Make in India: Cold Storage Rooms | part two

May 9, 2016

In the previous article, insights were give about material use and insulation capabilities to build adequate cold storage rooms.

In the concept of cold storage pre-cooling is essential. Pre-cooling helps to maximize results for both earning capabilities of Farmers and costs. In the current article I want to share some ideas about how to furnish the cold storage room itself. Furnishing well will influence the extension of the ripening period of a crop positively. The most important suggestions to take into account are listed below:

Use of crates

For the storage of the crops it is recommended to use well ventilated pallets, crates, boxes or bins.

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Movement of air through the Cold Room

Why? It is important that the cold moving air can easily go through to remove the heat coming from the products. For best result the crates should be stacked so that the moving air can contact all the container surfaces for adequate and rapid cooling. Ventilated crates can be used as they speed-up the cooling rate. The cool air should be divided equally over all crates that are placed.

Location of crates

The storage crates must be stacked to form air-channels which are 4 to 6 inches wide (10 to 15 cm) to help direct the air movement. There should also be space between the product and walls to allow refrigerated air to absorb the heat of conduction through the walls. In the figure below an overview is given of how the crates should be placed in the IGLOO design. A passageway is created in between the crates. This location set up will result in a better air circulation and the crates can easily be replaced or taken out when crops need to be sold. (Board, 2010)

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Overview of the location of the crates

Maximize capacity in the cold room
Different concepts are used the get the most out of the crate positioning capacity. The dimensions of the crate are a given (WxHxL):360x305x542mm. Since the roof height of our SINHBUILD concept is 2440mm, the maximum amount of crates that can be stacked is seven (height of 2135mm). We favor the concept in which three lines of crates are taken into stock. In between the crates a space is created of 10cm to allow refrigerated air to absorb the heat from any direction. On the right two lines of crates are placed on their long side. On the left one line of crates is place on their short side The passage width between the lines of the crates is 668mm which gives the opportunity to move a crate easily through (a crate is 542mm on the long side). The total amount of crates that can be stored is 210.

Shape and dimension of used crates
As mentioned before it is recommended to use ventilated pallets, crates, boxes or bins. Jut or nylon bags are not recommended since these materials won’t ventilate in a proper way. Further exact dimensions are not required because the only requirement is that the storage should be ventilated well.

Storage after harvest
It is recommended to transport all harvested crops to the cold room as rapidly as possible. For fresh crops one hour time loss at the field by a temperature of 35°C between harvest and pre-cooling can reduce quality as much as 20 hours in storage under proper conditions. Delay in pre-cooling or cooling overall results in loss of moisture from the product, causes weight loss and combined with active micro-biological organisms result in deterioration of quality and value loss.

Use of Cold Room Door
The cold room door is the only connection to the outside temperature and is thereby the most important point which should be taken into account considering cold air loss. The loading rate is another factor referring to the amount of use of the door. The higher the loading rate, the more energy loss or cold air loss is created. Generally the refrigeration system capacity is based upon 4% to 5% loading rates of the total cold store capacity. The loading pattern is also a design consideration for sizing the storage chamber capacity for optimal utilization and performance. It is therefore recommended to store all crops only once a day (as little as possible). The frequency of entry is then reduced to its minimum. Additionally it is recommended to store the crops in the morning or in the evening since the outside temperatures are relatively lower at these times. In Gujarat at noon the outside temperature is at its highest point which will result in a bigger delta T (temperature difference) between inside and outside and additionally more energy loss. (Board, 2010)

Conclusion

  • A perfect cold storage room needs a pre-cooling area. In the cooling area itself crates are used. Most important feature of crates is the support of ventilating cold air throughout the cooling unit.
  • The crates should be stored in a way that supports air flow.
  • The crates storage plan should allow maximization of number of crates.
  • The cold room door, and the use of it, is very important as it may ruin the efficiency of your unit.