VACUUM COOLING TUNNEL

Abstract: Vacuum cooling tunnel, in particular for cooling water containing products, such as for example salad, comprising a horizontal cylindrical housing 1 having an access door at at least one end for supplying or removing loads 7 of products on pallets 6 or the like, which loads 7 have a rectangular cross-section, in which in the spaces between the upstanding walls of the most width and acceptable load 7 and the cylindrical wall condensing bodies 4,5 extending in longitu­ dinal direction are arranged consisting of parallel pipes through which a cold means is fed, which pipes are arranged within an enclosure, the open upper side of which communi­ cates with the interior of the tunnel 1 and to which at least one vacuum pump is connected for generating an under pressure in the interior of the tunnel, whereby the horizontal cross-section of the passage for the medium to be withdrawn from the interior of the tunnel 1 and moved in each condensing body 4,5 perpendicular to the pipes by the vacuum pump(s) diminishes stepwise or continuously from the open upper side of the condensing body 4,5.

Description: Vacuum cooling tunnel. The invention relates to a vacuum cooling tunnel, in particular for cooling water containing products, such as for example salad, comprising a horizontal cylindrical housing having at at least one end an access door for supplying and removing products on pallets or the like, which loads have a rectangular cross-section, in which in the spaces between the upstanding walls of the most width and acceptable load and the cylindrical wall condensing bodies are arranged extending in longitudinal direction and consisting of parallel pipes through which a cooling means is fed, which pipes are arranged in a rectangular pattern within an enclosure the open upper side of which is in communication with the interior of the tunnel and to which at least one vacuum pump is connected for sucking off the medium present in the interior of the tunnel though each condensing body, perpendicular to its pipes. Such cooling tunnels are used among others in auction buildings for cooling salad, purslane or the like quickly and thereby keeping it fresh longer and are known from "Koeltechniek" vol.62, October 1969, the Hague, Holland, pages 211-215. The product generally packed in cases, crates or boxes is positioned in the tunnel on pellets or the like. Then, in the horizontal cylindrical tunnel a number of pallets stands on a conveying system behind each other and in juxta position having stacks of cases or the like thereon. By the type of said packing the entire load of the tunnel has the shape of a rectangular parallelepiped. It is clear that said arrangement does not use the cylindrical space optimally. Therefore, it is proposed before to give the tunnel a rectangular cross-section, see Dutch Patent Application 7404334, but for a vacuum tunnel being a pressurized vessel in fact, anyhow, a cylindrical shape is preferred. Then spaces remain between the side walls of the load and the tunnel wall, which in known way, may be used profitably for arranging the condensing bodies. The parallel pipes of the known condensing bodies extending in longitudinal direction of the tunnel are arranged in a rectangular pattern within an enclosure. Said enclosure is open at its upper side and to its lower side a vacuum pump is connected. When said pump is put in operation after loading the tunnel and closing the doors, it sucks medium, in particular air and water vapour away downwards over the horizontal pipes, through which the cold means is fed from an external cooling installation. In diminishing the pressure of the medium the more moisture of the product will evaporate and heat of evaporation is withdrawn from the product. After some time the vegetable is cooled sufficiently for removing from the tunnel and transferring to the cooled storage, truck or the like. Water withdrawn from the product by evaporation condenses on the cooling pipes and drips downwards. By condensing of water on the pipes the flow of medium decreases in downwards direction. Thereby, the velocity of the air decreases also in downwards direction by which the efficiency of the heat transfer of the known condensing bodies is rather bad. The invention has the object to improve said efficiency by which it can be cooled more quickly in a tunnel having a certain diameter. According to the invention, this is achieved because the horizontal cross-section of the passage for the medium diminishes stepwise or continuously from the open upper side of the condensing body. In this way, the velocity at which the medium flows downwards over the pipes remains substantially equal in each horizontal crosssection of the condensing body. By diminishing the cross-section according to the invention, so, from the rectangular pattern of pipes a greater portion is removed in downwards direction, i.e. at maintained pitch at the upper side more pipes are arranged next to each other then at the lower side. So, although by the measure according to the invention the velocity of the medium advancing perpendicular over the pipes is maintained sub- stantially constant, by which a favourable efficiency is attained, a useless space, i.e. not occupied by pipes arises by which the capacity of the condensing body is decreased. In order to remove said objection, according to a further feature of the invention, within the enclosure a guiding partition is arranged over the entire length of said enclosure, dividing the space occupied by the pipes within the enclosure into two compartments in each of which the horizontal cross-section diminishes in flow direction of the medium to be sucked, in which the vacuum pump or pumps is or are connected to the upper end of the second compartment. In this way in maintaining the rectangular pipe pattern a higher capacity is obtained. Because the connection for the vacuum pump or pumps is now at the upper side of the second compartment less or no liquid comes into the pump. The liquid accumulates at the under side of the condensing body into a receptacle. By making said receptacle as an integral part of the enclosure of the condensing body according to the invention, the condensed water is prevented from contacting the relatively hot tunnel wall. If this would be the case as in known constructions, evaporation occurs at the wall resulting in loss of capacity. The invention will be explained with reference to the drawing, in which: Fig. 1 is a cross-section through the vacuum cooling tunnel, both of the condensing bodies and the load, and Fig. 2 is an enlarged cross-section over the right hand condensing body. The cylindrical wall of the tunnel is indicated by 1, the floor by 2, rails by 3, condensing bodies by 4 and 5, pallets by 6 and cases by 7. The pallets 6 can be moved over rails 3 through wheels 8. In known way, the tunnel is closed at both ends by not shown head walls of which at least one is implemented as access door. After opening the door the tunnel is filled with pallets 6 having cases 7 on it. The load is of rectangular cross-section as indicated by dot and dash lines in Fig. 1. Between the vertical walls of the load and the inner wall of the tunnel the condensing bodies 4 and 5 are arranged and suspended from the tunnel wall 1 through suspension rods 4a and 5a. Now it is referred to Fig. 2 in which the condensing body 4 is shown in more detail. The condensing body 4 comprises pipes 9 extending in longitudinal direction of the tunnel and arranged in rectangular pattern having an equal pitch within an enclosure 10. The pipes 9 are interconnected and/or subdivided in different circuits and connected to supply and discharge ducts not shown. Through the pipes 9 the cold means is fed originating from an external conventional cooling apparatus. The enclosure 10 consists of two vertical walls and a trapezium shaped chamber 11. Within the enclosure 10 a guiding partition 12 is arranged extending over the entire length of the condensing body 4 and having a stepped appearence. Thereby in fact the enclosure 10 is subdivided in two compartments. To the upper side of the smaller compartment the suction duct 13 of a not shown vacuum pump is connected. The upper side of the enclosure 10 is open. Both of the compartments communicate with each other through the trapezium-shaped chamber 11. In at least one head side of the chamber 11 a discharge 14 for water is provided. Upon opening the door of the tunnel said water flows away to the outside. By the guiding partition 12 the horizontal section of the larger compartment becomes smaller in downwards direction, by which the velocity of the medium remains substantially constant in spite of the fact that by condensation of the evaporated water from the product onto the pipes 9 the density of the air diminishes in downwards direction. This means already an extreme improvement of the efficiency of the condensing body, however, also a lower capacity because fewer pipes are provided. Now, said diminished capacity is compensated according to the invention by feeding the medium behind the guiding partition 12 upwards again to the suction duct 13 of the vacuum pump. Thus, the pipes 9 are arranged in a rectangular pattern as in the known condensing body, but the space is subdivided in two compartments by the guiding partition 12. In each compartment the horizontal section decreases in the flow direction of the medium. Between both compartments the trapezium-shaped chamber 11 is located, in which water flowing from pipes 9 collects, which is discharged through the passage 14 simultaneously with opening of the tunnel door. The chamber 11 serves an efficient separation of gas and conden sate by which as few as possible condensate goes to the vacuum pump. Another advantage is that by receiving the condensate in the chamber 11 said condensate cannot contact the wall 1 of the tunnel. Thereby evaporation of the condensate and thereby loss of capacity is prevented. The left hand condensing body 5 is identical to the condensing body 4 but represents a mirror image thereof. Selfevidently, the guiding partition 12 may also be a flat partition arranged slantingly. The cooling tunnel operates as follows. The door is opened, the load is positioned in the tunnel as quick as possible, the door is closed and the vacuum pump or pumps is or are put in operation. The water of the product evaporates and condensates onto the pipes 9. After a vacuum is attained corresponding to the pressure of the water vapour relating to the desired product temperature, the vacuum is removed by admitting air, the door is opened and the load is transferred to a cooled space and stored therin. In this way load by load is treated. The vacuum cooling tunnel according to the invention cools much quicker than the known tunnels so that the cooling capacity is extremely higher. While it is spoken of a vacuum cooling tunnel it is also possible to cool therewith below freezing point in which case it could be spoken of a vacuum freezing tunnel.

Claims: C L A I M S. 1. Vacuum cooling tunnel, in particular for cooling water containing products, such as for example salad, comprising a horizontal cylindrical housing having an access door at at least one end for supplying or removing loads of products on pallets or the like, which loads have a rectangular cross-section, in which in the spaces between the upstanding walls of the most width and acceptable load and the cylindrical wall condensing bodies extending in longitudinal direction are arranged consisting of parallel pipes through which a cold means is fed, which pipes are arranged in an rectangular pattern within an enclosure, the open upper side of which communicates with the interior of the tunnel and to which at least one vacuum pump is connected for sucking off the medium present in the interior of the tunnel through each condensing body, perpendicular to its pipes characterized in that the horizontal cross-section of the passage for the medium diminishes stepwise or continuously from the open upper side of the condensing body. 2. Vacuum cooling tunnel according to claim 1, characterized in that within the enclosure a guiding partition is arranged over the entire length of the enclosure, dividing the space within the enclosure occupied by the pipes into two compartments in each of which the horizontal cross-section decreases in the flow direction of the medium to be sucked, in which the vacuum pump or pumps is or are connected to the upper end of the second compartment. 3. Vacuum cooling tunnel according to claim 2, characterized in that within the enclosure of each condensing body beneath the space occupied by the pipes and the guiding partition a chamber is formed extending over the entire length of the tunnel, in which the medium to be sucked varies its direction and condensed liquid can be collected, in which at at least one end of the chamber a discharge for the liquid is provided. 4. Vacuum cooling tunnel according to claim 3, characterized in that the chamber forms an integral part of the enclosure of the condensing body free from the tunnel wall. 5. Vacuum cooling tunnel according to claim 3, characterized in that said discharge is closed by the tunnel door.

Inventors: VERHOEF, HERMANUS JOHAN NICOLAAS
Applicants: GRASSO'S KONINKLIJKE MACHINEFABRIEKEN N.V.
Application year: 1981
Main classification: F25D31
IPC codes: A23L3, F25D31