A defrost system is disclosed that includes a cooling device disposed in a freezer, a heat exchanger pipe leading into a casing, a drain receiver unit; a refrigerating device for cooling and liquefying CO.sub.2 refrigerant; a refrigerant circuit for permitting the CO.sub.2 refrigerant to circulate to the heat exchanger pipe; a defrost circuit branched from the heat exchanger pipe forming a CO.sub.2 circulation path with the heat exchanger pipe; an on-off valve so that the CO.sub.2 circulation path becomes a closed circuit; a pressure adjusting unit for adjusting the pressure of the CO.sub.2 refrigerant; and a first heat exchanger unit for heating the CO.sub.2 refrigerant circulating with brine, disposed below the cooling device to which the defrost circuit and a first brine circuit in which brine, a first heating medium, circulates, are led, in which the CO.sub.2 refrigerant naturally circulates in the closed circuit when defrosting by a thermosiphon effect.

A refrigeration appliance includes a refrigeration circuit having a condenser and a heat circulation system for heating an element of the refrigeration appliance. The heat circulation system includes a heat conducting region. A heat exchanging element includes the condenser and the heat conducting region. The condenser and the heat conducting region in the heat exchanger element are thermally coupled in order to output heat from the refrigeration circuit to the heat conducting region of the heat circulation system.

A freezer structure (12) includes a floor structure (20), side walls (22) and a ceiling (24), each of which includes a substantially hollow inner or upper layer or zone (30) behind or beneath which is disposed an intermediate layer or zone (32) substantially filled with insulating filler material and a bottom or outer layer or zone (34) that is substantially hollow. A monitoring system (16) monitors the temperature, moisture level and pressure of a substantially dry gas circulating through the first layer or zone to maintain the first layer or zone in substantially dry condition.

A freezer structure (12) includes a floor structure (20), side walls (22) and a ceiling (24), each of which includes a substantially hollow inner or upper layer or zone (30) behind or beneath which is disposed an intermediate layer or zone (32) substantially filled with insulating filler material and a bottom or outer layer or zone (34) that is substantially hollow. A monitoring system (16) monitors the temperature, moisture level and pressure of a substantially dry gas circulating through the first layer or zone to maintain the first layer or zone in substantially dry condition.

A control device for air-conditioning equipment includes: an acquirer that acquires information relevant to occurrence of condensation on a surface of a door of a showcase having a storage in which a product stored therein is refrigerated, the storage having an opening that is opened and closed with the door; and a controller that causes an adjuster that adjusts a direction of cool air output from the air-conditioning equipment to direct the cool air to the showcase, upon determining that a possibility that condensation occurs on the surface of the door has increased, based on the information acquired by the acquirer.

A control device for air-conditioning equipment includes: an acquirer that acquires information relevant to occurrence of condensation on a surface of a door of a showcase having a storage in which a product stored therein is refrigerated, the storage having an opening that is opened and closed with the door; and a controller that causes an adjuster that adjusts a direction of cool air output from the air-conditioning equipment to direct the cool air to the showcase, upon determining that a possibility that condensation occurs on the surface of the door has increased, based on the information acquired by the acquirer.

A method and apparatus for controlling the direction of a defrost device for refrigeration coils includes measuring the current drawn by or the torque produced by a permanent magnet motor, wherein the permanent magnet motor powers a defrost device recurrently back and forth along refrigeration coils and reverses the direction of the permanent magnet motor when the measured current drawn or measured torque produced are at or above a first limit. The method omits the use of switches and sensors to signal when the defrost device is reversed to reduce failures and stoppages.

A method and apparatus for controlling the direction of a defrost device for refrigeration coils includes measuring the current drawn by or the torque produced by a permanent magnet motor, wherein the permanent magnet motor powers a defrost device recurrently back and forth along refrigeration coils and reverses the direction of the permanent magnet motor when the measured current drawn or measured torque produced are at or above a first limit. The method omits the use of switches and sensors to signal when the defrost device is reversed to reduce failures and stoppages.

A sublimation defrost system for a refrigeration apparatus including: a cooling device in a freezer, and includes a casing containing a heat exchanger pipe; a refrigerating device for cooling and liquefying a CO.sub.2 refrigerant; and a refrigerant circuit connected to the heat exchanger pipe permitting the cooled and liquefied CO.sub.2 refrigerant to circulate. The defrost system includes: a dehumidifier device; a CO.sub.2 circulation path in the heat exchanger pipe, an on-off valve in the heat exchanger; a circulating unit for the CO.sub.2 refrigerant; a first heat exchanger part exchanging heat between a brine as a first heating medium and the circulating CO.sub.2 refrigerant; and a pressure adjusting unit for the circulating CO.sub.2 refrigerant during defrosting so that a condensing temperature of the CO.sub.2 refrigerant becomes equal to or lower than a freezing point of a water vapor in the freezer inner air without a drain receiving unit.

A sublimation defrost system for a refrigeration apparatus including: a cooling device in a freezer, and includes a casing containing a heat exchanger pipe; a refrigerating device for cooling and liquefying a CO.sub.2 refrigerant; and a refrigerant circuit connected to the heat exchanger pipe permitting the cooled and liquefied CO.sub.2 refrigerant to circulate. The defrost system includes: a dehumidifier device; a CO.sub.2 circulation path in the heat exchanger pipe, an on-off valve in the heat exchanger; a circulating unit for the CO.sub.2 refrigerant; a first heat exchanger part exchanging heat between a brine as a first heating medium and the circulating CO.sub.2 refrigerant; and a pressure adjusting unit for the circulating CO.sub.2 refrigerant during defrosting so that a condensing temperature of the CO.sub.2 refrigerant becomes equal to or lower than a freezing point of a water vapor in the freezer inner air without a drain receiving unit.