Since single temperature-controlled refrigerated containers can not meet the storage needs of goods with different refrigeration temperature requirements, under the current conditions of diversification of cold chain logistics products, multi-temperature control Refrigerated Containers are more in line with the new characteristics of cold chain logistics. At the same time, the application of multi-temperature control Refrigerated Containers is conducive to saving logistics costs and integrating logistics resources, which is a new trend in the development of cold chain logistics.
Cimc Yangzhou Base analyzes the application of multi-temperature control Refrigerated Containers in multi-temperature control areas, starting with the structure of Refrigerated Containers and refrigeration systems.
1 Advantage Of Multi-Temperature Control Refrigerated Containers
The wide use of Refrigerated Containers in the logistics system brings great convenience to everyday life. Currently, most Refrigerated Containers use single-temperature refrigeration to maintain the refrigeration or freezing temperature required for the cargo in the box. Because different fruits and vegetables have different requirements for refrigeration temperature, unsuitable refrigeration temperature will affect the storage effect, accelerate the loss of nutrients of fruits and vegetables.
Single temperature refrigeration method can not meet the refrigerated and refrigerated cargo requirements simultaneously, especially in small-batch, multi-varieties of cold chain logistics needs on the short plate obvious.
Multi-temperature control Refrigerated Containers make up for the defects of single temperature-controlled Refrigerated Containers, can realize refrigeration and freezer control to meet the needs of storage and transport of goods with different refrigeration temperature requirements simultaneously.
The advantages of multi-temperature control Refrigerated Containers are mainly reflected in improving cold chain transportation, storage efficiency, and improving the utilization of Refrigerated Containers.
The basic working principle of multi-temperature control Refrigerated Containers is the same as household Refrigerated Containers, dividing the interior space into multiple storage rooms as needed, separate temperature control for each storage room to meet the needs of different cargo refrigeration or freezing.
Multi-temperature control Refrigerated Containers can be divided into double temperature Refrigerated Containers, three temperature Refrigerated Containers, and multi-temperature Refrigerated Containers, where more applications are double temperature Refrigerated Containers, followed by three temperature Refrigerated Containers.
2 Multi-Temperature Control Refrigerated Box Structure
Multi-temperature controlled Refrigerated Containers are usually separated internally by fixed or removable separators.
The size of the compartment separated by a fixed divider cannot be adjusted.
The advantage of using a movable separator is that it can adjust the size of each box room according to the loading volume of different cargo, used more flexibly and conveniently. Its disadvantage is better sealing than the fixed separator, easy to cause taste and heat loss between the boxes. Removable partitions can be divided into removable hardware separators and soft removable separators.
The soft removable separator has the advantages of light, good sealing (especially easy to seal the corner of the box). Still, its structural strength is less than the removable hardware separator.
Separators are arranged in the refrigerated box usually have two forms of a horizontal and longitudinal divider. The choice of separator form and box separator form needs to consider the refrigerated box’s specific use, the shape and size of the cargo loaded, and other factors.
In addition to the regular back-end door, the multi-temperature control refrigeration box is generally also on the side panel or other convenient cargo loading and unloading place additional door. The main purpose is to ensure that the box room can be independent loading and unloading without interfering with each other.
3 Multi-Temperature Control Refrigeration
Multi-temperature controlled Refrigerated Container refrigeration methods usually have single cycle refrigeration, dual cycle refrigeration (or multi-cycle refrigeration), and so on.
There is only one evaporator in a single circulating refrigeration system, which drives two chambers of refrigeration and the freezer.
When the cold machine is running, two chambers are refrigerated simultaneously. As long as one of the chamber temperature differences, the compressor starts to work. Then the other chamber is forced to refrigerate so that the air conditioning through the whole box large circulation.
This circulating cooling mode is prone to frequent chiller compressor start-up, high noise and power consumption, uneven cooling, especially when there is a Refrigerated Container and freezer chamber. In addition, the freezer chamber tends to be overcooled.
Two evaporators are installed in two chambers, each with a solenoid valve to control the coolant flow, thus achieving the individual cooling effect of each chamber and more accurate temperature control.
Dual-cycle refrigeration has a stronger cooling capacity, and energy-saving is better than single-cycle cooling. At present, most multi-temperature controlled Refrigerated Containers use double-cycle refrigeration for multi-temperature control.
Taking into account the relatively large volume of the container, to ensure uniform cooling, the evaporator uses air-cooled form to refrigerate, that is, through the fan inside the evaporator to send the air conditioning to all parts and forced cooling cycle through the return air to ensure the temperature balance. To ensure that the air conditioning can reach all parts of the box, the evaporator can not be installed in the dead corner of the box and should try to let the outlet in the relatively narrow direction rather than the wider direction to avoid the blindness of the air supply.
Single- and dual-cycle refrigeration is controlled by a single host, which is at the core of the entire refrigeration system, maintaining the operation and energy.
At present, there is a wide variety of cold machines used for Refrigerated Containers, from large categories can be divided into sea chillers and car chillers. However, multi-temperature control Refrigerated Containers are mainly used for land transport, so cold car machines generally use and support it.
Car cold machine is divided into trailer unit chiller and truck unit chiller.
The refrigeration system of the truck unit chiller is divided into non-independent (car drive) and standalone (self-driven).
Non-stand-alone chillers use truck engines to drive refrigeration unit compressors or power generators using generators to drive refrigeration unit compressors. Although non-independent units have limited cooling capacity due to the lack of their engine, especially in traffic jams and idle situations, especially in case of truck engine failure, non-independent refrigeration units will not work properly, which will undoubtedly affect the quality of food in the box and even lead to food change Quality.
Standalone chillers come with their engine (usually diesel) to drive the refrigeration system independently without needing a vehicle’s engine.
Due to the above disadvantages of non-stand-alone chillers, it is generally recommended to use standalone chillers.
The structure of the refrigeration unit is divided into one machine and a split machine.
The all-in-one unit combines the evaporator and the main unit. For multi-temperature control, only one remote evaporator must be installed, connected by a pipe to the host, while opening a large hole in the insulation board in the Refrigerated Container so that the evaporator extends from outside the box to the box. In the case of the placement of the evaporator has special requirements, and the one machine that can not meet the installation position requirements can be a split machine.
4 Multi-Temperature Control Refrigerated Container Cold Machine Selection
Land refrigerated transport cargo is usually pre-cooled before loading. The role of the chiller is mainly to supplement the heat lost due to the heat leakage of the box. The chiller’s power can be calculated based on the total leakage heat of the Refrigerated Container and the air of the goods (open doors frequently must also be considered when opening the door leakage).
At present, most chillers can meet the ambient temperature of 38℃, and the temperature in the box is -20 ℃ refrigeration requirements.
According to the cold machine parameters and relevant experience values provided by cold machine suppliers, with the development of inter-city point-to-point transport to scale, the optional cooling capacity of about 8000-13000W when the cold machine is more appropriate. Urban distribution to small lot, variety, multi-delivery point, optional 0℃ cooling capacity is 3OOO O~5OOOOW cold machine is more suitable.
5 Concluding Remarks
Multi-temperature control Refrigerated Containers meet the needs of diversified cold chain logistics, improve logistics efficiency, save logistics costs and resources have far-reaching significance.
A multi-temperature control Refrigerated Container is a complex system product. Multi-temperature control requires both from the cabinet itself, good design, planning the cabinet structure, reasonable choice of supporting cold machine system, scientific arrangement of the evaporator to ensure the quality of goods and improve transport quality.