The use of existing cold storage rooms is one of the most common system. The cold air flow across the packed containers and refrigeration capacity have to be increased in order to guarantee the adequate air circulation with respect the normal flow in a cold storage rooms. In the room precooling the distribution of pallet and container respect to the air flow is determinant. Air should flow in channels created between the rows of pallets. Pallets and container should be aligned in order to avoid obstruction of the air flow between and across the container. Adequate precooling rate are obtained if is possible to maintain on and around the product the cold air speed close to the value of 0.5 m/s and the refrigeration power inside of the cold storage room should be more than 0.28 kW/t considering a product average density of 0.20 t/m3.
It is necessary sometime to improve the air movement inside the cold room with mobile fans or/and to put the warm grapes quantity in proportion to the installed cooling power (generally this amount range between the 10÷20% of the total storage capacity of a cold storage room).
A great advantage of this technique is that the pallets may be cooled and subsequently stored in the same place without other moving. The design and subsequent use of the plant is very simple and, in relation to the precooling time which longer than other methods, the power of refrigeration machinery results lower respect to faster methods.
In contrast, the disadvantages are that longer pre-cooling time do not permit a dynamic organization of production. Long precooling time imposes a long pause in handling and rapid shipping is not possible. In the case of table grapes for long term storage, deterioration due to the long time exposure to an incorrect temperature, makes room cooling to be too slow.