In the following, the most important features of low-temperature applications in the temperature range from below 0°C to -160°C are explained and the potential required in the following applications is shown.
Due to the development of a COVID-19 vaccine and its special requirements, transportable low-temperature storage rooms are increasingly becoming the focus for upcoming distribution. Accordingly, the market is currently being flooded with solutions, making it increasingly difficult to distinguish between a suitable and an unsuitable product. With our overview page we create clarity and show the most important features that a low-temperature storage room should have.
The greater the outer surface and the temperature differences between the ambient and storage temperatures, the greater the heat input. Good insulation is therefore essential for cryogenic storage. One possibility is to increase the wall thickness, but above a certain point this hardly brings any improvement in percentage terms and also limits the storage volume. Combinations of PU foam and integrated vacuum panels can help, resulting in low wall thicknesses with high insulation values. The outer surface is significantly influenced by the geometry. Therefore, it makes sense to keep the ratio of volume to surface as small as possible. The quotient of the outer surface to the storage volume, which is referred to as the specific surface, is used as a reference value. To illustrate, consider multiple, individual refrigerators versus one large storage room. As a rule, larger machines are more efficient than small ones. But even if many refrigerators are operated in the same way compared to a storage room, they differ significantly in terms of energy consumption, because the individual refrigerators have a significantly larger specific surface area than the storage room. This can account for a factor of 10 in energy consumption.
Nature provides a perfect example here. When looking at two different species of penguins based on their habitats, you can see how drastic this influence is:
For low-temperature storage, it is important to have a correspondingly high-performance and efficient refrigeration technology. The energy input from the environment (transmission), waste heat from electrical installations and charging and discharging result in a corresponding power requirement. In addition, the moisture must be constantly removed from the cold room.
In the case of refrigeration technology, it must also be ensured that it does not fall under the current regulations or is regulated by them. This currently affects the "Global Warming Potential" (GWP) value, which is reduced to an average of approx. 500 by 2030 due to the quota regulation of the European F-Gas Regulation and already bans refrigerants with a GWP of over 2500 for normal applications.
We deliberately use the natural refrigerant ambient air for cooling. This makes you future-proof and environmentally friendly. In addition, you do not need any additional safety measures as with other natural refrigerants such as ethane, ammonia and CO2.
The low-temperature refrigerant R23 with a GWP of 14900 can still be used due to an exception in the regulations. However, this is definitely not advisable. It is currently massively affected by the shortage due to the quota system. New systems with this refrigerant are dubious and harmful to the environment. To make the environmental impact tangible, let's compare the CO2 equivalent of one kilo of R23 to the distance a car could travel to emit the same amount of CO2. In concrete terms, this means that a single kilo of R23 has as much global warming potential as the amount of CO2 that a car would emit by circling the earth twice. We deliberately use the natural refrigerant ambient air for cooling. This makes you future-proof and environmentally friendly. In addition, you do not need any additional safety measures as with other natural refrigerants such as ethane, ammonia and CO2.
Opening the access to the storage room creates a brief, large flow of air, which brings a lot of warm air into the cold room. This has a drastic effect, especially in low-temperature applications, since the difference in density between the storage room and the anteroom is high due to the temperature difference. This means that the cold air falls into the anteroom when the door is opened. Thanks to the integration of a lock, which as a buffer zone is only tempered by transmission and convection from the cooling chamber, the influence of loading/unloading remains low.
With conventional refrigeration systems, an evaporator is required in the cold room. This is equipped with a fan and a fan ring heater and must be thermally de-iced at regular intervals. Both components and the de-icing process bring a lot of heat into the cold room. In addition, no active cooling can take place during defrosting. With open cold air chillers, an evaporator is no longer necessary, which eliminates these heat sources and allows continuous cooling. As a result, the low-temperature storage room with cold air chillers is more efficient. Furthermore, all electrical installations should be well considered and suitable for the storage temperature
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