Refrigeration engeneering

Refrigeration engeneering

Effective cooling

Insulated containers are designed to maintain the cold chain during transport. The insulating capacity of the container protects your products from the ambient heat. Adding a cold source increases the cold storage time during transport.

The same insulated container can be used to transport chilled (fresh goods) or frozen goods. It is the refrigeration system selected that makes the difference.

OLIVO offers 2 cooling solutions

Cooling capacity

The products stored at the right temperature are loaded into the insulated container.

 

Cooling the container is intended to compensate for the entry of heat into the insulated container and keep the interior temperature constant throughout the transport time.

 

With the right amount of frigories (cooling capacity) the temperature of the load will remain stable until delivery and will not gain or lose heat.

Thermal analysis

The rate of heat loss of the insulated container is known: this is the K factor value.
The amount of cooling required depends on two things: the length of cold storage required and the external atmosphere during transport.

 

Remember that you will need to inform us about your transport conditions: we will be able to calculate the cooling load required very quickly. This will enable you to continue planning your project without any surprises regarding the technical equipment required and the economic impact.

 

Analysis of the thermal requirements is a service we offer entirely free of charge and with no obligation on your part. Our staff are always pleased to be able to share OLIVO’s expertise.

Pre-cooling

It is recommended that the insulated container be pre-cooled before loading it with the goods in order to avoid them being heated up by coming into contact with warm container sides.
Ideally the insulated container should be kept in a cold room, empty and with the door or lid open for 2 hours.
If it is not possible for you to store the insulated containers in a cold room, the cooling capacity required for the transport may be greater in order to integrate the energy consumed to bring the inner sides of the container to the right temperature.
Although it will vary according to the conditions, the energy required for pre-cooling the inside of the container represents approximately the amount of energy consumed over 2 hours of transport.

Mastering the Energy

OLIVO cooling consumes very little energy as the heat loss during transport is both known and limited.
Delivering to several customers using a refrigerated lorry uses a lot of energy. Every time the door is opened the air inside the vehicle is heated up and cooling it again rapidly consumes an enormous amount of energy.

 

In an OLIVO insulated container the goods and the cold are confined in a reduced space. The thermal balance remains stable and undisturbed, until the door is finally opened to empty the container.
So stop wasting energy and organise the distribution of your goods with totally silent refrigerated containers.

Green energy

The refrigeration systems offered by OLIVO use the physical phenomenon of natural convection.
With no forced ventilation, there is no need for electrical energy inside the container – the cold moves by convection. The grooves on the inside walls optimise the circulation of the cold air to produce a homogeneous interior temperature.
OLIVO refrigeration systems use the principle of phase change material (PCM) that releases frigories when it melts:

  • melting of a sub-zero eutectic solution
  • sublimation of dry ice

OLIVO eutectic solutions are stable, non-toxic and do not degrade over time.

The CO2 constituting the dry ice is a “2nd use” gas. It is CO2 generated by industrial processes that has been recovered and purified before being reused to make dry ice. Using dry ice does not emit more CO2 into the atmosphere.

Temperature control

OLIVO recommends checking the temperature of the load during transport, using temperature recorders. You will not need to equip all your insulated containers with recorders as the control can be done by sampling.
Checking the temperature on arrival with a probe-type thermometer is a more delicate operation:

  • as soon as the container is opened, the air inside it heats up very quickly and this can have a negative influence on the measurement
  • thermometers can have quite long stabilisation times, which can also affect the measurement
  • measuring the core temperature of a foodstuff with a probe is destructive and rather difficult to do when the goods are frozen

Air temperature

A recorder measures the air temperature inside the cold insulated cabinet. The air temperature can vary by a few degrees from the actual temperature of the load. This is a normal phenomenon:

  • at the beginning of the transport the interior air is colder than the load as the cooling system and the convection are just starting up
  • during transport the air temperature and the temperature of the goods are balanced by convection
  • at the end of the transport, the interior air may be slightly higher than that of the goods if the refrigerant has been used up

You will therefore need to include in your air temperature control a tolerance of several degrees. This tolerance must be defined taking into account the sensitivity of the goods in question. It will be very narrow for a sensitive product such as minced meat, but may be much wider for cut meat.
The precise tolerance appropriate can be worked out by experimentation. This will involve recording and comparing the respective changes in the air temperature and the temperature of the goods.

 

The temperature inside an insulated cabinet remains very homogeneous. The differences observed between the warmest and the coldest points are below the 2°C tolerance accepted for the maximum temperature variation.

Fill rate

It is pointless transporting empty space: optimise your transport costs by ensuring containers are full of goods.

 

A minimum load rate of 80% is recommended.

 

The container fill rate does not directly influence the amount of cooling required. But it will contribute to achieving a good thermal result.
The homogeneity and stability of the interior temperature are better in a well filled refrigerated container.

Door opening

Normally, once loaded, the insulated container will be closed and only opened again when it reaches the recipient.
Nevertheless, sometimes delivery rounds are organised with several recipients whose goods are transported in the same insulated container. This means the container will be opened several times during transport to take out the different recipients’ orders.
OLIVO has checked whether this practice is acceptable from a thermal point of view and if opening the door could be compensated for by the refrigeration.
The packages must be clearly marked and the time the door is open kept to a minimum.
On the graph opposite:
The transport of the chilled goods takes 12 hours and includes opening the door 12 times, with an exterior temperature of +30°C.
The graph shows that the air inside the container (in blue on the graph) heats up very quickly as soon as the door is opened, but the peak heating time does not exceed 30 seconds.
It can be seen that the core temperature of the product (shown in red on the graph) remains flat during the door openings: no heating of the goods is observed.
This practice should be used with moderation and after checking repetitiveness. Each time a recipient’s order is removed, the load inside the container is reduced. There is therefore less thermal inertia as the distribution goes on, while the volume of interior air liable to be heated up increases. Such a procedure needs to be analysed and the refrigerating mass must be able to compensate for the input of warm air.