Abstract: There is disclosed a heat exchanger tube for conducting refigerant in a heat exchanger. The inner surface of the tube has a convex portion having a broad tip and a plurality of inner fins. The area of the tip of the convex portion is larger than that of the tip of the inner fins. The height of the convex portion can be set at more than that of the inner fin. A heat exchanger according to the invention has a plurality of plate fins, each having a hole therein. Heat exchanger tubes pass through the holes of the plate fins. A method of manufacturing a heat exchanger comprises the steps of stacking a plurality of plate fins, each having a hole, with a predetermined space therebetween. Heat exchanger tubes are inserted through the holes. Then, the tubes are expanded to engage the plate fins. A refrigerating circuit utilizing a heat exchanger is also described.

Abstract: An air conditioning system in which each alternative refrigerant can be fully utilized so as to present as much as actual COP in comparison with the conventional HCFC22 and to achieve safe use as operating refrigerants.

Abstract: An air conditioner control apparatus measures coolant temperatures and pressures at both inlet side and outlet side of a compressor, or detects a electric capacity of the coolant and the like in order to determine the kind of coolant. For example, when a CPU 31 detects that the coolant R22 is used, the apparatus selects a data item of a fluorocarbone-based coolant R22 stored in a data selection means 35 storing pressure-temperature data items, and calculates a super-heated rate or a super-cooled rate according to the ability of a compressor 1 so that the room temperature reaches the predetermined one set by the operator and setting a calculation result. Next, a vapor temperature is calculated by each indoor air conditioner side, and during a cooling operation, electronic expansion valves 9, 11 are controlled so that target super-heated temperature are reached to the temperatures in temperature sensors 17 and 19.

Abstract: In an air conditioner having at least an indoor unit 9 and an outdoor unit 11 through which a coolant flows, a saturation temperature of the coolant at 50.degree. C. is not less than 2500 kPa, and the indoor heat exchanger in the indoor unit satisfies a relationship of Hi.times.Li/(Di.sup.3 .times.Ni.sup.2).gtoreq.150 and the outdoor heat exchanger in the outdoor unit satisfies a relationship of Ho.times.Lo/(Do.sup.3 .times.No.sup.2).gtoreq. 60.

Abstract: A cold storage system installed in a reservoir on the ground whose atmospheric temperature becomes 0.degree. C. or less in winter season comprises at least one heat exchanger having one end located in the water stored in the reservoir and the other end located in the atmosphere and for performing one-direction heat transfer in such a manner as to absorb heat from the water of the reservoir and emit it into the atmosphere, and a hold member for holding the heat exchanger in the reservoir.