AU2020100411A4 - Vapour heat treatment apparatus and method - Google Patents

Abstract

An apparatus for supplying heated and humidified air to fresh produce is described. The apparatus comprises a body comprising a structural ceiling, side walls and end walls and a treatment area for holding a plurality of produce containing containers. The body also has a heating arrangement for heating air and at least one exhaust fan for circulating a flow of air within the body such that heated air is drawn in a substantially horizontal flow through the held produce containers. An air flow restriction arrangement is positioned between the produce and the at least one exhaustfan. Figure 13 4- 7/S 3: Iz r4

Description

VAPOUR HEAT TREATMENT APPARATUS AND METHOD

TECHNICAL FIELD

The present disclosure relates to an apparatus and method for insect disinfestation of fresh produce such as fruits and vegetables.

DEFINITION

In the present specification and claims the term “comprising shall be understood to have a broad meaning similar to the term “including” and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term “comprising” such as “comprise” and “comprises”.

BACKGROUND

Many fruit and vegetables are hosts to insect pests and in particular fruit flies. In order to export to countries or locations with a fruit fly quarantine barrier, the produce must be subjected to a disinfection treatment approved by the importing country.

Chemical fumigation with agents such as diethylene bromide and methyl bromide is an effective disinfestation treatment and was traditionally the most widely used. However, chemical fumigation is being phased out as a result of concerns relating to toxicity and worker safety. Irradiation is also an effective disinfestation treatment but is relatively expensive, has poor consumer acceptance and significant adverse physiological effects, reducing shelf life and often cosmetic degradation over time as a result of necrosis.

Insect pests such as fruit fly may also be killed by temperature treatment to temperatures above or below that at which the insect larva may survive. Temperature treatment has the advantages of avoiding use of toxic chemicals or irradiation and has a high consumer acceptance. Cold storage holds fruit or vegetables at temperatures below 3° for about two to three weeks. Cold storage also has the advantage of preserving the produce. Heat treatment heats the fruit or vegetables to temperatures such that the internal temperature reaches above about 45°C for a predetermined period of time. Heat treatment can however adversely affect produce quality and may be a high cost treatment.

Some fruits and vegetables are sensitive to cold temperature and cold temperature treatment cannot be used as a disinfestation treatment. Tropical fruits are especially sensitive. For example, mangos suffer chill damage at below 13°C.

2020100411 18 Mar 2020

The temperature and time to which fruits or vegetables are heated and held is determined by the quarantine regulations of the importing country. For example some regulations require heating fruit to 46.5°C for twenty minutes whilst others require heating to 47°C for 15 minutes.

In order to minimise heat damage to the treated fruit it is desirable to raise the temperature as quickly and accurately as possible. Heat treatment at high humidity, known as vapour heat treatment or VHT is particularly effective. As water vapour condenses on the fruit, it gives up its latent heat and efficiently heats the fruit thereby facilitating heating rate.

VHT treatment is conventionally carried out by placing fruit in large plastic bins, stacking the bins and placing the bins in a sealed treatment chamber. The plastic bins have ventilation openings so as to allow air flow about the produce. Heated air is introduced into the chamber with a relative humidity of 90 to 100%. The plastic bins are configured to hold a maximum of about 500kg of produce.

The treatment chambers used for VHT treatment were originally based upon configurations used in conventional forced-air cooling chambers. With forced air cooling, produce is placed in ventilated plastic bins and placed in a refrigeration unit. The refrigeration units includes a fan system in a plenum to pull cold air through the bins. Air flow may be either horizontal or vertical. The plenum is generally provided with spaced rectangular outlets covered by a grill. The stacked bins are carefully aligned relative to an outlet so as to optimise cold air flow through the bins.

With VHT treatment it is critical that all produce is subjected to the “kill temperature” for the regulated period of time. Failure to do so can result in incomplete disinfestation if not all produce reaches the required temperature and/or for less than the regulated time. The result is that the entire load is rejected for quarantine purposes. On the other hand if the temperature is too high, a significant percentage of produce may be lost due to heat damage. Either scenario represents a significant commercial loss.

The treatment process is carefully monitored to ensure the internal (pulp) temperature of all produce being treated reaches the required temperature for the required period of time. Probes are placed into the largest fruits at different heights and locations within the chamber. The treatment is continued until the sensor at the coldest location reaches the regulated temperature and held for the regulated minimum time. The “cold spots” or spots with the longest heat up time are determined during a certification procedure for each treatment chamber.

2020100411 18 Mar 2020

In practice this means that a significant amount of the fruit is held at a higher temperature for longer. This can adversely affect fruit quality. There may be up to about 20 to 30% loss of fruit after a VHT process.

It is therefore desirable to produce uniform airflow and efficient heating so that all fruit is heated to the same temperature at the same time. There are a number of variables that may affect airflow within a treatment chamber, including air flow pattern such as vertical flow or horizontal flow through the chamber, lateral flow, design and arrangement of the plastic bins, relative sizes of fruit and the packing of the fruit into the plastic bins.

It is therefore desirable to provide an alternative apparatus and method for VHT treatment for disinfestation of fruits and/or vegetables.

SUMMARY

According to a first aspect of the disclosure there is provided an apparatus for supplying heated and humidified air to fresh produce comprising;

a body comprising a treatment area for holding a plurality of produce containing containers;

a source of heated and humidified air;

at least one exhaust fan for circulating a flow of air within the body such that air is drawn through the held produce containers, wherein an air flow restriction arrangement is positioned between the produce container and the at least one fan.

The present inventor has surprisingly discovered that by providing an air flow restriction arrangement between produce container and the at least one fan such that air is drawn through the air flow restriction arrangement can improve evenness of airflow through the produce containers.

The air flow restriction arrangement may be any suitable arrangement that may restrict air

The air flow restriction arrangement suitably has a sheet type body with a having a plurality of air flow openings separated by land areas such that air flow is restricted to flow through the openings. Suitably the air flow openings are uniformly spaced

2020100411 18 Mar 2020

Such types of restriction arrangements are characterised by the % open area. The open area is a ratio that reflects how much of the sheet is occupied as holes normally expressed as percent.

The air flow restricted arrangement may be a perforated sheet or grid having holes or slots through which air may pass.

The open area of the restriction arrangement is generally between about 10% to about 80%, suitably between about 15% to about 60%, suitably between about 20% to about 50%, suitably between about 25% to about 45%. In an embodiment the open area is about 30%.

The restriction arrangement may be in the form of a metal grill.

Suitably, the air flow restriction arrangement is a perforated metal sheet. Suitably the sheet is perforated with round holes. However, it will be appreciated that other hole configurations such as square, oblong, hexagonal or otherwise may be suitable.

In one aspect, the apparatus includes an exhaust chamber is in the form of an exhaust hood that is mounted to the ceiling of the apparatus such that there is a substantially vertical upwards flow of air through the produce containers.

According to an embodiment there is provided an apparatus for supplying heated and humidified air to fresh produce comprising a body comprising;

a treatment chamber for holding a plurality of produce containment containers, the treatment chamber comprising a ceiling and an exhaust hood below the ceiling so as to define a plenum air space between the exhaust hood and the ceiling;

at least one exhaust fan mounted in the hood for drawing air from the treatment chamber into the plenum air space;

an air flow restriction arrangement mounted to the hood below the at least one exhaust fan;

a heating chamber for heating air, the heating chamber being in fluid communication with the plenum air space for receiving exhausted air and also in fluid communication with the treatment chamber for the supply of heated air into the treatment chamber.

In another aspect the apparatus may be configured for a substantially horizontal flow air through the produce containers.

2020100411 18 Mar 2020

In an embodiment is described an apparatus for supplying heated and humidified air to fresh produce comprising;

a body comprising a structural ceiling, side walls and end walls, a treatment area for holding a plurality of produce containing containers;

an heating arrangement for heating air;

at least one exhaust fan for circulating a flow of air within the body such that heated air is drawn in a substantially horizontal flow through the held produce containers, wherein an air flow restriction arrangement is positioned between the produce and the at least one exhaust fan.

In this embodiment there is suitably a plenum air space defined between the ceiling and a fixed dropped ceiling.

The apparatus suitably comprises an internal dividing wall spaced from a side wall or an end wall so as to define an air flow receiving chamber on one side and a produce treatment chamber on the other side.

The air flow receiving chamber is suitably in fluid communication with the plenum space between the internal dividing wall and the side wall or end wall. The at least one exhaust fan is configured so as to draw air through the held produce containers into the air flow receiving chamber.

The internal dividing wall may comprise the air flow restriction arrangement.

The air flow arrangement may be continuous along the dividing wall.

Alternatively, the wall may have sections of air flow restriction separated by sections without or minimal air flow restriction. The section of air flow restrictions are configured to conform or substantially conform to the width and height of a stack of produce containers.

The internal dividing wall may be movable towards and away from the side wall so as to accommodate treatment loads having a reduced number of stacks of containers.

The apparatus may comprise a second internal dividing wall spaced from the opposite side wall or end wall so as to define an air inlet chamber in fluid communication with the plenum space for introducing air into the treatment chamber.

The source of heated air may be located in the air flow receiving chamber.

2020100411 18 Mar 2020

The at least one exhaust fan may be located above the heat source or below the heat source.

The produce containers when in the treatment area, have an air inlet side wall and an air outlet side wall. In an alternate embodiment, the outlet side walls of the produce containers may be configured to provide the air flow restriction arrangement. In this way, the overall surface area of the air flow restriction arrangement will be entirely consistent with t

In an alternate embodiment, the air flow restriction arrangement may be a separate panel that may be fixed to the air outlet side of one or more crates.

The apparatus comprises a source of heated air. The source of heated and humidified air may be located at any position within the body that allows for circulated air to be heated and humidified.

In one aspect the source of heated air is located in a heating chamber that is in fluid communication with the treatment chamber for introducing a supply of heated air into the treatment chamber.

With a vertical air flow configuration, the heated air may be introduced into the lower part of the treatment chamber so that the heated air may travel up through the containers for contacting the produce.

In one aspect, the apparatus has opposing side walls and two end walls. The heating chamber may be located along a side wall and separated from the treatment chamber by an internal dividing wall. The heating chamber and treatment chamber may share a common floor. The lower edge of the dividing wall may be spaced from the common floor so as to define an air inlet space through which heated air may be delivered into the treatment chamber. In this way, the heated air is distributed such that it flows across the floor.

In this aspect, the apparatus may include a grate located above the floor such that the containers may sit on top of the grate so as to allow heated air to travel upwards through the bottom of the lower most container.

BRIEF DESCRIPTION OF DRAWINGS

Figures 1 to 4 are schematic drawings showing air flow through prior art VHT treatments;

Figure 5 is a perspective view of a VHT chamber as disclosed herein;

2020100411 18 Mar 2020

Figure 6 is an end view of the VHT chamber shown in Figure 6;

Figure 7 is a section A-A of Figure 6;

Figure 8 is a section B-B of Figure 6;

Figure 9 is a schematic internal front elevation of the VHT chamber;

Figure 10 is a section C-C from Figure 9;

Figure 11 is a schematic top plan view of the VHT chamber;

Figure 12 is a schematic view of a model of a VHT chamber as used to conduct air flow trials;

Figure 13 is a schematic side view of air flow in a treatment chamber according to another embodiment; and

Figure 14 is a schematic plan view of the arrangement as shown in Figure 13.

DETAILED DESCRIPTION

Figure 5 is a perspective view of a VHT chamber 10 as disclosed herein. The chamber is an insulated container with a similar general construction to that of refrigerated containers that are known in the refrigeration transport art as Reefer units or containers. Reefer units are designed for bottom flow delivery of chilled air that is cooled by a refrigeration unit at one end.

The floor has a T-shaped decking floor to allow cool air to flow into the chamber through or around the cooled produce and warmed air is returned to the cooling system in the space between the top of the produce and the container ceiling.

The VHT chamber 10 is to be constructed using the bodies of three 40 ft Reefer containers.

A first container is modified by removing the refrigerator unit at one end, removing wall sheeting along one side and removing the roof panel to provide main section 12.

A second container is cut in half lengthways and the roof removed. One lengthways half provides side section 14.

A third container is cut in half through the horizontal axis. The upper half provides upper left section 16. The other half is cut again to provide upper right section 18.

The four sections are welded together to provide container 10. Doors 8 are installed at each end.

Figure 7 shows the section A-A as shown in Figure 6. The section has the T section floor 20 of the original Reefer container. The upper section 16 provides a ceiling space that will be described further below.

2020100411 18 Mar 2020

Figure 8 shows the section B-B as shown in Figure 6. Section 14 defines a space for heating coils or heating chamber. Section 12 defines a space for holding produce to be treated, a treatment chamber. The treatment chamber 12 and the heating chamber 14 are separated by an internal dividing wall 13. The internal dividing wall 13 has a bottom edge that is spaced form the floor 20 as will be discussed further with reference to Figure 10.

Figure 9 is a schematic side elevation view of the exhaust hood arrangement 22 that draws heated air upwardly from the floor 20 and through the produce. The hood arrangement 22 has a housing 24 that is trapezoidal in cross section. A series of exhaust fans 26 are mounted in the hood 22.

The housing 24 is mounted to the ceiling 30 by a winch arrangement such that the housing 24 may mover vertically towards and away from the roof. The housing 24 is closed off at the lower end by a 30% perforated steel sheet 32. The perforations are staggered round holes.

Figure 10 shows the section C-C from Figure 9 and schematically shows the air flow within the chamber 10.

Figure 11 is a plan view showing that there are two rows of nine fans 26 extending along each side of the chamber 10.

Heating coils 34 are housed within heating chamber 14 and provide a source of heated air HA. There is also a source of water to provide the required degree of humidity as is known in the art. The internal dividing wall 30 has a bottom edge 40 that is spaced from floor 20 so as to define a longitudinal air flow passage 44 that allows heated air HA to enter the treatment chamber 12 across and perpendicular to the T floor 20.

The stacks of crates 36 are placed above the floor 20 on a grid 42. This enables the hot air HA to be drawn upwardly through crates 36 of produce so as to heat the produce to the required temperature. After the hot air HA has passed through the crates 36 and drawn into the ceiling plenum space 16, the cooler air CA is recycled back to the heating chamber 14.

It may be seen that the hood housing 24 is directly above the crates 36.

The housing 24 is able to be lowered or raised to accommodate crate 36 stacks of different heights.

2020100411 18 Mar 2020

TRIALS

Air flow tests were conducted on a model hood arrangement 50 that is shown in Figure 12. The model hood arrangement 50 includes a hood 51 with a single extraction fan placed over a stack of crates. The hood 51 has a depending collar 53 that receives the upper end of the uppermost crate 36. The crates used for the tests were conventional produce crates that are used for refrigerated transport and thus have side vents for allowing flow through of chilled air. The crates were empty.

As explained above, air flow through crate sides is undesirable for VHT treatment. For the purpose of the tests, the crates were wrapped in a plastic film. Thus the combination of the plastic film and hood 51 fitting closely over the uppermost crate36, the flow of air is limited to up flow through the crates.

The crates 36 were placed on a slatted palette 52 that was in turn placed on empty crates 36 so as to space the bottom most crate from the ground.

The cross section of the crate stack 36 was divide into nine sections in a 3 x 3 grid. The exhaust fan 26 was turned on and air flow was measured (m/s) by placing an anemometer below the lower crate at a location corresponding to each of the nine sections.

Trial 1

A first trial was conducted without any means of flow restriction between the uppermost crate and the extraction fan.

The results are shown in Table 1.

Table 1

2020100411 18 Mar 2020

2.00 A	1.94 B	2.00 C
2.38	2.68	2.59
D	E	F
2.03	1.91	2.16
G	H	I
Maximum Air Flow	= (E) 2.68
Minimum Air Flow	= (H) 1.91
Maximum differential	= 0.77
Air flow differential %	= 40

Trial 2

A second trial was conducted with a 30% perforated steel mesh (staggered round hole configuration) placed at the lower part of the hood 51 immediately above the collar 53.

The results are shown in Table 2.

Table 2

2020100411 18 Mar 2020

30% Perforation Restriction

2.08 ' A	2.03 B	1.97 C
2.21 D	2.27 E	2.24 F
2.03 G	1.97 H	2.08 I

Maximum Air Flow =	(E)	2.27
Minimum Air Flow =	(H)	1.97
Maximum differential =		0.30
Air flow differential % =		15

The results from both trials show that the centre section E had the highest air flow being 2.68 and 2.27 respectively. The results also show that section H displayed the minimum air flows of 1.91 and 1.97 respectively.

The air flow differential % of Trial 1 at 40% was significantly higher than the air flow differential of 15% for Trial 2.

As discussed in the background section, a VHT treatment process is strictly monitored to ensure that the internal temperature of all produce is heated to the specified temperature and is held at that temperature for the specified period of time. In practice, it is not possible to measure each produce item. To ensure compliance for all produce, temperature probes are placed in produce that is located at those parts of the VHT chamber that are the coolest. In practice, this means that the produce in the hottest parts of the VHT chamber are subjected to higher temperatures for longer and the overheated produce is subject to heat damage. Constancy of temperature across the VHT chamber is highly desirable. Constancy of flow of hot air through the produce is one factor in achieving such consistency.

2020100411 18 Mar 2020

Turning now to the trials above, the sections of lowest air flow would correspond to the cooler parts of a VHT chamber. Thus in practice, temperature probes would be placed in produce located in sections B and H. For trial 1, the produce in section E would be subjected to considerably higher air flow and this higher temperatures than produce in sections B and H.

Trial 2 shows the differences in maximum and minimum air flow to be significantly less. This would convert in practice to a lesser difference between the in temperatures of the treated produce in sections E and H.

The present inventor has surprisingly and unexpectedly discovered that by providing an air flow restriction below the exhaust fan, air flow differential may be reduced.

Figure 13 shows another embodiment of a VHT chamber 10. The same reference numerals will be used for the same features as for the VHT chamber 10 described above.

The VHT chamber 10 is configured for a horizontal flow of air as described below. Thus there is a treatment area in the form of a treatment chamber 12 holding stacks of crates 36, an upper plenum air flow space 16, a heating chamber 14 with a heat source 34 (radiator) therein and a number of exhaust fans 26.

Heating chamber 14 is located at the end of the VHT chamber and is separated from the treatment chamber 12 by internal dividing wall 32. The heating chamber 14 is in fluid communication with the plenum air space 16.

It will be appreciated that the heating chamber may also be located along the side wall of the chamber 10, in a similar manner as in Figures 5 to 12.

The fan(s) 26 circulate air in an anticlockwise direction through the treatment chamber 12 as shown by the arrows in Figure 13. The cooled air CA is drawn that has passed through the crates and through the heat source 34 recirculated through the plenum 16 to the treatment chamber 12.

Thus the air passes through the side walls of the crates 36.

The exhaust fans 26 are shown as positioned above the heat source 34. The position of the heat source 34 and fans 26 may be in any suitable configuration provided heated air is circulated through the treatment chamber and the crates 36.

2020100411 18 Mar 2020

The wall 32 is a perforated sheet as described above so as to provide an air flow restriction arrangement between the crates 36 and the exhaust fans 26. The stack of crates 36 is loaded to the treatment chamber 12 in close proximity/abutment to wall 32. This proximity has the same advantage as described above by lowering the exhaust hood to the top crate in that it may provide for a more uniform air flow through the crates 36. Alternatively, or in addition to wall 32 may be moveable towards and away from the opposite side wall 56

The configuration of the exhaust fan arrangement is different to that shown in Figure 10 in that the fans 26 are not located directly above the stacked crates as shown in Figure 10 but are above and to side of the crates 36.

Figure 14 is a schematic plan view of the arrangement as shown in Figure 13. There is only a single row of fans. The sides 58 of the stacks of crates 36 transverse to the air flow are sealed with a plastic sheet or curtain. The air flow creates a vacuum in the crates that draws the sheet/curtain towards the walls 58.

It will be appreciated that various changes and modifications may be made to the invention as described and claimed herein without departing from the spirit and scope thereof.

2020100411 18 Mar 2020

VAPOUR HEAT TREATMENT APPARATUS AND METHOD

TECHNICAL FIELD

The present disclosure relates to an apparatus and method for insect disinfestation of fresh produce such as fruits and vegetables.

DEFINITION

In the present specification and claims the term “comprising shall be understood to have a broad meaning similar to the term “including” and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term “comprising” such as “comprise” and “comprises”.

BACKGROUND

Many fruit and vegetables are hosts to insect pests and in particular fruit flies. In order to export to countries or locations with a fruit fly quarantine barrier, the produce must be subjected to a disinfection treatment approved by the importing country.

Chemical fumigation with agents such as diethylene bromide and methyl bromide is an effective disinfestation treatment and was traditionally the most widely used. However, chemical fumigation is being phased out as a result of concerns relating to toxicity and worker safety. Irradiation is also an effective disinfestation treatment but is relatively expensive, has poor consumer acceptance and significant adverse physiological effects, reducing shelf life and often cosmetic degradation over time as a result of necrosis.

Insect pests such as fruit fly may also be killed by temperature treatment to temperatures above or below that at which the insect larva may survive. Temperature treatment has the advantages of avoiding use of toxic chemicals or irradiation and has a high consumer acceptance. Cold storage holds fruit or vegetables at temperatures below 3° for about two to three weeks. Cold storage also has the advantage of preserving the produce. Heat treatment heats the fruit or vegetables to temperatures such that the internal temperature reaches above about 45°C for a predetermined period of time. Heat treatment can however adversely affect produce quality and may be a high cost treatment.

Some fruits and vegetables are sensitive to cold temperature and cold temperature treatment cannot be used as a disinfestation treatment. Tropical fruits are especially sensitive. For example, mangos suffer chill damage at below 13°C.

2020100411 18 Mar 2020

The temperature and time to which fruits or vegetables are heated and held is determined by the quarantine regulations of the importing country. For example some regulations require heating fruit to 46.5°C for twenty minutes whilst others require heating to 47°C for 15 minutes.

In order to minimise heat damage to the treated fruit it is desirable to raise the temperature as quickly and accurately as possible. Heat treatment at high humidity, known as vapour heat treatment or VHT is particularly effective. As water vapour condenses on the fruit, it gives up its latent heat and efficiently heats the fruit thereby facilitating heating rate.

VHT treatment is conventionally carried out by placing fruit in large plastic bins, stacking the bins and placing the bins in a sealed treatment chamber. The plastic bins have ventilation openings so as to allow air flow about the produce. Heated air is introduced into the chamber with a relative humidity of 90 to 100%. The plastic bins are configured to hold a maximum of about 500kg of produce.

The treatment chambers used for VHT treatment were originally based upon configurations used in conventional forced-air cooling chambers. With forced air cooling, produce is placed in ventilated plastic bins and placed in a refrigeration unit. The refrigeration units includes a fan system in a plenum to pull cold air through the bins. Air flow may be either horizontal or vertical. The plenum is generally provided with spaced rectangular outlets covered by a grill. The stacked bins are carefully aligned relative to an outlet so as to optimise cold air flow through the bins.

With VHT treatment it is critical that all produce is subjected to the “kill temperature” for the regulated period of time. Failure to do so can result in incomplete disinfestation if not all produce reaches the required temperature and/or for less than the regulated time. The result is that the entire load is rejected for quarantine purposes. On the other hand if the temperature is too high, a significant percentage of produce may be lost due to heat damage. Either scenario represents a significant commercial loss.

The treatment process is carefully monitored to ensure the internal (pulp) temperature of all produce being treated reaches the required temperature for the required period of time. Probes are placed into the largest fruits at different heights and locations within the chamber. The treatment is continued until the sensor at the coldest location reaches the regulated temperature and held for the regulated minimum time. The “cold spots” or spots with the longest heat up time are determined during a certification procedure for each treatment chamber.

2020100411 18 Mar 2020

In practice this means that a significant amount of the fruit is held at a higher temperature for longer. This can adversely affect fruit quality. There may be up to about 20 to 30% loss of fruit after a VHT process.

It is therefore desirable to produce uniform airflow and efficient heating so that all fruit is heated to the same temperature at the same time. There are a number of variables that may affect airflow within a treatment chamber, including air flow pattern such as vertical flow or horizontal flow through the chamber, lateral flow, design and arrangement of the plastic bins, relative sizes of fruit and the packing of the fruit into the plastic bins.

It is therefore desirable to provide an alternative apparatus and method for VHT treatment for disinfestation of fruits and/or vegetables.

SUMMARY

According to a first aspect of the disclosure there is provided an apparatus for supplying heated and humidified air to fresh produce comprising;

a body comprising a treatment area for holding a plurality of produce containing containers;

a source of heated and humidified air;

at least one exhaust fan for circulating a flow of air within the body such that air is drawn through the held produce containers, wherein an air flow restriction arrangement is positioned between the produce container and the at least one fan.

The present inventor has surprisingly discovered that by providing an air flow restriction arrangement between produce container and the at least one fan such that air is drawn through the air flow restriction arrangement can improve evenness of airflow through the produce containers.

The air flow restriction arrangement may be any suitable arrangement that may restrict air

The air flow restriction arrangement suitably has a sheet type body with a having a plurality of air flow openings separated by land areas such that air flow is restricted to flow through the openings. Suitably the air flow openings are uniformly spaced

2020100411 18 Mar 2020

Such types of restriction arrangements are characterised by the % open area. The open area is a ratio that reflects how much of the sheet is occupied as holes normally expressed as percent.

The air flow restricted arrangement may be a perforated sheet or grid having holes or slots through which air may pass.

The open area of the restriction arrangement is generally between about 10% to about 80%, suitably between about 15% to about 60%, suitably between about 20% to about 50%, suitably between about 25% to about 45%. In an embodiment the open area is about 30%.

The restriction arrangement may be in the form of a metal grill.

Suitably, the air flow restriction arrangement is a perforated metal sheet. Suitably the sheet is perforated with round holes. However, it will be appreciated that other hole configurations such as square, oblong, hexagonal or otherwise may be suitable.

In one aspect, the apparatus includes an exhaust chamber is in the form of an exhaust hood that is mounted to the ceiling of the apparatus such that there is a substantially vertical upwards flow of air through the produce containers.

According to an embodiment there is provided an apparatus for supplying heated and humidified air to fresh produce comprising a body comprising;

a treatment chamber for holding a plurality of produce containment containers, the treatment chamber comprising a ceiling and an exhaust hood below the ceiling so as to define a plenum air space between the exhaust hood and the ceiling;

at least one exhaust fan mounted in the hood for drawing air from the treatment chamber into the plenum air space;

an air flow restriction arrangement mounted to the hood below the at least one exhaust fan;

a heating chamber for heating air, the heating chamber being in fluid communication with the plenum air space for receiving exhausted air and also in fluid communication with the treatment chamber for the supply of heated air into the treatment chamber.

In another aspect the apparatus may be configured for a substantially horizontal flow air through the produce containers.

2020100411 18 Mar 2020

In an embodiment is described an apparatus for supplying heated and humidified air to fresh produce comprising;

a body comprising a structural ceiling, side walls and end walls, a treatment area for holding a plurality of produce containing containers;

an heating arrangement for heating air;

at least one exhaust fan for circulating a flow of air within the body such that heated air is drawn in a substantially horizontal flow through the held produce containers, wherein an air flow restriction arrangement is positioned between the produce and the at least one exhaust fan.

In this embodiment there is suitably a plenum air space defined between the ceiling and a fixed dropped ceiling.

The apparatus suitably comprises an internal dividing wall spaced from a side wall or an end wall so as to define an air flow receiving chamber on one side and a produce treatment chamber on the other side.

The air flow receiving chamber is suitably in fluid communication with the plenum space between the internal dividing wall and the side wall or end wall. The at least one exhaust fan is configured so as to draw air through the held produce containers into the air flow receiving chamber.

The internal dividing wall may comprise the air flow restriction arrangement.

The air flow arrangement may be continuous along the dividing wall.

Alternatively, the wall may have sections of air flow restriction separated by sections without or minimal air flow restriction. The section of air flow restrictions are configured to conform or substantially conform to the width and height of a stack of produce containers.

The internal dividing wall may be movable towards and away from the side wall so as to accommodate treatment loads having a reduced number of stacks of containers.

The apparatus may comprise a second internal dividing wall spaced from the opposite side wall or end wall so as to define an air inlet chamber in fluid communication with the plenum space for introducing air into the treatment chamber.

The source of heated air may be located in the air flow receiving chamber.

2020100411 18 Mar 2020

The at least one exhaust fan may be located above the heat source or below the heat source.

The produce containers when in the treatment area, have an air inlet side wall and an air outlet side wall. In an alternate embodiment, the outlet side walls of the produce containers may be configured to provide the air flow restriction arrangement. In this way, the overall surface area of the air flow restriction arrangement will be entirely consistent with t

In an alternate embodiment, the air flow restriction arrangement may be a separate panel that may be fixed to the air outlet side of one or more crates.

The apparatus comprises a source of heated air. The source of heated and humidified air may be located at any position within the body that allows for circulated air to be heated and humidified.

In one aspect the source of heated air is located in a heating chamber that is in fluid communication with the treatment chamber for introducing a supply of heated air into the treatment chamber.

With a vertical air flow configuration, the heated air may be introduced into the lower part of the treatment chamber so that the heated air may travel up through the containers for contacting the produce.

In one aspect, the apparatus has opposing side walls and two end walls. The heating chamber may be located along a side wall and separated from the treatment chamber by an internal dividing wall. The heating chamber and treatment chamber may share a common floor. The lower edge of the dividing wall may be spaced from the common floor so as to define an air inlet space through which heated air may be delivered into the treatment chamber. In this way, the heated air is distributed such that it flows across the floor.

In this aspect, the apparatus may include a grate located above the floor such that the containers may sit on top of the grate so as to allow heated air to travel upwards through the bottom of the lower most container.

BRIEF DESCRIPTION OF DRAWINGS

Figures 1 to 4 are schematic drawings showing air flow through prior art VHT treatments;

Figure 5 is a perspective view of a VHT chamber as disclosed herein;

2020100411 18 Mar 2020

Figure 6 is an end view of the VHT chamber shown in Figure 6;

Figure 7 is a section A-A of Figure 6;

Figure 8 is a section B-B of Figure 6;

Figure 9 is a schematic internal front elevation of the VHT chamber;

Figure 10 is a section C-C from Figure 9;

Figure 11 is a schematic top plan view of the VHT chamber;

Figure 12 is a schematic view of a model of a VHT chamber as used to conduct air flow trials;

Figure 13 is a schematic side view of air flow in a treatment chamber according to another embodiment; and

Figure 14 is a schematic plan view of the arrangement as shown in Figure 13.

DETAILED DESCRIPTION

Figure 5 is a perspective view of a VHT chamber 10 as disclosed herein. The chamber is an insulated container with a similar general construction to that of refrigerated containers that are known in the refrigeration transport art as Reefer units or containers. Reefer units are designed for bottom flow delivery of chilled air that is cooled by a refrigeration unit at one end.

The floor has a T-shaped decking floor to allow cool air to flow into the chamber through or around the cooled produce and warmed air is returned to the cooling system in the space between the top of the produce and the container ceiling.

The VHT chamber 10 is to be constructed using the bodies of three 40 ft Reefer containers.

A first container is modified by removing the refrigerator unit at one end, removing wall sheeting along one side and removing the roof panel to provide main section 12.

A second container is cut in half lengthways and the roof removed. One lengthways half provides side section 14.

A third container is cut in half through the horizontal axis. The upper half provides upper left section 16. The other half is cut again to provide upper right section 18.

The four sections are welded together to provide container 10. Doors 8 are installed at each end.

Figure 7 shows the section A-A as shown in Figure 6. The section has the T section floor 20 of the original Reefer container. The upper section 16 provides a ceiling space that will be described further below.

2020100411 18 Mar 2020

Figure 8 shows the section B-B as shown in Figure 6. Section 14 defines a space for heating coils or heating chamber. Section 12 defines a space for holding produce to be treated, a treatment chamber. The treatment chamber 12 and the heating chamber 14 are separated by an internal dividing wall 13. The internal dividing wall 13 has a bottom edge that is spaced form the floor 20 as will be discussed further with reference to Figure 10.

Figure 9 is a schematic side elevation view of the exhaust hood arrangement 22 that draws heated air upwardly from the floor 20 and through the produce. The hood arrangement 22 has a housing 24 that is trapezoidal in cross section. A series of exhaust fans 26 are mounted in the hood 22.

The housing 24 is mounted to the ceiling 30 by a winch arrangement such that the housing 24 may mover vertically towards and away from the roof. The housing 24 is closed off at the lower end by a 30% perforated steel sheet 32. The perforations are staggered round holes.

Figure 10 shows the section C-C from Figure 9 and schematically shows the air flow within the chamber 10.

Figure 11 is a plan view showing that there are two rows of nine fans 26 extending along each side of the chamber 10.

Heating coils 34 are housed within heating chamber 14 and provide a source of heated air HA. There is also a source of water to provide the required degree of humidity as is known in the art. The internal dividing wall 30 has a bottom edge 40 that is spaced from floor 20 so as to define a longitudinal air flow passage 44 that allows heated air HA to enter the treatment chamber 12 across and perpendicular to the T floor 20.

The stacks of crates 36 are placed above the floor 20 on a grid 42. This enables the hot air HA to be drawn upwardly through crates 36 of produce so as to heat the produce to the required temperature. After the hot air HA has passed through the crates 36 and drawn into the ceiling plenum space 16, the cooler air CA is recycled back to the heating chamber 14.

It may be seen that the hood housing 24 is directly above the crates 36.

The housing 24 is able to be lowered or raised to accommodate crate 36 stacks of different heights.

2020100411 18 Mar 2020

TRIALS

Air flow tests were conducted on a model hood arrangement 50 that is shown in Figure 12. The model hood arrangement 50 includes a hood 51 with a single extraction fan placed over a stack of crates. The hood 51 has a depending collar 53 that receives the upper end of the uppermost crate 36. The crates used for the tests were conventional produce crates that are used for refrigerated transport and thus have side vents for allowing flow through of chilled air. The crates were empty.

As explained above, air flow through crate sides is undesirable for VHT treatment. For the purpose of the tests, the crates were wrapped in a plastic film. Thus the combination of the plastic film and hood 51 fitting closely over the uppermost crate36, the flow of air is limited to up flow through the crates.

The crates 36 were placed on a slatted palette 52 that was in turn placed on empty crates 36 so as to space the bottom most crate from the ground.

The cross section of the crate stack 36 was divide into nine sections in a 3 x 3 grid. The exhaust fan 26 was turned on and air flow was measured (m/s) by placing an anemometer below the lower crate at a location corresponding to each of the nine sections.

Trial 1

A first trial was conducted without any means of flow restriction between the uppermost crate and the extraction fan.

The results are shown in Table 1.

Table 1

2020100411 18 Mar 2020

2.00 A	1.94 B	2.00 C
2.38	2.68	2.59
D	E	F
2.03	1.91	2.16
G	H	I
Maximum Air Flow	= (E) 2.68
Minimum Air Flow	= (H) 1.91
Maximum differential	= 0.77
Air flow differential %	= 40

Trial 2

A second trial was conducted with a 30% perforated steel mesh (staggered round hole configuration) placed at the lower part of the hood 51 immediately above the collar 53.

The results are shown in Table 2.

Table 2

2020100411 18 Mar 2020

30% Perforation Restriction

2.08 ' A	2.03 B	1.97 C
2.21 D	2.27 E	2.24 F
2.03 G	1.97 H	2.08 I

Maximum Air Flow =	(E)	2.27
Minimum Air Flow =	(H)	1.97
Maximum differential =		0.30
Air flow differential % =		15

The results from both trials show that the centre section E had the highest air flow being 2.68 and 2.27 respectively. The results also show that section H displayed the minimum air flows of 1.91 and 1.97 respectively.

The air flow differential % of Trial 1 at 40% was significantly higher than the air flow differential of 15% for Trial 2.

As discussed in the background section, a VHT treatment process is strictly monitored to ensure that the internal temperature of all produce is heated to the specified temperature and is held at that temperature for the specified period of time. In practice, it is not possible to measure each produce item. To ensure compliance for all produce, temperature probes are placed in produce that is located at those parts of the VHT chamber that are the coolest. In practice, this means that the produce in the hottest parts of the VHT chamber are subjected to higher temperatures for longer and the overheated produce is subject to heat damage. Constancy of temperature across the VHT chamber is highly desirable. Constancy of flow of hot air through the produce is one factor in achieving such consistency.

2020100411 18 Mar 2020

Turning now to the trials above, the sections of lowest air flow would correspond to the cooler parts of a VHT chamber. Thus in practice, temperature probes would be placed in produce located in sections B and H. For trial 1, the produce in section E would be subjected to considerably higher air flow and this higher temperatures than produce in sections B and H.

Trial 2 shows the differences in maximum and minimum air flow to be significantly less. This would convert in practice to a lesser difference between the in temperatures of the treated produce in sections E and H.

The present inventor has surprisingly and unexpectedly discovered that by providing an air flow restriction below the exhaust fan, air flow differential may be reduced.

Figure 13 shows another embodiment of a VHT chamber 10. The same reference numerals will be used for the same features as for the VHT chamber 10 described above.

The VHT chamber 10 is configured for a horizontal flow of air as described below. Thus there is a treatment area in the form of a treatment chamber 12 holding stacks of crates 36, an upper plenum air flow space 16, a heating chamber 14 with a heat source 34 (radiator) therein and a number of exhaust fans 26.

Heating chamber 14 is located at the end of the VHT chamber and is separated from the treatment chamber 12 by internal dividing wall 32. The heating chamber 14 is in fluid communication with the plenum air space 16.

It will be appreciated that the heating chamber may also be located along the side wall of the chamber 10, in a similar manner as in Figures 5 to 12.

The fan(s) 26 circulate air in an anticlockwise direction through the treatment chamber 12 as shown by the arrows in Figure 13. The cooled air CA is drawn that has passed through the crates and through the heat source 34 recirculated through the plenum 16 to the treatment chamber 12.

Thus the air passes through the side walls of the crates 36.

The exhaust fans 26 are shown as positioned above the heat source 34. The position of the heat source 34 and fans 26 may be in any suitable configuration provided heated air is circulated through the treatment chamber and the crates 36.

2020100411 18 Mar 2020

The wall 32 is a perforated sheet as described above so as to provide an air flow restriction arrangement between the crates 36 and the exhaust fans 26. The stack of crates 36 is loaded to the treatment chamber 12 in close proximity/abutment to wall 32. This proximity has the same advantage as described above by lowering the exhaust hood to the top crate in that it may provide for a more uniform air flow through the crates 36. Alternatively, or in addition to wall 32 may be moveable towards and away from the opposite side wall 56

The configuration of the exhaust fan arrangement is different to that shown in Figure 10 in that the fans 26 are not located directly above the stacked crates as shown in Figure 10 but are above and to side of the crates 36.

Figure 14 is a schematic plan view of the arrangement as shown in Figure 13. There is only a single row of fans. The sides 58 of the stacks of crates 36 transverse to the air flow are sealed with a plastic sheet or curtain. The air flow creates a vacuum in the crates that draws the sheet/curtain towards the walls 58.

It will be appreciated that various changes and modifications may be made to the invention as described and claimed herein without departing from the spirit and scope thereof.

Claims (5)

1. An apparatus for supplying heated and humidified air to fresh produce comprising;

a body comprising a structural ceiling, side walls and end walls, a treatment area for holding a plurality of produce containing containers;

an heating arrangement for heating air;

at least one exhaust fan for circulating a flow of air within the body such that heated air is drawn in a substantially horizontal flow through the held produce containers, wherein an air flow restriction arrangement is positioned between the produce and the at least one exhaust fan.

2. The apparatus of claim 1, wherein the apparatus comprises a dropped ceiling so as to define a plenum space between the structural ceiling and the dropped ceiling and an internal dividing wall spaced from a side wall or an end wall so as to define an air flow receiving chamber in fluid communication with the plenum and the at least one exhaust fan is configured so as to draw air through the held produce containers into the air flow receiving chamber and the internal dividing wall comprises the air flow restriction arrangement.

3. The apparatus of claim 2, wherein the internal dividing wall is movable towards and away from the side wall.

4. The apparatus of claim 1, wherein the produce containers have an air inlet side wall and an air outlet side wall, wherein the air outlet side wall is configured to provide the air flow restriction arrangement.

5. The apparatus of any one of claims 1 to 4, wherein the open area of the restriction arrangement is between about 15% to about 60%, preferably between about 20% to about 50%, and more preferably between about 25% to about 45%.