Here's a quote from the Titanic--Voyage to Discovery web site about the ice making machine:
The Refrigeration Plant
The most interesting feature of the Titanic was the refrigeration plant. It had a huge ice-making and refrigerating machine and a number of provision rooms on the aft part on the Port site of the Tanktop - Deck and Orlop - Deck. There were separate rooms for mutton, beef, cheese, mineral water, fish, game, poultry, flowers, wines, spirits and champagne. All these rooms were maintained at different temperatures most suited to each. Perishable freight had a compartment of its own, on the aft part on the Starboard site of the Orlop - Deck, also chilled by the refrigeration plant.
Refrigeration and cooling of the provisions and the storerooms aboard the Titanic was accomplished by the installation of a large self-sustaining brine refrigeration system throughout the ship. Drinking water was cooled and supplied from a large number of different points. In the First, Second and Third - Class accommodation, the cooling water refrigeration plant was also used for cooling the wines and beers in the bars and a number of cold lockers in the various pantries.
In addition to these small units, a high capacity version was installed for ice-making and cooling the cargo beef chambers. The plant was supplied by two horizontal duplex CO2 machines, each of which comprised two self-contained units capable of independant working - so that actually four complete refrigeration units were provided. The refrigeration machine was designed and manufactured by Halls Thermotank Ltd. and was of the standard marine type.
Each compressor was manufactured from solid blocks of high tensile carbon steel with condensor coils of solid drawn copper contained in the base of each casting, which in turn were divided in two separate casings. Each machine was fitted with its own steam service condensor, a brass circulating pump, and air and feed pumps. A duplex brass-ended water pump was also provided as an emergency stand-by unit.
Each evaporator was internally divided into four separate units and was locked in an insulated recess above the machinery at the Orlop - Deck level. This recess also housed the three main brine pumps and their interchangeable connectors. The brine return tanks were placed at a higher level immediately above the evaporators.
Refrigerant circulation used the principal of open return with a separate flow and return for each circuit. All brine pipes throughout the system were externally galvanised to ensure protection against corrosion. The brine circuits were kept as short as possible and were interspersed with suspension chambers to ensure an even distribution of refrigerant throughout the system even in the remote possibility of one section becoming blocked.