General attention points to improve the performance of a passive cooling system
When we want to preserve the temperature of time-temperature sensitive products such as pharmaceuticals - healthcare products - food perishables - chemicals etc... with insulation material or a thermal packaging system, a passive cooling systems is created. This therefore means that the insulation quality and the set-up of the thermal packaging will determine the quality and performance of the passive cooling system. This page contains some practical tips and attention points to improve the performance of passive cooling systems.
Use the correct insulation material quality and insulating procedures
- If you use the wrong insulation quality, you will create wrong temperature results
- If you use the wrong insulating procedures, you will create wrong temperature results
- If you use the wrong protocol, you will create wrong temperature results
- If you use the wrong set-up of the thermal packaging, you will create wrong temperature results
Avoid thermal bridges - cold bridges
Ask yourself, what is the purpose of high quality building insulation in your house if you leave the door or window open? Indeed, nothing. This is the same with the temperature preservation of products and goods. If the insulation material or the set-up of the thermal packaging has "open cold bridges" where the air can float in or out of the thermal packaging system (convection flow), the temperature of the products will change vary fast depending on the air-exchange volume of the cold bridge or thermal bridge. Therefore it is absolutely important that cold bridges (thermal bridges) are avoided at all times
Thermal equilibrium - Insulating location
A. Impact during the packing process time
An attention point that is very often overlooked when passive cooling systems are applied, is the location where the time-temperature sensitive products are insulated or packed in the thermal packaging system. Most of the time the packing of the time-temperature sensitive products is done in an environment where an ambient temperature is generated (+18°C to +20°C) seeing this is the ideal work temperature to work in. Yet the question that most be asked is what the impact of this ambient temperature will be on the temperature of the time-temperature sensitive products. If these products have a temperature of let's say (+5°C), than the ambient temperature of (+20°C) will certainly have an impact. A thermal equilibrium will be created between the two temperatures. The next question that we than need to ask is for how long the products (+5°C) are exposed to the ambient temperature of (+20°C). This duration will determine the value of the thermal equilibrium and therefore the impact on the product temperature and its quality.
B. Impact during the closed thermal packaging time
When the products are packed in the thermal packaging system, the impact of the packing location will still continue. As we have seen in previous point, products (+5°C) were packed in an ambient temperature environment (+20°C) which also means that during the packing, this ambient air has been packed inside the thermal packaging. With other words, ambient air (+20°c) is now together with the products (+5°C) in the thermal packaging system. So even when the thermal packaging is closed, both temperatures in the thermal packaging system will still have a certain impact on each other and create a certain thermal equilibrium. The thermal energy of both temperature items will determine the result of this thermal equilibrium. Fact is that in a lot of cases, the product temperature is already influenced before the product is even shipped. This due to temperature mixtures in the packing locations.
Thermal equilibrium - pre-cooled insulation material + thermal accumulation
Another attention point that needs to be taken into consideration in temperature preservation of time temperature sensitive products with passive cooling systems, is the temperature of the insulation material or the thermal packaging system that is to be used. The insulation material or packaging system will have a certain temperature and will have an impact on the temperature of the time-temperature sensitive product if both temperatures are different. Again both temperatures will start to mix and create a certain thermal equilibrium in which the results of this equilibrium will be determined by the thermal energy of both items, the products and the thermal packaging. To avoid this temperature mixture it can be advisable to pre-cool the insulation material or the complete thermal packaging system to the same temperature as the temperature of the products. Please also be ware of thermal accumulations when the thermal packaging system is consistent out of multiple materials or substances like gel packs of ice packs. When each different material has a different temperature, a thermal accumulation can appear where again a different thermal equilibrium is created.
The above tips are just a few of the many possible faults that can be made in temperature preservation with passive cooling systems. Passive cooling systems are very reliable in temperature preservation and can close the cold chain completely from A to Z, yet they are very complex and need to be applied properly according to the thermally correct procedures. If not, strange and not understandable results will be noticeable which gives a lot of people headaches in finding the answer and solution. More practical tips can be found in our published book "Cold Chain Implementation Plan" which can be found on this website.
More advice in our published books
- TRM-plan "Temperature Risk Management"
- Cold Chain Impelamentation Plan
- Advanced temperature trailer mapping