Air-conditioning apparatus

Abstract

In a first cycle, a first heat exchanger, in which a first medium exchanges heat with the outside air, a second heat exchanger and a third heat exchanger, in which heat is exchanged between the first cycle and a second cycle and between the first cycle and a third cycle, respectively, are connected in series with a first reducing valve and a second reducing valve. In the second cycle and the third cycle that convey cooling energy and heating energy, the flow rates of a second medium in respective branches are adjusted by flow-rate-adjusting valves in accordance with the entrance and exit temperatures of indoor units, and the total flow rate is determined by controlling the rotation speed of a pump by a minimum resistance method. Therefore, even if there are a plurality of loads and the loads change significantly, a stable controlling operation is realized, enabling a highly efficient operation.

1 . An air-conditioning apparatus comprising:
 a first cycle through which a first medium circulates;   a second cycle through which a second medium circulates; and   a third cycle through which the second medium circulates,   the first cycle including a loop in which a compressor, a first heat exchanger, a first reducing valve, a flow-path switcher that switches the direction of flow of the first medium between forward and backward directions, a second heat exchanger in which the first medium circulating through the first cycle and the second medium circulating through the second cycle exchange heat therebetween, a second reducing valve, and a third heat exchanger in which the first medium circulating through the first cycle and the second medium circulating through the third cycle exchange heat therebetween are sequentially connected to one another with pipes,   the second cycle including the second heat exchanger, a first pump that drives the second medium, a first path that connects the second heat exchanger and the first pump, and at least one first branch path having one end thereof connected to one end of the first path and the other end thereof connected to the other end of the first path,   the third cycle including the third heat exchanger, a second pump that drives the second medium, a second path that connects the third heat exchanger and the second pump, and at least one second branch path having one end thereof connected to one end of the second path and the other end thereof connected to the other end of the second path,   each first branch path and second branch path including flow-path-switching valves, an indoor unit and a flow-rate-adjusting valve,   the flow-path-switching valves having a first flow-path-switching valve that connects to one ends of each first branch path and second branch path and that switches so as to communicate with one of the second cycle and the third cycle and a second flow-path-switching valve that connects to the other ends of the first branch path and the second branch path and that switches so as to communicate with one the same cycle out of the second cycle and the third cycle as the first flow-path-switching valve communicates with,   the air-conditioning apparatus that each indoor unit performs a heating operation or a cooling operation using the second medium provided with heating energy, cooling energy or both of heating energy and cooling energy by the second heat exchanger and the third heat exchanger, further comprising   switching-controlling means that controls the first flow-path-switching valve and the second flow-path-switching valve corresponding to each indoor unit according to a temperature or an amount of the second medium which is required by the indoor unit, if all the indoor units are performing a cooling operation or a heating operation.   
     
     
         2 . The air-conditioning apparatus of  claim 1 ,
 wherein, if all the indoor units are performing a cooling operation or a heating operation at different required temperatures in accordance with individual uses thereof, the indoor units are divided into two groups of a high-temperature indoor unit group and a low-temperature indoor unit group on the basis of the required temperatures, and   the switching-controlling means operates such that, in case of the cooling operation, the low-temperature indoor unit group connects to one of the cycles that has one of the second heat exchanger and the third heat exchanger in which the pressure of the first medium is relatively low, and such that, in case of the heating operation, the high-temperature indoor unit group connects to one of the cycles that has one of the second heat exchanger and the third heat exchanger in which the pressure of the first medium is relatively high.   
     
     
         3 . The air-conditioning apparatus of  claim 1  wherein, if all the indoor units are performing a cooling operation or a heating operation, the switching-controlling means operates such that an indoor unit corresponding to the flow-rate-adjusting valve whose opening-degree is almost fully open connects to one of the cycles having one of the heat exchangers in which the pressure of the first medium is relatively high. 
     
     
         4 . The air-conditioning apparatus of  claim 1  wherein, if all the indoor units are performing a cooling operation or a heating operation, the switching-controlling means operates such that an indoor unit whose required capacity is larger connects to one of the cycles in which the pressure of the first medium is relatively high. 
     
     
         5 . The air-conditioning apparatus of  claim 1  wherein, if all the indoor units are performing a cooling operation or a heating operation and are not of the rated loads, the switching-controlling means operates such that one of the second cycle and the third cycle, which has a smaller input among the pumps, is used. 
     
     
         6 . The air-conditioning apparatus of  claim 1  wherein the flow-rate-adjusting means identifies the respective flow-path resistances of the branches during a test operation and reflects the flow-path resistances in the normal operation. 
     
     
         7 . The air-conditioning apparatus of  claim 1  further comprising a pressure sensor and a flow-rate sensor,
 wherein the flow-rate-adjusting means identifies the flow-path resistance of a specific one of the plurality of branched paths in at least one of the second cycle and the third cycle on the basis of an output of the pressure sensor or an output of the flow-rate sensor and reflects the flow-path resistance in the normal operation. 
 
     
     
         8 . The air-conditioning apparatus of  claim 1 ,
 each branch path further comprising detecting means that detects a flow rate, the apparatus wherein   the flow-rate-adjusting means identifies the flow-path resistance of each branch path on the basis of a detected values of the detecting means before and after changing the opening-degree of the flow-rate-adjusting valve under certain amount flowing in each branch path and reflects in the normal operation.   
     
     
         9 . The air-conditioning apparatus of  claim 1  wherein the rotation-speed-controlling means sets the difference in pressures at an entrance and at an exit of the first pump in the second cycle or the second pump in the third cycle to a target value. 
     
     
         10 . The air-conditioning apparatus of  claim 1  wherein the rotation-speed-controlling means sets the pressure at an exit of the first pump in the second cycle or the second pump in the third cycle to a target value. 
     
     
         11 . The air-conditioning apparatus of  claim 9  wherein the target value is such a value as to maximize an opening-degree of a flow-rate-adjusting valve which has the highest valve-opening-degree in the plurality of flow-rate-adjusting valves provided in the second cycle or the third cycle. 
     
     
         12 . The air-conditioning apparatus of  claim 1  wherein in order to make an opening-degree of a flow-rate-adjusting valve that has the highest valve-opening-degree among the plurality of flow-rate-adjusting valves in the second cycle or the third cycle fully open, the rotation-speed-controlling means controls the first pump or the second pump that is used provided in one of the cycles, which has the flow-rate-adjusting valve that has the highest valve-opening-degree. 
     
     
         13 . The air-conditioning apparatus of  claim 1  wherein the first medium is a natural refrigerant. 
     
     
         14 . The air-conditioning apparatus of  claim 1  wherein the first medium is a low-GWP refrigerant. 
     
     
         15 . The air-conditioning apparatus of  claim 1  wherein the first medium is a fluorocarbon refrigerant.