Ship's Stores Refrigeration System

The ship's stores refrigeration plant is served by two compressors located in the engine room.

The ship's stores plant aft is the direct expansion type and uses Freon-12 as the refrigerant. Each of the compressor units has a capacity of 8.55 tons at -15° F. suction temperature and 105° F. condensing temperature. The plant supplies liquid refrigerant to the evaporators to maintain the refrigerated spaces listed below at the temperature indicated.

Compartment     Temperature    Type of Evap.   Quantity
Fish room           0° F.         Finned coils       57 sq.ft. surface 
Meat room           0° F.         Finned coils       739 sq.ft. surface 
Frozen foods        0° F.         Finned coils       303 sq.ft. surface 
Dairy room          32° F.        Cold diffuser      1 
Fruits & veg. rm.   32° F.        Cold diffuser      2 
Potato room         45° F.        Cold diffuser      1 
Cheese room         40° F.        Cold diffuser      1

The plant also provides refrigeration for two service box brine coolers, two ice water coolers, and may be used to serve the auxiliary water chiller.

The ship's stores plant consists of two compressor units inter-connected. One compressor can handle the entire load with the other compressor remaining as standby or, if necessary, being using to operate the auxiliary water chiller. Hot gas defrosting is provided for the coils in the 0° F. compartments. The entire plant requires a charge of approximately 434 lbs. of Freon-12 for proper operation.

The service box brine coolers supply the following service boxes with brine which is a 30% by volume solution of propylene glycol with a freezing point at +7° F. All these boxes are maintained at 40° F. using pipe coils.

Service  Volume 
Officer's mess  14.5 cu.ft. 
Crew's mess 14.5 cu.ft. 
Crew's pantry   14.5 cu.ft. 
Dispensary  4.0 cu. ft. 
Club bar box    1.0 cu. ft.


Ship's Cargo Refrigeration System

This ship's cargo reefer system located on the forecastle deck is identical to the ship's store plant except that it uses glycol for condenser cooling. These units supply R-12 to two evaporator coils located on either side of the machinery space. Each box can be used as a chill or a freeze box since each has two TEV's (one 32° and one 0°).

The auxiliary water chiller can be used with either brine or water and it may supply the air conditioning system under low load conditions or the cargo refrigeration plant condenser. The brine solution for this service is a 20% by volume propylene glycol solution with a freezing point of +19° F. The chiller is a shell and tube heat exchanger with water or brine flow through the shell and refrigerant through the tubes. It will cool 300 gpm of propylene glycol from 47° F. to 45° F. with an evaporating temperature of 37.5° F. The chiller cools the glycol for use as a cooling medium in the forward reefer units.

The low temperature (0° F) compartments are provided with a wall type direct expansion cooling coils. The coils are constructed of 1-1/4" O.D. seamless steel tubing of .083" wall thickness with 5" wide x .025" thick steel fins. The higher temperature compartments are provided with ceiling suspended type cold diffusers which contain a direct expansion cooling coil constructed of copper finned tubing enclosed in a galvanized casing with a drip pan. Each cold air diffuser has a propeller type fan mounted at the rear of the unit.

Chilled Water System

The chilled water system supplies ice cold water to all of the older scuttlebutt located around the ship as well as to rooms on the bridge, sun an "A" deck. The system is a closed loop. Water from the potable water system is either pumped directly into the system, or is directed to an insulated cooler located on the refrigeration flat, port side. After the water has passed through the cooler and it mixes with the returning water from a recirculating pump; it is then discharged throughout the ship.

The potable water to the cooler can be cooled from 90° F. to 50° F. with a 50 gph output from the cooler. The cooler itself uses Freon (R-12) mainly to cool the walk-in on "B" deck. From the main refrigeration system, liquid Freon may go through a hand expansion valve to the cooler. It may also pass through a liquid line dryer, an electrically operated solenoid, which senses cooler outlet temperature, and finally to the thermostatic expansion valve to the cooler. After the Freon has cooled the water, it passes through a back pressure regulator and continues back to the main system.

Water which doesn't go to the cooler, but instead goes to the recirculating pump, isn't as cool as water from the cooler. When mixed, it is referred to as ice water. The pump is a single stage centrifugal pump that can produce 25 gpm.