This text is machine translated.
About cooling boxes
Summer, sun and heat are great - but not when perishable goods or drinks need to be transported.
However, this problem can be solved quickly with a cool box. Then, at hot temperatures, well-chilled drinks are not only available at home.
If you buy frozen food or dairy products in the supermarket in the summer, I hope you have thought of a cooler. In the height of summer, the perishable goods can quickly thaw or damage them on their way home. That's why cold bags should always be included in the car. But when it comes to cooling food and drinks over a longer period of time, cooler bags are not the best solution. Coolers are much better suited for this purpose. But which is the right one?
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What types of coolboxes are there?
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How does a passive cooling box work?
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How does a thermoelectric cooling box work?
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How does a compressor cooling box work?
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How does an absorber cooler work?
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Advantages and disadvantages of the different cooling box systems
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What should be taken into account when purchasing a cooling box?
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Frequently asked questions about coolboxes
What types of coolboxes are there?
There are a lot of offers on the market and the overview can be easily lost. Cool boxes offered in all price segments and sizes do not make selection easy.
Active or passive cool box?
The most important difference in cooling boxes is the operating mode.
Passive cooling boxes do not have any components that actively contribute to the reduction of the internal temperature. Here, the food and drinks must be well pre-cooled when they are put in the box. The box is then equipped with a thick PU insulation so that the pre-cooled goods remain well cooled for a long period of time. In addition, frozen deep-freeze batteries can be placed in the box to support the cooling effect.
In active coolboxes, various techniques are used to actively lower the interior temperature of the box or to keep it at least at a lower level than the ambient air.
Active versions include thermoelectric cooling boxes, compressor cooling boxes and absorber cooling boxes. In part, the different techniques are also combined. In this case it is called hybrid cooling boxes, which have e.g. a thermocouple and a compressor installed.
How does a passive cooling box work?
There is not much to say about the function of a passive cooler. It is important to have good all-round insulation and that the cover is completely sealed. Only then can it be ensured that there is no too fast temperature compensation between indoor and outdoor areas.
In addition to the classic ice packs, ice cubes have also proved to be the ideal cold storage or cooling solution. Especially for beverage cans that do not have a label sticker, the all-round contact to ice cube water leads to maximum cooling and a really cool drinking pleasure.
For glass bottles with label stickers, ice packs are the better solution. Because bottle stickers floating in the ice water, which dissolve slowly, are rather unappetizing.
The functional description of the active cooling boxes becomes more interesting. Although the technology is sometimes very complex, we have tried to put the topic into simple words:
Passive cool box in classic design.
How does a thermoelectric cooling box work?
Peltier element design: Cold side (1), ceramic plate (2), N semiconductor (3), P semiconductor (4), ceramic plate on hot side (5), copper bridges (6).
The heart of a thermoelectric cooling box is a Peltier element. A Peltier element is constructed with numerous semiconductor elements (Dices). As current flows through the semiconductors, the charge carrier power level changes. Depending on the current direction, it is either higher or lower. This makes the Peltier element warm on one side and cold on the other side. In accordance with this temperature development, Peltier elements are installed in the cooling box wall or the cover.
For the best effect, the outside warm side is cooled to ambient temperature with a fan. The cold side is correspondingly lower.
The maximum temperature difference that can be achieved depends on the size of the element and the number of dices. And these in turn determine the power consumption and cooling performance. This is why manufacturers always indicate the temperature difference to the ambient air in thermoelectric cooling boxes.
And incidentally,
If you change the current direction through the Peltier element, the warm and cold sides of the element are swapped. The box can then not only cool but also be used as a keep-warm box.
How does a compressor cooling box work?
A compressor cooling box operates according to the same procedure as a refrigerator or air conditioning in the car. Therefore, a refrigerator is also ideal for function explanation. A gaseous refrigerant is pressurized using a compressor (1). This causes the refrigerant to become very warm. The effect can also be experienced by holding the valve connection with a bicycle air pump and then pushing the air in the pump together to the maximum. The pump will then also warm up in the compressed air area.
The compressed and gaseous refrigerant is then routed through a cooling loop (2) at the rear of the refrigerator (condenser or condenser). There, the coolant releases its energy to the air and becomes liquid. A restrictor (3), which in the simplest case can be a wound-up pipe with a very small cross-section, directs the refrigerant to the evaporator (4) inside the fridge.
The pipes in the evaporator provide sufficient space for the refrigerant to spread and return to the gaseous state. When evaporating, the coolant absorbs energy that it removes from the inside of the refrigerator. You can also experience this effect if you do not dry after bathing. The water on the skin can evaporate and thus remove the body from the necessary heat. That is why we freeze more or less at this moment.
From the evaporator, the gaseous refrigerant flows to the compressor, where the circuit begins again.
Refrigerant circuit: Compressor (1), condenser (2), restrictor (3) and evaporator (4).
How does an absorber cooler work?
At the first moment it sounds funny to produce cold with heat, but the principle works quite well in practice.
A mixture of water and ammonia is heated in a cooker (1). This can be done by a gas flame or by an electric heater. The heat separates ammonia and water. The gaseous ammonia (NH 3 ) thus rises to the condenser or condenser (2).
In the condenser, the ammonia vapor releases its energy via cooling fins to the environment and thereby becomes liquid. The liquid ammonia then continues to flow into the interior of the cooling box to the evaporator (3) where it evaporates at low pressure under the absorption of hydrogen (H). As with a compressor cooling box, the energy required for evaporation is removed from the interior or the food to be cooled in the form of heat.
The gas mixture of ammonia and hydrogen (NH 3 +H) then enters the absorber (4). There, the ammonia is absorbed (absorbed) from the water (H 2 O) from the cooker (1) and flows back to the cooker. The released hydrogen (H) is returned to the evaporator (3).
The different circuits are closed and the process can start again.
Refrigerant circuit: Cooker (1), condenser (2), evaporator (3) and absorber (4).
Advantages and disadvantages of the different cooling box systems
| Passive cooling box | Thermoelectric coolbox | Compressor cooling box | Absorber cooling box | |
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| Advantages: | - inexpensive - noiseless - low weight - no energy source required on site | - low intrinsic weight - coolant-free - noiseless, since no mechanically moving parts (except fans) - economical | - large cooling area - energy-efficient cooling - freezer function possible | - noiseless - power supply with gas or electricity |
| Disadvantages: | - no active cooling capacity - contents must be pre-cooled | - low cooling power depending on the outside temperature - high power consumption | - compressor operating noise - heavy weight - power supply required | - high energy consumption - floor space level required |
What should be taken into account when purchasing a cooling box?
Which model and, above all, which technology you choose depends largely on the purpose of use.
Technical design
The passive cooling box is primarily used in the leisure sector. Drinks, grilleed meat and other heat-sensitive goods such as chocolate can be stored very well for the barbecue excursion at the bathing pasture. Here the box plays its big advantage: It does not need any energy supply.
Those who travel a lot by car or truck will probably fall back on an active cooler. Especially since the vehicles have either a 12 or 24 V DC voltage. And the manufacturers take this into account and put their cooling boxes exactly on this power supply. There is no need to integrate a small power supply unit into the box, so that it can also be operated on the 230 V mains voltage in stationary operation.
Whether you decide on a thermoelectric cooling box or the variant with compressor is up to each user. However, if a freezer box is required, thermoelectric devices will be eliminated from the outset.
If, for example, no power connection is available in the weekend house, an absorber cooler plays its decisive advantage. These coolboxes can also be operated on a standard gas cylinder. This makes these coolboxes the first choice when camping and caravan. By the way, in conjunction with an electrically operated heating system, the silent absorber system is also ideal for mini fridges in hotel rooms.
Energy supply
Once you are clear about the technical design, the next question is the energy supply. It is not only important that the cooling box is supplied with power on site. When connecting to energy sources with limited power, such as a stationary vehicle or an island solar system, it is important that the cooling box has a low power consumption. If there is no indication of the energy efficiency class, a look at the technical data may help. In addition, the cooling box should be equipped with an undervoltage detection. This effectively prevents the harmful deep discharge of solar or car batteries.
Correct size
Another important purchasing criterion is the size or capacity in liters. One should consider how much liter of storage is actually needed. Because the larger the liter volume, the higher the required cooling capacity. However, the external dimensions must also be checked. It is certainly wonderful when many large PET bottles with 2 liters of content fit in the box. However, the box must not be too large for the planned installation location, especially in vehicle operation. If the cooler box is also to be transported by hand, the weight also plays a decisive role in addition to the size. Everyone knows this, who has worn a well-filled cool box with 40 liters capacity.
Frequency of use
If the cooler box is used only once or twice a year, purchasing a high-quality and expensive box makes far less sense than when the box is in use almost the whole year.
Frequently asked questions about coolboxes
Where is the best place for the cooler in the car?
The most important rule for storing the cooler box in the car is that the cooler box must not shift. A suitable place in the vehicle would be, for example, behind the front seats or in the boot. However, the latter should be secured with straps and should be stable. A strap or hook-and-loop fastener certainly provides good service.
If the cooling box is to be placed on the rear seat, the box should be fixed with a strap or similar to prevent unintentional slipping.
Can ich use my existing cooler battery set in an active cooler?
Yes, of course! It is even beneficial when frozen ice packs are added to the boxes. The boxes do not have to provide as much cooling power and an interruption of the power supply can be easily bridged.
Can ich combine a cooler and a cooler?
Yes, that makes sense, but only for passive cooling boxes. For example, a frozen chicken can first be wrapped in a cooler bag and then placed in the cooler box. In case of high heat or long transport, two or three cooling bags can be packed together. However, the capacity of the box (usually specified in liters) must then be large enough.
How long does the electric cooling box last when it is connected to the car battery?
Electrical cooling boxes usually have – exceptions are possible – 12 V connections for a car and 24 V connections for a truck
If the cooling box on the car battery is intended to be used for a longer period of time, the box should have an integrated voltage monitor. This allows the box to be switched off automatically. However, the power consumption from the car battery over several days should only take place in exceptional cases. Due to the relatively high power consumption, it is recommended to select a different power source outside the vehicle for thermoelectric models as soon as the destination has been reached.