HEAT EXCHANGER

TECHNICAL FIELD

The present invention relates to a heat exchanger. In particular, a heat exchanger suitable for heating or cooling of a large number of items as part of an automated process.

BACKGROUND ART

The present invention has particular application to automatic air-blast freezers such as are used widely in New Zealand, Australia, and Brazil for freezing cartoned product such as meat and poultry. However, this should not be seen as limiting as the present invention also has applications to other heat transfer processes. For ease of reference, the present invention will now be described in relation to an automatic air- blast freezer.

Existing air-blast freezers (freezers) receive cartons of product to be frozen into a freezer chamber through which the cartons are conveyed for a set period of time whilst being exposed to cooled air (i.e. air having an air temperature of at least substantially -18°C). The cooled air is circulated through the chamber via fans. The air temperature over time warms as part of the heat transfer process before it is re- cooled by passing through an evaporator.

However, with the need to process larger volumes of produce in faster turn around times this, has over time, led to the use of larger and larger fans, in order to increase the velocity of the frozen air to freeze the cartons more quickly. However, the downside is that, this in turn requires the use of larger evaporators to cope with the increased heat created by the larger fans.

Thus, existing freezers as a consequence of high through puts are generally expensive to run and relatively inefficient in terms of energy use.

A further problem with some existing air-blast freezers is that the flow of frozen air is often shielded in given areas from product by the support framework, shelves and associated machinery which conveys the product through the freezer. Accordingly, the shadow effect of the framework and machinery decreases the efficiency of the freezer.

Yet another problem with some existing air-blast freezers is due to the relatively short duration in which the temperature of the frozen air retains favourable heat transfer characteristics (i.e. the length of time the air temperature remains substantially at or near -18°C). This can lead to more time being required to freeze a given volume of product, or alternatively can lead to uneven freezing of products, dependent on where the product is situated in the freezer, with respect to the direction of airflow. For example, in some existing air-blast freezers the frozen air moves in a transverse direction with respect to the direction of product flow through the chamber. Thus, product situated near the tail end of the airflow just prior to the air re-entering the evaporator tends to take longer to freeze given the relative warmth of the air which has already absorbed heat from the product. This problem is particularly exacerbated in areas of the freezer where the frozen air comes in to contact with non-frozen or partially frozen product shortly or immediately after leaving the evaporator. As such product has the greatest draw on the heat transfer capabilities of the air and thus increases its temperature to the maximum extent as part of the heat transfer process.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency

of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION

According to one aspect of the present invention there is provided a heat exchange system between a product and a heat transfer medium wherein the system includes at least one heat exchange chamber wherein said chamber includes:

■ at least one heat exchanger;

^■ at least one Current Imparting Device (CID) which creates a flow direction and velocity to the heat transfer medium;

the heat exchange system characterised in that the heat exchange chamber is partitioned to effectively reduce the area through which the CID needs to impart a flow to the heat transfer medium without significantly reducing the overall volume of the chamber.

According to another aspect of the present invention there is provided a heat exchange system substantially as described above wherein the heat exchange system includes a conveyor system which conveys product through the chamber and wherein the heat exchange system is configured so that the heat exchanger and CID can create a flow of the heat transfer medium from the heat exchanger which is either co-current or counter-current with respect to the flow direction in which product is being moved through the chamber via the conveyor system.

According to a further aspect of the present invention there is provided a method of transferring heat to, or from, the product via a heat transfer medium as part of an automated production line characterised by the steps of: ' ^•

a. conveying products through a heat exchange chamber; and

b. imparting a fluid flow to the medium which is either co-current or counter-current with respect to the flow direction in which the product is moved through the chamber via the conveyor system.

The product may be any item packaged or unpackaged, processed or unprocessed, to which it is desired to heat or cool. For ease of reference only the product may be thought of as being cartoned meat (i.e. meat which is encased in plastic and/or a cardboard box or such like).

The heat exchange system of the present invention may be useful in relation to a multitude of heating or cooling applications.

The heat transfer medium may be any fluid which has suitable properties to transfer heat from the product to the medium or vice versa.

In some embodiments the heat transfer medium may be a liquid.

In general however, the heat transfer medium may be a gas. However, this should not necessarily be seen as limiting.

In preferred embodiments the heat transfer medium is air.

The heat exchanger may be any device capable of transferring heat to, or absorbing heat from, the heat transfer medium, dependent on whether the heat exchange system is being used for a heating or cooling application.

In some embodiments the heat exchanger may be at least one heating element.

In preferred embodiments the heat exchanger may be at least one cooling element. For example, the cooling element may be in the form of a condensing coil, evaporator or such like.

For ease of reference only, the present invention may now be thought of in relation to a heat exchange system in the form of an air-blast freezer.

The CID may be any device capable of moving the heat transfer medium.

In some embodiments the CID may be in the form of a pump.

In preferred embodiments the CID may be a fan.

The heat exchange chamber may come in a variety of different forms without departing from the scope of the present invention dependent on the type of heat exchanger application to which the present invention is applied.

In general the heat exchange chamber may be an at least substantially enclosed space suitably adapted so that items can be subject to the desired heat exchange process.

In preferred embodiments the heat exchange chamber is configured to minimise or prevent any heat transference between the chamber and the external environment.

The heat exchange chamber may be partitioned in a variety of different ways without departing from the scope of the present invention.

In general the heat exchange chamber may be partitioned so as to reduce the cross sectional area of the chamber.

In some embodiments the heat exchange chamber may include at least one vertical partition which divides:

• at least that portion of the chamber where the majority of the heat transfer is to take place; and

• the area through which the CID is initially to impart flow direction and velocity to the heat transfer medium.

In preferred embodiments the heat exchange chamber may include at least one horizontal partition which divides:

• at least that portion of the chamber where the majority of the heat transfer is to take place; and

• the area through which the CID is to initially impart flow direction and velocity to the heat transfer medium.

In some further embodiments the chamber may include a combination of vertical and

horizontal partitions.

In preferred embodiments the areas created by the partition(s) may be effectively or actually connected to one another at one or both ends thereof.

In some embodiments the present invention may be used in relation to a static heat transfer process where the product to be heated or cooled remains stationary within the chamber during the heat transfer process.

In preferred embodiments the present invention may be used in relation to a dynamic heat transfer process wherein the product is conveyed through the chamber during the heat transfer process.

Preferably, product is conveyed to and from the chamber as part of an automated production line having at least one conveyor system.

The conveyor system may come in a variety of different forms without departing from the scope of the present invention.

In some embodiments the conveyor system may employ at least one motor and at least one continuous belt/chain arrangement, which is/are moved via operation of the motor(s). The motor(s) employed by the conveyor system(s) may be variable speed motors.

In preferred embodiments the conveyor system may include a track, path or such like along which product may be conveyed via a motor, linear actuators such as pneumatic cylinders or such like or other pushing/pulling device.

In some preferred embodiments the product may be placed on shelves which are configured to be capable of moving along tracks.

In some embodiments the 'conveyor system' may encompass one conveyor belt or a

set of more than one conveyor belt.

In general the heat exchange system may include horizontal and/or vertical conveyor systems. In some embodiments the vertical conveyor system may be in the form of an elevator or such like.

In preferred embodiments more than one conveyor system may move product through the chamber for processing.

Preferably, the conveyor system(s) may have multiple conveyor lines (e.g. multiple conveyor belts or tracks).

In preferred embodiments there may be provided a first conveyor system and a second conveyor system which are separated by a partition. In each of the first and second conveyor systems there may be multiple conveyor lines.

In general the product may be moved by the first conveyor system in a horizontal direction which is opposite to that in which product is moved by the second conveyor system.

In preferred embodiments the first and second conveyor systems may be connected by at least one, but preferably two or three vertical conveyor system(s) which move(s) product between the partitions, and out of the chamber with or without the assistance of one or more horizontal conveyor system(s).

In preferred embodiments product must travel through more than one partition before exiting the chamber.

The heat exchange system can be configured in a multitude of ways so as to effect a flow of the heat exchange medium

In some embodiments the heat exchange system may have the flow of the heat exchange medium in substantially the same direction (i.e. co-current) as that in which the product is moved.

In preferred embodiments the heat exchange system may have the flow of the heat exchange medium being in a direction which is substantially opposite (i.e. counter- current) to that in which the product is moved.

In some embodiments the heat exchange system may have the ducting or channels which divert the flow of the heat transfer medium from the heat exchanger in a direction opposite to that in which the product is moved through the chamber.

In preferred embodiments the heat exchange system may have the heat exchanger located substantially within at least one partition and positioned at the end of the conveyor system within the partition, so that heat exchange medium exiting the exchanger travels in a direction towards oncoming product conveyed on the conveyor system.

In further preferred embodiments the CID may be located within the same partition as the heat exchanger and positioned to direct heat transfer medium through the heat exchanger before the heat transfer medium encounters product within said partition.

One advantage of arranging the CID and heat exchanger so that the flow of heat transfer medium is against the oncoming direction of the product is that this allows the heat transfer medium to encounter first the coldest product, relatively speaking, within the chamber first which helps maintain the temperature of heat exchange medium near its optimum (i.e. as the product at the tail end of the conveyor system with respect to the flow of the heat transfer medium has been within the chamber for the longest amount of time in a counter current application and the shortest time in a co current application).

Most preferably, the CID and heat exchanger may be positioned within the section of the chamber created by the partition through which the product moves before exiting the chamber.

Thus preferred embodiments of the present invention may have a number of advantages over the prior art which can include:

Less energy is required to freeze the same amount of product due to the partitioning effectively reducing the area in which motion needs to be imparted to the heat transfer medium so a less powerful fan and smaller heat exchanger can be used.

In addition, the reverse direction of heat transfer medium relative to the direction of product flow helps ensure the desirable characteristics of the heat transfer medium are maintained for as long as possible. Thus, in freezer applications the direction of flow increases the time it takes for the heat transfer medium (air) to increase in temperature.

Another advantage of the present invention is that having the direction of flow of the heat transfer medium co-current or counter-current to the direction of product flow helps reduce problems with the supporting frame work and conveyor arrangements creating a-shadow effect with respect to the heat transfer medium.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a schematic cross sectional side view of the preferred embodiment of the present invention.

Figure 2 is a schematic cross sectional side view of a further preferred embodiment of the present invention essentially as shown in Figure 1 but with an additional set of fans and evaporators.

BEST MODES FOR CARRYING OUT THE INVENTION

With respect to Figure 1 there is provided a heat exchange system generally indicated by arrow (1). The heat exchange system (1) has a heat exchange chamber (2).

For ease of reference only, the preferred embodiment shown in the drawings will now be discussed in relation to a freezer application, although this should not be seen as limitingr

The heat exchange process performed by the present invention occurs within the heat exchange chamber (2).

The chamber (2) has a partition (100) which spans across the width of chamber (2) and separates a first horizontal conveyor system (101) which moves product (5) in the direction of arrow (X) from a second horizontal conveyor system (102) which moves the product in the direction of arrow (Y).

The chamber (2) has apertures (not shown) which allow for product in-feed, as generally indicated by arrow (3), and for product out-feed as generally indicated by arrow (4), to allow for, product in the form of cartoned meat (5), to enter/exit the chamber (2).

In general, the product in-feed (3) and product out-feed (4) may be achieved by the use of conveyor systems or chutes (not shown).

Upon entering the chamber (2) the product (5) is moved onto a shelf (500) and then

moved vertically within the chamber (2) in the direction of arrow (6) via a vertical conveyor system in the form of an elevator (7) generally indicated by the dotted line.

The elevator (7) moves the product (5) up to a conveyor line (103) having tracks (not shown) in the first horizontal conveyor system which is in the form of a racking system (101).

The elevator (7) transfers the product and shelf (500) on to the conveyor line (103) by operation of a mechanical pushing device in the form of a linear actuator assembly (not shown).

Once the product (5) is on the conveyor line (103) it gradually moves in the direction of arrow (X) as a result of being shunted by further product (5) on shelves (500) being added to the conveyor line (103) from elevator (7) by the pushing device.

Once the product (5) reaches the end of conveyor line (103) it is collected via a second vertical conveyor system in the form of an elevator (8). The elevator (8) moves product in the direction of arrow (19) where it is delivered to one of the conveyor lines (104) having tracks (not shown) which form part of a second horizontal conveyor system also in the form of a racking system (102). Again, product (5) is transferred from the elevator (8) to a conveyor line (104) via a mechanical pushing device in the form of a linear actuator assembly (not shown), and the product (5) on the conveyor line (104) is gradually moved in the direction of arrow (Y) as further product (5) is placed on the conveyor line from elevator (8).

Once the product (5) reaches the end of the racking system (104) it is collected via a third vertical conveyor system in the form of an elevator (9) which moves product (5) vertically within the chamber in the direction of arrow (10) to a horizontal conveyor system in the form of a conveyor belt (11) which moves the product in the direction of arrow (12) towards the product out-feed (4).

In operation, the product (5) is cooled as a result of a CID in the form of fans (15) blowing air in the direction of arrow (20). The fans (15) blow the air towards a heat exchanger in the form of an evaporator (21). After exiting the evaporator (21) the cooled air first comes into contact with product (5) at the end of conveyor belts (104) in the second horizontal conveyor system (102). The cooled air travels in the direction of arrows (22) until it reaches the back wall (52) of the chamber (2). At this point the air moves in the direction of arrow (23) before it continues to travel in the direction of arrow (24) through the first horizontal conveyor system (101) and past conveyor lines (103).

As can be seen in operation the direction of cooled air is controlled so that it ^• encounters the coldest product first to help maintain the optimum low temperature of the air exiting the evaporator for as long as possible.

Once the air exits the first horizontal conveyor system (101) it hits the front wall (51) moves in the direction of arrows (24) to re-enter the fans (15) and repeat the process.

In Figure 2 an optional further set of fans (15a) and evaporators (21a) may assist with blowing air in the direction of arrows (24).

- Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the appended claims.