Abstract:
An ice storage element ( 28 ), especially for the auxiliary air conditioning system of a motor vehicle, with a hollow body for forming at least one storage space ( 34 ) for an ice storage medium ( 36 ) which is liquid in the thawed state and which can be brought into heat-conductive connection with a refrigerant. The ice storage medium ( 36 ) contains a thickening agent to suppress sloshing of the ice storage medium ( 36 ) in the thawed state and to ensure freezing of the ice storage medium ( 36 ) in the form of a slush.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an ice storage element, especially for the auxiliary air conditioning system of a motor vehicle, with a hollow body for forming at least one storage space for an ice storage medium which is liquid in the thawed state and which can be brought into heat-conductive connection with a refrigerant. 
     2. Description of Related Art 
     Conventional ice storage elements of the above described type are provided with complex, and thus expensive, volume equalization elements, for example, of rubber or plastic, in order to ensure volume compensation of the ice storage medium which expands in a phase transition, e.g., freezing. The disadvantage in the known ice storage elements of the type under consideration is, moreover, that the thawed ice storage medium within the storage space of the ice storage element produces a sloshing noise while driving which is a nuisance, since it is perceived by the driver or passenger when the storage element is located in or directly against the passenger compartment. 
     Furthermore, an ice storage element known from published German Patent Application DE 35 31 158 A1 has a housing formed of a hollow polyethylene section into which metallic refrigerant pipelines are inserted and fixed relative to the walls by additional holding parts. Heat transfer from the cold storage medium within the housing to the air flowing past externally is poor due to the plastic housing. The refrigerant pipelines must be secured with additional components in a complex manner, due to which such an ice storage element is expensive to manufacture. 
     SUMMARY OF THE INVENTION 
     Therefore, the primary object of this invention is to devise a ice storage element which uses simple and economical means to withstand expansion of the ice storage medium in a phase transition/freezing without damage and which has an ice storage medium which does not produce sloshing noise in the thawed state. 
     This object is achieved by the ice storage medium containing a foaming or thickening agent in a quantity and quality such that sloshing of the ice storage medium in the thawed state is suppressed and freezing of the ice storage medium in the form of slush is ensured during at least one phase of volume expansion. 
     In other words, in accordance with the invention, the properties of the ice storage medium are modified such that, in the installed state, a foamy or gel-like consistency develops which prevents sloshing motion of the thawed medium. Moreover, the property of the ice storage medium is changed by the added foaming agent or thickening agent such that during freezing, i.e., in the transition from the liquid to the solid state, a slush is formed which ensures uniform expansion of the ice storage medium during freezing so that the wall of the storage space of the ice storage element is uniformly loaded and can withstand the volume expansion of the ice storage medium which is freezing. The slush which forms is comparable to crusted snow or finely crushed ice in terms of consistency. 
     Except for an air cushion which is conventionally provided in the storage space of the ice storage element, no additional volume equalization element is necessary by means of the measure according to the invention to freeze and thaw the ice storage medium in the closed, rigid storage container which forms the storage space. In addition, sloshing noise is reliably suppressed because the thawed ice storage medium is foamy or viscous such that it is too inert to slosh. 
     Advantageously, a water-based ice storage medium is used. The thickener added to the ice storage medium can, for example, be a gelling agent. 
     The thickening agent or gelling agent can be any known agent with this property which is matched to the ice storage medium used, which is, for example, preferably water-based. Advantageously, an inorganic agent with thickening or gelling properties is used as the thickening agent or gelling agent. Alternatively, an organic thickening agent can be used, for example, in the form of a polymer which is capable of swelling or in the form of a biological thickening agent. 
     Advantageously, the thickening agent can also be present in the form of a mixture of different thickening additives and/or foaming agents in order to acquire the desired consistency of the ice storage medium. 
     In the following the invention is detailed by way of example using the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic, partially broken away view of a cab of a truck with a compression refrigeration system and several ice storage units; and 
     FIG. 2 is a cross-sectional view through an ice storage module with several ice storage elements. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the embodiment in FIG. 1, part of a truck  1  is shown in which, within the cab  2 , the vehicle interior is formed. The cab  2  is bordered to the top by the roof  3  and to the back by the rear wall  4 . Within the rear part of the cab there is a horizontal partition  5  as is conventionally provided as a reclining surface for partitioning of the sleeping cove in a long haul truck in which the rear part of the cab  2  is made as a sleeping compartment  6 . 
     In the engine compartment  7  of the truck  1 , there is a compressor  8  which can be connected via a V-belt by a magnetic clutch  9  to a vehicle drive motor which is not shown. The compressor  8  is incorporated into a first refrigerant loop, its being connected to an expansion element via a feed line  11  via a condenser  10 , a collector  12  and a first evaporator  13 . The refrigerant which circulates in the first refrigerant loop is returned from the first evaporator  13  via a return line to the compressor  8 . 
     Between the collector  12  and the first evaporator  13 , there is a reversing valve  15  in which a branch feed line  16  which belongs to a second refrigerant loop branches off from the feed line  11 . One or more ice storage units are integrated into this second refrigerant loop and they each include a second evaporator with an expansion element and an ice storage which surrounds it. The first ice storage unit  17  is located in the area of the rear wall  4  of the truck  1 . The refrigerant which flows via the branch feed line  16  can be routed via a branch line  18 , optionally by means of another reversing valve which is not shown, to a second ice storage unit  19  and a third ice storage unit  21 . The second ice storage unit  19  is located in the horizontal partition in the area of the sleeping compartment  6 . 
     There is a third ice storage unit  21  in the area of the roof  3 . It is connected via another branch line  18  to the refrigerant branch feed line  16 . The ice storage units  17 ,  19  and  21  are connected to a common return line  22  which, for its part, is connected to the refrigerant return line  14  to the compressor  8 . A return valve  27  located in the return line  22  thus prevents backflow of refrigerant gas to the ice storage units  17 ,  19 , and  21  and condensation there. 
     The ice storage unit  17  is located in a receiving space  23  which is formed by the rear wall  4  of the cab  2  and an intermediate wall  24  located a distance in front of it. Selectively, the ice storage unit can also be inserted into a cutout of the rear wall. Likewise, the ice storage unit  21 , which is provided optionally or alternatively in the roof area, and another ice storage unit  21 , which is provided optionally or alternatively in the area of the horizonal partition  5 , are each located in a receiving space  23  which is formed by the double walls. 
     The receiving spaces  23  are each connected by an inlet  23 A and an outlet  23 B to the cab  2 , such that air flow can take place through the doubled-walled receiving space  23 . This through air flow which takes place either by convection as a result of temperature-induced density differences of the air in the cab  2  or forced by a fan  25  which is optionally provided can be controlled by a shutoff device  26 . The shutoff device  26  is made, for example, as a swinging flap which is shown, by way of example, on the top end of the receiving space  23  for the ice storage unit  17 . The flap can be actuated manually or by motor and can be replaced by other corresponding shutoff devices, such as movable screens or slides. Even if this is not shown in FIG. 1, it goes without saying that the other receiving space  23  for ice storage units  19  and  21  can each be equipped with a corresponding shutoff device and/or a fan. Air flows through the inlet  23 A in the direction shown by arrow A into the receiving space  23 , is routed past the respective ice storage unit  17 ,  19  or  21 , and in doing so, is cooled and leaves the receiving spaces  23  as cooled air in the direction toward the cab  2  through the outlet openings  23 B as indicated by the arrow B. 
     The system is preferably designed such that the compressor  8  has enough power to make available not only enough cold for the first evaporator  13  for normal cooling of the cab  2  while driving even with a high demand for cold during operation of the engine, but in addition to charge one or more of the ice storage units  17 ,  19 ,  21  by conversion of the storage medium into ice so that, during a subsequent stop, the cab  2  can be cooled by simple air flow through the respective receiving spaces  23 . This ensures that the driver finds himself in a pleasant climate in the cab  2  during rest stops or sleeping stops even in hotter countries. 
     FIG. 2 shows one of the ice storage units  17 ,  19 ,  21  in cross section. While the reference number  17  is used, the following comments apply to units  19  and  21  as well. Within a surrounding housing outside wall  38  and an insulating layer  47 , in the illustrated embodiment, there are a total of six ice storage elements  28  next to one another with an outside wall bordered by an elongated profile body  29 A. The profile body is preferably produced as an extruded profile of lightweight metal, for example, aluminum, and as required, can be cut to the required length. In the cross section of the profile body  29 A, two refrigerant pipes are integrated through which refrigerant flows from the branch feed line  16  to the ice storage units, and thus, to the ice storage elements  28  located therein. Within an ice storage unit  17 ,  19 ,  21 , the ice storage elements  28  are connected in series and/or in parallel in terms of flow by pipe bends which are not shown and which are located in the area of the faces. 
     The profile bodies  29 A have two fork-shaped ribs  31  on the outside wall and bridge-shaped ribs  32  on the opposite wall. In this case, there is a receiving groove formed on the front end of a fork-shaped rib  31  for holding a bridge-shaped rib  32  of an adjacent ice storage element  28 . Modular ice storage units of any size can be assembled from any number of ice storage elements  28  in a self-supporting structure by the form-fit engagement of the ribs  31  and  32 . In this case, in the area of the ribs  31  or  32 , there can be additional connecting elements, such as clips, transverse screws or beads of cement. 
     Further details of the construction of such ice storage units can be obtained by reference to commonly-owned, co-pending U.S. patent application Ser. No. 09/149,293, which is hereby incorporated by reference. 
     According to the invention, as the cold storage medium in the ice storage elements  28 , a water-based storage medium is used to which a thickening agent or a mixture of thickening agents, preferably a gelling agent, is added, in a quantity and quality such that, when the ice storage medium thaws, it is ensured that sloshing noise is suppressed as the vehicle or truck is driving because the ice storage medium is correspondingly thick. In addition, according to the invention, the thickening of the ice storage medium is achieved by means of the added thickening agent such that, when the ice storage medium is frozen, i.e., in the freezing transition phase, a slush forms first which ensures uniform expansion of the ice storage medium during the freezing process, and thus, uniform loading of the receiving space of the ice storage element. 
     The substances explained in the following embodiments have proven to be suitable storage media. 
     EXAMPLE 1 
     A mixture of from 4 to 7%, preferably 5.87% fatty alcohol C-10, for example, 1-decanol as is available from Sigma Aldrich, 89555 Steinheim, Germany, optionally, 0.01 to 0.05%, preferably 0.03% tenside, 4 to 9 per mil, preferably 6.5 per mil of a polymer with the ability to swell, such as Favorpac 300 which is available from Chemische Fabrik Stockhausen, 47805 Krefeld, Germany, and the remainder de-ionized water. 
     EXAMPLE 2 
     Mixture of roughly 15 to 22%, preferably 20% dialcohol, 4 to 6%, preferably 5% highly foaming special tenside, remainder de-ionized water. 
     While in example 1 the polymer with the ability to swell provides for a slushy structure of the frozen substance which is gel-like in the thawed state, the substance in the second example is highly foamy in the thawed state and in the frozen-state is similar to crusted snow. 
     EXAMPLE 3 
     Mixture of: 
     2 to 2.3%, preferably 2.17% polyvinyl alcohol, 
     0.3 to 0.5%, preferably 0.39% borax, 
     0.15 to 0.26%, preferably 0.21% biocide and as the remainder de-ionized water. 
     The substance in Example 3 is highly viscous (gel-like) in the thawed state and in the phase transition into the frozen state is like crusted snow. 
     While various embodiments in accordance with the present invention have been shown and described, it is understood that the invention is not limited thereto, and is susceptible to numerous changes and modifications as known to those skilled in the art. Therefore, this invention is not limited to the details shown and described herein, and includes all such changes and modifications as are encompassed by the scope of the appended claims.