WO2005005897A2

WO2005005897A2 - Snow into a freezing or cooling chamber and use of a one-way valve as an expansion nozzle in such a device

Info

Publication number: WO2005005897A2
Application number: PCT/EP2003/007607
Authority: WO
Inventors: Noël HUTSEBAUT
Original assignee: Packo Inox Nv
Priority date: 2003-07-11
Filing date: 2003-07-11
Publication date: 2005-01-20
Also published as: AU2003254350A1; AU2003254350A8; WO2005005897A3

Abstract

The invention relates on the one hand to a device for spraying carbon-dioxide snow into a freezing or cooling chamber, comprising - a reservoir for liquid carbon-dioxide; - one or more expansion nozzles (2a, 2b, 2c) for producing the carbon-dioxide snow from liquid carbon-dioxide and introducing the snow into the freezing or cooling chamber;.- a supply line (3) for transporting the liquid carbon-dioxide from said reservoir to the expansion nozzles (2a, 2b, 2c); - a manual opening/closing valve (4) to introduce a flow of liquid carbon-dioxide under pressure from the reservoir into the supply line (3); in which a proportional valve (5) is provided in the supply line (3) for continuously adjusting the quantities of liquid carbon-dioxide introduced into the expansion nozzles (2a, 2b, 2c) and said expansion nozzles (2a, 2b, 2c) are one-way valves. On the other hand, the invention relates to the use of a one-way valve as an expansion nozzle (2a, 2b, 2c) for such a device.

Description

DEVICE FOR SPRAYING CARBON-DIOXIDE SNOW INTO A FREEZING OR COOLING CHAMBER AND USE OF A ONE-WAY VALVE AS AN EXPANSION NOZZLE FOR SUCH A DEVICE

The invention relates to a device for spraying carbon-dioxide snow into a freezing or cooling chamber, comprising a reservoir for liquid carbon-dioxide; one or more expansion nozzles for producing the carbon-dioxide snow from liquid carbon-dioxide and introducing the snow into the freezing or cooling chamber; a supply line for transporting the liquid carbon-dioxide from said reservoir to the expansion nozzles; a manual opening/closing valve to introduce a flow of liquid carbon-dioxide under pressure from the reservoir into the supply line; - a proportional valve which is provided in the supply line for continuously adjusting the quantities of liquid carbon-dioxide introduced into the expansion nozzles.

The invention relates furthermore to the use of a one-way valve as an expansion nozzle for a device for spraying carbon-dioxide snow into a freezing or cooling chamber. Of course such a one-way valve can also be used as an expansion nozzle for other devices for spraying carbon-dioxide snow than the one described in this patent application.

Such freezing or cooling chambers occur in different types of cryogenic freezing machines, such as - batch freezers or coolers; - tunnel freezers or coolers; - tumbler freezers or coolers; - spiral freezers or coolers; - etc. In known carbon-dioxide refrigeration systems for cooling material, such as in U.S. 3,815,377, a freezing chamber is provided in which high pressure liquid carbon- dioxide from a storage tank is expanded through nozzles to produce carbon-dioxide snow which is applied to material being cooled. A supply line for liquid carbon- dioxide leads from the storage tank into said freezing chamber. The expansion nozzles are disposed at the end of this line in the freezing chamber. Usually, a throttle valve is provided in the supply line which regulates the flow-through. To attain and maintain the desired operating temperature in the freezing chamber, the temperature in the freezing chamber is measured and carbon-dioxide is usually sprayed in cycles into the freezing chamber. The initiation and the cut-off of carbon- dioxide is typically effected with magnet valves disposed in the supply line outside the freezing chamber. If the temperature is below a set limit value, the valves are closed through which the supply of carbon-dioxide-snow into the freezing chamber is cut off. After the supply has been cut off, the pressure in the adjoining pipe and the expansion nozzles drops to an ambient pressure of about 1 bar. If the pressure drops below the triple-point pressure of 5,18 bar (pressure in which a phase conversion occurs from liquid carbon-dioxide into carbon-dioxide snow and vapour), the solid carbon-dioxide snow clogs the supply line because it can no longer exit the expansion nozzles. This can lead to a blockage of the valves, and in extreme cases, large portions of the entire pipe lines. To prevent such clogs, the liquid line behind the valve and the expansion element are re-rinsed by means of gaseous carbon- dioxide which comes from a second line which is in contact with the upper gas region of the storage tank. The carbon-dioxide flowing in, forces the liquid out of the supply line and prevents a pressure drop below the triple point as long as carbon- dioxide liquid is in the pipeline.

A disadvantage of such known systems is that additional carbon-dioxide is required for rinsing the supply line and for maintaining the pressure in this supply line with the carbon-dioxide gas. This carbon-dioxide gas does not contribute to the cooling capacity of the carbon-dioxide refrigeration system. To the contrary, this used carbon-dioxide gas additionally warms the atmosphere in the freezing chamber. Subsequently, the carbon-dioxide consumption is undesirably high.

Another disadvantage of such system is that the temperature in the freezing chamber is not constant over time, but fluctuates between an upper and a lower set limit value, through which product quality is affected. To reduce such fluctuations, the setting of the upper and lower limit values can be done in a smaller range, which has the disadvantage that this again reduces the period of a cooling cycle, and subsequently also the switching frequency of the spraying cycles. Because the re-rinsing process with carbon-dioxide has to be performed after each spraying cycle, the losses due to the warm carbon-dioxide gas increase.

A further disadvantage is that the amount of liquid carbon-dioxide which is provided to the nozzles can only be all or nothing because of the use of an on/off valve. The control of the snow-making operation in this system is done by employing snow nozzles which have variable orifices. This kind of control is very delimiting.

It is an object of the invention to provide in a device for spraying carbon-dioxide snow into a freezing or cooling chamber according to the invention, in which there is no more clogging of the device, and subsequently the consumption of carbon-dioxide is reduced because no more re-rinsing of the supply lines of the device is necessary, and in which there is a continue control of the amount of liquid carbon-dioxide introduced into the expansion nozzles.

This object of the invention is achieved by providing a device for spraying carbon- dioxide snow into a freezing or cooling chamber, comprising a reservoir for liquid carbon-dioxide; one or more expansion nozzles for producing the carbon-dioxide snow from liquid carbon-dioxide and introducing the snow into the freezing or cooling chamber; a supply line for transporting the liquid carbon-dioxide from said reservoir to the expansion nozzles; a manual opening/closing valve to introduce a flow of liquid carbon-dioxide under pressure from the reservoir into the supply line; in which a proportional valve is provided in the supply line for continuously adjusting the quantities of liquid carbon-dioxide introduced into the expansion nozzles and said expansion nozzles are one-way valves.

In a preferred embodiment of the device according to the invention said supply line comprises a first part onto which the expansion nozzles are mounted, and a second part which is splitted of of the first part before the first expansion nozzle, and which rejoins the first part after the last expansion nozzle. Subsequently, the carbon- dioxide which is situated in the first part is in liquid form, while it in the second part is in gaseous form. Furthermore, there is a continue equilibrium between the two phases which prevents clogging in the supply line.

In a more preferred embodiment of the device according to the invention, the expansion nozzles are provided with an aperture through which the carbon-dioxide snow is sprayed, and the utmost expansion nozzles have an aperture with a diameter of 1,1 mm, while the intermediate expansion nozzles have an aperture with a diameter of 1 ,3 mm.

This embodiment has the advantage that each expansion nozzle introduces about the same amount of snow into the freezing or cooling chamber.

In another embodiment of the device according to the invention, each expansion nozzle is provided in a pipe, and one pipe is provided around one or more expansion nozzles.

Providing such a pipe prevents that a phase conversion occurs from carbon-dioxide snow into gaseous carbon-dioxide, because the little snow particles coagulate with each other so that they remain in their solid form, subsequently having a much greater cooling capacity when sprayed onto the product.

In a more preferred embodiment of the device according to the invention, a signal generator is provided which gives an electrical or electronical signal to the proportional valve, through which the proportional valves opens more or less. Preferably, the said signal generator is a temperature sensor, for instance a ptlOO or a thermo couple. It can also be any other temperature measurement system.

In a most preferred embodiment of the device according to the invention, said signal generator is a gas analyser.

Another object of the invention is the use of a one-way valve as an expansion nozzle for a device according to the invention and as described above.

Further distinctive features and characteristics will be clarified in the following description of a specific embodiment of the invention as represented in the attached drawings. It should be noted that this embodiment is only given by way of example and implies no restriction in the general scope of the invention as that appears from the above description and from the claims at the end of this text.

In the attached drawings: figure 1 is a schematic representation of the device of the invention; figure 2 is a detailed view of the expansion nozzles as used in a device as shown in figure 1.

As shown in figure is, the device (1) for spraying carbon-dioxide snow into a freezing or cooling chamber (not shown in the figure), comprises: a reservoir for liquid carbon-dioxide (not shown in the figure); - one or more expansion nozzles (2) for producing the carbon-dioxide snow from liquid carbon-dioxide; a supply line (3); a manual opening/closing valve (4); a proportional valve (5) and a controller/signal generator (not shown on the figure).

The liquid carbon-dioxide is held in the reservoir under a pressure of about 18 bar and at a temperature of about - 23°. When the manual opening/closing valve (4) is opened, a flow of the liquid carbon-dioxide under pressure is introduced in the supply line (3), which leads the liquid carbon-dioxide to the expansion nozzles (2). The quantity of liquid carbon-dioxide introduced into the expansion nozzles (2) is continuously adjusted by a proportional valve (5) which is provided in the supply line (3).

The supply line (3) is splitted into two parts, namely a first part (3a) onto which the one or more expansion nozzles (2a, 2b, 2c) are mounted, and a second part (3b) which is splitted of of the first part (3a) before the first expansion nozzle (2a) and which rejoins the first part (3a) after the last expansion nozzle (2c). By using such a ring structure, the carbon-dioxide in the first part (3a) is in a liquid form, while the second part (3b) appears in a gaseous form, in which there is a continue equilibrium between the two phases. Because of this equilibrium, clogs are prevented in the supply line (3).

The expansion nozzles (2) as shown in figure 2 are one-way valves and comprise a steel ball (7), a spring (8) and a plate (9) with an aperture (10) through which the carbon-dioxide snow is sprayed. The plate (9) is preferably flat. The liquid carbon- dioxide which is under pressure (18 bar) presses against the ball (7) which, due to the spring (8), moves forward. Because there is an opening, the liquid carbon-dioxide which flows through the aperture (10) is subjected to a pressure drop to a pressure which lies below the triple point of carbon-dioxide, causing a phase conversion of liquid carbon-dioxide into solid carbon-dioxide snow particles. The triple point of carbon-dioxide at a temperature of 216,6 K is situated at a pressure of 516 kPa. To obtain that an equal amount of carbon-dioxide snow is sprayed out of each of the expansion nozzles (2), the utmost expansion nozzles (2a en 2c) have an aperture (10) with a diameter of 1,1 mm, while the intermediate expansion nozzles (2b) have an aperture (10) with a diameter of 1,3 mm.

To obtain a coagulation of the little snow particles which are sprayed out of the oneway valves into bigger snow particles, each expansion nozzle (2) is provided in a pipe (6). One possibility is that each expansion nozzle (2) is provided in one pipe (6). An other possibility is that two or more expansion nozzles (2) are provided in a pipe (6), which is then preferably a flat pipe. If no pipe (6) is provided around the expansion nozzles (2), the little snow particles sublimate immediately and go into the gas phase. It is herewith remarked that the cooling capacity of carbon-dioxide snow is much greater than the cooling capacity of carbon-dioxide gas when sprayed onto the product.

In the freezing or cooling chamber, a signal generator, for example a temperature sensor (a pt 100, a thermo couple or any other temperature measurement system) or a gas analyser (for instance an O₂-analyser), is provided which gives an electrical or electronical signal (11) to the proportional valve (5) to open more or less, through which the amount of liquid carbon-dioxide which is introduced into the expansion nozzles (2) is regulated continuously, and also the amount of snow which is introduced into the freezing or cooling chamber is regulated. This is necessary when, for instance, a warm product which has to be frozen or cooled is introduced into the freezing or cooling chamber. The usual temperature which is maintained in a freezing or cooling chamber is - 60 °C. Nevertheless, the temperature can be less or more. When a warm product which has to be frozen or cooled is introduced into the freezing or cooling chamber, the temperature rises for instance to - 58 °C. The signal generator receives this signal and opens the proportional valve (5) more, through which more carbon-dioxide snow is sprayed into the freezing or cooling chamber.

Claims

C L A I M S

1. Device for spraying carbon-dioxide snow into a freezing or cooling chamber, comprising a reservoir for liquid carbon-dioxide; one or more expansion nozzles (2a, 2b, 2c) for producing the carbon-dioxide snow from liquid carbon-dioxide and introducing the snow into the freezing or cooling chamber; - a supply line (3) for transporting the liquid carbon-dioxide from said reservoir to the expansion nozzles (2a, 2b, 2c); a manual opening/closing valve (4) to introduce a flow of liquid carbon- dioxide under pressure from the reservoir into the supply line (3); characterised in that a proportional valve (5) is provided in the supply line (3) for continuously adjusting the quantities of liquid carbon-dioxide introduced into the expansion nozzles (2a, 2b, 2c) and said expansion nozzles (2a, 2b, 2c) are one-way valves.

2. Device according to claim 1, characterised in that said supply line (3) comprises a first part (3 a) onto which the expansion nozzles (2a, 2b, 2c) are mounted, and a second part (3b) which is splitted of the first part (3a) before the first expansion nozzle (2a), and which rejoins the first part (3a) after the last expansion nozzle (2c).

3. Device according to claim 1 or 2, characterised in that the expansion nozzles (2a, 2b, 2c) are provided with an aperture (10) through which the carbon-dioxide snow is sprayed, and the utmost expansion nozzles (2a, 2c) have an aperture (10) with a diameter of 1 , 1 mm, while the intermediate expansion nozzles (2b) have an aperture (10) with a diameter of 1,3 mm.

4. Device according to any one of claims 1 up to 3, characterised in that each expansion nozzle (2a, 2b, 2c) is provided in a pipe (6), and one pipe (6) is provided around one or more expansion nozzles (2a, 2b, 2c).

5. Device according to any one of claims 1 up to 4, characterised in that a signal generator is provided which gives an electrical or electronical signal to the proportional valve (5), through which the proportional valves (5) opens more or less.

6. Device according to claim 5, characterised in that said signal generator is a temperature sensor.

7. Device according to claim 6, characterised in that said temperature sensor is a ptlOO or a thermo couple.

8. Device according to claim 5, characterised in that said signal generator is a gas analyser.

9. Use of a one-way valve as an expansion nozzle (2a, 2b, 2c) for a device according to any one of the preceding claims.