FR2477688A1 - Controlled enclosure for transport of medical supplies - uses peltier cooling of insulated and part evacuated enclosure with power supplied by roof mounted photocells - Google Patents

Abstract

The self-controlled, controlled temperature enclosure is particularly applicable to the transport of medicines and vaccines which require controlled temps. to maintain their potency. A double walled enclosure is mfd. from a thermally insulating material. The space defined by the enclosure is loaded with the goods to be transported then lightly evacuated to reduce heat transfer to the walls. Arrays of Peltier effect devices inserted into the side walls provide cooling of the interior of the enclosure. Power is provided by an array of photo cells mounted on the roof of the transporting vehicle and linked to the Peltier devices by cables. An electric heating element is attached to the Peltier device casing to provide heating if required.

Description

Improvements to air conditioning units operating independently
The present invention relates to improvements made to air conditioning apparatus for cooling or heating a relatively large use volume and intended to operate autonomously in an environment at a different temperature (respectively hotter or colder) than that of the use volume. .

Certain products - (such as for example medicines or vaccines) must be kept at a determined temperature until they are used, both during storage and transport to bring them to the place of use .

 These storage conditions can result in the need to produce cold when the ambient temperature is high (case of equatorial regions for example) or, on the contrary, to produce hot when the ambient temperature is too low (case of polar regions by example).

 Devices have already been produced having a relatively large volume of use (that is to say of the order of a hundred or a few hundred liters), therefore easily embarkable on board a light motor vehicle. However, these devices were equipped with an internal combustion engine, which made them heavier and more bulky, polluting and above all uneconomic, both because of the cost of the fuel necessary for their operation and because of poor insulation. which increased their consumption even more, and therefore their cost of use.

 The object of the invention is essentially to remedy these drawbacks by proposing a refrigeration unit with autonomous operation having reinforced insulation reducing thermal exchanges with the outside so that an autonomous source of low power can be used.

The invention also aims to ensure that, while using a low-power autonomous energy source, the volume of use of the device is large enough to contain a significant amount of products to be maintained at a temperature determined, and this as well for the storage of said products in a place where no suitable source of energy (electric among others) is available, that, and especially, for the transport of these products using light motor vehicles .

For these purposes, the air conditioning apparatus of the invention comprises in combination - two closed enclosures, one surrounding the other for
delimit a capacity in which a vacuum is established, - a plurality of Peltier cells comprising
each at least one external heat exchange member
arranged on the external face of the external enclosure, at
less an internal heat exchange member disposed on
the internal face of the internal enclosure, and at least one
thermo-element interposed between the abovementioned heaters
external and internal thermal exchange, - and a generator of direct electric current to function
autonomous operation to supply the thermo-element with
direct current with polarity such as the exchanger
external thermal either a hot heat exchanger and
the internal heat exchanger is an exchanger
cold thermal (cooling of the user volume
tion) or vice versa such as the heat exchanger
external is a cold heat exchanger and the eJ
internal thermal changer, i.e. a heat exchanger
warm (heating of the operating volume).

It is the combination of these different characteristics that makes it possible to obtain a device that perfectly meets the conditions of use for which it was designed.

 Indeed, the use of Peltier cells is particularly advantageous because of their relatively low energy consumption, which allows the use, pqur power1 an autonomous generator of limited power.

 Furthermore1 the two closed enclosures, delimiting between them a capacity in which a relative vacuum is established, reduce to a minimum the heat losses by convection and by conduction, which is particularly advantageous in the case of an association with effect cells. Peltier because of their poor performance.

 Taking into account these particular structural arrangements and using an appropriate number of Peltier cells, it is possible, as desired, to produce an apparatus having a relatively large use volume (for example a hundred or of a few hundred liters), which was not possible until now without using an electric generator driven by an internal combustion engine.

To ensure total autonomy of the power supply to the device, it is advantageous to provide that the electric generator is constituted by a set of solar cells. To ensure, however, the continuity of cooling or heating and to minimize temperature variations in the volume of use outside the periods of operation of the solar cells, provision is made to have, inside the internal enclosure, a thermal accumulator to diffuse cold (cooling of the volume of use) or heat (heating of the volume of use) when the solar cells are not exposed to a luminous flux (nocturnal periods).

Given the good thermal insulation of the device and the relatively low power (of the order of a few tens of watts) necessary for its operation, the use of solar cells proves to be extremely advantageous because, in combination with the 'thermal accumulator, they ensure the total autonomy of the device, as well with regard to the energy source (luminous flux) as with regard to maintenance which is minimal. In addition, it is easy to add deployable and optionally orientable flaps carrying the solar cells to the apparatus in the case of static use, or else in the case of a device on board a vehicle. , to place the solar cells on the roof of the vehicle itself.

When the solar cells are not in operation, there is a risk of producing a significant heat exchange from the interior of the device, given the external atmosphere via the thermal bridge formed by the thermally conductive elements of the air conditioning system (radiators , thermo-elements, metal spacers).

In this case, the thermal reserve, constituted by the thermal accumulator, will prove to be insufficient to maintain the desired temperature for a relatively long period (for example overnight).

To overcome this drawback, provision is made to have, between the internal heat exchange member and the thermoelements, a thermally conductive element constituted in the form of a unidirectional heat exchange member arranged to allow heat exchanges from the volume of use towards the outside atmosphere, but to prohibit heat exchanges in the opposite direction.

Advantageously, this member comprises a chamber delimited in particular by a first thermally conductive wall in thermal contact with one of the heat exchange members and by a second thermally conductive wall in thermal contact with the corresponding face of the thermo-elements, two others thermally insulating walls being provided between the aforesaid first and second walls to close the chamber, a reserve of liquid at a vaporization point chosen according to the operating conditions of the device, and a layer of a material absorbing said liquid placed on the face facing the interior of the chamber of that of the above first and second walls of the chamber which is warmer than the other.

 A particular aspect of the invention relates to a refrigerator appliance having a relatively large useful volume and intended to operate autonomously in an environment at relatively high temperature, characterized in that it comprises in combination - two closed enclosures, the one surrounding the other to delimit a capacity in which a vacuum is established, - a plurality of Peltier cells each comprising at least one hot heat exchange member disposed on the external face of the external enclosure, at least one organ cold heat exchange disposed on the internal face of the internal enclosure, and at least one thermoelement interposed between the aforesaid hot and cold heat exchange members, - and a set of solar cells electrically connected to the thermoelements to power them- this in direct current.

The invention will be better understood on reading the following description of some of its embodiments given by way of illustrative examples, but in no way limiting. In this description, reference is made to the appended drawings in which
Fig. 1 shows, very schematically, an apparatus according to the invention.

 Fig. 2 is a sectional view of part of the apparatus of FIG. 1.

 Fig. 3 is a sectional view of an element which can be incorporated in the part of the apparatus shown in FIG. 2.

Referring first to Figs. 1 and 2, we will now describe a refrigerator device arranged in accordance with the invention, because it is in this case that the invention seems to have to find its most interesting applications, it being understood that it is not limited to this only type of device and that it also includes devices that generate heat in relation to the atmosphere.

The refrigerator appliance 1 comprises two enclosures, an external enclosure 2 and an interior enclosure 3 with
enclosure 2, closed (the access door was not
shown), and kept apart from each other
by spacers 4. The two enclosures 2,3 and
the spacers 4 are made of a ther material
only insulating, and preferably moldable for
authorize the manufacture of the two enclosures according to
known simple techniques.

Optionally, a metal envelope (not re
shown) can be provided to protect the external enclosure 2 from impact and impact.

Speakers 2 and 3 delimit between them a
cavity 5, in which a vacuum is produced. For some
mechanical resistance issues of enclosures 2 and 3
and to simplify the maintenance of the device, it
it is not necessary that this vacuum be very high and a
vacuum of the order of î0-2Torr is ideal for
reduce heat losses to an acceptable minimum
by conduction and convection in the cavity 5.

Two opposite side surfaces are provided
Peltier effect cooling devices 6 connected by conductive wires 7 to solar cells 8, possibly via a regulating device (not shown).

Fig. 2 represents on a larger scale and in
detail one of the cooling devices 6! in
the occurrence on the right in fig. 1.

The device 6 includes a hot radiator 9
outside the external enclosure 2, and a radiator
cold 10 inside the internal enclosure 3, these two ra
diators being made of thermally material
good conductor such as aluminum. Between the faces in
look of radiators 9 and 10, are thermo
elements II and a metal spacer 12, by
example made of aluminum, made integral, for example by
crimping, of the spacer 12, the thermo-elements 11
and at least part of the spacer 12 being arranged
in a recess 13 made in the double wall 2,3
of the device.

Clamping means, such as bolts 14, cons
with an insulating material (for example plas
tick) provide a mechanical connection between the radiator 9 and the spacer 12 and allow the thermo-elements 11 to be forcibly tightened between the opposite faces of these two parts.

Wedges 15, 16, for example annular, are interposed between the radiators 9, 10 and the walls 2,3 respectively to hold the device 6 relative to said walls, on the one hand, and to ensure the thermal sealing of the passage of the double wall, on the other hand.

Furthermore, electrical connection means constituted by conductive wires 7 connect the thermoelements 11 to a source of direct current, in this case the solar cells 8, with appropriate polarities.

One can, for example, provide a sealed passage of the radiator 9 for the wires 7.

 Finally, there is provided inside the internal enclosure 3 a reservoir 17 for an appropriate eutectic liquid (in particular as regards its composition and volume) under the operating conditions of the device.

This liquid acts as a buffer, that is to say that it absorbs frigories when the cooling device 6 is in operation (daytime period) and that it restores said frigories when the cooling device is not no longer in operation (night period) and the internal temperature of enclosure 3 tends to increase.

 The addition of such a thermal buffer proves to be particularly advantageous because, despite the discontinuity of operation of the cooling device during a full day, it ensures the maintenance of a determined temperature, with a good approximation, at inside the enclosure 3.

Advantageously, the reservoir 17 is made in one piece with the cold radiator 10.

 It will be noted that, when the thermo-elements 11 are not supplied with direct current (for example at night), the metal parts constituting the cooling device 6 form a thermal bridge which favor the evacuation of the frigories from the interior of the enclosure 3 towards the outside, and therefore favor a reheating of the volume of use of the device, which reheating is, of course, all the more rapid as the temperature difference between the inside of enclosure 3 and the interior is more important.

 To avoid this drawback, it is conceivable to replace the metal spacer 12 with a unidirectional heat exchange member 18, shown in FIG. 3, arranged to allow heat exchange from the inside of the enclosure 3 to the outside, but to prohibit heat exchange in the opposite direction.

 The member 18 is constituted in the form of a hermetically closed chamber 19 delimited by two metal walls 20, 21 (for example made of aluminum) facing each other and by four walls made of a thermally insulating material (which can, for example, be the same as that constituting the enclosures 2 and 3). The wall 20 is in thermal contact with the cold radiator 10, while the wall 21 is in thermal contact with the thermo-elements 11.

On the inner face of the wall 20 is deposited a coating 22 of an absorbent material (capill2irc material).

 In the chamber 19 is provided a certain quantity of a liquid with a vaporization point chosen according to the operating conditions of the refrigerator appliance, and such that the chamber contains gas under pressure, with a liquid phase 23 and a gaseous phase . A thickness of insulating material 24a is provided along the wall 21 to isolate the latter from the liquid 23.

Above the level of the liquid phase, it is possible to see a plate 24, made of thermally insulating material, possibly pierced with holes 25, avoiding splashes of liquid on the walls 20, 21. It will be noted that the plate 24 is attached to the insulating side walls of the chamber, but that it is not in contact with the wall 20 to leave a free space 26 in which the absorbent coating is engaged. 22, in such a way that the lower part thereof bathes in liquid 23.

 The operation of the unidirectional heat exchange member 18 is as follows.

When the heat elements 11 are supplied with direct current, the internal face of the thermo-elements (face which supplies the cold) is cooler than the volume of use, therefore than the cold radiator 10. As a result, the wall 21 of the member 18 is cooler than the wall 20.

In the chamber 19, liquid 23 is absorbed by capillary action by the absorbent coating 22 and therefore rises along the wall 20, which is the warmest, relatively.

 By choosing a liquid with an appropriate vaporization point, the liquid 23 vaporizes on contact with the wall 20, then, by convection, the vapors come into contact with the wall 21, which is cooler the vapors condense there and flow to the liquid mass 23.

 Given the fact that the vaporization and condensation processes are respectively endothermic and exothermic, it can be considered that the cycle which has just been described is accompanied by a removal of calories from the wall 20 and a supply of calories to wall 21.

 In other words, there is cooling of the wall 20 (and therefore of the volume of use by means of the radiator lo) and heating of the wall 21.

 On the other hand, when the thermo-elements 11 are not supplied, the wall 21 is brought almost to the outside temperature and is therefore hotter than the wall 20 which is in contact with the volume of use cooled by the thermal accumulator 17.

 The liquid absorbed by the absorbent coating 22 cannot vaporize on contact with the cold wall 22: therefore, no convection heat exchange cycle can be established between the walls 20 and 21.

 Nor can any heat transfer be established by conduction since the other walls of the chamber are made of a thermally insulating material.

 The member 18 therefore authorizes the evacuation of the heat from the volume of use to the outside (periods of operation of the thermo-elements) but prohibits the passage of heat in the opposite direction (periods of non-operation of the thermos -elements).

 All the provisions provided for the design of the refrigerator appliance makes it possible to reduce heat losses to a minimum and therefore authorizes the production of an appliance having a large volume of use (of the order of one hundred or of a few hundred liters) powered by solar cells which provide relatively low power and / or poor performance.

Such a refrigerator appliance can therefore be used for the transport of medicaments and / or vaccines maintained at a relatively low temperature (for example of the order of 50C) while the ambient temperature is high, of the order of 400C for example.

 The refrigerator device can for this purpose be taken on board a light motor vehicle 27 (see fig. 1), the solar cells 8 then being advantageously arranged on the vehicle roof.

Of course, nothing prevents the refrigerator appliance from being used in a fixed position, for example by providing deployable and, optionally, orientable, articulated shutters on the body of the appliance itself and carrying the solar cells.

 An identical arrangement can be provided, by means of a reversal of the polarity of the supply voltage of the photoelements and a reversal of the direction of conduction of the unidirectional heat exchange member in order to produce a heating device intended for the preservation of products higher than room temperature.

 As goes without saying, and as it already follows from the above, the invention is in no way limited to those of its modes of application and embodiments which have been more particularly envisaged; on the contrary, it embraces all its variants.

Claims (10)

1. Air conditioning apparatus for cooling or heating a relatively large use volume and intended to operate autonomously in an environment at a different temperature (respectively hotter or colder) than that of the use volume, characterized in that it comprises in combination - two closed enclosures, one surrounding the other for  delimit a capacity in which a vacuum is established, - a plurality of Peltier cells comprising each at least one external heat exchange member  disposed on the external face of the external enclosure, at least one internal heat exchange member disposed  on the internal face of the internal enclosure, and at least a thermo-element interposed between the above-mentioned organs of external and internal heat exchange, - and a generator of direct electric current to function autonomous operation to power the thermo-elements  in direct current with a polarity such as the sample  external heat exchanger, i.e. a hot heat exchanger  and that the internal heat exchanger is an exchanger cold thermal (cooling of the use volume)  or vice versa such as the external heat exchanger  either a cold heat exchanger and that the exchanger  internal thermal either a hot heat exchanger (reheating of the operating volume). 2. Air conditioning apparatus according to claim 1, characterized in that the electric generator is constituted by a set of solar cells and in that there is provided, inside the internal enclosure, a thermal accumulator for diffusing cold (cooling of the operating volume) or heat (heating of the operating volume) when the solar cells are not in operation. 3. Air conditioning apparatus according to claim 2, characterized in that the internal heat exchange member and the thermal accumulator are produced in the form of a single piece. 4. Air conditioning apparatus according to any one of claims 1 to 3, characterized in that between the internal heat exchange member and the thermo-elements is interposed a thermally conductive element serving as a spacer.  5. An air conditioning device according to claim 4, characterized in that the thermally conductive bracing element is formed in the form of a unidirectional heat exchange member arranged to allow heat exchanges from the volume of use to the 'outdoor atmosphere, but to prohibit heat exchange in reverse. 6. Air conditioning apparatus according to claim 5, characterized in that the member has unidirectional heat exchange comprises a chamber defined in particular by a first thermally conductive wall in thermal contact with one of the heat exchange members and by a second thermally conductive wall in thermal contact with the corresponding face of the thermo-elements, two other thermally insulating walls being provided between the abovementioned first and second walls to close the chamber, a reserve of liquid with vaporization point chosen according to the conditions of operation of the device, and a layer of a material absorbing said liquid disposed on the face facing the interior of the chamber of that of the above first and second walls of the chamber which is warmer than the other. 7. Air conditioning unit according to any one of claims 1 to 6, characterized in that the two enclosures are made of a moldable polymerizable material.  8. Air conditioning apparatus according to any one of claims 2 to 7, characterized in that the solar cells are arranged on deployable movable flaps. 9. Air conditioning apparatus according to any one of claims 2 to 7, intended to be taken on board a motor vehicle or the like, characterized in that the solar cells are arranged on an external surface, in particular the roof, of said vehicle. .  continued.  to the thermo-elements to supply them with current  hot and cold heat exchange components, - and a set of electric cells connected electrically minus one thermo-element interposed between the above on the internal face of the internal enclosure, and at  at least one cold heat exchange member arranged  disposed on the external face of the external enclosure,  each at least one hot heat exchange member  established, - a plurality of Peltier cells comprising  delimit a capacity in which a vacuum is 10. Refrigerating appliance having a relatively large useful volume and intended to operate autonomously in a relatively high temperature environment, characterized in that it comprises in combination - two closed enclosures, one surrounding the other for