Condensation vessels are well-known within the technological field of refrigerating. In a refriger- ating system the condensation vessel serves to con- densate the gaseous refrigerant to liquid refrigerant before it. is recycled into the refrigerating process.

Moreover, refrigerating systems has been adapted for use on transport units, such as vans and mobile containers. In particular an increased use of mobile containers has appeared as global trade are expanding. The mobile containers are extremely useful for transporting goods due to the fact that they are easily loaded from ships onto trucks or railway goods wagons and vice versa. As trade with goods like food- stuff, e. g. fruit and meat, which requires cooling during transportation and storing, has increased the need for refrigerated mobile containers has increased as well.

Refrigerated mobile containers are normally equipped with an individually cooling system, and the known systems are capable of providing a satisfactory cooling effect under normal conditions. The known cooling systems are dependent on a condensation de- vice, which is cooled by air. The air-cooled conden- sation device works perfectly well when the refriger- ated mobile container is transported on a truck or

train as one or more fans and the wind caused by the movement of the truck or train will provide satisfac- tory cooling for the condensation process. However, when several refrigerated mobile containers are stored, e. g. in a container ship or a warehouse, it is very difficult or impossible for the air-cooled condensation devices to provide a satisfactory cool- ing. This is in particular true with regard to con- tainer ships. The loading capacity and the economical demands require that the containers are loaded very closely. The loading causes the air scoop and circu- lation of the air to be significantly reduced. More- over, if the ship is in a tropical environment, the temperature of the air may be very high. These condi- tions reduce the capacity of the air-cooled device.

If the condensation device do not work satisfactorily or fails to work, the pressure in the cooling system may rise to undesired high levels, which may cause damages to the system.

As a result of the inappropriate conditions there is a need for a condensation vessel for refri- gerating systems mounted in mobile containers, which condensation vessel is capable of working satisfacto- rily under conditions with relative high temperatures and little or no convection of air.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a condensation vessel for a cooling system for a refrigerated mobile container, which can work independently of the ambient temperature and cooling availability of the air.

Furthermore, it is an object of the present in- vention to provide a condensation vessel, which has a minimal size compared to capacity.

Moreover, it is an object of the present inven-

tion to provide a condensation vessel, which can op- erate with a pressure up to 30 bar.

It is furthermore an object of the present in- vention to provide a condensation vessel, which pro- vides better options for temperature control relative to air-cooled condensation devices.

A further object of the present invention is to provide a condensation vessel, which is resistant to corrosion.

These objects and other objects are achieved by the invention as defined in the claims DETAILED DESCRIPTION OF THE INVENTION The condensation vessel according to the inven- tion provides a condensation vessel with high capac- ity in relation to size, and also enables efficient temperature control and minimizes the required space for condensers in a mobile refrigerating system.

Moreover, the condensing vessel according to the in- vention can function properly in places where the air-cooled condensing devices are unsuitable for use.

The invention is particularly useful for refrigerated containers when these are stored on board a container ship. In this situation the condensation vessel may be cooled by seawater and, consequently, provides a cheap and highly effective cooling for the condenser.

In a first aspect, the invention relates to a condensation vessel for a cooling system for a re- frigerated mobile container, comprising - a horizontal cylindrical body part, - a top part closing said body upwards, - a bottom part closing said body part downwards, - a pipe reeled up as a horizontal coil placed in the body part and near the interior surface of said body

part and coaxial therewith, - an inlet through the wall of said container for supplying cooling water to said coil, - an outlet opening for discharging spent cooling wa- ter from said coil, - an inlet for the gaseous refrigerant in said top part, an outlet communicating with the interior of said bottom part for recovering liquid refrigerant, and - a guiding plate positioned below said inlet for the gaseous refrigerant and above said coil, which plate covers the space encircled by the coil-reeled pipe to direct gaseous refrigerant introduced through said inlet toward the area between the coil and the cylin- drical body part.

The top part, the'body part, and the bottom part are preferably manufactured from metallic material with a wall thickness from 1 to 5 mm and, preferably, welded together. The welding provides a strong assem- bling of the parts, which makes the vessel safe for use with elevated pressure, e. g. pressures up to 30 bar.

The guiding plate serves to lead the gaseous refrigerant towards the periphery part of the cylin- drical body part where the refrigerant is cooled by contact with the surface of the pipe within the cy- lindrical body part. Furthermore, the guiding plate serves to prevent the hot gaseous refrigerant to en- ter the central part of the coil and cylindrical body part, which would cause contact between the hot gase- ous refrigerant and the liquid condensed refrigerant.

Such a contact is highly undesired as it would have a negative influence on the effect of the condensation

vessel due to the fact that it would cause condensed liquid refrigerant to evaporate.

The pipe reeled up to form the coil is prefera- bly made from a bendable metallic alloy, e. g. alloys comprising cupper. The metallic alloy should be re- sistant to corrosion caused by seawater due to the fact that it would be advantageous to use seawater as cooling water for the coil on container ships. The inner diameter of the pipe is preferably from 10 to 30 mm and the wall thickness between 1 and 5 mm.

In a preferred embodiment the outer surface of the coil comprises cooling fins, which increases the surface area and the cooling capacity of the coil significantly. In order to optimize the ratio between capacity and size of the condensation vessel, it is preferred that the surface area of the coil is at least 0.25 m2 per litre of the condensation vessel volume.

Moreover in order to optimize the properties of the condensation vessel, it is preferred that the spacing between the parts of the coil closest to the interior surface of the body part and the interior surface of the body part is from 0 to 3.5 mm and, preferably, between 0.1 and 3.0 mm. Thus, it is pos- sible to secure that the gaseous refrigerant will ob- tain good contact with the cooling surface and con- densate into liquid refrigerant. The liquid refriger- ant is recovered from the bottom part of the vessel via the outlet for liquid refrigerant.

As a further feature for securing satisfactory contact between the gaseous refrigerant and the cool- ing surface, it is preferred that the spacing between adjacent convolutions of the coil is between 0 and

3.5 mm and, preferably, between 0.1 and 3.0 mm.

In a preferred embodiment of the condensation vessel according to the invention, the cylindrical body part has a diameter between 120 and 160 mm and a height of 210 to 250 mm. The embodiment is suitable to fit into cooling systems for conventional mobile containers.

To obtain satisfactory properties with regard to pressure the top part and the bottom are prefera- bly shaped as a part of a sphere. It is well-known that a spherical shape provides the best properties with regard to resisting pressure.

In a preferred embodiment, the guiding plate is formed to have an upper surface substantially paral- lel with the lower surface of the top part. Conse- quently, the guiding plate should be formed as a part of a sphere when the top part is formed as a part of a sphere. This embodiment provides an even distribu- tion of the gaseous refrigerant from the inlet to the upper periphery of the condensation vessel.

In another preferred embodiment, the perimeter of the guiding plate has a diameter of 110 to 155 mm and the guiding plate should at least cover the cen- tral opening of the cooling coil.

For cooling systems in which the refrigerants are used, conditions with elevated pressure are nor- mally chosen and, therefore, preferred that the con- densation vessel according to the invention is con- structed to operate with pressures up to at least 3x106 Pa (30 bar).

In order to reduce the unloaded weight of the refrigerated mobile container, it is desirably to re- duce the weight of the units and preferably, the con-

densation vessel has a product weight of less than 11 kg. Furthermore, in order to achieve high capacity per volume unit the condensation vessel preferably has a capacity of at least 2 kW per litre of volume of the condensation vessel.

In a second aspect, the invention relates to a method of condensing a refrigerant in a condensation vessel, which vessel includes a horizontal substan- tially cylindrical body part closed at the top and at the bottom end with a top part and a bottom part, said method comprises the step of: i) feeding the gaseous refrigerant to the top of the condensation vessel; ii) guiding the refrigerant towards the internal surface of the upper portion of the body part of the condensation vessel; iii) allowing the refrigerant to pass over a cool- ing surface constituted by a cooling coil, from the peripheral part of the vessel to the central part of the vessel, while condensing from gaseous refrigerant to liquid refriger- ant; iv) recovering the liquid refrigerant from the bottom of the condensation vessel In step ii), the gaseous refrigerant is guided to- wards the internal surface of the upper portion of the body part of the condensation vessel, preferably, by means of a guiding plate covering the upper cen- tral part of the cylindrical body part and the core part of the cooling coil. As the gaseous refrigerant is forced towards the periphery part of the vessel, the pressure at the periphery will be a little higher than the pressure in the central part of the vessel.

The difference in pressure will be a driving force for the gaseous refrigerant to move from the periph- ery of the vessel towards the centre while passing the cooling surface of the cooling coil, which will cause a major part of the gaseous refrigerant to con- dense into liquid refrigerant. The liquid refrigerant is collected at the bottom of the condensing vessel, from where it is recovered for recycling in the re- frigerating system. A highly effective method for condensing refrigerant is obtained by the invention.

When preferred refrigerants like R134A are used, it is preferred that the pressure in the vessel is between 2 and 15 bar and the temperature of the cooling surface is between 0 and 40°C in order to achieve the best possible outcome by the method ac- cording to the invention.

As the method is highly effective, the refrig- erant is condensed in a volume preferably less than 5 litres. Moreover, the refrigerant is condensed on a cooling surface of at least 0.2 m2 per litre volume of the condensation vessel. Hereby, the size of the con- densation vessel may by reduced to fit into known mo- bile refrigerating systems.

The cooling coil is cooled with water, which may be ordinary tap water, seawater, or water from a river or lake. Thus, the method is particularly use- ful for refrigerated mobile containers on a container ship.

Types of refrigerants, which may be condensed according to the method are refrigerants of type R134A and similar refrigerants.

The invention will now be described in fur- ther details with reference to the drawing illustrat-

ing an embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the drawing: Figure 1 is a horizontal section of an embodiment of a condensation vessel according to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT In Figure 1, a condensation vessel 1 according to the invention is seen. The condensation vessel comprises a horizontal cylindrical body part 2. The cylindrical body part is closed upwards with a top part 3, and closed downwards with a bottom part 4.

Within the body part 2 a pipe 5 is reeled up as a horizontal coil. The coil is double-winded to provide a efficient cooling. The coil 5 has an inlet 6 for cooling water and an outlet 7 for spent cooling wa- ter, both placed near the bottom part of the vessel.

Moreover, the top part 3 has an inlet 8 for the gase- ous refrigerant and an outlet 9 for recovering the liquid refrigerant. The outlet 9 communicates with the interior of the bottom part 4 of the condensation vessel 1 in order to recover the liquid refrigerant, which is collected in the bottom part 4. Below the inlet 8 for the gaseous refrigerant a guiding plate 10 is positioned. The guiding plate 10 covers the space encircled by the coil-reeled pipe 5 to direct the gaseous refrigerant, which is introduced at high pressure through the inlet 8, towards the area be- tween the coil 5 and the cylindrical body part 2.

Preferably, the guiding plate 10 contacts the upper surface of the outer uppermost winding of the coil 5.

Typically, the shell material for the vessel 1 is steel alloy SA240 type 304 or 316 and the wall thickness is 3 mm. The top part 3 and the bottom part 4 are connected to the cylindrical body part by weld- ing making the vessel resistant to elevated pressure.

The vessel is able to resist a pressure of at least 4. 5x106 Pa (45 bar). The top part 3 and the bottom part 4 are shaped as a part of a sphere with a radius of 98 mm. The spherical shape provides maximum pres- sure resistance.

Preferably, the pipe 5 has an inner diameter of 19 mm and an outer diameter of 25 mm. The pipe is manufactured from alloy CUNI (cupper with nickel, re- sistant to salt water) and reeled up to form a dou- ble-coil constituted by an outer coil and an inner coil. The cooling water first enters into the inner coil via inlet 6 and to the top of the coil, where the cooling water enters the outer coil and flows downwards and leaves the outer coil via outlet 7.

This coil construction secures that the vessel is cooled intensively in the bottom part, from where the liquid refrigerant is recovered. Hereby the liquid refrigerant may be recovered at lower temperature.

The outer surface of the pipe 5 is provided with cooling fins to obtain a larger cooling surface.

The guiding plate 10 is positioned in the upper part of the vessel 1 and covers the central space of the coil. This construction has the advantage that the hot gaseous refrigerant entering the vessel via inlet 8 is prevented from moving downwards into the centre of the coil 5 thereby causing the liquid re- frigerant in the bottom part 4 to evaporate. More- over, the guiding plate 10 directs the gaseous re- frigerant from the inlet 8 to the area between coil 5 and the cylindrical body part 2 providing efficient cooling as the condensing refrigerant passes from the periphery of the vessel 1 to centre of the vessel along the surface of the-cooling coil 5. In order to

secure a efficient contact between the cooling sur- face and the condensing refrigerant, the spacing be- tween the windings of the coil and the interior wall of the body part 2 is small and preferably less than 3.5 mm. Furthermore, the spacing between neighbouring windings of the coil is narrow and, preferably, less than 3.5 mm.

The material chosen for the construction of the coil is preferably a steel alloy resistant to corro- sive substances like seawater.