WO2008116722A1

WO2008116722A1 - Cooling vehicle having a plurality of cooling systems and cooling method

Info

Publication number: WO2008116722A1
Application number: PCT/EP2008/052479
Authority: WO
Inventors: Franz Lürken; Helmut Heinrich; Reinhard Kost
Original assignee: L'air Liquide Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude; Air Liquide Deutschland Gmbh
Priority date: 2007-03-28
Filing date: 2008-02-29
Publication date: 2008-10-02
Also published as: DE102007015391A1

Abstract

The present invention relates to a cooling vehicle (1 ) having at least one cooling chamber (2 ), at least one mechanical cooling assembly (3 ) and at least one cooling system (4 ) based on liquef ied gas, the cooling chamber (2) being assigned at least one container (8 ) for a cold storage medium ( 9). The cold storage medium ( 9 ) is preferably a eutectic storage medium with a phase transition, in particular between the liquid and solid phase, in proximity to a desired temperature (Tdes) of the cooling chamber (2 ). The container ( 8) with cold storage medium ( 9 ) is connected via heat exchange surfaces (10)- to the cooling chamber (2 ).

Description

Cooling vehicle having a plurality of cooling systems and cooling method

The present invention relates to a cooling vehicle having at least one cooling chamber and at least one mechanical cooling assembly and also a cooling system based on liquefied gas, also known as a hybrid cooling vehicle. A cooling method for the cooling chamber of such a cooling vehicle is also the subject of the invention.

Cooling vehicles are used for the transport of cooled commodities, the present invention relating mainly to the distribution of cooled commodities, in which a cooling vehicle repeatedly stops for a loading and/or unloading operation, the cooling chamber or cooling chambers of the cooling vehicle being opened.

With good insulation, a closed cooling chamber consumes only a low cooling power which can be furnished either by a mechanical cooling assembly or by a cooling system based on liquefied gas. For deliveries, what are referred to as hybrid systems are also known, in which, for example, low-temperature liquid CO2 is carried in a liquid-gas tank which is used, in particular, for rapid recooling after a cooling chamber has been opened. On longer journeys or at a standstill, without the cooling chamber being opened, a mechanical cooling assembly is generally sufficient to ensure that the stock of liquid carbon dioxide can be protected.

In cooling systems based on liquefied gas, there is, on the one hand, the possibility of providing indirect cooling, in which the air in a cooling chamber is cooled via heat exchanger surfaces by the liquefied gas which evaporates again. On the other hand, there is the possibility of spraying the liquefied gas directly into a cooling chamber. This type of cooling is particularly effective, but, before the cooling chamber is entered, it first requires complete ventilation, in order to provide a safely breathable atmosphere.

The present invention does not generally involve the type of cooling system based on liquefied gas, nor the exact type of construction of the mechanical cooling assembly and the type of supply of cold to the cooling chamber. What is important, however, is the fact that a mechanical cooling assembly, if it has a reasonable rating, can scarcely deliver sufficient refrigerating power for the rapid recooling of a cooling chamber which has warmed up by being opened, and that cooling systems based on liquefied gas may be limited during deliveries when the cooling chamber is opened frequently, because of the limited quantity of liquefied gas which is carried. Moreover, in the case of cooling chambers cooled directly by liquefied gas, this cooling system cannot be used during loading and unloading. Furthermore, the two cooling systems have different effectiveness in terms of the primary energy to be employed for a specific cooling power. Proceeding from this prior art, the object of the present invention is to provide a cooling vehicle having at least one cooling chamber, which cooling vehicle can reliably maintain a prescribed temperature range of the transported cooled commodities by the particularly effective use of primary energy, even during deliveries when the cooling chamber is opened frequently. The object of the invention is also to provide a method for largely maintaining or undershooting a desired temperature in a cooling space of a cooling vehicle, along with the beneficial use of primary energy and the protection of a carried stock of liquefied gas. A cooling vehicle according to Claim 1 and a method according to Claim 9 serve for achieving these objects. Advantageous developments and refinements are specified in the respectively dependent claims. A cooling vehicle according to the invention having at least one cooling chamber possesses at least one mechanical cooling assembly and at least one cooling system based on liquefied gas. Moreover, the cooling chamber is assigned at least one container for a cold storage medium. A container with a cold storage medium is often also designated as a cooling accumulator. According to the invention, the cold storage medium forms a third means for the supply of cooling power to the cooling chamber, in particular exactly at the times when it is used. In the simplest instance, it is sufficient to arrange a container with cold storage medium in the cooling chamber, preferably to suspend it beneath the ceiling.

In a particularly beneficial embodiment, the cold storage medium is a eutectic storage medium with a phase transition, in particular between the liquid and the solid phase, in proximity to a desired temperature of the cooling chamber to which it is assigned. The high heat or cold storability in a very small temperature interval is typical of eutectic storage media. In the simplest instance, water may be used, which, as is known, during the transition to ice absorbs large cold quantities which are discharged again during melting. The temperature for phase transition may be varied by the admixture of, for example, salt or alcohol.

In order to achieve effective heat exchange between the cooling chamber and cold storage medium, it is advantageous to form the connection between the cold storage medium and cooling chamber by suitably shaped exchange surfaces of suitable size.

It is also possible, by passive and/or active means of assistance, to assist the heat exchange between the cooling chamber and the cold storage medium. These may be, for example, ducts which run through the container, cooling ribs or else a storage fan. In this case, cooling ribs or cooling tubes may, if appropriate, assist natural convection in the cooling chamber, while a fan can generally assist heat exchange by the generation of suitable air flows along the heat exchanger surfaces. The presence of a cold storage medium in a cooling chamber or heat exchange between a cooling chamber and a cold storage medium can basically contribute to approximately maintaining the temperature in the cooling chamber. A cooling chamber largely filled with cooled commodities has automatically a high heat or cold capacity, so that it neither cools down quickly nor heats up quickly. The lower the load in the cooling chamber is, however, the more highly the temperature can change during loading and unloading operations. This is counteracted by a cold storage medium, in particular a eutectic storage medium, so that, even in a cooling chamber which is almost empty, it is possible for the temperature to be kept approximately constant.

It is also expedient to employ a cold storage medium, in particular, for cooling vehicles having at least two cooling chambers of different desired temperature, of which a second cooling chamber with a lower desired temperature can be entered only through a first cooling chamber with a higher desired temperature. This application arises when deep-frozen commodities and merely cooled commodities are supplied at the same time during deliveries. Such vehicles typically have at the rear a door and a cooling chamber of higher desired temperature, after passing through which the loading personnel reach the second cooling chamber with a lower desired temperature. Containers according to the invention with cold storage medium may profitably be arranged in one or in both cooling chambers.

In other cooling vehicle types, there are two or more cooling chambers which can be entered separately and do not necessarily have to have different desired temperatures. There are longitudinally divided cooling vehicles and those with a transverse subdivision and lateral doors. Here, too, the use of containers with cold storage medium is highly effective.

The special advantages of the invention arise, above all, by virtue of the management of the method, that is to say by virtue of the control of the various possibilities of supplying cold to a cooling chamber as a function of the respective situation and of other boundary conditions.

In the method according to the invention for largely maintaining or undershooting a desired temperature in a cooling space of a cooling vehicle, which has at least one mechanical cooling assembly, a cooling system based on liquefied gas and at least one container with cold storage medium, the cold storage medium is cooled preferably using the mechanical cooling assembly when the cooling space is at or below its desired temperature. The cooling assembly of a cooling vehicle, in general, requires the lowest use of primary energy for a specific cooling power and is available to a virtually unlimited extent, since it obtains its energy directly or indirectly from the fuel tank of the cooling vehicle. With a reasonable rating in relation to the size of the cooling vehicle, however, its peak power is not sufficiently high for specific situations. However, it can generate more refrigerating power than is lost through the insulation, with the cooling chamber closed, when the cooling chamber is at desired temperature. In such a situation, therefore, cooling power from the mechanical cooling assembly is available, which can be employed beneficially in order to cool the cold storage medium and bring about its phase transition into the solid phase, along with the absorption of high cold quantities. The control or regulation required is very simple, as described in more detail below. Thus, for example, during the journey between two loading operations, a large part of the cooling power of the mechanical cooling assembly can be used in order to cool the cold storage medium. The stored cold is then available, in addition to the cooling power of the mechanical cooling assembly, when the cooling chamber is next opened, in order, during loading or unloading, to keep the temperature in the cooling chamber as far as possible in proximity to the desired value. If this is not achieved, that is to say if the temperature in the cooling space overshoots a specific tolerance temperature during the opening time, the cooling system based on liquefied gas is cut in, since this system can provide a substantially higher cooling power.

Of course, with the cooling chamber open, only an indirect cooling system based on liquefied gas can be employed, in which the gas is not injected directly into the cooling chamber. In direct cooling systems based on liquefied gas, a possible overshooting of the tolerance temperature has to be accepted, until the cooling chamber is closed, but a very rapid recooling caused by the injection of the liquefied gas can then take place. As compared with the quantity of liquefied gas required in order to keep the temperature in the cooling chamber constant, without the use of cold storage medium, the consumption of liquefied gas is reduced considerably when the cold storage medium is used according to the invention, may extend the range of the cooling vehicle or markedly increase the number of possible loading and unloading operations with a liquid-gas filling. Furthermore, use of primary energy for a predetermined distribution journey is reduced.

The cold storage medium preferably used is a eutectic storage medium, in particular with a solidification temperature of 0.5 to 10 Kelvin below the desired temperature of the cooling space. If refrigerating power is supplied to the cooling space from the mechanical cooling assembly between two loading or unloading operations, the cooling space initially cools down only to about the solidification temperature of the storage medium and remains at this temperature or slightly below, for example, until the entire storage medium is solidified. The temperature then falls further, so that the mechanical cooling assembly can be cut out. The cooling space is then prepared for an opening of the door or can maintain its desired temperature for a relatively long time without the mechanical cooling assembly or the cooling system based on liquefied gas being cut in. Such a time may also be utilized, for example, for defrosting the mechanical cooling assembly if ice has formed in individual components. By a suitable choice of the temperatures at which the mechanical cooling assembly is cut out or cut in again and by the choice of a tolerance temperature which lies somewhat above the desired temperature and at which (if appropriate, only after the closing of the door) the cooling system based on liquefied gas is cut in, a very high quality of cooling in the cooling chamber can be achieved, along with a low use of primary energy, in spite of frequent loading and unloading operations.

As already mentioned, liquefied gases not breathable by humans are typically used for cooling, for example carbon dioxide or nitrogen. In such cooling systems, all known safety measures and procedures for economical use may continue to be used together with the present invention. The presence of a container with cold storage medium in one or more cooling chambers or elsewhere in the cooling vehicle does not have an adverse influence on these systems.

It is particularly advantageous for a flexible use of all systems if the mechanical cooling assembly and the cooling system based on liquefied gas and also, if appropriate, other active components present in the cooling vehicle, in particular at least one fan, are controlled by a central control unit, the control unit also comprising a data storage unit, from which data on expected journey times and loading times are taken as a basis for the departure of the cooling systems to be activated. Cooling vehicles generally travel along foreseeable routes having foreseeable loading or unloading stations, so that the probable journey times and loading times are approximately known. If, for example, there is only a very short journey distance between two loading operations, it may be expedient to use not only the mechanical cooling assembly, but also the cooling system based on liquefied gas, for cooling the cold storage medium, particularly in the case of systems which are cooled directly with liquefied gas and which cannot be employed during the loading operation. If, on the other hand, there is a long journey distance before the next loading operation, it is entirely sufficient to cool the cold storage medium by means of the mechanical cooling assembly during the journey and to protect the liquid-gas stock for later loading operations in shorter sequence.

In this connection, it is particularly preferred to connect the data storage unit to a navigation system which delivers data on a planned journey route and, from these, on probable journey times. Such a system, in conjunction with suitable sensors relating to the temperature in the cooling chamber or cooling chambers, the liquid-gas stock still available and, if appropriate, the fuel stock, allows a flexible cooling strategy adapting to various conditions prevailing during deliveries. By means of different stipulations, the use of primary energy, the consumption of liquid gas and/or maintaining a specific temperature range can be made the main aim of the regulation.

An exemplary embodiment of the invention is illustrated diagrammatically in the drawing which illustrates partially diagrammatically an exemplary embodiment of a cooling vehicle according to the invention. The invention, however, is not restricted to this exemplary embodiment, but may be used, in particular, for other types of mechanical cooling assemblies and of cooling systems based on liquefied gas and for different arrangements of cooling chambers.

In the drawing:

Fig. 1 shows a diagrammatic side view of a cooling vehicle according to the invention, and

Fig. 2 shows diagrammatically a view of a cooling vehicle from above with two cooling chambers arranged one behind the other. Fig. 1 shows a cooling vehicle 1 with a cooling chamber 2 on which a mechanical cooling assembly 3 is arranged at the front, on top and on the outside. A cooling system 4 based on liquefied gas is fed from a liquid- gas tank 5 located beneath the cooling vehicle 1. Cooling may take place directly by means of liquid-gas cooling 6, in particular injection into the cooling chamber 2, or by means of a heat exchanger system, not illustrated here. The supply of liquid gas can be regulated by means of a liquid-gas valve 7. A container 8 with a eutectic cold storage medium 9 is located in the cooling chamber 2. A eutectic cold storage medium can store considerable cold quantities by phase transition from the liquid phase to the solid phase. It is particularly beneficial if this phase transition lies at a temperature slightly below the desired temperature Tdes of the cooling chamber 2, in particular approximately 0.5 to 10 Kelvin below this. The container 8 may have cooling ducts 10 which run through its interior and assist the storage and discharge of cold. An additional storage fan 11 may assist the storage or discharge of cold. The container, depending on its arrangement in the cooling vehicle 1, may also be equipped with a separate connection, not illustrated here, to the mechanical cooling assembly 3 and/or to the liquid-gas tank 5, in order, as required, to make it possible to charge (cool) the cooling store by means of one of the two cooling systems. A door 12 allows access to the cooling chamber 2. When the door is opened, warm air enters the cooling chamber from the surroundings, so that the temperature of the air in the cooling chamber 2 and consequently gradually also the temperature of the commodities stored there rise. This is counteracted by the presence of the container 8 with eutectic cold storage medium 9, in any event as long as stored cold can be discharged by the cold storage medium 9. For assistance, with the door 12 open, the mechanical cooling assembly 3 can also be put into operation. When the loading operation has ended and the cooling chamber 2 has warmed up to too great an extent, very rapid cooling to the desired temperature Tdes again can take place by cutting in the cooling system 4 based on liquid gas. The mechanical cooling assembly 3 can then continue to run until the cold storage medium 9 has solidified again completely.

A central control unit 13 is equipped with sensors for measuring various parameters, in particular with a temperature sensor 16 for measuring the temperature in the cooling chamber and with those (not illustrated) for measuring the liquid-gas stock in the liquid-gas tank and the state of the door. Moreover, the central control unit 13 is connected to the mechanical cooling assembly 3 and to the cooling system 4 based on liquefied gas and, if appropriate, also to the storage fan 11. Moreover, a data storage unit 14 is present, which contains data on future journey times and loading times. In particular, a navigation system 15 may also be present, which, when destination addresses are input, delivers the probable journey times. By means of such information, the central control unit can carry out according to specific stipulations, for example a minimization of the consumption of liquefied gas, regulating operations which are adapted to each operating situation and are performed by means of the various system components.

Fig. 2 shows a cooling vehicle from above, with a first cooling chamber 2a and with a second cooling chamber 2b which are connected by means of a door. The desired temperature Tides of the first cooling chamber 2a is typically higher than the desired temperature T2des of the second cooling chamber 2b. When the door 12 is opened, a person initially enters the first cooling chamber 2a and also warm ambient air initially only enters this first cooling chamber 2a, so that the cold losses of the second cooling chamber can be kept low. By means of a container 8 with cold storage medium 9, therefore, the temperature in the second cooling chamber 2b can be kept low for a certain time span even when the door is open. The first cooling chamber 2a heats up somewhat during the loading operation, but can subsequently be cooled rapidly again by means of the cooling system 4 based on liquefied gas.

The present invention increases the flexibility on use of a cooling vehicle, in particular during deliveries, and, along with a highly economical use of primary energy and a sparing employment of the liquefied gas carried, makes it possible to have a high quality of cooling, that is to say a reliable maintaining of specific temperature conditions in one or more cooling chambers .

List of reference symbols:

1 Cooling vehicle

2 Cooling chamber

2a First cooling chamber

2b Second cooling chamber

3 Mechanical cooling assembly

4 Cooling system based on liquefied gas

5 Liquid-gas tank

6 Liquid-gas cooling (injection or via heat exchangers) Liquid-gas valve

Container for cold storage medium

9 (Eutectic) cold storage medium

10 Heat exchange surfaces

11 Storage fan

12 Door

13 Central control unit

14 Data storage unit

15 Navigation system

16 Temperature sensor

Tdes Desired temperature

Tides Desired temperature in the first cooling chamber 2a T2des Desired temperature in the second cooling chamber 2b Ttol Tolerance temperature, tolerance threshold

Claims

Patent claims:

1. Cooling vehicle (1) having at least one cooling chamber (2), at least one mechanical cooling assembly (3) and at least one cooling system (4) based on liquefied gas, characterized in that the cooling chamber (2) is assigned at least one container (8) for a cold storage medium (9) .

2. Cooling vehicle (1) according to Claim 1, characterized in that the cold storage medium (9) is a eutectic storage medium with a phase transition, in particular between the liquid and the solid phase, in proximity to a desired temperature (Tdes) of the cooling chamber (2) to which it is assigned.

3. Cooling vehicle (1) according to Claim 1 or 2, characterized in that the container (8) with cold storage medium (9) is connected via heat exchange surfaces (10) to the cooling chamber (2) to which it is assigned.

4. Cooling vehicle (1) according to Claim 1, 2 or 3, characterized in that the container (8) with cold storage medium (9) has passive and/or active means of assistance for reinforcing the heat exchange with the cooling chamber (2), in particular a fan (11).

5. Cooling vehicle (1) according to one of the preceding claims, characterized in that the cooling vehicle (1) has at least two cooling chambers (2a, 2b) of different desired temperature (Tides, T2des) , a second cooling chamber (2b) with a lower desired temperature (T2des) being enterable only through a first cooling chamber (2a) of higher desired temperature (Tides) .

6. Cooling vehicle (1) according to one of Claims 1 to 4, characterized in that the cooling vehicle (1) has at least two separately enterable cooling chambers (2c, 2d) .

7. Cooling vehicle (1) according to one of the preceding claims, characterized in that the mechanical cooling assembly (3), the cooling system (4) based on liquefied gas and, if appropriate, fans (11) present are connected to a central control unit (13) and can be controlled by the latter.

8. Cooling vehicle (1) according to Claim 7, characterized in that the central control unit (13) is connected to a data storage unit (14) and/or a navigation system (15), from which expected times for journey segments and loading operations can be taken as a basis for controlling the cooling.

9. Method for largely maintaining or undershooting a desired temperature (Tdes) in a cooling space (2) of a cooling vehicle (1) which has at least one mechanical cooling assembly (3), a cooling system (4) based on liquefied gas and at least one container (8) with cold storage medium (9), characterized in that the cold storage medium (9) is cooled preferably using the mechanical cooling assembly (3) when the cooling space

(2) is at or below its desired temperature (Tdes), the cold storage medium (9) discharging its cold to the cooling space (2) preferably in the case of an increased cooling requirement in the latter, the cooling system (4) based on liquefied gas being used only for a peak demand when a tolerance temperature (Ttol) is overshot.

10. Method according to Claim 9, characterized in that the cold storage medium (9) used is a eutectic storage medium, preferably with a solidification temperature of 0.5 to 10 K below the desired temperature (Tdes) of the cooling space (2), which cold storage medium is connected to the cooling space (2) via heat exchange surfaces (10), and in that, during normal operation, cold is supplied to the cooling space (2) by the mechanical cooling assembly (3) until the temperature lies below the solidification temperature of the eutectic storage medium.

11. Method according to Claim 10 or 11, characterized in that, in the case of an increased cooling power requirement in the cooling space, for example when a door to the cooling space is opened, the cooling power of the container (8) with cold storage medium (9) is first utilized, the mechanical cooling assembly (3) is then cut in when the desired temperature (Tdes) is overshot, and the cooling system (4) based on liquefied gas is used additionally or alternatively only when a tolerance temperature (Ttol) is overshot.

12. Method according to Claim 10 or 11, characterized in that the cooling system (4) based on liquefied gas is based on carbon dioxide or nitrogen which is injected directly into the cooling space (2), ventilation with air taking place before the cooling space (2) is entered, and the cooling power required for maintaining the desired temperature (Tdes) in the cooling space (2), with a door (12) open, being furnished only by the container (8) with cold storage medium (9) and by the mechanical cooling assembly (3) .

13. Method according to one of Claims 9 to 12, characterized in that the mechanical cooling assembly (3) and the cooling system (4) based on liquefied gas and other active components (11) of the cooling vehicle (1) which are present, if appropriate, are controlled by a central control unit (13), the control unit (13) also comprising a data storage unit (14), from which data on expected journey times and loading times are taken as a basis for selecting the cooling systems (3, 4, 8) to be activated.

14. Method according to Claim 13, characterized in that the central control unit (13) and/or the data storage unit (14) are/is connected to a navigation system (15) which delivers data on a planned journey route and, from these, on probable journey times, which data are used as a basis for selecting the cooling systems (3, 4, 8) to be used for individual time segments, preferably with the stipulation that the system (4) based on liquefied gas is cut in as rarely as possible.