WO2019110628A1

WO2019110628A1 - System and method for cooling a gas stream by means of an evaporator

Info

Publication number: WO2019110628A1
Application number: PCT/EP2018/083564
Authority: WO
Inventors: Audrey KEUNEBROCK
Original assignee: Starklab
Priority date: 2017-12-07
Filing date: 2018-12-05
Publication date: 2019-06-13
Also published as: FR3074889A1; FR3074889B1

Abstract

The system for cooling a main gas stream (A) includes an evaporator (1) which comprises an inlet (11), an outlet (12) and an exchanger in which a fluid flows, and which makes it possible to cool a gas stream (B) flowing through the evaporator between the inlet and the outlet of the evaporator, a mixer (2) comprising a main inlet (21) intended during operation for being supplied with the main gas stream (A), a secondary inlet (22) and an outlet (23) which is connected to the inlet (11) of the evaporator (1), and recirculating means (3) for recirculating a portion of the cooled gas stream (C), which include a channel (30) connecting the outlet (12) of the evaporator (1) to the secondary inlet (22) of the mixer (2) and which have the function of collecting a portion of the cooled gas stream (C) at the outlet of the evaporator (1) in the form of a recirculated gas stream (D) and of redirecting this recirculated gas stream (D) to the secondary inlet (22) of the mixer. The mixer (2) makes it possible, during operation, to mix the main gas stream (A) with the cooler recirculated gas stream (D), so as to obtain a more homogeneous secondary gas stream (B) at the inlet of the evaporator (1), with a maximum temperature difference in the secondary stream (B) that is less than 10% of the temperature difference between the main gas stream (A) and the recirculated gas stream (D) and/or with a maximum temperature difference in the secondary stream (B) that is less than 5°C, preferably less than 2°C.

Description

SYSTEM AND METHOD FOR COOLING A GAS STREAM USING AN EVAPORATOR

Technical area

The present invention relates to the cooling of a gas stream, and in particular of moist air, by means of an evaporator. It finds its application in various fields, and for example non-exhaustively in the field of energy recovery in a gas stream by means of a heat pump comprising an evaporator, or dehumidification of a gas stream at by means of an evaporator, or the recovery of water in the atmosphere, or the adjustment of the humidity in a refrigerating device, of the refrigerator, freezer, cold room, ....

Prior art

It is known to this day to cool a gas stream and in particular air, by circulating it in contact with an evaporator. Usually an evaporator comprises an exchanger in which circulates a fluid, preferably a refrigerant, which is vaporized in contact with the gas flow with the exchanger by absorbing the thermal energy of the gas stream.

Generally this evaporator is an integral part of a refrigerant circuit in which the evaporator is associated at least with a condenser, and wherein the fluid circulates in a closed circuit.

These refrigerating circuits are for example used in heat pumps for recovering the thermal energy of the circulating fluid in the refrigerant circuit or in devices for dehumidifying a gas stream in which all or part of the water is recovered. in the gas stream by condensation on the surface of the evaporator exchanger. These dehumidification devices can in particular be used in refrigerating devices such as refrigerators, cold rooms, etc.

When it is desired to cool a moist airflow by means of a evaporator, for example a moist air flow at a temperature above 15 ° C to bring it to a temperature slightly above 0 ° C, there is a significant risk of frost formation on the surface of the heat exchanger. the evaporator, because generally to obtain this result the fluid flowing in the evaporator must be at a temperature below 0 ° C. In the case of frost formation, it is necessary to implement a reverse defrost cycle, which is costly in terms of time and energy.

A conventional solution to reduce this phenomenon of icing consists in increasing the dimensions of the exchanger of the evaporator, so as to increase the contact surface of the exchanger of the evaporator with the gas stream to be cooled, which allows comparable results of increasing the temperature of the fluid in the evaporator exchanger. In this solution, the greater the temperature difference between the gas stream to be cooled and the gas flow obtained after cooling, and the larger the dimensions of the exchanger must be important to prevent the phenomenon of icing. This solution quickly finds its limits because increasing the dimensions of the exchanger of the evaporator increases the manufacturing cost of the exchanger and may in some applications pose congestion problems.

Objectives of the invention

A main objective of the invention is to propose a new solution for cooling a gas flow, and in particular an air flow, by means of an evaporator, which in general makes it possible to improve the operation of the evaporator without increasing the dimensions of the evaporator exchanger.

More particularly, an object of the invention is to propose a novel solution for cooling a gaseous flow, and in particular an air flow, by means of an evaporator, which makes it possible to obtain the same lowering of the temperature of the gas flow with a higher temperature of the fluid flowing in the evaporator and without increasing the dimensions of the exchanger of the evaporator and / or with the same temperature of the fluid flowing in the evaporator and by reducing the dimensions of the exchanger of the evaporator or which makes it possible to obtain a greater lowering of the temperature of the gas flow without modifying the temperature of the fluid circulating in the evaporator, nor the dimensions of the exchanger of the evaporator.

More particularly, in the field of dehumidification, a secondary objective of the invention is to propose a new solution for cooling a wet gas stream, and in particular a moist air stream, by means of an evaporator, which makes it possible to obtain a dehumidified gas stream with a lower water weight, without modifying the dimensions of the evaporator exchanger.

More particularly, a secondary objective of the invention is to propose a new solution for cooling a gas flow, and in particular an air flow, by means of an evaporator, which makes it possible to reduce, and preferably to avoid frost formation on the evaporator exchanger, and in particular by lowering the temperature of the gas stream to a temperature close to 0 ° C.

Summary of the invention

The invention thus relates to a cooling system of a main gas stream (A) which has the following technical characteristics. The cooling system comprises an evaporator which comprises an inlet, an outlet and an exchanger in which a fluid circulates, and which makes it possible to cool a gas stream (B) flowing through the evaporator between the inlet and the outlet of the evaporator, a mixer comprising a main inlet intended for operation to be fed with the main gas stream (A), a secondary inlet and an outlet which is connected to the inlet of the evaporator, and means for recycling a part a cooled gas flow (C), which comprises a pipe connecting the outlet of the evaporator to the secondary inlet of the mixer and whose function is to take a part of the cooled gas flow (C) at the outlet of the evaporator under the recycled gas stream (D) and to redirect this recycled gas stream (D) to the secondary inlet of the mixer; said mixer in operation allows mixing the main gas stream (A) and the recycled gas stream (D) of lower temperature, so as to obtain at the inlet of the evaporator a secondary gas stream (B) more homogeneous, with a maximum temperature difference in the secondary stream (B) which is less than 5 ° C, and preferably 2 ° C.

In the invention, recycling and mixing with the main gas stream to be cooled of a part of the cooled air stream at the outlet of the evaporator advantageously make it possible to improve the operation of the evaporator by reducing the difference between temperature between the temperature of the gas stream (secondary gas stream) at the inlet of the evaporator and the temperature of the gas stream cooled at the evaporator outlet, compared to a system without recycling and without mixer.

In the invention, the recycled gas stream being taken at the outlet of the evaporator, the temperature of the recycled gas stream at the secondary inlet of the mixer is preferably substantially identical to the temperature of the cooled gas stream at the outlet of the evaporator. evaporator.

More particularly, the cooling system of the invention may comprise the following additional and optional features, taken alone, or in combination with each other:

- The mixer has a perforated wall or a grid interposed on the path of the main gas stream (A) and the recycled gas stream (B).

- The mixer comprises a stirring means and more particularly a fan, for stirring and mixing the main gas stream (A) and the recycled gas stream (D) and / or comprises a stirring means and more particularly a fan, allowing stir and mix the secondary gas stream before leaving the mixer.

- The cooling system comprises means for automatically regulating the flow of the main gas stream (A) and / or the flow rate of the recycled gas stream (D). The cooling system comprises first means for measuring the temperature of the cooled gas stream (C) or the recycled gas stream (D), the automatic regulation means being able to automatically adjust the flow rate of the main gas stream (A) and / or the flow rate of the recycled gas stream (D), as a function of the temperature measured by said first measuring means.

The cooling system comprises second means for measuring the temperature of the secondary gas flow (B), the automatic control means being able to automatically adjust the flow rate of the main gas flow (A) and / or the flow rate of the recycled gas stream ( D), as a function of at least the temperature measured by said second measuring means.

The automatic regulation means are capable of automatically adjusting the flow rate of the main gas flow (A) and / or the flow rate of the recycled gas stream (D), as a function of at least the temperature measured by said first measuring means and the temperature measured by said second measuring means.

The cooling system comprises means for measuring the temperature of the main gas stream (A), the automatic regulation means being able to automatically adjust the flow rate of the main gas stream (A) and / or the flow rate of the recycled gas stream (D). ), as a function of at least the temperature of the main gas stream (A) measured by said temperature measuring means.

The cooling system comprises first means for measuring the weight of water in the cooled gas stream (C) or in the recycled gas stream (D), the automatic regulation means being able to automatically adjust the flow rate of the main gas stream (A). and / or the flow rate of the recycled gas stream (D), as a function of at least the water weight measured by said first measuring means.

The cooling system comprises second means for measuring the weight of water in the main gas stream (A), the automatic control means being able to automatically adjust the flow rate of the main gas stream (A) and / or the flow rate of the recycled gas stream (D), as a function of at least the water weight measured by said second measuring means.

- The mixer is able to produce said secondary flow (B) with a maximum temperature difference in the secondary flow (B) which is less than 10% of the temperature difference between the main gas stream (A) and the recycled gas stream (D).

- The recycling means, the mixer, and optionally the automatic control means, are able to produce said secondary gas stream (B) and said cooled gas stream (C) with a maximum temperature difference between the secondary gas stream ( B) and the cooled gas stream (C) which is sufficiently low to prevent frost formation on the surface of the evaporator exchanger.

- The recycling means, the mixer, and optionally the automatic control means, are able to produce said cooled gas stream (C) at a temperature below 5 ° C.

- The recycling means, the mixer, and optionally the automatic control means, are able to produce the secondary gas flow (B) and the cooled gas flow (C) with a maximum temperature difference between the secondary gas flow ( B) and the cooled gas stream (C) which is less than 5 ° C and preferably less than 2 ° C.

- The recycling means, the mixer, and optionally the automatic control means are capable of producing the cooled gas stream (C) with a water weight of less than 5 g / kg.

The invention also relates to a use of the aforementioned cooling system for cooling a gas flow, and in particular an air flow.

The invention also relates to a method of cooling a main gas stream (A) in which the gas stream is mixed principal (A) with a recycled gas stream (D) of lower temperature, so as to obtain a more homogeneous secondary gas stream (B) with a maximum temperature difference in the secondary stream (B) which is less than 10% of the temperature difference between the main gas stream (A) and the recycled gas stream (D) and / or with a maximum temperature difference in the secondary stream (B) which is less than 5 ° C, and preferably 2 ° C, and this secondary gas stream (B) is cooled in contact with the exchanger of an evaporator in which circulates a fluid absorbing the thermal energy of the secondary gas stream (B), so as to obtain at the output of the evaporator a cooled gas stream (C), a part of this cooled gas stream (C) being taken by means of a pipe (30) connecting the outlet (12) of the evaporator (1) to an inlet (22) of the mixer (2) for forming said recycled gas stream (D).

More particularly, the process of the invention may comprise the following additional and optional features, taken alone, or in combination with each other:

- The maximum temperature difference between the secondary gas stream (B) and the cooled gas stream (C) is sufficiently low to prevent the formation of frost on the surface of the evaporator exchanger.

- The cooled gas stream (C) is at a temperature above 0 ° C and below 5 ° C, and preferably below 2 ° C.

- The maximum temperature difference between the secondary gas stream (B) and the cooled gas stream (C) is less than 5 ° C and preferably less than 2 ° C.

- The water weight of the cooled gas stream (C) is less than 5 g / kg.

- The main gas stream (A) at the inlet of the mixer is a main gas stream (A ') which is cooled, before it enters the mixer, by means of a portion (E) of the gas stream which, at the outlet of the evaporator (1), is cooled and not recycled to the mixer.

The invention also relates to an energy recovery installation in a gas stream comprising a cooling system abovementioned and means for recovering at least a portion of the thermal energy in the fluid after passage of this fluid in the evaporator.

The invention also relates to a dehumidification installation of a gas stream comprising a cooling system referred to above, and more particularly comprising means for recovering the condensation water at the surface of the exchanger of the evaporator.

In a particular variant embodiment, the dehumidification installation of a gas flow comprises, in addition to an exchanger, which makes it possible to produce the main gas flow (A) at the mixer inlet from a first main gas stream (A ') which is cooled, before entering the mixer, transferring, upstream of the mixer, a portion of the thermal energy of the first gas stream (A') to the portion (E) of gas stream which, at the output of the evaporator is not recycled to the mixer.

Brief description of the figures

The features and advantages of the invention will appear more clearly on reading the detailed description below of several particular embodiments of the invention, which particular embodiments are described by way of non-limiting and non-exhaustive examples of the invention and with reference to the accompanying drawings in which:

- Figure 1 schematically shows an alternative embodiment of a cooling system of the invention.

FIG. 2 represents a known structure of an energy recovery installation in a gas stream of heat pump type (PAC).

- Figure 3 shows a known structure of a dehumidification installation of a gas stream.

- Figures 4 to 7 respectively show four embodiments of a mixer of a cooling system of the invention. FIG. 8 is a diagram of an improved variant of a dehumidification installation of the invention.

detailed description

FIG. 1 is a schematic diagram of a cooling system of a main gas stream A according to the invention. With reference to this FIG. 1, this cooling system comprises an evaporator 1 which is known per se and which is associated with a mixer 2 and means 3 for recycling a part of the cooled gas stream at the outlet of the evaporator 1 , and means 1 'for circulating a gas flow, and in particular an air flow, through the mixer 2 and through the evaporator 1, in the form of, for example, a fan or compressor.

In the particular example of FIG. 1, these means 1 'for circulating a gas flow are positioned downstream of the evaporator 1 and make it possible to create a gas flow by suction. In another variant, these means 1 'for circulating a gas flow may for example be positioned upstream of the mixer 2 and allow to create a gas flow by blowing.

The evaporator 1 is a device for cooling a gas flow which is known per se, and which comprises an exchanger in which circulates a fluid, preferably a refrigerant, which is vaporized in contact with the gas flow with the heat exchanger. absorbing the thermal energy of the gas stream. The shape and / or the structure of the exchanger of the evaporator 1 are of no importance for the invention.

In the context of the invention, the evaporator 1 may be a direct evaporator, that is to say an evaporator in which the gaseous flow to be cooled is in direct contact with the exchanger in which the fluid which is vaporized circulates. . The evaporator 1 may also be an indirect evaporator, that is to say an evaporator comprising at least two exchangers: an intermediate exchanger in which circulates a cooling fluid, such as for example water, and in contact with which the gas stream to be cooled is fed, said cooling fluid making it possible to take thermal energy in the gas stream to be cooled without being vaporized; an exchanger in which circulates a fluid, preferably a refrigerant, which is vaporized by absorbing a portion of the thermal energy of the fluid of the intermediate exchanger.

FIGS. 2 and 3 show two known installation examples comprising a circuit implementing a direct evaporator 1 in which the fluid F circulates in a closed circuit.

In FIG. 2, the circuit constitutes a heat pump and comprises, in a manner known per se, an evaporator 1 comprising an exchanger 10 connected to the inlet of the exchanger 50 of a condenser 5 via a compressor 4. The exchanger 50 condenser 5 is connected to the exchanger 10 of the evaporator 1 via a pressure reducer 6, so as to form a closed loop in which the fluid F, which is preferably a refrigerant, circulates.

In operation, the gas stream B, for example a stream of air, at a given temperature is circulated in contact with the exchanger 10 of the evaporator 1, the fluid F being circulated in a closed loop in the circuit by means of 4. In the exchanger 10 of the evaporator, the fluid F, at a temperature below the temperature of the gas stream B, absorbs a portion of the thermal energy of the gas stream B, by vaporizing. The gas stream B is thus cooled in contact with the exchanger 10. The fluid F is then condensed in the exchanger 50 of the condenser 5, which makes it possible to recover a portion of the thermal energy in the fluid by heating the exchanger 50. By circulating a gas stream B 'in contact with the exchanger 50 of the condenser 5, said gas flow B' is heated. In another variant, instead of a gas B ', a liquid could be heated, such as water by circulating it in contact with the exchanger 50 of the condenser 5.

FIG. 3 shows the known block diagram of a dehumidifier comprising a circuit in which a fluid F, which is preferably a refrigerant, circulates in a closed loop. In a similar manner to the circuit of FIG. 2, this circuit comprises an evaporator 1 comprising a coil-shaped exchanger 10, a condenser comprising a exchanger 50 in the form of a coil, a compressor 4 and a pressure reducer 6. A fan 7 corresponding, for example, to the fan 1 'of FIG. 1, is used to circulate a hot and humid gas flow B, for example a flow of air heated in moisture, first in contact with the exchanger 10 of the evaporator 1, then in contact with the exchanger 50 of the condenser 5. This gas stream B hot and humid is initially cooled in the form of a cold and dry gas stream B ', all or part of the water vapor contained in this stream B condensing on the surface of the exchanger 10 of the evaporator 1. The condensation water is recovered by gravity in a receptacle 8 and discharged by means of a water pump or by gravity. Then this cold dry gas stream B 'is heated in the form of a hot and dry gas stream B' circulating in contact with the exchanger 50 of the condenser 5.

In FIG. 1, for the sake of simplification, only the evaporator 1 has been shown, it being specified that this evaporator 1 may for example be an integral part of a closed circuit of an energy recovery installation (heat pump). the type of that of Figure 2 or for example be part of a closed circuit of a dehumidifier of the type of that of Figure 3.

The evaporator 1 comprises an inlet 1 1 of gas flow, an outlet 12 of gas flow and an exchanger 10 (not shown in FIG. 1) in which the fluid F circulates. This evaporator 1 serves the function of cooling a circulating gas flow. through the evaporator between the inlet 1 1 and the outlet 12 of the evaporator 1.

The mixer 2 is positioned upstream of the evaporator 1 and comprises a main gas flow inlet 21, a secondary gas flow inlet 22 and a gas flow outlet 23, which is connected to the inlet 1 1 of the evaporator 1.

The recycling means 3 have the function of taking a part of the cooled gas stream C at the outlet 12 of the evaporator 1 in the form of a recycled gas stream D and of redirecting this recycled gas stream D to the secondary inlet 22 of the mixer 2. These recycling means 3 comprise a return pipe connecting the outlet 12 of the evaporator 1 to the secondary inlet 22 of the mixer. Part of the cooled gas flow C is directed into this return pipe in the form of said recycled gas stream D. The temperature of the cooled gas stream C at the outlet of the evaporator is thus substantially identical to the temperature of the recycled gas stream D at secondary inlet 22 of the mixer 2.

In an alternative embodiment, the return pipe may be equipped with an additional fan or compressor allowing, as the case may be, to suck or push in said pipe a part of the cooled gas stream C at the outlet 12 of the evaporator 1, under the form of said recycled gas stream D, to the secondary inlet 22 of the mixer 2.

In operation, the main gas stream A to be cooled, and for example a flow of air that can be humid, is mixed in the mixer 2, upstream of the evaporator 1, with the recycled gas stream D of lower temperature, in order to obtain a more homogeneous secondary gas flow B at the inlet of the evaporator 1. Then this secondary gas stream B is cooled in contact with the exchanger of the evaporator 1 in which circulates the fluid F absorbing the thermal energy of the secondary gas stream B. A cooled gas stream C is obtained at the outlet of the evaporator 1 , part of this cooled gas stream C being taken up by the recycling means 3.

The "more homogeneous" nature of the secondary gas stream B results in a more homogeneous temperature in the secondary gas stream B compared to the temperature difference between the main gas stream A and the recycled gas stream D at the inlet of the mixer 2 with a maximum temperature difference in the secondary flow (B) (temperature difference between the hottest point and the coldest point in the secondary gas flow) which is less than 10% of the temperature difference between the flow main gas A and the recycled gas stream D and / or with a maximum temperature difference in the secondary flow B which is less than 5 ° C, and preferably below 2 ° C.

The maximum temperature difference in the secondary gas stream B (difference in temperature between the hottest point and the coldest point in the secondary gas stream) is thus in practice lower, and preferably much lower, away. maximum temperature between the main gas stream A and the recycled gas stream D.

Different embodiments of a mixer 2 are shown in FIGS. 4 to 7, it being specified that these examples are not limiting of the invention and that other mixer structures fulfilling the same function can be envisaged.

In FIG. 4, the mixer 2 comprises a mixing chamber 23, in which is mounted at least one grid 24 or a perforated plate 24 which separates the chamber 23 into two upstream and downstream chambers 26, the two gas flow inlets. 21 and 22 being formed in the upstream chamber 25, and the evaporator 1 being mounted in the downstream chamber 26.

In operation, the main gas stream A and the recycled gas stream D are introduced into the upstream chamber 25. The function of the grid or the perforated plate 24 is to create, in the upstream chamber 25, on the path of the gas flows A and D, a pressure drop which allows turbulently mixing the two gas flows A and B and to obtain a more homogeneous secondary gas flow B which passes through the grid or the perforated plate 24. This more homogeneous secondary gas flow B leaves the downstream chamber 26 by contacting the evaporator 1.

The rate of opening of the grid or perforated plate 24 (ratio between the sum of the sections of the openings of the grid or perforated plate 24 traversed by the gas flow and the total surface of the grid or the perforated plate 24 ) and the openings section of the grid or the perforated plate 24 will be chosen in particular according to the degree of homogeneity desired for the secondary air flow B and flow rates A, D and B flows.

The mixer 2 of FIG. 5 has been improved with respect to mixer of Figure 4 by adding a stirring means 27, including a fan in the upstream chamber 25, upstream of the grid or the perforated plate 24. This stirring means 27 improves the homogeneity of the gas flow secondary B, by stirring and mechanically mixing the main gas stream and the recycled gas stream D in the upstream chamber 25.

The mixer 2 of FIG. 6 has been improved with respect to the mixer of FIG. 4 by adding a stirring means 27, and in particular a fan in the downstream chamber 26, downstream of the grid or the perforated plate 24. This means brewing device 27 makes it possible to improve the homogeneity of the secondary gas stream B by stirring and mechanically mixing the secondary gas stream B in the downstream chamber 26 before it leaves the mixer 2.

FIG. 7 represents another example of mixer 2 which differs from that of FIG. 4 in the shape of the downstream chamber 25 which forms a Y-connection.

Recycling the air flow D upstream of the evaporator advantageously makes it possible to lower the temperature difference between the inlet and the outlet of the evaporator. Compared to a conventional solution without recycling and without mixer, it is thus possible for example to obtain at the outlet of the evaporator 1 the same lowering of the temperature of the gas stream (temperature difference between the main gas stream A and the gas flow cooled C) with a higher temperature of the fluid F flowing in the evaporator 1 and without increasing the dimensions of the exchanger of the evaporator 1 and / or with the same temperature of the fluid F circulating the evaporator 1 and decreasing the dimensions of the evaporator exchanger 1. Compared to a conventional solution without recycling and without mixer, it is also possible for example to obtain a greater lowering of the temperature of the gas flow (temperature difference between the main flow stream A and the cooled gas flow C) without modifying the the temperature of the fluid F circulating in the evaporator or the dimensions of the evaporator exchanger.

The mixture of the main gas stream A and the recycled gas stream D by the mixer 1 is important in order to avoid the presence in the secondary gas flow of cold spots, especially at the temperature of the recycled gas stream D and hot spots, especially at the temperature a main gas flow A which could locally cause the formation of frost on the exchanger of the evaporator 1.

For the implementation of the invention, it is preferable that the secondary flow B at the output of the mixer 2 is as homogeneous as possible.

More particularly, the mixer 1 is designed to obtain a maximum temperature difference in the secondary flow B (difference in temperature between the hottest point and the coldest point in the secondary gas flow) which is less than 5 ° C. , and preferably less than 2 ° C and / or so as to obtain a maximum temperature difference in the secondary flow B (temperature difference between the hottest point and the coldest point in the secondary gas flow) which is less than 10% of the temperature difference between the main gas stream A and the recycled gas stream D at the inlet of the mixer 2.

The combination of recycling a part of the cooled gas stream C and the mixture with the main gas stream A makes it possible more particularly in certain applications, such as, for example, energy recovery or dehumidification, to lower the temperature of the cooled gas stream. C. at values close to 0.degree. C., and especially below 5.degree. C., and preferably at 2.degree. C., avoiding the formation of frost on the surface of the exchanger of the evaporator 1 and without implementing large surface exchangers.

More particularly in many applications, the recycling means 3 and the mixer 2 are designed so as to obtain a maximum temperature difference between the secondary air flow B and the cooled air flow C which is low enough to avoid the formation of frost on the surface of the exchanger of the evaporator 1 and / or in order to obtain a gap maximum temperature between the secondary air stream B and the cooled air flow C which is less than 5 ° C and preferably less than 2 ° C.

Also the combination of recycling a part of the cooled gas stream C and the mixture with the main gas stream A allows more particularly in certain applications, such as for example dehumidification, to reduce the weight of water in the cooled gas stream C at very low values, without using large surface heat exchangers.

More particularly, the recycling means 3 and the mixer 2 are designed so as to obtain a cooled air flow C having a water weight of less than 5 g / kg of dry air.

In a particular implementation of the cooling system of the invention, it is up to the person skilled in the art, depending on the application, for example to adjust case by case the flow rate of the recycled gas stream D with respect in particular to flow rate of the main gas flow A and the characteristics of the main gas flow A (in particular temperature, weight in water) at the inlet of the mixer as a function, in particular, of the temperature deviation sought in steady state between the temperature of the secondary flow at the the inlet of the evaporator 1 and the temperature of the cooled gas flow C at the outlet of the evaporator 1 or as a function of the target temperature, under stationary conditions, for the cooled gas flow C at the outlet of the evaporator 1, or in function the target water weight, in stationary mode, in the cooled gas stream C at the outlet of the evaporator 1.

In another particular variant embodiment, the cooling system may comprise automatic regulation means RA of the flow rate of the main gas stream A and / or the flow rate of the recycled gas stream D, these automatic regulation means RA being able in particular to control the means 1 'of circulating the gas stream. These automatic regulation means are implemented in the form of, for example, a programmable logic controller or any other equivalent electronic control circuit. More particularly, the cooling system may comprise first measuring means T1 for the temperature of the cooled gas stream C or the recycled gas stream D (for example temperature probe or equivalent placed in the cooled gas stream C or in the recycled gas stream D), the automatic regulation means RA being able to automatically adjust the flow rate of the main gas stream A and / or the flow rate of the recycled gas stream D, as a function of the temperature measured by said first measuring means.

More particularly, the cooling system may comprise second measuring means T2 for the temperature of the secondary gas flow B at the inlet (for example temperature probe or equivalent placed in the gas flow B), the automatic regulation means RA being adapted to automatically adjust the flow rate of the main gas stream A and / or the flow rate of the recycled gas stream D, as a function of the temperature measured by said first measuring means and the temperature measured by said first measuring means.

More particularly, the cooling system may comprise means T3 for measuring the temperature of the main gas stream A at the inlet of the mixer 2, the automatic regulation means RA being able to automatically adjust the flow rate of the main gas stream A and / or or the flow rate of the recycled gas stream D, as a function of at least the temperature of the main gas stream A measured by the said temperature measuring means, and, if appropriate, as a function of the temperature of the cooled gas flow measured by the said first means of measuring and optionally, if appropriate, the temperature in the secondary gas stream B measured by said second measuring means.

More particularly, the cooling system may comprise first means H1 for measuring the weight in water in the cooled gas stream C or in the recycled gas stream D (for example a humidity probe or equivalent placed in the gas stream C or in the gas stream recycled D), the automatic regulation means RA being able to automatically adjusting the flow rate of the main gas stream A and / or the flow rate of the recycled gas stream D, as a function of the weight in water measured by said first measuring means.

More particularly, the cooling system may comprise second means H2 for measuring the water weight in the main gas stream A, for example a hygrometric probe or equivalent placed in the main gas stream A, the automatic regulation means RA being able to adjust automatically the flow rate of the main gas stream A and / or the flow rate of the recycled gas stream D, as a function of at least the water weight measured by said second measuring means.

FIG. 8 shows an alternative embodiment of a dehumidification installation which makes it possible to produce a dehumidified gaseous stream F, and in particular a dehumidified airflow F at a temperature Tf + DT, from a wet gas stream A ', and in particular a moist air stream, at a temperature Te.

This dehumidification installation comprising a cooling system with mixer 2 and evaporator 1 as previously described, and a heat exchanger G, for example a heat exchanger of the double flow or heat pipe type, which makes it possible to transfer, upstream of the mixer 2, a part of the thermal energy of the gaseous flow A 'wet towards the gaseous flow E which is not recycled at the outlet of the evaporator 1, so as to produce said flow of dehumidified air F at a temperature Tf + DT. The main gas stream A at the inlet of the mixer 2 of the cooling system corresponds to the wet gas stream A 'cooled to a temperature Tc-DT after passing through the exchanger G.

By way of example only, the temperature Te can be 30 ° C; the temperature Tf can be 4 ° C; The temperature difference DT may be 12 ° C. The dehumidified gas stream F is at a temperature of 16 ° C (Tf + DT). In this case, the cooling device of the invention needs to cool the main gas stream A only from 18 ° C (Te-DT) to 4 ° c (Tf), which represents a significant energy saving . The implementation of this exchanger G therefore advantageously reduces energy expenditure for dehumidification.

Claims

A system for cooling a main gas stream (A), comprising an evaporator (1) which comprises an inlet (11), an outlet (12) and an exchanger (10) in which a fluid (F) circulates, and which makes it possible to cool a gas stream (B) circulating through the evaporator between the inlet and the outlet of the evaporator, a mixer (2) comprising a main inlet (21) intended for operation to be fed with the gas flow main (A), a secondary inlet (22) and an outlet (23) which is connected to the inlet (11) of the evaporator (1), and means for recycling (3) a part of the gas flow cooled (C), which comprise a pipe (30) connecting the outlet (12) of the evaporator (1) to the secondary inlet (22) of the mixer (2) and whose function is to take a part of the gas flow cooled (C) at the outlet of the evaporator (1) in the form of a recycled gas stream (D) and redirecting this recycled gas stream (D) to the secondary inlet (22) of the mixer, said mixer (2), in operation, for mixing the main gas stream (A) and the recycled gas stream (D) of a lower temperature, so as to obtaining at the inlet of the evaporator (1) a secondary gas stream (B) more homogeneous with a maximum temperature difference in the secondary stream (B) which is less than 10% of the temperature difference between the gas stream main (A) and the recycled gas stream (D) and / or with a maximum temperature difference in the secondary stream (B) which is less than 5 ° C, and preferably 2 ° C.

2. Cooling system according to claim 1, wherein the mixer (2) comprises a perforated wall (24) or a grid (24) interposed on the path of the main gas stream (A) and the recycled gas stream (B).

3. Cooling system according to any one of the preceding claims, wherein the mixer (2) comprises a stirring means (27) and more particularly a fan, for stirring and mixing the main gas stream (A) and the recycled gas stream (D) and / or comprises a stirring means (27) and more particularly a fan, for stirring and mixing the secondary gas stream (B) before leaving the mixer (2).

4. Cooling system according to any one of the preceding claims, comprising means for automatic regulation (RA) of the flow rate of the main gas stream (A) and / or the flow rate of the recycled gas stream (D).

5. Cooling system according to claim 4, comprising first measuring means (T1) of the temperature of the cooled gas stream (C) or the recycled gas stream (D), the automatic regulation means being able to automatically adjust the flow rate. the main gas flow (A) and / or the flow rate of the recycled gas stream (D), as a function of the temperature measured by said first measuring means.

6. Cooling system according to claim 4 or 5, comprising second means (T2) for measuring the temperature of the secondary gas flow (B), the automatic regulation means being able to automatically adjust the flow rate of the main gas flow (A). and / or the flow rate of the recycled gas stream (D), as a function of at least the temperature measured by said second measuring means (T2).

7. Cooling system according to claims 5 and 6, wherein the automatic control means are adapted to automatically adjust the flow of the main gas stream (A) and / or the flow rate of the recycled gas stream (D), depending at least the temperature measured by said first measuring means (T1) and the temperature measured by said second measuring means (T2).

8. Cooling system according to any one of claims 4 to 7, comprising means for measuring (T3) the temperature of the main gas stream (A), the automatic control means being adapted to automatically adjust the flow of the gas stream main (A) and / or the flow rate of the recycled gas stream (D), as a function of at least the temperature of the main gas stream (A) measured by said temperature measuring means (T3).

9. Cooling system according to any one of claims 4 to 8, comprising first means (H1) for measuring the weight in water in the cooled gas stream (C) or in the recycled gas stream (D), the means for automatic regulation being able to automatically adjust the flow rate of the main gas stream (A) and / or the flow rate of the recycled gas stream (D), as a function of at least the water weight measured by said first measuring means (H1).

10. Cooling system according to any one of claims 4 to 9, comprising second means (H2) for measuring the weight in water in the main gas stream (A), the automatic regulation means being able to automatically adjust the flow rate. the main gas stream (A) and / or the flow rate of the recycled gas stream (D), as a function of at least the water weight measured by said second measuring means (H2).

11. Cooling system according to any one of the preceding claims, wherein the temperature of the recycled gas stream (D) at the secondary inlet (22) of the mixer (2) is substantially identical to the temperature of the cooled gas stream (C ) at the outlet of the evaporator (1).

Cooling system according to one of the preceding claims, in which the recycling means (3), the mixer (2) and, if appropriate, the automatic control means, are capable of producing said secondary gas stream (B). ) and said cooled gas stream (C) with a maximum temperature difference between the secondary gas stream (B) and the cooled gas stream (C) which is sufficiently small to prevent frost formation on the surface of the heat exchanger. evaporator (1).

13. Cooling system according to any one of the preceding claims, wherein the recycling means (3), the mixer (2), and optionally the automatic control means, are adapted to produce said cooled gas stream (C ) at a temperature above 0 ° C and below 5 ° C.

14. Cooling system according to any one of the preceding claims, wherein the recycling means (3), the mixer (2), and optionally the automatic control means, are able to produce the secondary gas flow (B ) and the cooled gas stream (C) with a maximum temperature difference between the secondary gas stream (B) and the cooled gas stream (C) which is less than 5 ° C and preferably less than 2 ° C.

15. Cooling system according to any one of the preceding claims, wherein the recycling means (3), the mixer (2), and optionally the automatic control means, are able to produce the cooled gas stream (C) with a water weight of less than 5 g / kg.

16. Use of the cooling system of any one of the preceding claims for cooling a gas flow (A), and in particular a flow of air.

17. A method of cooling a main gas stream (A), wherein the main gas stream (A) is mixed in a mixer (2) with a recycled gas stream (D) of a lower temperature, so as to obtain a secondary gas stream (B) more homogeneous with a maximum temperature difference in the secondary stream (B) which is less than 10% of the temperature difference between the main gas stream (A) and the recycled gas stream (D) and / or with a maximum temperature difference in the secondary stream (B) of less than 5 ° C, and preferably at 2 ° C, and this secondary gas stream (B) is cooled in contact with the exchanger of an evaporator ( 1) in which circulates a fluid (F) absorbing the thermal energy of the secondary gas stream (B), so as to obtain at the outlet of the evaporator (1) a cooled gas stream (C), a part of this gas stream cooled (C) being withdrawn by means of a pipe (30) connecting the outlet (12) of the aporator (1) at an inlet (22) of the mixer (2) to form said recycled gas stream (D).

18. Cooling method according to claim 17, wherein the maximum temperature difference between the secondary gas stream (B) and the cooled gas stream (C) is sufficiently low to prevent frost formation on the surface of the exchanger. of the evaporator (1).

19. The method of cooling according to any one of claims 17 to 18, wherein the cooled gas stream (C) is at a temperature above 0 ° C and below 5 ° C, and preferably below 2 ° C.

20. The method of cooling according to any one of claims 17 to 19, wherein the maximum temperature difference between the secondary gas stream (B) and the cooled gas stream (C) is less than 5 ° C and preferably lower at 2 ° C.

21. The method of cooling according to any one of claims 17 to 20, wherein the weight of water of the cooled gas stream (C) is less than 5 g / kg.

22. A method of cooling according to any one of claims 17 to 21, wherein the main gas stream (A) at the inlet of the mixer (2) is a main gas stream (A ') which is cooled, before its entry in the mixer (2), by means of a portion (E) of the gas stream which, at the outlet of the evaporator (1), is cooled and not recycled to the mixer (2).

23. The method of cooling according to any one of claims 17 to 22, wherein the temperature of the recycled gas stream (D) at the secondary inlet (22) of the mixer (2) is substantially identical to the temperature of the cooled gas flow. (C) at the outlet of the evaporator (1).

24. Apparatus for recovering energy in a gas stream comprising a cooling system of any one of claims 1 to 15 and means (4, 5) for recovering at least a portion of the thermal energy in the fluid (F) after passage of this fluid in the evaporator (1).

25. Dehumidification installation of a gas stream comprising a cooling system of any one of the claims

1 to 15, and more particularly comprising means (4, 5, 8, 9) for recovering the condensation water at the surface of the exchanger of the evaporator (1).

26. Apparatus for dehumidifying a gas stream according to claim 25, further comprising an exchanger (G), which makes it possible to produce the main gas stream (A) at the inlet of the mixer (2) from a first main gas stream (A ') which is cooled, before it enters the mixer (2), transferring, upstream of the mixer (2), a portion of the thermal energy of the first gas stream (A') to the part (E) gas stream which, at the outlet of the evaporator (1) is not recycled to the mixer (2).