FIELD

The present invention relates to cooling of a storage container in phases by dry ice. BACKGROUND

US5363670 discloses a self-contained cooler/freezer apparatus for carrying items in a frozen or refrigerated environment. The apparatus comprises an insulated container which is divided into two portions. The first portion is utilized for item storage and the second portion houses a pressurized coolant compartment for storing a dry ice. The pressurized coolant compartment comprises removable insulation panel. In essence, the pressurized coolant compartment is a controllable heat sink. Within a short period of time, the dry ice starts to sublimate, thereby forming cold gaseous carbon dioxide at a high pressure. The cold gaseous carbon dioxide is circulated throughout the insulated container via a solenoid actuated gas feed valve, thereby further cooling the first portion of the insulated container. A thermostatic controller activates the gas feed valve based upon temperature readings from thermocouples located within the first portion of the insulated container. A pressure relief valve is positioned within the insulated container to prevent the pressure within the insulated container from building beyond a maximum value. The sublimation of the dry ice causes pressure that is relieved outside the apparatus.

When cold gaseous carbon dioxide formed from sublimation of the dry ice is conducted out of the apparatus, the carbon dioxide cannot be used for cooling anymore.

The efficiency of cooling by sublimed dry ice depends on the sublimation rate. It can take a long time to reach low temperatures by cooling using the cold gaseous carbon dioxide formed from sublimation of the dry ice.

BRIEF DESCRIPTION OF SOME EMBODIMENTS

An object of the present invention is to provide a method, an apparatus and a computer program that alleviates at least part of the disadvantages identified above. The object of the present invention is achieved by a method, a computer program and an apparatus characterized by what is stated in the independent claims. The dependent claims describe embodiments of the present invention.

Some embodiments provide rapid cooling of a storage container by dry ice and maintaining the storage container in a target temperature. BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, wherein like reference signs refer to like parts throughout, and in which

Figure 1 illustrates an apparatus according to an embodiment, Figure 2 illustrates a temperature control system according to an embodiment,

Figure 3 illustrates an apparatus for rapid cooling according to an embodiment;

Figure 4 illustrates a temperature control system for rapid cooling according to an embodiment;

Figure 5 illustrates a method for different cooling phases according to an embodiment;

Figures 6a and 6b illustrate operation of convection element according to an embodiment; and

Figure 7 illustrates a method of controlling cooling phases according to an embodiment.

DETAILED DESCRIPTION

Various embodiments herein describe utilising dry ice as coolant. Dry ice is the solid form of carbon dioxide (CO ₂ ). Dry ice sublimes at -78.5 °C at Earth atmospheric pressures. In sublimation of the solid dry ice, the dry ice is transitioned directly from a solid phase to a gas phase without passing through an intermediate liquid phase. In the following sublimed dry ice refers to dry ice in the gas phase. The extreme cold of the solid dry ice makes the solid dry ice dangerous to handle without protection due to burns caused by freezing (frostbite). While generally not very toxic, the outgassing from it can cause hypercapnia due to buildup in confined locations.

Figure 1 illustrates an apparatus according to embodiment. The apparatus may comprise at least one sealed container 3a, 3b, 3c for dry ice. The sealed container may be referred as a dry ice container. The dry ice container may be enclosed within another sealed 1 container that may be referred to as an enclosure. The dry ice container may be operatively connected to a storage container 2 for cooling the storage container to a target temperature or to a target temperature range by sublimed dry ice from the first container. The dry ice container may be operatively connected to the enclosure for conducting sublimed dry ice from the dry ice container to the enclosure when the target temperature or temperature range of the storage container is met. Accordingly, the dry ice may be used for cooling the enclosure and/or to the storage container by feeding the sublimed dry ice from the dry ice container to the enclosure and/or to the storage container. The target temperature or temperature range may be met, when the current temperature within the storage container is at the target temperature or temperature range or less than the target temperature or temperature range.

In this way the dry ice may be first used as coolant for cooling the storage container 2 and after the target temperature or temperature range has been reached within the storage container, the dry ice may be used for cooling the dry ice container. Since the coolant fed to the enclosure is sublimed dry ice that has not been used for cooling the storage container, the coolant has a high cooling capacity and the coolant may efficiently cool down the container for dry ice and thereby the dry ice within the container. The cooling capacity of the coolant may be determined as the capability, for example measured in Watts, of removing heat. Cooling the container for dry ice provides that the sublimation rate of the dry ice may be controlled, e.g. reduced. The sublimation rate may be defined by weight of dry ice sublimed per a time unit, e.g. kg/h.

The sublimation of the dry ice may be caused by warming-up of the dry ice. The warming-up of the dry ice may be caused by the prevailing temperature in the environment of the apparatus being higher than the sublimation temperature of dry ice.

The target temperature or temperature range of the storage container may be defined by the type of items stored in the storage container. The items may be organic items that require storing in a specific temperature or temperature range such that their properties may be maintained during the time the items are stored the storage container. Examples of organic items comprise human organs, animal organs, living matter, bacteria growth and viral growth. It should be appreciated that the target temperature or temperature range may be represented by a pressure value or a pressure range within the storage container. The dry ice container and the enclosure may be sealed such that the containers may hold a pressure caused by gas generated from sublimation of the dry ice. The dry ice container and the enclosure may be connected together such that they form a sealed entity for efficient transfer of sublimed dry ice between the storage container, the enclosure and the dry ice container within the enclosure.

In an embodiment, the apparatus may comprise a plurality of dry ice containers 3a, 3c, 3b that are operatively connected to the storage container. The number of dry ice containers may be determined according to the needed cooling capacity. The needed cooling capacity may be determined on the basis of a plurality of factors comprising for example outside temperature of the apparatus, target temperature or temperature range of the storage container and volume of the storage container.

In an embodiment, the enclosure 1 may have a door for removal of one or more dry ice containers. Since the storage container is sealed, the dry ice containers may be removed through the door without the sublimed dry ice being released from the storage container.

In an embodiment the storage container 2 and the enclosure 1 may be connected such that, when a pressure within the storage container exceeds a threshold for pressure within the storage container, sublimed dry ice that has a reduced cooling capacity from cooling the storage container may be relieved from the storage container to the enclosure. In this way sublimed dry ice from the storage container may be used to heat up the sealed container holding the dry ice and increase the sublimation rate of the dry ice. The sublimed dry ice may be relieved through a relief valve 8 that connects the storage container and the enclosure.

In an embodiment the enclosure 1 may have a relief valve 9 that is caused to relieve sublimed dry ice from the enclosure and out of the apparatus, when a threshold for pressure within the enclosure is exceeded. The relief valve may provide that accumulation of sublimed dry ice within the apparatus may be prevented.

Preferably the relief valves 8, 9 may be caused to relief the sublimed dry ice before the pressure reaches the triple-point of dry ice. In this way the pressure within the apparatus may be kept sufficiently low, i.e. below the triple point, to avoid the sublimed dry ice from transforming into liquid. The relief valves maybe caused to relieve sublimed dry ice on the basis of the pressure difference of the connected spaces. The relief valves also provide that the relieved sublimed dry ice flows only in one direction, thereby preventing relieved sublimed dry ice from returning.

In an embodiment the apparatus may comprise a fluid line 10 for connecting the dry ice container 3 and the storage container 2, and a temperature controllable valve 7 arranged get to regulate the flow of sublimed dry ice to the storage container from the fluid line on the basis of the temperature within the storage container. The temperature controllable valve may enable and disable flow of the sublimed dry ice to the storage container such that the storage container may be maintained at the target temperature or the target temperature range.

The flow of the dry ice may be enabled by opening the valve, and the flow of the dry ice may be disabled by closing the valve. Accordingly, when the temperature controllable valve is open the sublimed dry ice may flow to the storage container from the fluid line. When the temperature controllable valve is closed, the sublimed dry ice cannot enter the storage container.

The temperature controllable valve may operate as a thermostat that may capable of sensing the temperature within the storage container by a sensor 'S'. The temperature controlled valve may be connected to the sensor 'S' for obtaining temperature measurements from inside of the storage container and for enabling or disabling the flow of the sublimed dry ice into the storage container on the basis of the temperature measurements from the sensor. When the temperature within the storage container is above the target temperature, the flow of sublimed dry ice into the storage container may be enabled and when the temperature within the storage container is at the target temperature or lower than the target temperature the flow of sublimed dry ice in to the storage container may be disabled.

In an embodiment a fluid line 10 may be connected to the enclosure by a valve 6 that may be controlled on the basis of at least one of a pressure within the fluid line and control of the flow of sublimed dry ice by a temperature controllable valve 7 arranged to regulate the flow of sublimed dry ice to the storage container. When the pressure within the fluid line exceeds a threshold for pressure, the valve 6 may be controlled to open and allow the sublimed dry ice to flow to the enclosure 1 . The threshold pressure may be defined on the basis of the amount of dry ice and with respect to a cooling need of the storage container 2. The cooling need may be determined on the basis of whether the storage container is at the target temperature or target temperature range. The cooling need causes the control of the temperature controlled valve. When the storage container is not at the target temperature or the target temperature range, the temperature controllable valve 7 arranged to regulate the flow of sublimed dry ice to the storage container from the fluid line may be opened, and when the storage container is at the target temperature or the target temperature range, the storage container does not need to be cooled and the temperature controllable valve may be closed. Accordingly, the valve 6 may be arranged to open when the temperature controllable valve is closed and the threshold for pressure within the fluid line is exceeded. In this way the sublimed dry ice may be conducted to the enclosure for cooling the dry is container without further cooling the storage container.

On the other hand, the valve 6 may be closed if the threshold for pressure within the fluid line is not exceeded and/or when the temperature controllable valve 7 is open. Accordingly, the fluid line may hold sublimed dry ice to be fed to the storage container for cooling the storage container, and on the other hand if there is no need for cooling the storage container the sublimed dry ice may be conducted to the enclosure for cooling down the dry ice container such that the sublimation rate of the dry ice may be reduced.

The connections between the dry ice container, the storage container and the enclosure may be provided by means for conducting sublimed dry ice. Examples of such means comprise a fluid line 10, a fluid passage and a fluid duct and a fluid hose. The means for conducting sublimed dry ice may be controllable to provide operative connections between the dry ice container, the storage container and the enclosure. The operative connections may allow enabling and disabling the flow of sublimed dry ice between the dry ice container and the storage container, and between the dry ice container and the enclosure. The control of the conduction of the dry ice may be provided by one or more valves 5a, 5b, 5c, 6, 7, 8 that may be opened for enabling flow of sublimed dry ice, and closed for disabling flow of sublimed dry ice. The opening and closing of the valves may be controlled by pressure of the sublimed dry ice and/or temperature of the storage container.

In an example of controlling a valve by pressure of the sublimed dry ice, the valve may be manually set a threshold pressure. When the threshold pressure is met, the valve may be opened and if the threshold pressure is not met, the valve may be closed. The threshold pressure may be set such that the storage container may be maintained in the target temperature or temperature range. It should be appreciated that also magnetic valves may be used. The magnetic valve may be caused to open and close on the basis of the current temperature within the storage container and a result of the comparison of the current temperature with the target temperature or with the target temperature range. The current temperature may be measured by sensor 'S'. On the other hand, and particularly, when the sublimed dry ice is not conducted to the storage container the dry ice may be conducted to the enclosure for cooling the dry ice container. However, once the storage container needs cooling, the cooling of the dry ice container is topped and the sublimed dry ice is conducted to the storage container. The cooling need of the storage container may be determined on the basis of the target temperature or target temperature range not being met in the storage container.

In an embodiment one or more dry ice containers may be connected to the fluid line 10 by a quick-release coupling 4a, 4b, 4c and a back-pressure valve 5a, 5b, 5c. The back-pressure valve 5a, 5b, 5c provides that sublimed dry ice discharged from the dry ice container does not return to the dry ice container and the sublimed dry ice may be kept within the fluid line, when the dry ice container is released e.g. when being replaced. Accordingly, the backpressure valve and the quick-release coupling may form a part of the fluid line 10. In this way the storage container may be cooled down by the sublimed dry ice preserved within the fluid line after the dry ice container is disconnected from the fluid line.

In an embodiment, components of the apparatus that generate heat may be installed within the enclosure 1 . In this way the heat generated from the components may be used to increase the sublimation rate of the dry ice. In one example, one or more parts of the temperature control system of Figure 2 may be installed to the enclosure. The temperature control system may comprise magnetic valves that may be opened by electric current that cause generation of heat in the valve. Heat may be generated, for example, when the temperature controllable 7 valve is a magnetic valve and electric current is fed to the valve for opening the valve. Thanks to the location of the temperature controllable valve within the enclosure, the heat generated by the temperature controllable valve may be used to increase the sublimation rate of the dry ice. In this way production of sublimed dry ice may be increased for further cooling of the storage container. Then, when the target temperature of the storage container has been reached the temperature controllable valve may be closed by cutting-off the current. In this position, the temperature controllable valve does not generate heat and the sublimation rate of the dry ice may be reduced. Further reduction of the sublimation rate may be achieved by conducting the sublimed dry ice directly to the enclosure from the fluid line via valve 6.

Figure 2 illustrates a temperature control system according to an embodiment. The temperature control system may be used to control flow of sublimed dry ice into the storage container 2 or into the enclosure 1 or both the storage container and the enclosure in the embodiments described herein. The temperature control system is now described with reference to same or corresponding items in Figure 1 . The temperature control system may comprise one or more temperature controllable valves 6, 7, a temperature sensor 'S' and a controller 'CNTU connected to the sensor and valves such that the valves may be opened and closed on the basis of the measurements of the sensor. The sensor 'S' may be arranged within the storage container to obtain temperature measurements for controlling the valve. The temperature controlled valve may operate as a thermostat that may sense the temperature within the storage container by the sensor and enables and disables flow of the sublimed dry ice to the storage container such that the storage container may be maintained at the target temperature or the target temperature range.

In the following, embodiments for rapid cooling by dry ice are described. The above described embodiments and one or more features described therein may be implemented in the following embodiments for rapid cooling for obtaining explicit or implicit advantages described above, and for implementing the embodiments. It should be appreciated that some features described below may be implemented in the above embodiments for obtaining explicit or implicit advantages in the above embodiments.

Figure 3 illustrates an apparatus for rapid cooling according to an embodiment. The apparatus may comprise at least one dry ice container 3a, 3b, 3c for dry ice, said at least one dry ice container 3a, 3b, 3c for dry ice enclosed within another sealed container 1 , referred to as an enclosure. The at least one dry ice container 3a, 3b, 3c for dry ice is operatively connected to a storage container 2 for cooling the storage container to a target temperature or to a target temperature range by sublimed dry ice from the at least one dry ice container 3a, 3b, 3c for dry ice, and said apparatus comprising at least one convection element 11 a, 11 b, 11 c for convective heat transfer from the storage container 2 to dry ice within the dry ice container 3a, 3b, 3c, wherein said convection element 11 a, 11 b, 11 c is arranged between the dry ice in the dry ice container and the storage container, and the apparatus comprising a fluid flow control element 7 for controlling flow of sublimed dry ice into the storage container, and at least one sensor arranged for measuring temperature within the storage container. The cooling capacity of the dry ice may be utilized to cool the storage container in at least two ways by controlling the flow of sublimed dry ice via the fluid flow control element to the storage container and controlling the heat transfer via the convection element. It is feasible that at least one or both of the flow of sublimed dry ice and convective heat transfer are used at a time.

In the apparatus for rapid cooling, the connections for allowing flow of sublimed dry ice to and/or from the units may be provided as described in the above embodiments described with reference to Figures 1 and 2 for enabling flow of sublimed dry ice between various units. Accordingly, in the apparatus for rapid cooling connections for flowing sublimed dry ice may be provided by one or more or a combination of a fluid line, a valve, a relief valve, a temperature controllable valve. It should be appreciated that a valve may be referred to as a fluid flow control element.

The fluid flow control element may be controllable to enable and disable flow of the sublimed dry ice to the storage container from the dry ice container. The fluid flow control element may be a valve, for example a temperature controllable valve. The fluid flow control element may be controlled by a controller of a temperature control system.

The convection element may be capable of conducting heat between the storage container and the dry ice without flow of sublimed dry ice from the dry ice container to the storage container. The convection element may have at least two surfaces, one of which is connected to dry ice and one of which is connected to the fluid inside the storage container for transferring heat from the storage container to the dry ice. The convection element causes rapid cooling of the fluid next to the convection element, which causes convection in the storage container. In convection, the fluid within the storage container is moved by the temperature difference of the fluid cooled down by the convection element and the fluid at a higher temperature in the storage container. In one example, the fluid in the storage container is the warmer the longer the distance to the convection element is, whereby in convection fluid cooled down by the convection element is moved away from the convection element and warmer fluid is moved towards the convection element. The fluid in the storage container may be gas, for example air, sublimed dry ice, air and their mixture.

In an embodiment, the convection element 11 a, 11 b, 11 c is arranged in a wall in the dry ice container 3a, 3b, 3c and the storage container has a receptacle for receiving the wall for transferring heat to the dry ice by the convection element in the wall positioned in the receptacle. In this way the convection element may be brought into contact with the fluid inside the storage container.

In an example, the convection element may be formed in a wall of the dry ice container 3a, 3b, 3c. The dry ice within the dry ice container may rest on the convection element that may transfer heat from the storage container to the dry ice. The wall of the storage container may comprise holes that each serve as a receptacle for a dry ice container. Accordingly, dry ice containers may be received in the holes. The dry ice containers positioned in the holes may be sealed such that fluids may not flow through the holes between the storage container and the dry ice container. Seals may be provided on either the dry ice container or the holes to avoid the leakage of fluid through the holes.

In one implementation example, the surface of the convection element connected to the dry ice may be a surface directed upwards and the surface connected to the fluid within the storage container may be a surface directed downwards. Accordingly, the dry ice may be supported on the surface directed upwards.

The convection element may be of suitable material and structure for conducting heat. Examples of the suitable materials comprise metals, such as steel, aluminium and copper. Examples of the suitable structures comprise structures that prevent flow of gas such as a sheet.

Figures 6a and 6b illustrate operation of convection element according to an embodiment. In Figures 6a and 6b, the convection element may be controllable to enable and disable the conduction of heat. In Figure 6a the conduction of heat is disabled by the convection element. In Figure 6b the conduction of heat is enabled by the convection element. The convection element may comprise a part 21 that is movable between a closed position illustrated in Figure 6a and an open position illustrated in Figure 6b. The convection element may be positioned in a hole in the storage container, for example. In the following the part 21 will be referred to as door. In the open position of the door the fluid within the storage container is connected to the convection element and heat may be transferred from the fluid inside storage container to the dry ice in the dry ice container. Accordingly, heat conduction from the storage container to the dry ice is enabled in the open position of the door. In the closed position of the door the fluid within the storage container is separated from the convection element. Accordingly, in the closed position the fluid is not in contact with the convection element and heat conduction from the storage container by the convection element is disabled.

The door may be movable between the closed position and the open position for example by an electric motor that may be controlled by a controller of a temperature control system. In this way the temperature control system may control to enable or disable convective heat transfer.

Referring to Figure 3, in an embodiment, in the apparatus for rapid cooling, the enclosure 1 has a relief valve 9 that is caused to relieve sublimed dry ice from said enclosure 1 and out of the apparatus and a CaO2 container 13 is connected to the relief valve 9 for capturing sublimed dry ice consumed in the cooling phases. The connection 14 between the apparatus for rapid cooling and the CaO2 container may be releasable such that the CaO2 container may be replaced. The connection may comprise quick release connector or a fluid line having at least one quick release connector for releasable connection of the CaO2 container. The CaO2 container contains CaO2 that reacts with the carbon dioxide from the sublimed dry ice. The reaction of the carbon dioxide from the sublimed dry ice and the CaO2 may be expressed as follows:

CaO ₂ + CO ₂ = CaCO ₃ + O ₂ (1 ).

Accordingly, the sublimed dry ice input to the CaO ₂ container may be captured by the CaO2 container into Calcium Carbonate, CaCO3, and Oxygen. In this way the sublimation of the dry ice does not increase the level of carbon dioxide outside of the apparatus. The level of carbon dioxide is important in many environments, where people are present, since a too high level of carbon dioxide in the air may cause some people feel drowsy and even suffocation of people. Moreover, since the carbon dioxide is captured, there are no carbon dioxide emissions from the apparatus due to sublimation of the dry ice.

It should be appreciated that although the CaO ₂ container is described with reference to the apparatus for rapid cooling in Figure 3, the CaO ₂ container 13 may be connected to the apparatus described in Figure 1 , where the cooling of the storage container is performed without the rapid cooling provided by the convective heat transfer.

Referring to Figure 3, in an embodiment, the apparatus for rapid cooling may comprises a controllable vent 12 for heating the storage container 2 by free air flow from outside the storage container 2. The vent may be controlled to open and close. When the vent is open, air from outside the apparatus may enter the storage container through an opening in the vent. When the vent is closed, air from outside the apparatus may not enter the storage container through the opening. In the open position of the vent, the amount of air flow may be controlled as needed by setting the opening of the vent. The target temperature of the storage container may be lower than the temperature outside the apparatus. The vent provided that air outside of the apparatus may be used to increase the temperature within the storage container. In this way the temperature within the storage container may be adapted quickly to changes in the target temperature and/or to a too low temperature within the storage container. The opening of the vent may be set to different positions comprising for example, the closed position, the open position, and at least one intermediate position between open position and closed position. The opening of the vent may be controlled to move to a specific position for example by an electric motor that may be controlled by a controller of a temperature control system. In this way the temperature control system may control to enable heating, disable heating and/or to adjust the amount of heating by the air from outside the storage container.

Referring to Figure 3, in an embodiment, in the apparatus for rapid cooling, the at least one dry ice container 3a, 3b, 3c for dry ice is operatively connected to said enclosure 1 for conducting sublimed dry ice from the at least one dry ice container 3a, 3b, 3c for dry ice to said enclosure 1 , when the target temperature of the storage container is met. Accordingly, similar to explained with Figure 1 above, in this way the dry ice may be first used as coolant for cooling the storage container 2 and after the target temperature or temperature range has been reached within the storage container, the dry ice may be used for cooling the dry ice container.

Figure 4 illustrates a temperature control system for rapid cooling according to an embodiment. The temperature control system may be used in the apparatus for rapid cooling illustrated in Figure 3. The temperature control system may be used for controlling convective heat transfer, heating of the storage container, flow of sublimed dry ice into the storage container 2 and/or flow of sublimed dry ice into the enclosure 1 in the embodiments described herein. The temperature control system may comprise a controllable vent 12 for heating the storage container and one or more convection elements 11 a, 11 b, 11 c for convective heat transfer from the storage container to the dry ice. The sensor 'S' may be arranged within the storage container to perform temperature measurements for controlling one or more of the fluid flow control element, e.g. a valve, the controllable vent and the convection element on the basis of the measured temperature within the storage container. The temperature measurements from the sensor 'S' may be fed to the controller. The controller may determine on the basis of the temperature measurements the current temperature in the storage container and/or a deviation of the current temperature from the target temperature of the storage container. The deviation may be used to determine whether the storage container should be cooled down or heated. Depending on the amount of deviation the storage container may cooled down by different cooling phases comprising convective heat transfer by the convection element or by a flow of sublimed dry ice to the storage container by the fluid flow control element. A more detailed explanation of the cooling phases is provided below with Figure 5, and a more detailed explanation of the heating is provided below with Figure 7.

The controller may be connected to a user interface 15 for allowing a user to enter the target temperature and for the user to monitor the current temperature of the storage container. Accordingly, the user interface may be provided by a combination of user input means and user output means. Examples of the user input means comprise a button, a keypad, a keyboard and touch screen. Examples of the user output means comprise a display, a touch screen, an audio speaker, a lamp. The functionalities of the user interface may be provided by an application that is executed on a computer, for example a tablet computer or a smart phone. At least part of the functionalities of the controller or all the functionalities of the controller may be implemented in the application executed in the computer.

Figure 5 illustrates a method for different cooling phases according to an embodiment. The method may be performed by a temperature control system of Figure 4 for example in the apparatus described in Figure 3. The temperature control system for rapid cooling may be installed to the enclosure 1 similar to described with the temperature control system of Figure 2 in an embodiment. The method comprises cooling a storage container in a current temperature to a target temperature in at least two phases comprising a phase of convective heat transfer 56 from the storage container and a phase of flowing 58 sublimed dry ice to the storage container. The phases may represent separate functionalities which are performed at different time instants. The time instants may follow one another in a sequence.

The method may start 50, when temperature measurements may be obtained from the storage container for controlling the cooling. The measurements may be obtained, when the temperature control system is operational. A deviation of the current temperature from the target temperature may be measured 52. The current temperature may be a measurement of the temperature inside the storage container. Preferably the current temperature represents the temperature in a defined time period or one or more time instants. The target temperature may be a fixed temperature or set by user via a user interface. The deviation of the current temperature from the target temperature may be compared 54 with a threshold value.

If 54 the deviation of the current temperature inside the storage container is higher than a threshold value for the deviation, the storage container may be cooled by convective heat transfer 56 from the storage container to dry ice. The convective heat transfer may be performed by a convection element.

In an embodiment, if 54 the deviation of the current temperature inside the storage container is not higher than a threshold value for the deviation, the storage container may be cooled by flowing 58 sublimed dry ice to the storage container. The flow of sublimed dry ice may be provided by a fluid flow control element.

The method may end 59 after the dry ice is consumed or the cooling of the container is stopped otherwise, for example by the user. In an embodiment sublimed dry ice consumed in the cooling phases may be conducted out of the storage container and captured in CaO2. The CaO2 container may be connected to the apparatus as described in Figure 3, for example.

It should be appreciated that the method steps 52, 54, 56 and 58 may be repeated and the measurement 52 may be performed at the same time with the cooling, i.e. during the cooling, in step 56 or step 58. Accordingly, the current cooling phase in step 56 or 58 may be maintained until a new deviation is measured 52 that meet the condition for changing the cooling phase to another cooling phase. The cooling phases of the method allow cooling down the storage container rapidly to the target temperature or close to the target temperature by the convective heat transfer when the deviation is high. When the deviation is small, the cooling may be performed by the flow of sublimed dry ice. The flow of sublimed dry ice may be controlled for efficient utilisation of the cooling capacity as described in the embodiments with reference to Figures 1 and 2.

In an embodiment, the threshold value for the deviation is the same for applying 56 the convective heat transfer and the cooling 58 by flow of sublimed dry ice. The same threshold value may allow determining the cooling phase to be applied based on the measured deviation.

In an embodiment, when the current cooling phase is the phase of flowing 58 sublimed dry ice to the storage container, the threshold value for evaluating the deviation may be high and when the current cooling phase is the phase of convective heat transfer 56, the threshold for evaluating the deviation may be low. The different threshold values allow avoiding frequent changes from one cooling phase to another. Accordingly, the different thresholds allow avoiding a ping-pong effect between the cooling phases. The actual values for the threshold may be designed according to implementation.

Figure 7 illustrates a method of controlling cooling phases according to an embodiment. The method may be performed by a temperature control system of Figure 4 for example in the apparatus described in Figure 3. The method allows cutting-off the cooling phases, whereby the storage container may be heated.

The method may start 70, when at least one cooling phase is applied. The cooling phase may be applied as described in step 56 or 58 in Figure 5. During the cooling, a current temperature of the storage container may be measured 72. If 74 the current temperature of the storage container is below the target temperature, the storage container may be heated 76 by a free air flow from outside the storage container. The free air flow may be provided via a controllable vent in the storage container. The cooling phases applied to the storage container may be cut-off 76 during the heating. Accordingly, the convective heat transfer may be stopped and/or the flow of sublimed dry ice to the storage container may be stopped, when the storage container is heated.

In an embodiment, during the heating the cooling phases to the storage container may be cut-off and sublimed dry ice from the dry ice container may be used to cool down the dry ice container for controlling the sublimation rate of the dry ice. The dry ice container may be operatively connected to the enclosure for conducting sublimed dry ice from the dry ice container to the enclosure, when the target temperature of the storage container is met. Accordingly, since the current temperature is less than the target temperature, the target temperature is met and the sublimed dry ice may be conducted to the enclosure for cooling the dry ice container. The operative connection between the dry ice container and the enclosure may be provided by the fluid line 10 and the coupling 4a, 4b, 4c and the valve 6 in Figure 1 , for example.

The method may end 78 if 74 the current temperature is at the target temperature or temperature range from the target temperature, or higher. Since the current temperature is not less than the target temperature or a temperature range, heating is not needed and the heating may be stopped. When the current temperature is higher than the target temperature or temperature range storage container may be cooled by convective heat transfer and/or flow of sublimed dry ice described in various embodiments herein.

The units of the temperature control system in Figure 2 and 4 may be implemented as single units or the units may be combined into larger units. In one example, the temperature controllable valve 7 may include the controller 'CNTU. The connections between the units in Figure 2 and 4 may be electrical connections by electrical wires for example. Accordingly, the valves in Figures 2 and 4 may be magnetic valves controlled by electric current from the controller. It is also possible to employ wireless short range connections between the units. Examples of the wireless short range connections comprise Bluetooth and IEEE 802.11 based Wireless Local Area Network connections.

The controller may be a processor, microcontroller or a Field Programmable Gate Array (FPGA) for example. The controller may have a memory for storing a computer program for execution by the controller. The controller and the memory may form processing means for carrying out an embodiment described herein. The processing means may be a computer or a part of computer. Examples of the computer comprise a tablet computer, a desktop computer and a smart phone.

In an embodiment there is provided a computer program comprising computer program code for execution on a computer to cause one or more functionalities according to an embodiment, when said product is run on a computer. The computer program may be embodied on a computer -readable storage medium.

In an embodiment there is provided a computer program product for a computer, comprising a computer program according to an embodiment.

An embodiment concerns a computer program embodied on a computer -readable storage medium, the computer program comprising program to execute a process comprising a method according an embodiment.

When the temperature within the storage container is at the target temperature or the temperature range, the temperature controllable valve 7 may be closed such that sublimed dry ice cannot flow to the storage container. When the temperature within the storage container is higher than the target temperature or temperature range the temperature controllable valve 7 may be opened such that sublimed dry ice may flow to the storage container for cooling the storage container. It should be appreciated that instead or additionally to using a temperature sensor, a pressure sensor may be used, whereby the pressure measured by the pressure sensor may be used for controlling the valve in a similar manner as the measured temperature.

In various embodiments described above, sublimed dry ice from the dry ice container may be conducted to the storage container for cooling the storage container to a target temperature or to a target temperature range. The dry ice may flow out of the storage container provided by the pressure within the dry ice container being higher than the pressure within the storage container, the pressure within the enclosure around the dry ice container and/or the pressure within the fluid line. Accordingly, the apparatus according to various embodiments described herein may operate as powered by the sublimation of the dry ice and without further power sources. However, some embodiments may be implemented using magnetic valves, whereby accurate control of the temperature in the storage container and control of the sublimation rate may be obtained.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.