The invention to which this application relates is to apparatus and a method which allows for the cryo-preservation of items and products to be stored in an efficient and controlled manner in order to allow the product to be available for use in a desired condition when required.

The provision of storage means which allow items and products to be stored and retained in a required condition for at least a predetermined period of time, is known but, the particular conditions for storage and the particular requirements of the condition of the product, at the time of use, differ from product to product and may differ depending on the subsequent use and/ or ambient environmental conditions.

In particular, although not necessarily exclusively, the current invention relates to the technical field of cryo-preservation of items or products for a relatively longterm storage period and in particular, products in the form of biological materials including, but not limited to, mRNA, gamete, whole or part organs and/ or other functional tissues such as, for example, bone marrow. Further fields include the storage and/ or production of reactive organic and inorganic materials, including UV sensitive adhesives.

The applicant in their co-pending patent application GB2012280.0 discloses a system for generating a cryogenic environment which is for use, primarily, in the recovery of a person’s body when in the said environment and may, for example, be used by athletes and the like.

It has now been realised that the content of that co-pending application, the contents of which are incorporated herein by reference, may be used to provide further unexpected benefits such as, for example, the provision of a solution to the problem of how to safely store products which are required to be available for use within a predetermined period of time and in a predetermined condition which is critical as if the products are not stored in the required condition, then the products are rendered useless.

Conventionally, the storage of cryo-preserved materials has been achieved within a small volume plastic container and the materials are immersed in the liquid or cold vapour of a cryogen material. However, these methods of cooling generate large amounts of waste vapour as the cryogen material evaporates. Furthermore, direct exposure to LN2/ CO2 cryogens produces a significant risk to users, including burns and asphyxiation to the persons who come in contact with the same and so safety clothing and materials are required to be used which limits the utilisation of the apparatus. The provision of the cryo-preservation is typically carried out either using dry ice (-78 degrees Celsius) or liquid nitrogen (-190 degrees Celsius) (commonly known as cryogens) with the dry ice being provided as a solid form which is safer to handle and therefore is the preferred method during transportation of materials and liquid nitrogen is more commonly used for longer term storage, but as indicated above, there are significant risks with both options.

Furthermore, many types of products cannot be stored in the relatively small volumes that are conventionally provided. For example, for bone marrow the use of these cryogens is problematic because of the large amount of the cryogen quantity required and the associated greater handling risks.

An aim of the present invention is therefore to provide a cryogenic cooling system which allows a stable, cooling environment in a storage volume to be maintained for a predetermined period of time for products to be stored therein whilst, at the same time, providing the cooling environment in a manner which allows the same to be efficiently achieved and with a reduced environmental impact by operation of the apparatus. A further aim of the present invention is therefore to provide a cooling system which achieves their required cooling characteristics to within the required, relatively tight tolerances, whilst at the same time avoiding or minimising the use of potentially harmful cryogen material such as liquid nitrogen and/ or dry ice.

In a first aspect of the invention, there is provided apparatus for the creation and provision of a cryogenic cooling environment for at least a predetermined period of time within a predefined volume in a first chamber with a heat exchanger, said apparatus including a second chamber with a heat exchanger and means for utilising ambient air, refrigeration apparatus to cool said ambient air to or below a predetermined temperature to create the cryogenic cooling environment in at least the second chamber at or below -110 degrees Celsius and wherein the apparatus includes a compressor and control means for control of the operation of the apparatus to create an initial controlled ambient air cool down stage to create cooled air followed by the use of a vapour cycle refrigeration system in which the said cooled air is used as the means to create the cooling medium for said volume.

In one embodiment, the temperatures which are achieved for the cryogenic cooling environment are below -110 degrees Celsius.

In one embodiment, the cooling apparatus utilises a reduced Total Equivalent Warming Impact (TEWI) gas charge.

In another embodiment the cooling apparatus utilises a refrigerant gas charge with a TEWI close or equal to zero.

In one embodiment, the apparatus reduces its environmental impact through increased thermal efficiency and the refrigeration apparatus includes a compressor and control means for the refrigeration apparatus operation. The effect of this is to achieve energy consumption per unit cooling between 5 and 15 times less than alternative technologies. In one embodiment, the cooling environment is created in a volume defined by a chamber of a container in which the products can be placed.

In one embodiment, the container is an insulated Dewar flask.

In another embodiment, the cooling environment is provided within a volume of a largescale bio storage facility within a building in which said one or more chambers are formed or alternatively, within a transportable container such as a vehicle trailer in which said one or more chambers are formed.

In one embodiment the use of atmospheric air as the direct cooling medium permits manual handling within a relatively large scale bio storage facility without protective breathing apparatus being necessary.

In one embodiment, the apparatus includes a means for sterilising the cooling medium to prevent cross contamination of materials should for example, items in which the product is held become damaged and/ or leakage of the product occur and/ or to remove pathogens or pyrogens from the cooling medium.

In one embodiment, the controlled environment allows storage temperatures below the glass transition point of water (GTW) of less than 132 degrees Celsius to be achieved.

In one embodiment, when creating the cooling environment, the apparatus provides an initial controlled cooldown stage and then optimisation of a vapour cycle refrigeration system in which air is used as the means to create a cooling medium which is capable of being colder than GTW and thereby eliminating the risks and limitations of using the conventional cryogen materials as described previously. In one embodiment, the refrigeration system creates direct cooling by evaporation of one or more mixed refrigerants using an air heat exchange surface or surfaces at an elevated internal pressure.

In one embodiment, the one or more direct heat exchange surfaces are used to cool ambient air to temperatures colder than -90 degrees Celsius, and more typically colder than -110 degrees Celsius to allow cryo-preservation in the cooling medium environment.

In one embodiment, a refrigerant mixture is used comprising a hydrofluoroolefins (HFO) and/or hydrohaloalkenes (I II IO/ 1 II Ac) as refrigerants.

In one embodiment, trans-l-chloro-3,3,3-trifluoropropene is used.

In one embodiment a halogen free refrigerant including ethane mixture is used.

In one embodiment, the refrigerant mixture includes difluoromethane when below or at its lower flammability limit in order to achieve an Al classification.

In one embodiment, there is provided a refrigeration system which is capable of being returned relatively quickly back to an ambient condition for maintenance and/or relocation purposes through use of a gas discharge from at least one compressor.

In one embodiment the rate of warming to ambient condition is controlled to facilitate optimal product integrity.

In one embodiment, the apparatus allows direct cooling of the air within the closed insulated treatment volume in which the products are placed by evaporation of a compressible vapour which is part of a closed circuit. In one embodiment, there is provided the direct cooling of air and a controlled flow by evaporation of one or more refrigerants using an air heat exchange surface or surfaces at elevated pressures.

In one embodiment the cooled air is directed to a localised point for controlled rate freezing of the material.

In one embodiment, there is provided for the variable control of metering elements to stabilise an auto cascade refrigeration process with or without multiple evaporators being used. In one embodiment the auto-cascade refrigeration process is that as described in the applicant’s co-pending application.

In one embodiment, the control system is closed and is provided such that there is a cryogen of mixed and variable composition changes phase but is recirculated.

In one embodiment, regenerative cooling is optimised to improve performance at lower evaporator temperatures.

In one embodiment, a controlled cooldown of the storage volume is achieved in order to optimise efficiency and the process when cooling from ambient to temperatures colder than -90-degrees Celsius.

In one embodiment, improved cooldown energy conversion through combining desiccant dehumidification and forced airflow with bio preservation is achieved.

In one embodiment a single step compression cooling procedure is used by utilising a mixture of gasses within an air heat exchanger for use in cryo-preservation and storage is achieved. In one embodiment, the refrigerant cooling blend within the air heat exchanger contains at least two of the following, trifluoromethane, tetrafluoromethane, methane, argon, nitrogen, ethane.

In one embodiment, the air heat exchanger is maintained at a pressurised condition at or above 0.5 barg.

In one embodiment, the inlet temperature of the heat exchanger is less than -115 degrees Celsius.

In one embodiment there is provided a single compression step to achieve temperatures colder than -110 degrees Celsius within the storage cryo-chamber.

In one embodiment, the heat exchanger is an evaporator which in one embodiment may be of direct expansion or of indirect (remote) expansion type.

In one embodiment, the evaporator expansion device may be a valve or capillary type and the refrigeration process may be integrated within a single module for thermal efficiency.

In one embodiment, energy removed from the point of cryo-storage is recovered as useful heat at temperatures above 40 °C air or water cooled.

In one embodiment, the compressor and/ or auto cascade apparatus are separated by a distance of greater than 1 metre.

In one embodiment, the heating of the heat exchangers is achieved by direct injection of hot gas whilst the system cools other heat exchangers.

In one embodiment, there is provided a system and method for increasing the low temperature cooling capacity of cooling apparatus whilst maintaining system stability during standby operation. In one embodiment, any water which leaves the system is warmed to a temperature of, for example, plus or greater than 60 degrees Celsius to allow for the recovery of heat for non-potable applications.

In one embodiment, parts of the refrigeration system may be separated some distance from the point of evaporation of the final fluid.

In one embodiment, the apparatus defines a closed insulated cooling environment, typically defined by said first chamber of the apparatus, and the air within said environment is directly cooled by evaporation of a compressible vapour. In one embodiment the compressible vapour is contained within a closed circuit. In one embodiment the said first chamber is that in which a cryogenic cooling effect is achieved and is insulated and said second chamber which provides an additional thermal barrier and also an additional level of sample security by reducing the size and duration of any thermal excursions which may be caused by the loading and unloading of the storage system. In one embodiment, there is provided a partial or permeable thermal barrier between the two chambers in the form of an inner first storage chamber and a second outer transfer chamber and the rate of thermal exchange may be controlled to reduce the overall temperature excursions within the storage chamber during addition or removal of stored products.

The safety profile and lower weight of the invention enable application in a wider range of locations and geographies than is achievable by the conventional use of cryogens. This is because safety considerations restrict the use of cryogens in certain locations and transport of cryogens to many geographic locations is not possible.

In one embodiment there is provided refrigeration apparatus, said apparatus includes a means to allow direct cooling of one or more refrigerants by evaporation and wherein said apparatus includes at least one air heat exchange surface and means to generate an elevated pressure of said one or more refrigerants. In one embodiment, the apparatus includes flow control means to guide the flow of the air through the said environment.

In one embodiment, the cooled air is directed and recirculated within a confined area using conventional or modified cryogenic storage systems.

In one embodiment, the system is adapted for inclusion within a standard refrigerated shipping container (Reefer).

In one embodiment, the apparatus includes control means to allow the variable control of metering elements to allow any, or any combination of, the controlled speed of cooling down, lower end temperatures and/ or rate of energy conversion to be achieved, whilst maintaining acceptable operating conditions for the compressor.

In one embodiment, in the closed system, a cryogen of mixed and variable composition changes phase and is recirculated.

Typically the heat exchangers used are evaporators.

Typically, the control of regenerative cooling is optimised through metering devices to improve the performance at low evaporator temperatures.

In a further aspect of the invention there is provided apparatus including means to allow direct cooling of one or more refrigerants by evaporation and wherein said apparatus includes at least one air heat exchange surface and means to generate an elevated pressure of said one or more refrigerants in order to provide a direct cooling effect on air.

In a further aspect of the invention there is provided apparatus for the creation and provision of a cryogenic cooling environment for at least a predetermined period of time within a predefined volume in a first chamber with a heat exchanger, said apparatus including a second chamber with a heat exchanger and means for utilising ambient air, refrigeration apparatus to cool said ambient air to or below a predetermined temperature to create the cryogenic cooling environment in at least the second chamber at or below -110 degrees Celsius and wherein the apparatus includes a compressor and control means for control of the operation of the apparatus to create an initial controlled ambient air cool down stage to create cooled air followed by the use of a vapour cycle refrigeration system in which the said cooled air is used as the means to create the cooling medium for said volume.

In accordance with another aspect of the invention there is provided a method of allowing an intervention in the operation of a refrigeration system for creating a cryogenic storage environment, wherein said method including steps to allow the system to regain a substantially ambient temperature condition to allow said intervention by injecting a flow of hot gas into a high pressure side of the refrigeration system at a location after the location of an autocascade refrigeration system and controlling system pressures and temperatures to allow the work done by a compressor of the system to heat the refrigeration process to near ambient temperatures.

This method therefore allows the intervention to be relatively quickly possible without resort to use of external heating systems.

In one embodiment the return flow of the injected gas may pass either directly through or bypass the heat exchanger of the chamber.

This therefore overcomes the problem caused by operating internal components achieving very low temperatures, which, because of the required insulation against heat gain, means that assessment of the system, maintenance or relocation can be significantly delayed by the requirement of the system to regain ambient temperatures throughout the system. In one embodiment the invention makes use within the gas blend unsaturated alkene organic compounds composed of hydrogen, one or more halogen atoms and carbon, with a double bond between one or more carbon atoms. Such molecules are known as hydrofluoroolefins (HFO) or hydrohaloalkenes (HHO / HFAe) included a part of the refrigerant blend an example of which is Trans-l-chloro-3,3,3- trifluorop ropene .

In one embodiment the gas blend consists of at least 5-50% HFO e.g. Trans-1- chloro-3,3,3-trifluoropropene, plus one or more of the following compounds, Trans-l-chloro-3,3,3-trifluoropropene, Difluoromethane, Trifluoromethane, etrafluoromethane, Ethane, Methane, Argon, Nitrogen, Iso-butane has improved performance and reduced global warming equivalence.

Specific embodiments of the invention are now described wherein:

Figure 1 illustrates apparatus in accordance with one embodiment of the invention;

Figure 2 illustrates the apparatus of Figure 1 in greater detail;

Figure 3 illustrates an embodiment of control valves for the system to allow the operation of the apparatus during a normal operation phase; and

Figure 4 illustrates a system in one embodiment to take into account the formation of ice in the apparatus and allow the operation of two independent evaporators.

Referring firstly to Figure 1, there is illustrated an arrangement of two chambers, the storage chamber 2 and the handling point chamber 4 and the relative positions of heat exchangers 6, 8. The storage chamber includes the secondary heat exchanger 8 located therein and the handling point chamber includes the primary heat exhanger 6. A pre-treatment space of the handling point chamber 4 is maintained at a temperature between -20 and —85 degrees Celsius and the purpose of this is principally to provide a regulated thermal barrier to minimise thermal excursions within the body of the storage facility. A secondary advantage is that a regime of very low humidity is maintained, so preventing ingress of moisture which may cause interference with automated handling devices.

In one embodiment there are provided two heat exchange surfaces independently controlled and driven from either a single or multiple Autocascade system. The construction of the system can utilise relatively high efficiency vacuum insulated panels (VIP) to reduce to a minimum heat gain generated by the very high differential temperature maintained by the system. The use of a pre and treatment chamber reduces thermal gain by acting as a load lock.

The refrigeration system utilises an Autocascade process 10, to achieve both low temperatures and maintain efficient operation. However the conventional systems are unstable and have to be operated in a no cool condition until a stable condition is achieved and at which time cooling can commence. However, because there are in effect more than two refrigeration processes occurring prior to liquified refrigerant being introduced to a heat exchanger, any overload from the product being cooled can cause the system to breakdown resulting in litle or no cooling. Thus, in the conventional systems, in practice the system is in an unstable condition if the returning refrigerant from the evaporator is warmer than -80 degrees Celsius.

An embodiment of an autocascade system is defined in the applicant’s patent EP2867596, and the contents of which are incorporated herein by reference

The characteristics of large scale cryo-storage, possibly with associated handling equipment, as proposed is that there is a very high initial heat flow to reduce the chamber and its fittings from ambient to colder than -80 degrees Celsius required followed by a moderate (20% of initial load) which is typically a stable load. To ensure the system is not overloaded during the initial reduction in temperature from ambient in excess of 30 kW of heat may need to be removed but the under use load may be one tenth of this value.

In the case of transport based storage systems the requirement is for a compact and efficient system as possible the invention envisages that elements of the whole system may be separated into functional elements without detrimental impact upon performance.

In order to overcome inherent limitations and limited cooling capacity at higher temperatures, the invention controls both the internal cascade process and the heat flow from the evaporators to maintain correct and stable operating conditions.

Figure 1 illustrates the indicated differentially controlled temperature zone chambers 2,4 and an embodiment of a scheme for the control of the flow of air to coolant heat exchangers 6, 8 and a method for distribution of cooling fluid from a single cooling system as shown in Figure 2. The shaded area 10 represents the principal autocascade refrigeration process which operates at a temperature which is significantly below the ambient temperature. There are provided in the system, a series of valves A which are used to control upper stages of the auto cascade refrigeration process. A direct feed 12 of warm gas from a compressor 14 is regulated by valve B to individual evaporator control valves E,F. Valves C and D regulate the flow of cold refrigerant from the auto cascade process to the heat exchangers as indicated in Figures 2 and 3.

In order to carry out an assessment or service intervention the system it is a requirement that the shaded area 10 is brought to a standardised temperature which is close to or at ambient.

Referring now to Figure 3, then during the normal operation phase, the valves C,D are cycled to achieve the required temperature T4 at the heat exchanger 8 of the chamber 2 and T2 at the heat exchanger 6 of the chamber 4. The valve 16 at Pl is operated only when there is no cooling demand required to the cryo-chamber 2. The valves A are controlled to maintain sufficient flow to maintain a correct temperature at T3 (at the sub-cooler) and T6 which is the auto cascade return flow 20. The maintenance of correct return gas pressure to the compressor at P3 is also modulated within acceptable use by control of the valves A,C and D. Under conditions of high heat flow from the chamber heat exchangers, flow is restricted so that the pressure at P3 and the temperatures T3 and T6 are maintained and such conditions ensure that the auto cascade process is stable, and the compressor is not subject to excessive load.

Referring to figure 4 during the operational phase as described in previous paragraphs, ice / frost will build up on the cold surfaces which in turn leads to degradation of performance. The invention places the two similar or differently sized heat exchangers 6,8 into a single or dual volume chamber system. When these heat exchangers evaporators become overloaded with ice the drop in efficiency can be witnessed by a reduction in forced air flow (pressure increase) reduction in the differential between inlet and out, pressure decrease in the returning gas to the compressor, or the temperature of the exit from the condenser becoming lower than the air or product cooled. The return flow from the evaporator / heat exchanger which is subjected to heating by injection of gas direcdy derived from the compressor maybe wholly or partially routed away from the autocascade process 10 as shown by path 24 to directly re-enter the circuit after said Autocascade process. This maybe achieved either through a 4 way spooling type valve 22 or similar arrangement of valves to achieve a similar effect.

With reference to Figures 2, 3 and 4, the invention utilises the gas heated by compression and by partially bypassing the refrigeration process within the shaded area. As shown in Figure 2 the gas circulates back to the inlet of the suction side of the refrigeration process 10 by which means the components which are at very low temperatures are directly heated by the gas. The introduction of the heated gas may be either before or after the heat exchanger with the current invention as depicted in the Figures, showing the heated gas being introduced before the heat exchanger. The valves A are controlled to ensure the pressure and temperature of the returning gas is maintained within acceptable limits for the compressor 14. During this normalisation process, the warmed and expanded gas is contained and temporarily stored within a buffer tank. The circulation of gas from the hot high-pressure side in a reverse direction through the cold suction/ return line is maintained until the temperature at the coldest point reaches a predetermined point which is typically between 0 and 10 degrees Celsius above the ambient temperature. At this point, the compressor is deactivated, and all valves are opened, and the system is deemed ready for assessment or intervention.

The invention therefore provides apparatus and a method which allow for the improved provision of a reliable and controlled source of a cooled environment for bio-preservation and storage techniques. Furthermore, the invention envisages the possibility of a controlled rate of both cooling and heating within practical physical constraints in order to optimise the viability of the cryo-stored material from the storage chamber post thaw. The control of low temperatures is achieved in an efficient and more environmentally friendly manner than is conventionally achieved, as the cooling medium to which the stored material or their container or parts thereof are exposed is cold air directly or indirecdy cooled by the invention.