Cold Storage Rooms

To determine the cooling requirements for cold rooms, attention must be paid to the requirements of the commodities stored; humidity content, air changes, cooling or freezing duration, type of storage, etc. Also, consider the specific heat of the goods, internal environment, method of manufacture, position, heat from lighting and movements within the cold store.

Calculation of the cooling requirement takes the following form:

  1. Cooling/refrigeration of the goods (cooling to the freezing point – freezing – super cooling) (Q = m x cp x ~t); if goods are to be frozen solid, the necessary heat must be removed at the freezing point, and, subsequently, the specific heat of the frozen goods is lower; the humidity extraction is approximately 5%.
  2. Cooling and drying of the extracted air.
  3. Heating effects t rough walls, ceiling, floor.
  4. Losses: movements in and out of storage (door opening), natural and electric lighting, pump and ventilator operation.
  5. Condensation of water vapour on walls

 

The cold storage of freshly slaughtered meat is cooled from 303.15 K to a temperature of 288.15 K. This is achieved by placing it in a temperature of 280.15 – 281.15  K at a relative humidity of 85-90 % in the pre-cooling room for 8 – 10 hours, and then storing it at 275.15 K – 281.15 K at a relative humidity of 75 % for up to 28 – 30 hours in the cool room. Cooling and storage takes place separately. Weight loss over 7 days is 4 – 5 %. Today, rapid cooling is used increasingly, no pre-cooling stage, meat is cooled from a slaughter temp. of 303.15 K to a storage temp. of 27 4.15 K, with 60 – 80 circulations of the air per hour and at a relative humidity of 90 – 95%.

storage temperature and duration of storage

Meat cooling and refrigeration

The freezing process changes the condition and distribution of the water in meat, while the meat composition remains unchanged.

Beef is frozen to 261.15 K and pork to 258.15 K, at a relative humidity of 90 %.
Duration of freezing: mutton, veal, pork, 2 – 4 days; beef, hindquarters 4 days, forequarters, 3 days. Correct thawing period: 3 – 5 days to 278.15 – 281.15 K, restores the meat to a fresh condition.

Recently, mainly in the USA, rapid freezing methods have been employed, at temperatures of 248.15 – 243.15 K, involving 120 – 150 air circulations per hour.
The advantages are: lower weight loss, increase in tenderness, replacement of the curing process, lower liquid loss, good consistency and preservability after thawing.

Storage duration is dependent on the storage temperature; for example, for beef the storage duration is 15 months at 255.15 K, 4 months at 261.15 K and 3 months at 263.65 K.

Cold room volume: 1 m3 is suitable for the storage of 400 – 500 kg of mutton, 350 – 500 kg of pork, 400 – 500 kg of beef, with a standard stacking height of 2.5 m.

 

Refrigeration of fish
Fresh fish can be maintained in this condition on ice at 272.15 K and at a relative humidity of 90 – 100 % for a period of 7 days. Longer storage times can be achieved through the use of bactericidal ice (calcium hypochlorite or caporite). For even longer storage, rapid freezing to 248.15 – 233.15 K is required, if necessary use glazing with fresh water to keep air out and prevent drying up. Fish crates are 90 x 50 x 34, giving a weight of approx. 150 kg.

 

Refrigeration of butter
Butter refrigerated to 265.15 K has a storage duration of 3 – 4 months and a duration of 6 – 8 months at a temperature of 258.15 – 252.15 K. Lower temperatures can provide a period of up to 12 months. The relative humidity should be 85 – 90 %. Butter drums are 600 mm high with a diameter of 350 – 450 mm, resulting in a weight of 50 – 60 kg.

 

Refrigeration of fruit and vegetables
Immediate cooling is required, since a reduction of temperature to 281.15 K delays ripening by 50 %. Storage duration depends on air quality (temperature, relative humidity, movement), variety, maturity, soil quality, fertilizing, climate, transportation, pre-cooling, etc.

 

Taken from: Architects’ Data by Ernst and Peter Neufert

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