Modification And Performance Evaluation Of A Cold Room Storage Structure

iii.    Air circulation: Cooling in cold room of accomplished by transferring the heat to an air stream. Heat to be transferred depend in the product temperature the respiration rate in the case of fruits and vegetable and the heat entering the storage room by heat transfer through the walls are by air exchange. During the cooling down period a large heat load must be removed and during the storage period it is important to reduce temperature differences to a minimum. However some spread of temperature must be accepted in order to allow transfer of heat from the room to the cooler as well as from the produce to the air. Air is the transport vehicle of heat; therefore air circulation needs full consideration.(Anon, 2000).
iv.    Ventilation: Because of economic considerations, ventilation air change or air renewal (introduction of outside air) should be kept to the minimum only clean, uncontaminated and odor free air should be supplied to the cold store. Some ventilation may be essential in the storage of fruits, vegetables and other commodities such as cheese, which give off odoriferous products. Often enough are supplied by infiltration, change in atmospheric pressure, opening of doors, etc.But for certain food stuffs, such as citrus, special facilities for ventilation may be necessary
v.    Volatile Substances: Because certain produce (such as fish, citrus, apples) give off strong specific doors and other produce (such as eggs, butter, meat) may absorb them very easily, the cold storage operator must be very careful in storing different produce or even different varieties of the same kind of produce in the same store at the same time, ventilation may help here. Even if different foods are not stored in the same room at the same time, the second lot of food may be tainted by doors, which remain from the first lot. This may also apply to odorless volatile substance, such as ethylene, produced by one food stuff but which are detrimental to another. Therefore, storage rooms should be thoroughly cleaned from time to time and deodorized if necessary.
vi.    Hygiene: cleaning is of course, also necessary to maintain the cold store in hygiene condition because microbial growth can be rapid, of temperature above 00c. In addition to frequent removal of dirt and an food debits the following point may be noted.
(i)    Mold growth appearing on walls and ceilings may be indicative of detective insulation and for detective moisture vapor barriers apart from renewal of the affected area, only palliative measure, such as frequent disinfection can be used.
(ii)    When mold attack occurs on walls, ceilings, dusts, pillars etc. which are in good physical condition through cleaning and disinfection should be undertaken at the first opportunity.
 (iii)    Fungicidal additive to wall paints may be useful at high relative humidity in the store.
viii    Condensation: On removal from cold stores care must be taken to present condensation on the surface of the cold produce, this will happen when the dew point of the air is higher than the surface temperature of produce or of its packaging materials. The package in which the commodity is packed may act as a barrier to condensation on its content. Tight packages for dried fruit, shelled nut and canned good, offer good protection. Sometimes a pallet load of packages can be covered until it warns to above the dew point of the surrounding, thus avoid heavy condensation. If condensation occurs, step must be taken to dissipate condensed moisture as soon as possible.
2.7    Principle of Refrigeration
The components of vapor compression refrigeration system are evaporator, compressor, condenser and the expansion valve. Figure 2.1Schematic diagram Processes of refrigeration employed in the cold room