WO2012118387A2

WO2012118387A2 - Improvements to conditioning systems

Info

Publication number: WO2012118387A2
Application number: PCT/NZ2012/000025
Authority: WO
Inventors: Robert Marshall BARNES
Original assignee: Drying Solutions Limited
Priority date: 2011-03-02
Filing date: 2012-03-02
Publication date: 2012-09-07
Also published as: NZ591125A; WO2012118387A3

Abstract

There is provided a conditioning system, and in a preferred embodiment a drying apparatus. The apparatus includes refrigerant flow paths that may provide improved efficiency in energy use and uniquely configured drying surfaces and/or supports that define drying gas flow paths.

Description

IMPROVEMENTS TO CONDITIONING SYSTEMS

TECHNICAL FIELD

The present invention relates to improvements to conditioning systems. BACKGROUND ART

Devices to regulate temperature and humidity of air or gases are known. These are used in domestic and commercial applications such as heat pump air conditioners or in devices to remove moisture from products (product dryers).

Drying devices remove moisture from products to improve their storability or suitability for a particular use. These devices generally include a drying chamber, a heat circulation system, and an evaporator. Air is heated and circulated through the drying chamber so as to move around the product being dried. The heated air removes (absorbs) moisture from the product being dried. The evaporator is used to remove moisture from the heated air.

Some drying apparatus do not include an evaporator, rather the heated moisture laden air is simply expelled from the drying chamber. New air is heated, before being circulated through the chamber.

One particularly efficient type of drying apparatus is known as a Heat Pump Dryer. This uses a heat pump to warm/heat air so that it can be used to remove moisture from the product being dried.

A heat pump is a thermal transfer device that can take energy from one system and transfer that to another system and vice versa. That transfer of energy can be used to cool or heat a system. A refrigerant, initially in the form of a cool gas, is first compressed so as to increase its temperature (via increasing the pressure). That heated refrigerant is circulated through a transfer mesh. Air is then circulated so that it contacts the outside surface of the transfer mesh. This heats the air. In relation to product drying, the heated air can then be used to remove moisture (dry) a product.

The refrigerant is passed through a cycle of steps to return it to a cool gas before returning to the condenser so that the process can repeat.

Significant work has been done on increasing the efficiency of heat pump dryers and to optimise these for drying different types of products. However the available dryers do not provide all of the requirements for drying. In addition, while heat pumps are efficient they still require the input of energy. Accordingly any improvements to the efficiency of a drying apparatus would be beneficial.

A selection of prior art will now be discussed to provide background to the present invention.

New Zealand Patent No. 524469 discloses drying apparatus with an evaporator having a variable area. The device directs a drying gas across a given area of evaporator according to the load required e.g. how hard the drying apparatus must work due to the volume of product being dried, or a required drying profile. This is claimed to decrease energy use thereby increasing the efficiency of the

evaporator.

However, there is no ability to optionally direct refrigerant through different paths. Therefore, the system has limited ability to control temperature, and its efficiency may be affected.

New Zealand Patent No. 524270 discloses a dehumidifying heat pump dryer. Refrigerant flow rates through the dryer's components are regulated so as to control dry bulb temperature and optionally vary the wet bulb temperature. It is alleged that this may improve conditions inside the drying apparatus e.g. make the drying apparatus more efficient due to maximising the moisture removed from the product. The device is designed to maintain a constant moisture removal from a material.

The apparatus of Patent No. 524270 is intended for maximising the moisture removal in drying timber. A vent allows outside air into the drying cavity. It is not possible to use the apparatus of this patent in drying of foodstuffs or fine particulate matter.

Furthermore, using dry bulb temperature to control drying in the manner described in Patent No. 524270 can be restrictive. It is also likely to be a complicated control mechanism.

New Zealand Patent No. 502038 discloses a microwave drying plant. The product is conveyed through a drying chamber using a conveyer belt. The product is exposed to heated air and microwaves. The combination of air and microwaves removes moisture from the product. The moist air is subsequently dehumidified or removed from the drying chamber.

Yet another problem with the known drying apparatus is their lack of suitability for use in multiple applications. For instance, optimising the efficiency of an apparatus for drying one type of product, or at a particular set of operating parameters, is unlikely to be an optimal configuration for other applications/products. Therefore, even though the known drying devices may be suitable for use in one application, they are not suitable for use in all applications.

In light of the failings of the prior art it would be advantageous to have a drying apparatus and methodology with improved efficiencies.

In addition, it would be an advantage to have a drying apparatus with increased flexibility and modes of operation so as to provide greater flexibility in drying of products.

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

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.

Throughout this specification, the word "comprise", or variations thereof such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

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 THE INVENTION

According to one aspect of the present invention there is provided a conditioning system, including a chamber; a heat transfer system that includes: a compressor, a first heat exchanger, a second heat exchanger, a condenser, and a variable heat exchanger; the drying apparatus characterised in that a refrigerant flows through the variable heat exchanger before flowing through the condenser.

According to another aspect of the present invention, there is provided a method of conditioning a gas in a system, wherein the system includes a chamber; a heat transfer system that includes: a compressor, a first heat exchanger, a second heat exchanger, a condenser, and a variable heat exchanger; and wherein the heat transfer system is configured so that a refrigerant flows through the variable heat exchanger before flowing through the condenser; the method including the steps of:

(a) engaging a fan to move a gas through the chamber;

(b) using the heat transfer system to remove moisture from the gas. According to another aspect of the present invention, there is provided a drying apparatus, including a mesh material to support a product to be dried, characterised in that the apparatus defines a flow path for a drying gas that is either:

(a) on both sides of the mesh material; or

(b) through the mesh material which support the product.

According to another aspect of the present invention, there is provided a drying apparatus, including: a support surface to hold a substance to be dried, characterised in that at least a portion of the support surface is a mesh material.

According to another aspect of the present invention, there is provided a method of drying a product, the method using a support surface-at least a portion of which is mesh material, the method including the steps of:

(a) providing the support surface in a drying chamber;

(b) providing a product to be dried onto the mesh material; characterised by the step of circulating a drying gas through a flow path that is either:

• on both sides of the mesh material; or

• through the mesh material.

The present specification describes improvements to conditioning systems. The broadest aspects of the present inventions relate to:

• refrigerant flow paths that may provide improved efficiency in energy use;

• uniquely configured drying surfaces and/or supports that define drying gas flow paths.

These inventions provide a number of advantages which should become clearer from the following description.

Throughout the present specification reference to the term "conditioning system" should be understood as meaning a device that can regulate the temperature and/or humidity of a gas.

In particularly preferred embodiments, the present inventions find application in drying apparatus to remove moisture from products. Therefore, reference will be made herein to the conditioning system being a product drying apparatus and to a gas as being a drying gas.

However, this should not be seen as limiting on the scope of the present invention. It is also envisaged that the inventions may find use in other applications. For instance, the refrigerant flow paths may be used in regulating the temperature and/or humidity of work spaces or factories. That control may be particularly beneficial where accurate temperature and/or humidity control, and efficient use of energy, are required.

In preferred embodiments the present inventions are intended for use in combination with each other. Reference herein will be made as such. However, this should not be seen as limiting and it is envisaged that the present inventions can be used independently of each other or in combination with other drying apparatus. Throughout the present specification reference will be made to transferring heat. It should be understood as referring to the transfer of energy from one place/substance to another. The transfer of heat (energy) may occur using one of several mechanisms, including mechanical work or across a thermal gradient.

Throughout the present specification reference will be made to different modes of operation of the drying apparatus. These modes each perform specific functions in relation to the drying of products. Examples include:

• A heating mode in which the temperature of a drying gas is increased.

• A heating mode to higher temperature, in which the refrigerant flow is adjusted so that additional heat is available to increase the temperature of a drying gas.

• A dehumidifying mode at constant temperature in which moisture is being removed from a drying gas and the temperature of the drying gas temperature is maintained as substantially constant.

• A dehumidifying mode to lower temperature in which moisture is removed from a drying gas and the temperature of the drying gas is decreased.

These modes differ in their respective refrigerant flow paths and drying gas flow paths.

The modes are selected according to the desired drying profile for a product, or other reasons such as to increase the efficiency of the drying apparatus. These aspects of the present invention should become clearer from the following description. Throughout the present specification, reference to the term "heat transfer system" should be understood as referring to an assembly of components that transfers heat into or out from a substance such as a drying gas.

In the particularly preferred embodiment the components of the heat transfer system are connected together so that refrigerant can flow through several pathways (as is discussed below).

The heat transfer system is configured such that each of the pathways is a refrigeration circuit. This is essential to operation of the heat transfer system.

However, the Applicant has found that certain flow path of refrigerant through the components of the transfer system can improve the efficiency of the drying apparatus.

This is for a number of different reasons, each of which applies to a different mode of operation.

For instance, in some modes of operation, it is important to ensure that the temperature of drying gas does not exceed a pre-determined maximum. This may be due to the type of produced being dried and the way in which it releases moisture, or to minimise or eliminate conditions favorable for microbe and bacterial reproduction. In such embodiments, the variable heat exchanger acts as a heat sink, transferring heat from the refrigerant to the surroundings (outside of the drying apparatus).

In such embodiments, the rate of heat transferred by the variable heat exchanger is determined according to the amount of heat that must be transferred to the surroundings so as to maintain the drying gas at a pre-determined temperature e.g. the variable heat exchanger transfers more or less heat to the surroundings according to the desired temperature of the drying gas.

Alternatively, the variable heat exchanger may transfer heat from the surroundings (outside of the drying chamber) into the refrigerant. This is beneficial as it assists in ensuring that heat is available to increase the temperature of the drying gas e.g. the refrigerant is heated so that as the drying gas moves into the second heat exchanger, heat is available to be transferred to drying gas in contact with the second heat exchanger.

These aspects of the present invention should become clearer from the following description.

Furthermore, the ability to change between different modes and refrigerant flow paths increases the flexibility of the drying apparatus.

Throughout the present specification, reference to the term "compressor" should be understood as meaning a device to compress a refrigerant.

In a preferred embodiment, the compressor may be a compressor as used in refrigeration, heat pumps, and/or drying apparatus. Compression of the refrigerant causes this to heat up and thereby increases its temperature. This provides the refrigerant with heat which it can be transferred to another component or substance. This is as should be known to those skilled in the art.

Throughout the present specification, reference to the term "heat exchanger" should be understood as meaning a device which can transfer heat between a refrigerant and another substance.

In its preferred embodiment the present invention incorporates a first heat exchanger, a second heat exchanger and a variable heat exchanger. In a preferred embodiment, the first heat exchanger is configured to transfer heat from the refrigerant to the drying gas. Therefore the first heat exchanger is located inside the drying chamber, and more preferably in the dehumidifying path (as will be discussed below).

However, it is also envisaged that the first heat exchanger could be outside of the chamber, so that it heats a drying gas prior to that entering the chamber. Accordingly the foregoing should not be seen as limiting on the scope of the present invention.

In the particularly preferred embodiment the first heat exchanger is a heating coil as should be known to those skilled in the art. In use the refrigerant passes through the heating coil. A drying gas is directed over the heating coil so as to facilitate heat transfer. This is as should be known to those skilled in the art.

The inventor has identified that the use of the heating coil, and more particularly the preferred embodiment, may help to provide greater efficiency in energy use. This is because the refrigerant cycle can be uniquely used to take energy from one part of the drying apparatus for use in another part. This should become clearer from the following discussion.

However, it is also envisaged that the first heat exchanger could take other forms as should be known to those skilled in the art. Accordingly the foregoing should not be seen as limiting.

In a preferred embodiment the second heat exchanger is configured to transfer heat from the refrigerant to the drying gas. In use, a refrigerant flows through the second heat exchanger. A drying gas passes by, or in contact with, the second heat exchanger so as to facilitate the transfer of energy. In a particularly preferred embodiment, the second heat exchanger is configured to transfer heat into the drying gas as that exits the condenser. In this embodiment, the second heat exchanger is in the dehumidifying path (as is discussed below). This arrangement of the second heat exchanger and condenser is advantageous as it may allow energy (heat) absorbed to be reused in another part of the drying apparatus.

In a particularly preferred embodiment, the second heat exchanger is a refrigerant sub-cooling coil as should be known to those skilled in the art.

However, the foregoing should not be seen as limiting and alternatives are envisaged.

Throughout the present specification, reference to the term "variable heat exchanger" should be understood as meaning a component that can selectively transfer heat into or out from a refrigerant, and the outside of the drying apparatus. Therefore, the variable heat exchanger acts as both a heat source and heat sink for the refrigerant (and therefore the drying apparatus). This is useful as it may improve or facilitate accurate control of the drying gas temperature.

The function which the variable heat exchanger will perform is determined according to a mode of operation in which the drying apparatus is set. That mode of operation determines the pathway through which a refrigerant flows, and thereby the order in which the refrigerant flows through the components of the heat transfer system.

This should become clearer from the following description.

In a particularly preferred embodiment, the heat transfer system is configured such that the variable heat exchanger is at the same phase/stage of the refrigeration circuit as the first heat exchanger. This is important as it allows the variable heat exchanger to remove heat from the refrigerant, thereby limiting the amount of heat which is transferred to a drying gas by the first heat exchanger.

In a particularly preferred embodiment the variable heat exchanger is configured to transfer heat into or out from the refrigerant at different rates.

Throughout the present specification, reference to the term "different rates" should be understood as meaning an amount of energy (heat) transferred per unit time.

This feature of the variable heat exchanger is beneficial as it may facilitate accurate control of the temperature of the drying gas in the drying chamber. For instance, in some modes of operation, the temperature of the drying gas may increase above a temperature optimum for drying a particular product. In such cases it can be important to quickly remove heat from the refrigerant. In contrast, in other cases, it may not be as important to remove heat as quickly, and therefore the variable heat exchanger transfers heat from the refrigerant at a slower rate.

This should become clearer from the following description.

However, the foregoing should not be seen as limiting on the scope of the present invention.

In a preferred embodiment, the operation of the variable heat exchanger is selected according to a desired mode of operation, parameters of the drying gas, and/or drying chamber. For instance, in a heating mode, the variable heat exchanger may be configured to transfer heat from the surroundings into the refrigerant. This ensures that the refrigerant has additional heat which it can transfer to the drying gas.

Alternatively, in a dehumidifying mode, the refrigerant removes heat from the drying gas, and the variable heat exchanger transfers that heat away from the drying chamber (such as to the surroundings, another drying apparatus, or another component of the drying apparatus). The rate at which that heat is transferred is determined according to the desired temperature of the drying gas in the drying chamber.

However, the foregoing should not be seen as limiting on the scope of the present invention and alternatives are envisaged.

Throughout the present specification, reference to the term "condenser" should be understood as referring to a component configured to remove moisture from the drying gas.

In a particularly preferred embodiment, the condenser may be an evaporator coil. In use, the refrigerant is directed through the evaporator coil. Drying gas is brought into contact with the evaporator coil so as to facilitate transfer of heat from the drying gas into the refrigerant thereby cooling the drying gas.

However, the foregoing should not be seen as limiting and other alternatives are envisaged.

Throughout the present specification, reference to the term "refrigerant" should be understood as meaning a substance which is capable of transforming between a liquid and a gas. The refrigerant's phase change between a liquid and a gas, or otherwise heating and cooling, is utilised to transfer heat that transfer may be between two or more components in the drying apparatus, and into or out from the drying gas.

The term "refrigerant" is as should be understood by those skilled in the art. Throughout the present specification, reference to the term "refrigerant flow path" should be understood as referring to a pre-determined order in which the refrigerant moves through components of the present invention.

The refrigerant flow paths are configured to facilitate transfer of heat between components in the drying apparatus. That includes between the drying gas and the heat transfer system, and the heat transfer system and the surroundings. This is beneficial in controlling the temperature at which a product is dried. In addition, the efficiency of the drying apparatus according to the present invention may be greater than that of the prior art devices. These aspects of the present invention should become clearer from the following discussion.

In a particularly preferred embodiment, the heat transfer system includes a plurality of refrigerant flow paths, including:

(a) Through the compressor, the first heat exchanger, the variable heat exchanger, and back to the compressor.

(b) Through the compressor, the variable heat exchanger, the second heat exchanger, the condenser and back to the compressor.

(c) Through the compressor, the first heat exchanger, the condenser, and back to the compressor.

(d) Through the compressor, the first heat exchanger, the variable heat exchanger, the second heat exchanger, the condenser and back to the compressor.

Which of these flows paths is used at any given time is selected according to the desired mode of operation of the drying apparatus. This may depend on: the conditions in the drying chamber, drying gas temperature, a desired humidity level for the drying gas, the characteristics of the product and how it releases moisture etc. It should also be appreciated that the refrigerant may flow through other components which facilitate a change in state necessary for a refrigeration circuit. This could include expansion valves as should be understood by those skilled in the art.

In a preferred embodiment, the present invention may include a flow control system.

The term "flow control system" should be understood as meaning components that control the flow path of the refrigerant. For instance, the flow control system can include valves, solenoid valves, check valves, and controllers to open and close the valves.

In a particularly preferred embodiment, the "gas" is a gas to absorb moisture from a product and thereby facilitate drying of the product.

Accordingly, reference will be made herein to the "drying gas".

However, the gas could be air in a work space, factory, or house/dwelling.

To remove moisture, the drying gas is heated and circulated past the product being dried. This heats the product and causes it to release moisture into the drying gas. This is as should be understood by those skilled in the art.

The drying gas is preferably air. The air may be filtered, purified, or otherwise treated, to ensure that it is suitable for use with drying the product.

However, the drying gas may also be an inert gas such as nitrogen, or a mixture of gases. Therefore the foregoing should not be seen as limiting. In a particularly preferred embodiment, the chamber is a cavity within which a product to be dried may be placed, and through which a drying gas is circulated. Therefore, reference throughout the present specification will be made to the chamber as "a drying chamber".

It is also envisaged that the chamber may be a factory workshop, residential space, or other space. Accordingly, the forgoing should not be seen as limiting on the scope of the present invention.

In a particularly preferred embodiment, the drying chamber is, or may be capable of being, sealed. That is, the drying chamber is a substantially or completely fluid tight container. Accordingly, the temperature and humidity of a drying gas may be more accurately regulated.

In addition, particulate matter or other contaminant such as bacteria is less likely to enter into the drying chamber. This helps to make drying apparatus according to the present inventions better suited for use with drying of food grade products.

It is also envisaged that the present inventions may be utilised in continuous type drying apparatus/processes. In these, product is moved into and through a drying chamber on a conveyor or similar device. Therefore, the drying chamber is not sealed, or is sealed for selected time periods. Accordingly, the foregoing should not be seen as limiting.

Throughout the present specification reference to the term "drying gas flow path" should be understood as meaning the route that the drying gas follows.

In a particularly preferred embodiment, drying apparatus according to the present inventions are configured to circulate the drying gas through a plurality of pathways. The pathways vary depending on the mode in which the drying apparatus is operating and how the parameters of the drying gas are being altered.

For instance, in one mode of operation, the drying gas may be substantially circulated through or around the first heat exchanger only. In this mode of operation heat is transferred to the drying gas by the first heat exchanger so as to increase the temperature of the drying gas. It is however, also envisaged that the drying gas could also pass through the dehumidifying path (discussed below), but that the condenser is not operating so as to remove moisture from the drying gas.

In another mode of operation, the drying gas is circulated through a dehumidifying path in which moisture is removed from the drying gas. When moving along this path the drying gas preferably travels through components in the following order: the condenser, second heat exchanger, and the first heat exchanger.

In addition, the drying gas may also travels through a preconditioning component before entering the condenser.

The present invention also provides a number of drying gas flow paths defined with respect to the product to be dried. In these, the drying gas is caused to circulate through, or on either side of, a mesh surface on which a product is supported. This may enable the drying gas to more effectively remove moisture from the product.

It should be appreciated that reference to the path of a drying gas through the drying chamber is separate, and in addition to, the drying gas flow path through the dehumidifying circuit. These path ways are preferably interrelated in that together they may provide increases to the drying apparatus' efficiency. However, they do not need to be used exclusively together, and efficiencies are provided when utilised separately.

In a preferred embodiment, the support surface, and/or racks to receive and hold the support surface may define the path of the drying gas within the drying chamber.

In one particularly preferred embodiment, this may be achieved by having directional openings which guide the movement of the drying gas. In this embodiment, each tray or rack has a plurality of openings on one side of the mesh material, and a plurality of openings on another side of the mesh material. Therefore, in use, the drying gas enters through a first plurality of openings, the direction of flow then causes the drying gas to pass through the mesh material, and exit through the second plurality of openings.

Alternatively, the support tray, racks or drying apparatus may also include flanges, valves, or supplementary fans which direct movement of the drying gas through the drying gas flow path. Accordingly, the foregoing should not be seen as limiting on the scope of the present invention.

In a particularly preferred embodiment, the support surface may be incorporated into a tray or rack.

This enables product to be dried to be easily loaded into the drying apparatus.

It should be clear from the foregoing description that the present invention provides a number of advantages. These may include greater flexibility in drying products, improved efficiency, greater suitability for use in drying specific types of products that have unique or difficult drying profiles, accurate control of temperature and humidity levels of a gas in a chamber.

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: is a cross sectional schematic showing components of a drying apparatus according to the present invention and airflow paths there through; is schematic showing components of a drying apparatus and refrigerant flow path; is a view of Figure 2a showing a refrigerant flow path in a first mode of operation; is a view of Figure 2a showing a refrigerant flow path in second, fourth and fifth modes of operation; is a view of Figure 2a showing a refrigerant flow path in a third mode of operation; is a rear perspective view showing one embodiment of a drying apparatus according to the present invention; is a side view of a drying rack according to the present invention; is a time versus temperature profile showing the different modes of operation; is a representative profile of temperatures and humidity versus time for a drying apparatus in-use; is a perspective view of a drying tray; is a close up side view of a variable heat exchanger; Figure 8 is a side on view of a drying apparatus. BEST MODES FOR CARRYING OUT THE INVENTION

There is provided a conditioning system in the form of a drying apparatus (1 ).

The drying apparatus (1 ) includes a housing (2) made from insulated materials. The housing (2) includes a cavity (3) that provides a chamber in which drying occurs.

The housing (2) is mounted on a trailer (4) and has external dimensions of 4.2 metres in length, 1.2 metres width, and 2.5 metres height.

In a preferred embodiment, the housing (2) may be releasably secured to the trailer (4).

The cavity (3) has internal dimensions of 7.85 metres length by 1.050 metre width.

Housing (2) has walls (5A - 5D). Wall (7a) has an opening (6).

A horizontal bi-fold door in wall (5D) is formed from a first portion (7A) and a second portion (7B). A hinge (8) is provided between first door portion (7A) and second door portion (7B).

First door portion (7A) is hinged to housing (2) on top edge (9) of opening (6). Second door portion (7B) is coupled to housing (2) by runners (10, 1 1). The runners sit within tracks (not visible) secured to side edges of opening (6). The runners (10, 1 1 ) and track (not visible) facilitate moving the door (7) between open and closed configurations.

A detachable folding ramp (12) is provided. The ramp (12) engages bottom edge (13) of opening (6) or trailer (4). The ramp allows drying racks (14) to be easily moved into and out of the cavity (3).

Drying racks (14) include a frame (15) and wheels (16).

The frames (16) can slidably receive drying trays (17).

The frames (16) and drying trays (17) are configured so as to define a flow path for a drying gas. This aspect will be discussed in more detail.

Drying trays (17) each include a drying surface (18) with openings (19) having a diameter of 2 mm. The size of the openings (19) can vary according to the type of product to be dried and a desired drying gas flow path. These aspects should become clearer from the following description.

Drying tray side walls (20) extended upwardly from the drying surface (18).

The drying apparatus (1) includes a heat transfer system with components to heat up, cool down, circulate, and remove moisture from, a drying gas. The components include:

• a fan (21) inside the cavity;

• a first heat exchanger (22) inside the cavity;

• a second heat exchanger (23) inside the cavity;

• a condenser (24);

• a compressor (36);

• a variable heat exchanger (25) outside of the cavity.

The heat transfer system is a refrigeration circuit. Therefore, it also includes expansion valves (26) and non-return valves (27), which assist in ensuring that a refrigerant is in the correct state to facilitate heat transfer. Solenoid valves (28) also assist in controlling the path (order) in which a refrigerant flows through the components of the heat transfer system.

This is as should be known to those skilled in the art, and will become clearer from the following description and attached Figures.

Variable heat exchanger (25) is shown in Figure 7. The variable heat exchanger (25) includes a mesh (29) or other medium through which a refrigerant can flow. A fan (30) is positioned adjacent to the mesh. In use, the fan (30) rotates at different speeds so as to circulate variable amounts of air past the mesh ( 29). This facilitates transfer of different amounts of heat into or out from the refrigerant.

The components of the heat transfer system are connected by conduits (31) so as to facilitate refrigerant flow between them through a variety of different pathways. The connection of the components is best explained by Figures 2A - D.

A four way valve (32) has an inlet (33) and three outlets (34, 35, 36). Outlet (34) is connected to a first inlet/outlet (37) in variable heat exchanger, outlet (35) is connected to compressor (36), and outlet (35) is connected to a second inlet/outlet (38) in variable heat exchanger. In use, the four way valve (32) is configured to cause refrigerant to flow through the components of the heat transfer system in specific orders (which should become clearer from the following description).

Solenoid valves (28) also assist in defining the refrigerant flow paths.

The drying apparatus (1) includes a dehumidifying path generally indicated by arrow (39) through which a drying gas may be directed. When passing through the dehumidifying path (39) condenser (24) can remove moisture from the drying gas. This should become clearer from the following description. " The drying apparatus (1) also includes a heating circuit generally indicated by arrow (40). The heating circuit is a pathway through which the drying gas may be directed to facilitate transfer of heat into the drying gas by the heat transfer system. This should become clearer from the following description.

An air flow valve (41) is configured to selectively move incrementally between an open position and a closed position. When the air flow valve (41) is fully open, the drying gas flows through drying chamber and through heating circuit (40). When the air flow valve (41) is fully closed the drying gas flows through the cavity (3), dehumidifying path (39), and into heating circuit (40).

When the air flow valve (41) is partially open or closed the drying gas can flow through the dehumidifying circuit into heating circuit, but drying gas will also flow through air flow valve and directly into heating circuit (40). Therefore the air flow valve (41) is able to control the amount and rate of drying gas flowing through dehumidifying circuit (39). This may help to improve the efficiency of the condenser (24).

A secondary refrigerant system in dehumidifying circuit (39), indicated generally by (42) is also provided. The secondary refrigerant system ( ) includes a pair of run around coils (43, 44). The run around coils (43, 44) are in communication with each other so that a refrigerant can travel between them. First run around coil (43) is positioned towards the entrance to dehumidifying path (39) so that drying gas passes through first run around coil (43) prior to entering condenser (24). Second run around coil (44) is positioned in dehumidifying path so that after a drying gas exits the condenser (24) it passes through second run around coil (44).

In use, refrigerant in the first run around coil (43) absorbs heat from the drying gas. This causes the refrigerant to boil and helps to move this to the second run around coil (44). Refrigerant in the second run around coil (44) transfers heat to the drying gas as that exits from the condenser (24). This causes the refrigerant to condense into a liquid and helps to move the refrigerant to the first run around coil.

The secondary refrigerant system (42) acts as a preconditioning step for a drying gas prior to that entering the condenser (24). Accordingly, the secondary refrigerant system (42) may help to improve the efficiency of the second heat exchanger (23) and condenser (24). This is because the first run around coil (43) lowers the temperature of the drying gas before it enters the condenser (24), meaning that condenser (24) does not need to remove as much heat from the drying gas to condense out the moisture it contains. The first run around coil (43) is removing sensible heat from the drying gas, helping to ensure that the condenser (24) needs to remove primarily latent heat only which is necessary to condense moisture from the drying gas.

It is also a useful way to remove and return heat to the drying gas e.g. heat taken at one point can be reintroduced at a later stage with minimal loss.

The drying apparatus (1) includes a plurality of sensors (45, 46) configured to determine the humidity and/or temperature of the drying gas at a particular position within the drying apparatus (2).

Sensor (45) determines temperature and/or humidity of drying gas within the cavity (3). Preferably the sensor (45) determines the temperature and/or humidity of a drying gas after it has removed moisture from a product on drying trays (17) and prior to entering dehumidifying circuit (39).

Sensor (46) is configured to determine the temperature and/or humidity of drying gas as that exits condenser (24). The sensors (45, 46) are connected to controller (47).

The controller (47) is programmed to monitor the temperature and/or humidity readings determined by the sensors (45, 46). The controller (47) is programmed to analyse the temperature and/or humidity levels determined by the sensors and change the mode of operation of the drying apparatus (1).

This is useful where the sensors indicate that drying gas temperature has exceeded a predetermined threshold. In such a situation, the drying apparatus (1) may be switched to a mode to remove heat from the refrigerant. Alternatively, if humidity levels appear to be decreasing the drying apparatus (1) may be switched to a mode in which drying gas temperature is increased.

The controller (47) is in communication with all components of the drying apparatus (1). The controller contains pre-programmed drying profiles. Each drying profile is suited for drying particular products. The controller (47) may also allow manual control of the drying apparatus (1).

General Operation

Product is provided on the drying surfaces (18). Trays (17) are slid into racks.

The drying racks (14) are wheeled into cavity (3) via ramp (12).

The door (7) is closed so as to seal the cavity (3). Therefore air cannot flow into or out of the cavity (3) helping to ensure that the drying apparatus (1) is suitable for use with drying food stuffs.

The controller (47) is engaged so as to start a drying profile chosen according to the product. E.g. the controller (47) can vary the parameters and operation of the drying apparatus (1), including: • drying gas flow rate;

• drying gas temperature;

• period of time for drying gas to be at a given temperature;

• condenser work load; and/or

• drying gas flow rate through the dehumidifier circuit.

Four way valve (32) controls refrigerant flow through one of multiple pathways so as to achieve a desired temperate for drying gas.

Aspects of the drying apparatus (1) will now be described with reference to different modes of operation. Figure 2A is a general schematic showing connection of the components in a heat transfer system according to the present invention.

In Figures 2B - 2D the direction of refrigerant flow is shown by arrows.

1. Heating Mode

The heating mode includes two sub cycles, each referred to as modes 1A & 1 B.

Cycle 1A is shown in Figure 2B and involves heating the drying gas using latent heat released by the fan (21) during its operation to circulate the drying gas. In this sub cycle, refrigerant flows through the following components: the compressor (36), first heat exchanger (23), four way valve (32), variable heat exchanger (25) and back to compressor (36) and so on.

During cycles 1A and 1 B the refrigerant may optionally be directed through receiver (48), drying apparatus (49), and sight glass (50). During cycle 1A, air flow valve (41) is fully open. Therefore, drying gas flows substantially through heating circuit (40). Minimal, if any, drying gas flows through dehumidifying circuit (39). In addition, condenser (24) and second heat exchanger (23) are not in use.

Cycle 1 B is shown in Figure 2D and involves the drying gas being heated to a higher temperature.

Air flow valve (41 ) is entirely or partially closed. This causes action of fan (21) to circulate drying gas through dehumidifying circuit (39). After passing through dehumidifying circuit (39) the drying gas passes through heating circuit (40).

The variable heat exchanger transfers heat from outside of the drying apparatus (1) into the refrigerant. This ensures that the refrigerant has heat that it can transfer to drying gas via first heat exchanger (22).

Operation of fan (21) which is inside the cavity (3), may also assist in heating up drying gas. Steady State (Constant Drying Temperature)

This mode is shown in Figure 2C and will be referred to herein as mode 2.

During mode 2 the drying apparatus (1) does not require a significant amount of additional heat from the surroundings to maintain the drying gas at a desired temperature. Therefore, the variable heat exchanger (25) is disengaged. Accordingly, refrigerant passes through components in the following order: compressor (36), first heat exchanger (22), four way valve (32), compressor (36) and so on. During mode 2 the refrigerant may also pass through receiver, drying apparatus, and sight glass.

In mode 2 the refrigerant contains more heat than in modes 1A and 1 B. That heat is transferred to the drying gas by the first heat exchanger (22). Drying-Increase Temperature

This mode is shown in Figure 2B and referred to herein as mode 3.

During mode 3 the drying gas temperature may be required to be increased to a higher level. This could be to remove residual moisture from product in drying apparatus (1). Therefore, variable heat exchanger (23) is used to transfer heat from the surroundings into the refrigerant so that this is available to be transferred to drying gas.

Refrigerant flows through components in the following order: compressor (36), first heat exchanger (22), four way valve (32), variable heat exchanger (25), second heat exchanger (23), condenser (24), compressor (31 ), and back to compressor (36) to repeat the cycle.

The refrigerant passes through the second heat exchanger (22) after passing through the variable heat exchanger (21). This is useful for two reasons. First, it transfers heat to the drying gas after the gas exits the condenser (24). In addition, heat is removed from the refrigerant before that floes into the condenser (24). Therefore, the refrigerant may have a lower temperature as it enters into the condenser (24), which is beneficial in increasing the condenser's efficiency.

During mode 3 the refrigerant may also pass through receiver, drying apparatus, and sight glass). It is also possible that variable heat exchanger (225) can be used to decrease head pressure in the refrigerant flow path. In this embodiment the variable heat exchanger (25) does not transfer heat from the surroundings into the refrigerant. Rather, the variable heat exchanger (25) is used as a flow path through which the refrigerant passes simply to reduce head pressure. Drying Cooling Cycle

Refrigerant flow in this mode is shown in Figure 2B and is referred to herein as mode 4.

During mode 4 refrigerant is used to remove heat from the drying chamber. This may facilitate removing moisture from product, and may be useful where residual moisture is present in the product that cannot be easily removed using mode 2.

Fan (21) rotates faster than mode 3 thereby increasing air flow over variable heat exchanger (25). Accordingly, variable heat exchanger transfers more heat from refrigerant into the surroundings. Variable heat exchanger is therefore acting as a heat sink.

Drying gas still flows through dehumidifying circuit (39). Therefore, condenser (24) removes moisture from the drying gas.

Drying Gas Flow Paths

The drying apparatus (1) according to the present invention can provide multiple drying gas flow paths so as to provide flexibility and efficiency in drying of products. When air flow valve (41) is fully open, fan (21) circulates drying gas through cavity (3) and heating circuit (40). Some drying gas may flow through dehumidifying circuit (39). However, that is minimal compared to the amount of drying gas flowing through heating circuit (40).

Air flow valve (41) can be selectively set so as to control the amount of drying gas flowing through dehumidifying path (39).

Drying gas flowing through dehumidifying path (39) passes through the components in the following order: first run around coil (43), second heat exchanger (23), condenser (24), second run around coil (44), and into heating circuit (25).

Sensor (46) is positioned between condenser (24) and second run around coil (44). This enables accurate measurement of drying gas temperature as this exits condenser (24). Controller is configured to monitor the temperature determined by sensor (40). The controller can communicate with airflow valve (41) so as to control the amount of drying gas flowing through dehumidifying path (39) based on the temperature determined by sensor (46). This enables the efficiency of condenser (24) to be maximised. That control enables the energy needed to remove moisture from the drying gas to be minimised. In addition, less external energy may be needed to remove moisture from product into the drying gas.

Support Surfaces

Drying racks (14) and drying trays (17) are configured so as to define drying gas flow paths with respect to openings (19). This includes:

(i) a first drying gas flow path through openings (19); (ii) a second drying gas flow path on either side of openings (19).

First drying gas flow path may be beneficial when the drying apparatus (1) is used to remove moisture from a granular type product such as pollen or grain. This drying gas flow path is shown by arrows (52) in Figure 4.

The first drying gas flow path is defined by rack (14) being directional. The frames have an opening indicated generally by (53). When a tray (17) is disposed within opening (53) the opening is above top edge (54) of side walls (20).

Side (55) of rack has a second opening (56). The second opening (56) is below bottom edge (57) of side walls (20).

The drying racks (14) include upper deflectors (58) and lower deflectors (59). There is a pair of an upper deflector (58) and a lower deflector (59) per drying tray (17).

The pairs of deflectors (58, 59) are positioned so that when a drying tray (17) is inserted in rack (14) the upper and lower deflectors (58, 59) are

respectively above and below the drying tray.

The deflectors (58, 59) are inclined with respect to the openings (53, 56). The orientation is such that drying gas entering through opening (53) is forced down through support surface (18). Bottom deflector (59) then directs drying gas out through opening (56).

Each bottom deflector acts as a top deflector in relation to a drying tray below, and vice versa.

Second drying gas flow path may be beneficial when drying apparatus (1) is used to remove moisture from a product having a large surface area.

Examples of this type of product include fruit slices or meats. The drying gas passes more efficiently around the product to be dried so as to remove moisture using 2^nd drying gas flow path.

An amount of moisture is retained in the product so as to provide desirable flavour and taste characteristics for the dried product. However, a protective layer of product is formed from which moisture has been removed.

Claims

What We Claim is:

1. A conditioning system, including

a chamber;

a heat transfer system that includes:

a compressor,

a first heat exchanger,

a second heat exchanger,

a condenser,

a variable heat exchanger;

characterised in that

a refrigerant in the heat transfer system flows through the variable heat exchanger before flowing through the condenser.

2. The conditioning system as claimed in claim 1 wherein the variable heat exchanger is outside of the drying chamber.

3. The conditioning system as claimed in claim , wherein the variable heat

exchanger is configured to selectively transfer heat into or out from the refrigerant.

4. The conditioning system as claimed in any one of claims 1 - 3, wherein the

variable heat exchanger is configured to remove heat from the refrigerant at a plurality of different rates.

5. The conditioning system as claimed in any one of claims 1 - 4, including a

dehumidifying path through which a gas may selectively be directed to remove moisture from the gas.

6. The conditioning system as claimed in claim 5, conditioning system is configured so that the rate the gas flows through the dehumidifying path is adjustable.

7. The conditioning system as claimed in claim 6, wherein the rate the gas flows

through the apparatus is determined according to the temperature of the drying gas as it exits the condenser.

8. The conditioning system as claimed in either one of claims 6 or, wherein the rate of drying gas flowing through the dehumidifying circuit is determined according so as to maximise the efficiency of the condenser.

9. The conditioning system as claimed in any one of claims 6 to 8, is configured so that the gas passes through the second heat exchanger prior to entering the condenser.

10. The conditioning system as claimed in any one of claims 1 to 9, wherein the

variable heat exchanger is configured to remove heat from the refrigerant so as to reduce the temperature of a gas in the chamber.

11. The conditioning system as claimed in any one of claims 1 to 10, wherein the

chamber is a drying chamber configured to receive a product to be dried.

12. The conditioning system as claimed in claim 11 , wherein the chamber is sealed.

13. A method of controlling the flow of a refrigerant through a conditioning system, wherein the conditioning system includes a chamber; a heat transfer system that includes: a compressor, a first heat exchanger, a second heat exchanger, a condenser, and a variable heat exchanger; and wherein the heat transfer system is configured so that a refrigerant flows through the variable heat exchanger before flowing through the condenser; the method including the steps of:

(a) engaging a fan to move a gas through the chamber so as to remove moisture from the product in drying chamber;

(b) removing moisture from the gas using the condenser.

14. The method as claimed in claim 13, including the step of placing a product to be dried in the chamber. 5. The method as claimed in claim 13 or 14, including the step of monitoring the

temperature and humidity of a gas in the chamber.

16. The method as claimed in claim 15, including the step of adjusting the operation of the conditioning system so as to regulate the temperature and/or humidity of a gas in the chamber.