| 摘要 |
<p>A food freezer (10) having a mechanical refrigeration system (54) comprising first (56) and second (58) closed-loop fluid circuits, wherein the first fluid circuit (56) employs carbon dioxide as its refrigerant and transfers heat to the second fluid circuit (58), which in turn transfers heat to the environment or to another fluid circuit. In the first fluid circuit evaporator (60), carbon dioxide is maintained at pressures between 60.4 psig and 120 psig. In a preferred embodiment of the invention, the freezer (10) employs at least two separate blowers (44), (86) or fans for circulation of air or other gas in the freezer enclosure. One blower/fan (44) operates continuously to maintain circulation of cold air or gas in the freezer (10). The other blower/fan (86) operates intermittently or at variable speeds to vary air flow across the evaporator (60), and thereby increase or decrease heat transfer from the freezer (10) interior to the first fluid circuit evaporator (60) to maintain the freezer (10) interior at a desired temperature or within a desired temperature range.</p> |
