet 33 through which cold coolant 18 enters the condenser 2 and a coolant outlet 34 through which the now hotter coolant 18 exits the condenser 2. In this embodiment the coolant 18 is brine but in another embodiment the coolant 18 could be water or another form of natural or artificial coolant suitable for exchanging heat in a condenser 2.
In this embodiment the refrigerant 16, 17 being condensed in the condenser 2 is R717 (ammonia) but in another embodiment the refrigerant 16, 17 could be R290 (Propane), R600 (Butane), R600a (Isobutane), R744 (Carbon dioxide), a HFC gas, water vapour or another fluid suitable for acting as a refrigerant 16, 17 in a condenser 2.
When the gaseous refrigerant 16 condenses in the condenser 2 the liquid refrigerant 17 will gather and build up in the refrigerant conduit 3 at the bottom 10 of the condenser 2 from where it is drawn from the condenser 2 through a buffer liquid outlet 8 of a liquid conductor 7 to buffer liquid inlet 9 of a buffer tank 6 and a liquid refrigerant outlet 19 through which the liquid refrigerant 17 leaves the condenser arrangement 1.
In this embodiment the buffer tank 6 is formed as a vertically elongated cylinder with a closed upper part 14 and the buffer liquid inlet 9 is arranged at the bottom part 35 of the buffer tank 6. However, in another embodiment the buffer tank 6 could have a different shape, such as square, polygonal or other.
In this embodiment the condenser arrangement 1 is also provided with a gas conductor 11 forming fluid communication between a gaseous refrigerant outlet 12 of the refrigerant conduit 3 in the condenser 2 and a buffer gas inlet 13 arranged at the closed upper part 14 of the buffer tank. The gaseous refrigerant outlet 12 is arranged at a desired liquid refrigerant level 15 in the condenser 2 as will be discussed in more details in the following.
In this embodiment the buffer tank 6 is arranged fully separate from the condenser 2 next to the condenser 2 but in another embodiment the buffer tank 6 could be more or less integrated with the condenser 2, it could be connected to the condenser 2 or it could be placed in a different room, on a different floor or even outside the building in which the condenser 2 is located.
In this embodiment the condenser arrangement 1 is arranged to cool the content of the buffer tank 6 to a temperature below the condensation temperature of the refrigerant 16, 17 by arranging the buffer tank 6 in an ambient medium 24 - which in this case is the air surrounding the buffer tank 6 - so that the buffer tank 6 may be cooled by the surrounding air. As previously mentioned, the refrigerant is R717 in this embodiment and in this embodiment the pressure inside the condenser is around 4,100,000 Pa (41 Bar) which means that the condensation temperature of the refrigerant 16, 17 is around 81 degrees Celsius. So even on a hot summer day the surrounding air will be sufficient to ensure that the content of the buffer tank 6 is cooled to below the condensation temperature of the refrigerant 16, 17. It is obvious to the skilled person that the specific condensation temperature is dependent on the specific operating pressure no matter which refrigerant is used. I.e. if the refrigerant was e.g. water and the average operating pressure in in the condenser 2 was 100,000 Pa (1 Bar) the condensation temperature would be around 100 degrees Celsius.
When the condenser arrangement 1 is in operation, gaseous refrigerant 16 will condense in the condenser 2 and the level of liquid refrigerant 17 will rise in the condenser 2 and some of the liquid refrigerant 17 will run into the buffer tank 6 through the liquid conductor 7. This will continue until the liquid refrigerant 17 reaches the desired liquid refrigerant level 15 in the condenser 2 where it will cover the gaseous refrigerant outlet 12. When the gaseous refrigerant outlet 12 is "blocked " by the liquid refrigerant 17 the condensing of the gaseous refrigerant 16 in the buffer tank will create an underpressure that will suck the liquid refrigerant 17 out through the liquid conductor 7 and up into the buffer tank 6 so that the level of the liquid refrigerant 17 in the buffer tank 6 rises above the level of the liquid refrigerant 17 in the condenser 2. Depending on the dimensioning of the liquid conductor 7 and the buffer tank 6 and of the efficiency of the cooling of the content in the buffer tank 6, the level of the liquid refrigerant 17 in the buffer tank 6 can be lifted high above the level of the liquid refrigerant 17 in the condenser 2 - several meters or more if necessary - by means of this suction effect.
The buffer tank 6 will continue to draw up liquid refrigerant 17 until the level of liquid refrigerant 17 falls below the gaseous refrigerant outlet 12 in the condenser 2. At this point the gas conductor 11 will draw gaseous refrigerant 16 into the buffer tank 6 and equalise the pressures in the upper part 14 of the buffer tank 6 after which at least some of the liquid refrigerant 17 in the buffer tank 6 will run back into the condenser 2 until the liquid refrigerant 17 reaches the desired liquid refrigerant level 15 in the condenser 2 and covers the gaseous refrigerant outlet 12 again. In this way the level of the liquid refrigerant 17 in the buffer tank 6 may fluctuate while the level of the liquid refrigerant 17 in the condenser is maintained substantially at or just around the desired liquid refrigerant level 15. To increase the chance of stable level control and reduce the risk of self-oscillation it is advantageous if capacity (cross sectional area) of the liquid conductor 7 is significantly bigger than the capacity of the gas conductor 11 - preferably at least four times bigger, such as ten, twenty, fifty, hundred, two hundred times bigger or even more dependent on the specific refrigerant 16, 17, the mutual position and design of the condenser 2 and buffer tank 6 and other.
While the level of liquid refrigerant 17 is maintained substantially constant in the condenser additional liquid refrigerant 17 is constantly formed in the condenser 2 and liquid refrigerant 17 is constantly drawn from the condenser arrangement 1 through the liquid refrigerant outlet 19. The amount drawn from the condenser arrangement 1 may vary dependent on the specific usage and load and the amount condensed in the condenser 2 may vary e.g. due to variation in coolant inflow temperature due to seasonal variations and the amount of liquid refrigerant 17 will therefore vary. But by means of the suction effect of the buffer tank 6 these variations will only affect the amount of liquid refrigerant 17 in the buffer tank 2 and not the amount of liquid refrigerant 17 in the condenser 2.
In this embodiment the liquid refrigerant outlet 19 is arranged in the liquid conductor 7 to ensure that the constant flow of liquid refrigerant 17 from the condenser and out of the condenser arrangement 1 does not heat up the colder content of the buffer tank and thereby reduces the suction effect - or at least causes that more energy should be used to cool the buffer tank 6. Placing the liquid refrigerant outlet 19 in the liquid conductor 7 is also advantageous in that this location enables ample space to form liquid refrigerant chicane means 21 that will cause the flow of liquid refrigerant 17 to take sharp turn which will hurl heavier fluids - such as oil - out of the refrigerant flow. Thus, in this embodiment a collection hollow 22 is arranged in the bottom of the buffer tank 6 where the heavier fluids may settle and from which the heavier fluids may be draw out of the condenser arrangement 1 through a heavier fluid outlet (not shown).
Fig. 2 illustrates a condenser arrangement 1 comprising active cooling means 25 with coolant 18 from the condenser 2, as seen from the side.
In this embodiment the condenser arrangement 1 comprises a condenser 2 and a subcooler 36 arranged as plate stacks inside the same continuous shell 37. The function of the subcooler 36 is to cool the liquid refrigerant 17 further before it leaves the condenser arrangement 1. Thus, in this embodiment the liquid refrigerant outlet 19 is arranged near the top of the subcooler 36.
In this embodiment the liquid conductor 7 will draw the liquid refrigerant 17 out of the condenser 2 and into the bottom part 35 of the buffer tank 6 where the liquid refrigerant 17 flow will turn 180 degrees around chicane means 21 and continue into the subcooler 36 through the subcooler conductor 38. Thus, in this embodiment the condenser arrangement 1 is provided with a collection hollow 22 both in the liquid conductor 7 and in the bottom of the buffer tank 6.
In this embodiment the ambient medium 24 is not cold enough to cool the buffer tank 6 at all times and in this embodiment the buffer tank 6 is therefore provided with active cooling means 25 which in this embodiment comprises a cooling spiral 39. Through a coolant conductor 28 and a pump 26 of the active cooling means 25 a flow of coolant from the condenser 2 is generated through the spiral 39 to additionally cool the content of the closed upper part 14 of the buffer tank 6 to generate the suction effect. However, if the condenser arrangement 1 forms part of a closed cooling circuit, the medium flowing through the cooling spiral 39 could be refrigerant 16, 17 that was passed through an circuit expansion valve 29 (see fig. 5) to reduce the pressure and lower the temperature of the refrigerant 16, 17.
Fig. 3 illustrates a condenser arrangement 1 comprising active cooling means 25 with circulating buffer coolant 27, as seen from the side.
In this embodiment the active cooling means 25 comprises a pump 26 circulating a separate buffer coolant 27 in a separate cooling cycle. The buffer coolant 27 is guided through a radiator 42 in which it is cooled by passing cold air through the radiator 42 by means of a fan 41. However, the skilled person would know that the active cooling means 25 could be designed in numerous other ways.
Fig. 4 illustrates a condenser arrangement 1 comprising displacement means 30, as seen from the side.
In this embodiment the condenser 2 is designed with an additional thermal length to subcool the condensed refrigerant 17 below the condensation temperature before it leaves the condenser 2. To better control this process it is advantageous if the level of liquid refrigerant 17 in the condenser 2 can be controlled to the specific needs and the specific design. Thus, in this embodiment the condenser arrangement 1 is provided with displacement means 30 enabling that the vertical position of the gaseous refrigerant outlet 12 may be adjusted in the condenser 2 to thereby adjust the desired liquid refrigerant level 15 in the condenser 2. In this embodiment the displacement means 30 comprises a releasable clamp fixing position of the gas conductor 11 in the condenser 2. Thus, is the desired liquid refrigerant level 15 in the condenser 2 is to be adjusted, the clamp of the displacement means 30 is loosened and the vertical position of the gaseous refrigerant outlet 12 is adjusted in the condenser 2 where after the clamp is tightened again. However, in another embodiment the displacement means 30 could also or instead comprise threaded connections, wedging arrangement or other.
Fig. 5 illustrates an embodiment of a closed cooling circuit 31.
Closed cooling circuits 31 - also called Vapour-compression refrigeration or vapor-compression refrigeration system (VCRS) - is a circuit in which the refrigerant undergoes phase changes. Such circuits 31 can be used for cooling or refrigeration purposes but the closed cooling circuit 31 can also be used as a heat pump where heat is absorbed from a cold medium and released to a warmer one.
In this embodiment the condenser arrangement 1 according to the present invention is used for condensing a refrigerant 16, 17 in a closed cooling cycle 31. I.e. after the condensed refrigerant 17 leaves the condenser arrangement 1 it is typically directed to a circuit expansion valve 29, which will reduce the pressure making at least some of the refrigerant 16, 17 evaporate and thus making its temperature of the refrigerant 16, 17 drop drastically. At this stage the cold refrigerant 16, 17 is guided through an evaporator 40 used for cooling purposes by which the entire refrigerant 16, 17 evaporates. In this embodiment the evaporator 40 is a heat exchanger in which the cold refrigerant 16, 17 exchanges heat with another medium used for refrigeration purposes. If the closed cooling circuit 3 1 is used as a heat pump the evaporation could e.g. take place by passing the expanded refrigerant 16, 17 through an ambient medium such as through the ground, through the sea or by air and the heat absorbed from this ambient medium can then be released to the coolant 18 in the condenser arrangement 1.
After the evaporator 40, the gaseous refrigerant 16 is then directed through a compressor 43 compressing the refrigerant 16, which in turn raises its temperature drastically. The hot gaseous refrigerant 16 is then lead to the condenser arrangement 1 where the gaseous refrigerant 16 is condensed into a liquid refrigerant 17. In an embodiment the gaseous refrigerant 16 could also be led through a de-superheater (not shown), where the refrigerant's temperature is lowered to just above the condensation temperature before it enters the condenser arrangement 1. And in this embodiment the liquid refrigerant 17 is cooled further in a subcooler 36 before the cycle is repeated.
In this embodiment the coolant 18 of the condenser arrangement 1 is circulated through a radiator 42 in which it is cooled by a fan 41 passing cold air through the radiator 42. However, it would be obvious to the skilled person that the coolant 18 in another embodiment could be cooled in numerous other ways.
In this embodiment the active cooling means 25 comprises a cooling conduit 44 arranged to draw (i.e. branch off) liquid refrigerant 17 from the buffer tank 6 and guide it through an expansion valve 45 which will drastically lower the temperature of the refrigerant 17. The cooling conduit 44 then guides the cold refrigerant 17 through a cooling spiral 39 arranged in the buffer tank 6 to cool the content of at least the upper part of the buffer tank 6 to generate the suction effect. From there the cooling conduit 44 will guide the refrigerant 16, 17 back into the closed cooling circuits 31 after the circuit expansion valve 29 and before the evaporator 40.
The invention has been exemplified above with reference to specific examples of condenser arrangements 1, condensers 2, buffer tanks 6 and other. However, it should be understood that the invention is not limited to the particular examples described above but may be designed and altered in a multitude of varieties within the scope of the invention as specified in the claims.

List

1.: Condenser arrangement
2.: Condenser
3.: Refrigerant conduit
4.: Coolant conduit
5.: Wall
6.: Buffer tank
7.: Liquid conductor
8.: Buffer liquid outlet
9.: Buffer liquid inlet
10.: Bottom of condenser
11.: Gas conductor
12.: Gaseous refrigerant outlet
13.: Buffer gas inlet
14.: Closed upper part of buffer tank
15.: Desired liquid refrigerant level in condenser
16.: Gaseous refrigerant
17.: Liquid refrigerant
18.: Coolant
19.: Liquid refrigerant outlet
20.: Vertical middle of buffer tank
21.: Liquid refrigerant chicane means
22.: Collection hollow
23.: Cooling means
24.: Ambient medium
25.: Active cooling means
26.: Pump
27.: Buffer coolant
28.: Coolant conductor
29.: Circuit expansion valve
30.: Displacement means
31.: Closed cooling circuit
32.: Refrigerant inlet
33.: Coolant inlet
34.: Coolant outlet
35.: Bottom part of buffer tank
36.: Subcooler
37.: Shell
38.: Subcooler conductor
39.: Cooling spiral
40.: Evaporator
41.: Fan
42.: Radiator
43.: Compressor
44.: Cooling conduit
45.: Expansion valve

Claims

A condenser arrangement (1) comprising
a condenser (2) including a refrigerant conduit (3) and a coolant conduit (4), wherein said refrigerant conduit (3) and said coolant conduit (4) are separated by a wall (5) through which a refrigerant (16, 17) flowing through said refrigerant conduit (3) and a coolant (18) flowing through said coolant conduit (4) may exchange heat to condense at least a part of said refrigerant (16, 17),
a buffer tank (6),
a liquid conductor (7) arranged to form liquid communication between a buffer liquid outlet (8) of said refrigerant conduit (3) and a buffer liquid inlet (9) of said buffer tank (6), wherein said buffer liquid outlet (8) is arranged at a bottom (10) of said condenser (2),
a gas conductor (11) arranged to form fluid communication between a gaseous refrigerant outlet (12) of said refrigerant conduit (3) and a buffer gas inlet (13) of said buffer tank (6), wherein said buffer gas inlet (13) is arranged at a closed upper part (14) of said buffer tank (6), wherein said gaseous refrigerant outlet (12) is arranged at a desired liquid refrigerant level (15) in said condenser (2), and
wherein said condenser arrangement (1) further is arranged to cool gaseous refrigerant (16) in said buffer tank (6) to a temperature below the condensation temperature of said refrigerant (16, 17).
A condenser arrangement (1) according to claim 1, wherein at least an upper part (14) of said buffer tank (6) is formed as a cul-de-sac.
A condenser arrangement (1) according to claim 1 or 2, wherein said condenser arrangement (1) further comprises a liquid refrigerant outlet (19) through which liquid refrigerant (17) leaves said condenser arrangement (1) and wherein said liquid refrigerant outlet (19) is arranged in said liquid conductor (7) or below a vertical middle (20) of said buffer tank (6).
A condenser arrangement (1) according to claim 3, wherein said condenser arrangement (1) further comprises liquid refrigerant chicane means (21) arranged to alter the flow direction of said liquid refrigerant (17) before it leaves said condenser arrangement (1) through said liquid refrigerant outlet (19).
A condenser arrangement (1) according to any of the preceding claims, wherein said buffer tank (6) and/or said liquid conductor (7) comprises a collection hollow (22).
A condenser arrangement (1) according to claim 3 and 5, wherein said collection hollow (22) is arranged at or after said liquid refrigerant outlet (19).
A condenser arrangement (1) according to any of the preceding claims, wherein said condenser arrangement (1) is arranged to cool gaseous refrigerant (16) in said buffer tank (6) to a temperature below the condensation temperature of said refrigerant (16, 17) by means of cooling means (23).
A condenser arrangement (1) according to claim 7, wherein said cooling means (23) comprises an ambient medium (24) arranged to enclose at least a part of said buffer tank (6).
A condenser arrangement (1) according to claim 8 or 9, wherein said cooling means (23) comprises active cooling means (25) in or on said buffer tank (6).
A condenser arrangement (1) according to claim 9, wherein said active cooling means (25) comprises a pump (26) arranged to establish an actively driven flow of buffer coolant (27) in or on said buffer tank (6).
A condenser arrangement (1) according to claim 9 or 10, wherein said active cooling means (25) comprises a coolant conductor (28) arranged for guiding coolant (18, 27) in or on said buffer tank (6) and between said condenser (2) and said buffer tank (6).
A condenser arrangement (1) according to any of claims 9 to 11, wherein said active cooling means (25) comprises an expansion valve (45).
A condenser arrangement (1) according to any of the preceding claims, wherein said gaseous refrigerant outlet (12) comprises displacement means (30) by means of which said gaseous refrigerant outlet (12) can be displaced vertically.
A condenser arrangement (1) according to any of the preceding claims, wherein said condensation temperature of said refrigerant (16, 17) is between 0 and 150 degrees Celsius, preferably between 15 and 120 degrees Celsius, and most preferred between 25 and 95 degrees Celsius.
A condenser arrangement (1) according to any of the preceding claims, wherein the minimum cross-sectional area of said liquid conductor (7) is at least three times bigger than the minimum cross-sectional area of said gas conductor (11).
A method for controlling a liquid refrigerant level in a condenser (2), said method comprising the steps of:
guiding a flow of gaseous refrigerant (16) into a condenser (2),

condensing said gaseous refrigerant (16) to form liquid refrigerant (17) in said condenser (2) by heat exchange with a flow of coolant (18) being guided through said condenser (2) by means of a coolant conduit (4) thereby cooling said gaseous refrigerant in said condenser (2),

arranging a liquid conductor (7) between said condenser (2) and a buffer tank (6) and guiding said liquid refrigerant (17) out of said condenser (2) by means of said liquid conductor (7), wherein said liquid conductor (7) is arranged at a bottom (10) of said condenser (2),

arranging a gas conductor (11) at a desired liquid refrigerant level (15) in said condenser (2) to enable fluid communication between said condenser (2) and a closed upper part (14) of said buffer tank (6),

cooling the content of said closed upper part (14) of said buffer tank (6) to a temperature below the condensation temperature of said refrigerant (16, 17).
A method according to claim 16, wherein said content of said closed upper part (14) of said buffer tank (6) is cooled by heat exchanging with the ambient medium (24) surrounding said buffer tank (6).
A method according to claim 16 or 17, wherein said method further comprises the step of locating at least said upper part (14) of said buffer tank (6) in an ambient medium (24) having a temperature below the condensation temperature of said refrigerant (16, 17).
A method according to any of claims 16 to 18, wherein said method further comprises the step of cooling said content of said closed upper part (14) of said buffer tank (6) to a temperature below the condensation temperature of said refrigerant (16, 17) by means of said coolant (18).
A method according to any of claims 16 to 19, wherein said method further comprises the step of cooling said content of said closed upper part (14) of said buffer tank (6) to a temperature below the condensation temperature of said refrigerant (16, 17) by actively cooling said content by means of dedicated cooling means (23).
A method according to any of claims 16 to 20, wherein said method further comprises the step of guiding liquid refrigerant (17) out of said condenser arrangement (1) through a liquid refrigerant outlet (19) arranged in said liquid conductor (7) or below a vertical middle (20) of said buffer tank (6).
A method according to claim 21, wherein said method further comprises the step of changing the flow direction of said liquid refrigerant before guiding said liquid refrigerant (17) out of said condenser arrangement (1).
A method according to claim 22, wherein said flow direction is changed by guiding said liquid refrigerant (17) around liquid refrigerant chicane means (21).
A method according to any of claims 21 to 23, wherein said method further comprises the step of arranging a collection hollow (22) at or after said liquid refrigerant outlet (19) as seen in the flow direction of said liquid refrigerant (17) during normal use.
A method according to any of claims 16-24, wherein said method is performed on a condenser arrangement (1) according to any of claims 1-15.
Use of a condenser arrangement (1) according to any of claims 1-15 for controlling a liquid refrigerant level in a condenser (2) forming part of a closed cooling circuit (31).