Ice machine

An ice machine, comprising:

• a heat exchanger, including
• a shell defining an internal cavity, and
• a plurality of cooling tubes positioned in and extending through the internal cavity, each cooling tube including an inner tube and an outer tube extending around the inner tube, thus defining an annular cavity between the inner tube and the outer tube;
• a water source operably connected to a water pump to provide water which flows through the inner tube in a first direction;
• and
• a refrigerant source operably connected to a refrigerant pump to provide a refrigerant which flows through the annular cavity in a second direction opposite the first direction;
• wherein no refrigerant can pass between the annular cavity defined by each of the plurality of cooling tubes and the internal cavity of the shell.

An ice machine, comprising:

• a heat exchanger, including
• a shell defining an internal cavity,
• a plurality of cooling tubes positioned in and extending through the internal cavity, each cooling tube including an inner tube and an outer tube extending around the inner tube, thus defining an annular cavity between the inner tube and the outer tube;
• an upper tubesheet defining a plurality of holes, with a lower end of one of the outer tubes mated to the upper tubesheet at each of the holes,
• a middle tubesheet spaced apart from the upper tubesheet, the middle tubesheet defining a plurality of holes, with one of the inner tubes extending through and mated to each of the holes, such that a cavity defined between the upper tubesheet and the middle tubesheet is in fluid communication with the annular cavity between the inner tube and the outer tube, and
• a lower tubesheet spaced apart from the middle tubesheet and opposite the upper tubesheet, the lower tubesheet defining a plurality of holes, with a lower end of one of the inner tubes mated to the lower tubesheet at each of the holes, such that a cavity is defined between the lower tubesheet and the middle tubesheet,
• a water source operably connected to a water pump to provide water which flows through the inner tube in a first direction;
• and
• a refrigerant source operably connected to a refrigerant pump to provide a refrigerant which flows through the annular cavity in a second direction opposite the first direction;
• wherein the refrigerant pump causes the refrigerant to initially flow through the cavity defined between the lower tubesheet and the middle tubesheet before flowing through the cavity defined between the upper tubesheet and the middle tubesheet and then through the annular cavity.