Abstract: An alternating type heat pump has first to third rows of outdoor unit coils adapted to selectively perform the functions of an evaporator and a condenser in accordance with the outdoor conditions and the load variations, thereby improving the performance of the heat pump, and is capable of allowing the first to third rows of outdoor unit coils to be operated as a condenser in an alternating manner under the conditions where frost on the outdoor unit coils may be formed especially in winter seasons, thereby basically preventing the conditions on which the frost is formed.

Abstract: An alternating type heat pump has first to third rows of outdoor unit coils adapted to selectively perform the functions of an evaporator and a condenser in accordance with the outdoor conditions and the load variations, thereby improving the performance of the heat pump, and is capable of allowing the first to third rows of outdoor unit coils to be operated as a condenser in an alternating manner under the conditions where frost on the outdoor unit coils may be formed especially in winter seasons, thereby basically preventing the conditions on which the frost is formed.

Abstract: Disclosed is a cooling and heating air conditioner capable of performing heating more stably, preventing frost formation on coils of an outdoor unit even at subzero temperature in winter by using first and second heat exchangers and an auxiliary expansion valve. The air conditioner according to the present invention comprises an electronic control valve opened when the outside temperature is less than a preset value, a first heat exchanger performing heat exchange between high temperature liquid coolant and coolant passed through the outdoor unit and an auxiliary expansion valve, and a second heat exchanger disposed in front of the outdoor unit to induct thereinto the high temperature coolant. Since the second heat exchanger heats up the outside air through heat exchange before supplying the air to the outdoor unit, evaporation of the coolant can be stably performed in the outdoor unit, while preventing frost formation. Accordingly, heating can be performed constantly.

Abstract: An apparatus and method for connecting copper tubes are developed to facilitate welding operation in the refrigerating device. The new apparatus will reduce the poor welding rate so that it will effectively prevent clogging of the copper tubes and leaking the refrigerant. It also has merit to easily determine a suitable heating time while the copper tubes are welding. Thus, the rate of poor welding is reduced, as well as a method for connecting copper tubes by using the tube connecting apparatus.