Apparatus for cooling items and corresponding method

The present invention relates to an apparatus for cooling or freezing items like food products and to a method for operating such an apparatus.

Background of the invention

Various items, in particular, food products have to be cooled or frozen after production in order to allow, e.g., long storage times. In order to facilitate such cooling or freezing for a large number of items, specific apparatuses can be used. Such an apparatus, typically, comprises a chamber with an inlet and an outlet, a conveyor means like a conveyor belt that is configured for transporting the items through the chamber, from the inlet to the outlet (typically, also from outside the chamber into the chamber via the inlet and, accordingly, out of the chamber via the outlet). Also, several blowers or fans are arranged or installed inside the chamber that allow circulating gas like air inside the chamber, in particular, blowing the gas across the food products. The gas can be actively cooled, for example, by means of cooling medium provided inside the chamber. Such apparatuses are also called tunnel freezer or cross-flow tunnel freezer. The cross-flow aspect means that the main gas flow is across the conveyor means, i.e. , orthogonal to the conveyor direction.

A problem with such apparatuses is that during operation warm air is sucked into the chamber (infiltration) via the inlet and/or the outlet due to the so-called Venturi effect (based on low-pressure zones inside the chamber). This has negative effects on energy efficiency of the apparatus since the cooling of gas inside is traversed. It is therefore an object of the present invention to overcome such problem.

Disclosure of the invention

This object is achieved by providing an apparatus for cooling or freezing items and to a method for operating such an apparatus with the features of the independent claims. Embodiments of the invention are the subject of the dependent claims and of the description that follows. 2

The invention relates to an apparatus for cooling or freezing items like food products as described above, a so-called cross-flow tunnel freezer, comprising a chamber with an inlet and an outlet, a conveyor means like a conveyor belt being configured for transporting the items through the chamber, from the inlet to the outlet, and blowers. The apparatus also comprises a center baffle (or baffle plate) arranged inside the chamber and above the conveyor means, facing a top side of the conveyor means, on which side the items are to be placed. The center baffle, in particular, is arranged horizontally above the conveyor means and along the conveying direction. Note that such center baffle may also be composed of several individual components arranged next to each other.

The several blowers (or fans) are arranged inside the chamber, each blower above the center baffle, opposite the top side of the conveyor means. Further, the several blowers are arranged along the conveying direction of the conveyor means from the inlet to the outlet and on one side of the chamber with respect to the conveying direction. If the apparatus is looked at or viewed from the top side with the inlet at the left side and the outlet at the right side, this means that the blowers are all arranged at the upper side (inside the chamber) or at the lower side. Looking through the apparatus from the inlet to the outlet, this means that all the blowers are arranged at the left or at the right side. Further, the blowers are rotationally operated radial blade blowers with a rotational axis oriented orthogonal to the top side (i.e. , orthogonal to a plane defined by the top side of the conveyor means), and the blowers are configured for circulating the gas or cooled air inside the chamber around an edge of the center baffle. In this way, the gas is circulated form the side of the blowers (essentially) across the center baffle (and in a direction orthogonal to the conveying direction), the gas then being urged downwards and around the edge of the center baffle such that the gas flows back to the side of the blowers, then between the center baffle and the conveyor means. Since the items are placed at the top side of the conveyor means, the gas flow thus cools (or freezes) the items. For a way to cool or freeze the gas, it is referred to later remarks.

A typical way to operate the blowers or fans is operating all of them in the same way, which is all with the same rotational direction; when viewing from the top, this rotational direction is either clockwise or counter-clockwise. As mentioned before, this results in low-pressure zones either at the inlet or at the outlet. A reason for that is the gas being 3 reflected at an edge or corner inside the chamber (see Figs and corresponding description for further explanation).

Within the present invention a specific operation of some of the blowers is proposed in order to overcome this problem. At least the blower, which is arranged closest to the inlet is configured to operate such that the gas is, at the side of the inlet (i.e., between the inlet and the blower closest to the inlet), drawn to the side of the chamber at which the blower is arranged. In the case that, if the apparatus is viewed from the top side with the inlet at the left side and the outlet at the right side, and the blowers all arranged at the upper side, this means that blower is operated in clock-wise direction.

A further detailed description will be provided with respect to the Figs. This specific operation results in that the gas is, by means of the blower closest to the inlet, urged in a direction away from the corner opposite the blower and at the side of the inlet. Then, the gas is urged downwards and around the center baffle (as mentioned before) and, thus, not reflected at the corner. This results in that the gas will not create a low- pressure zone at the inlet and, thus, no warm air is drawn into the chamber.

Correspondingly, at least the blower being arranged closest to the outlet is configured to operate such that the gas is, at the side of the outlet, drawn to the side of the chamber at which the blower is arranged. This will result in the same situation as mentioned for the inlet, i.e., there will be no low-pressure zone near the outlet.

Preferably, also the two blowers closest to the inlet are operated in that way. This holds also true for the two blowers closest to the outlet. In this way, the effect can be further improved. Any of the remaining blowers (if there are any) that are not operated in that specific way, are preferably operated such that gas is, at the side of the inlet or outlet, whichever (of inlet and outlet) the blower is arranged from farer away, is drawn to the side of the chamber at which the blower is arranged. Note that typically, there is no blower that is exactly in the center between inlet and outlet (and, thus, neither farer away from any of inlet and outlet). If there is such blower, it could be operated either way.

It is of further advantage if at least one further baffle is provided that is arranged between two of the blowers at a position facing the top side of the conveyor means, 4 and being oriented orthogonal to the conveying direction. Such baffle is, preferably, further arranged above the center baffle, opposite the top side of the conveyor means. This helps further improving the flow of the gas created by the specifically operated blowers closest to the inlet and the outlet. In case of several of such further baffles, one further baffle can be arranged next to a first or second blower closest to the inlet, and/or one further baffle can be arranged next to a first or second blower closest to the outlet in order to take advantage of the effect of guiding the gas in the chamber best.

As mentioned above, the gas (or air) used in the apparatus needs be cooled gas or needs to be cooled inside the apparatus. A preferred way to achieve this is that the apparatus comprises spraying means being configured to spray cooling medium (e.g., liquid nitrogen) from above the top side of the conveyor means into the chamber, in particular, directed to the top side of the conveyor means. The spraying means can include, for example, spraying nozzles distributed in the chamber above the conveyor means and, in particular, below the center baffle. The spraying nozzles can be supplied with the cooling medium, e.g., by means of appropriate pipes or the like.

The invention also relates to a method for operating an apparatus for cooling or freezing items or products like food products. An apparatus as described above is operated in a way that the items are transported through the chamber by means of the conveyor means and gas is circulated by means of the blowers. At least the blower arranged closest to the inlet is operated such that the gas is, at the side of the inlet, drawn to the side of the chamber at which the blower is arranged. And, at least the blower being arranged closest to the outlet is operated such that the gas is, at the side of the outlet, drawn to the side of the chamber at which the blower is arranged. The gas (or air) is, preferably, cooled in that cooling medium is brought into the chamber, e.g., by means of spraying means like nozzles.

With respect to any further embodiments and advantages of the method, it is referred to the remarks with respect to the apparatus above, which apply correspondingly.

Short description of the figures

Fig. 1 illustrates an apparatus according to the invention in a preferred embodiment. 5

Fig. 2 illustrates the apparatus of Fig. 1 in another view.

Fig. 3 illustrates an apparatus according to the invention in a further preferred embodiment.

Detailed description of the figures

In Figs. 1 and 2, an apparatus 100 according to the invention in a preferred embodiment is illustrated. In Fig. 1, the apparatus 100 is shown in a view from the top and in Fig. 2 apparatus 100 is shown in view from the side (it might be considered a cross section view). Directions are indicated x, y and z wherein z is a vertical direction (when the apparatus is placed on a ground). In the following, the apparatus is described with respect to both, Figs. 1 and 2.

The apparatus 100 is for cooling or freezing items like food products indicated 180 in Fig. 1 and indicated 181 to 185 in Fig. 2 and is called a cross-flow tunnel freezer. The apparatus 100 comprises a chamber110 (it typically is inside a housing 111) with an inlet 112 and an outlet 114, each being an opening in the housing 111. In Fig. 2, only the outlet 114 is shown (in dashed lines). Apparatus 100 further comprises a conveyor means like a conveyor belt 130, being configured for transporting the items 180-185 through the chamber 110, from the inlet 112 to the outlet 114. In Fig. 1 , the conveyor belt 130 is indicated with dashed lines as far as it is arranged inside the chamber 110.

The apparatus 100 also comprises a center baffle or baffle plate 140 arranged inside the chamber 110 and above the conveyor means 130, facing a top side 132 of the conveyor means, on which side the items are to be placed. The center baffle is arranged horizontally in x-y-plane above the conveyor belt 130 and along the conveying direction, which is in positive x direction. In Fig. 1, the center baffle 140 is indicated with dashed lines

Further, the apparatus 100 comprises several blowers, which are arranged inside the chamber 110. By means of example, four blowers 120, 122, 124 and 126 are provided (in Fig. 2, only blower 126 can be seen). Each blower is arranged above (in z-direction) the center baffle 140, opposite the top side 132 of the conveyor belt 130. Further, the several blowers are arranged along the conveying direction (positive x-direction) of the 6 conveyor belt 130 from the inlet 112 to the outlet 114 and on one side of the chamber with respect to the conveying direction. In the shown example in Fig. 1, in which the apparatus 100 is or viewed from the top side with the inlet 112 at the left side and the outlet 114 at the right side, the blowers are all arranged at the upper side (inside the chamber 110). Further, the blowers are rotationally operated radial blade blowers with a rotational axis 128 (only shown in Fig. 2 for blower 126) oriented orthogonal to the top side 132 of the conveyor belt 130 i.e. , orthogonal to the x-y-plane.

The blowers are configured for circulating gas like air inside the chamber 110. By means of example, air as such a gas is indicated with arrows A, each arrow also indicating a flow direction. When operated, the blowers circulate the air inside the chamber and around an edge 142 of the center baffle 140. In particular, as shown in Figs. 1 and 2, the air A essentially flows, starting from the blowers, in negative y direction (downwards in Fig. 1 and left in Fig. 2), then around the edge 142 in negative z-direction (into the paper, at the lower side of the chamber, in Fig. 1 and downwards at the left side in Fig. 2), and then across the conveyor belt 130, between the conveyor belt 130 and the center baffle 140 in positive y-direction (from the lower to the upper side in Fig. 1 , indicated with dashed lines in Fig. 2, and from the left to the right side in Fig. 2).

In this way, the air A is circulated form the side of the blowers (essentially) across the center baffle 140 (and in a direction orthogonal to the conveying direction x), the air A then being urged downwards and around the edge 142 of the center baffle 140 such that the air A flows back to the side of the blowers, then between the center baffle 140 and the conveyor belt 130. Since the items are placed at the top side 132 of the conveyor belt 130, the air flow thus cools (or freezes) the items.

Further, the apparatus 100 comprises spraying means 150 (not shown in Fig. 1) being configured to spray cooling medium M, e.g., liquid nitrogen, into the chamber 110, in particular, directed to the top side 132 of the conveyor belt 130. The spraying means can include, for example, spraying nozzles distributed in the chamber 110 above the conveyor belt 130 and below the center baffle 140. The spraying nozzles can be supplied with the cooling medium M, e.g., by means of a medium supply 152 and appropriate pipes or the like. 7

As mentioned above, air infiltration, i.e. drawing in of warm air through the inlet 112 and/or outlet 114 is a problem. This is overcome by a specific way of operating the blowers. In the example shown, the blower 120 (see Fig. 1), which is the one closest to the inlet 112, is operated (or is configured to operate) such that the air A is, at the side of the inlet 112 (i.e., between the inlet 112 and the blower 120, at the very left side of the chamber 110 in Fig. 1), drawn to the side of the chamber 110 at which the blower 120 is arranged. When viewed from the top (as shown in Fig. 1), this corresponds to the blower 120 being operated in clock-wise direction as indicated with the arrow left to the blower 120 in Fig. 1 (rotational directions are indicated with R, the reference numeral only provided for blower 126). The blower 122, the one arranged second closest to the inlet 112, is operated in the same rotational direction. This specific operation of blowers 120, 122 results in that the air A is, by means of these to blowers, urged in a direction away from the corner opposite the blowers 120, 122 and at the side of the inlet 112; this corner is, in Fig. 1 , the corner shown at the lower left side. This direction is indicated with the arrow A directing from blower 120 downwards and right. The direction of flow has, thus, components in negative y-direction and in positive x- direction. Then, the air A is urged downwards (into the paper, in Fig. 1) and around the center baffle 140) and, thus, is not reflected at the corner. Rather, the air A is directed towards the inlet 122. This direction is indicated with the arrow directing from lower side upwards and to the left (to the inlet 122), represented in dashed-line. This, in turn, results in that the air will not create a low-pressure zone at the inlet 112 and, thus, no warm air is drawn into the chamber 110.

Correspondingly, the blowers 124, 126 which are arranged closest to the outlet 114 are operated the other direction, i.e., counter-clockwise. This, correspondingly, results in that the air will not create a low-pressure zone at the outlet 114 and, thus, no warm air is drawn into the chamber 110.

Further, a baffle 144 is provided that that is arranged between the two blowers 122 and 124 at a position facing the top side 132 of the conveyor belt 130, and being oriented orthogonal to the conveying direction x. Baffle 144 is further arranged above the center baffle 140, opposite the top side 132 of the conveyor belt 130. This helps further improving the flow of the air created by the specifically operated blowers closest to the inlet 112 and the outlet 114. In particular, the flow of the air is prevented from being directed to far away from the inlet 112 or outlet 114, respectively. 8

Note that operating the blowers closest to the inlet 112 in clockwise direction and the blowers closest to the outlet 113 in counter-clockwise direction is true only for the specific situation shown. If the blowers were arranged at the other side of the chamber 110 (at the lower side in Fig. 1), the directions of operating the blowers would have to be exchanged. The relevant aspect is the air flow generated by the blowers.

Measurements and simulations have shown that this specific way of operating the blowers results in outward flow of air at the inlet and the outlet or, at least, no flow inwards. Also, the measurements show that the specific flow across the inlet and outlet (such different positions represented with the items 181 to 185 in Fig. 2) varies, there is no flow inwards, i.e. , no air infiltration. Operating all of the blowers in the same direction would result in air infiltration at the inlet but not at the outlet or vice versa. Either way, however, is disadvantageous.

In Fig. 3, an apparatus 200 according to the invention in a further preferred embodiment is illustrated. The apparatus 200 basically corresponds to the apparatus 100 of Figs. 1 and 2; however, the length in x-direction is greater. Like components are denoted with like numerals. Due to the greater length, there are two additional blowers 220, 222 in the middle of the apparatus 200 in x-direction. Also, two baffles 144, 244 are provided, each arranged between two blowers. While the blowers 120,122, 124, 126, which are closest to the inlet 112 and outlet 114, respectively, are operated as described with respect to Figs. 1 and 2, the further blowers 220, 222 are operated in different manner.

These blowers are operated such that the air is, at the side of the inlet 112 or outlet 114, whichever the blower is arranged from farer away, is drawn to the side of the chamber 110 at which the blower is arranged. In the example shown, this means that blower 220 is operated in counter-clockwise direction since it is farer away from the outlet 114 than from the inlet 112. Blower 222 is operated in clockwise direction since it is farer away from the inlet 112 than from the outlet 114. In other words, bother blowers 220, 222 are operated in an outward mode, i.e., rotated such that the air is (essentially) blown outward, which is the one of inlet and outlet that is nearer to the blower.