A climate-control system can be used to heat or cool a space. The climate-control system may include first and second vessels between which refrigerant and co-fluid may be circulated. The refrigerant may be absorbed into the co-fluid within the first vessel at a first rate. The refrigerant may desorb from the co-fluid within the second vessel at a second rate. Ultrasonic energy may be used to adjust the second rate to substantially match the first rate.

An absorption refrigerator using a circulation cycle of a regenerator, a condenser, an evaporator, and an absorber includes temperature sensors, a storage unit storing the approximation function for obtaining the second concentration based on second detection results obtained by each of the temperature sensors, a calculation unit to apply the second detection results to the approximation function to obtain the second concentration and a control unit to execute control in accordance with the second concentration. The approximation function is obtained using a response surface method by interpolation or approximation, based on data including first detection results obtained by temperature sensors and first concentrations each corresponding to when each of the first detection results has been obtained.

A vapor compression system (20) comprises: a compressor (24) having a suction port (26) and a discharge port (28); a refrigerant flowpath (33) from the discharge port and returning to the suction port; a first heat exchanger (30) along the refrigerant flowpath; a second heat exchanger (50) along the refrigerant flowpath; and a vaporizer system (22; 300). The vaporizer system comprises: a first vaporizer (68A; 368A) and a second vaporizer (68B: 368B) each comprising: a vessel (86; 386) having an inlet (84), a vapor outlet (124), and a liquid outlet (130); and a gas bypass flowpath (160) in heat transfer relation with an interior of the vessel.

A vapor compression system (20) comprises: a compressor (24) having a suction port (26) and a discharge port (28); a refrigerant flowpath (33) from the discharge port and returning to the suction port; a first heat exchanger (30) along the refrigerant flowpath; a second heat exchanger (50) along the refrigerant flowpath; and a vaporizer system (22; 300). The vaporizer system comprises: a first vaporizer (68A; 368A) and a second vaporizer (68B: 368B) each comprising: a vessel (86; 386) having an inlet (84), a vapor outlet (124), and a liquid outlet (130); and a gas bypass flowpath (160) in heat transfer relation with an interior of the vessel.

A carbon dioxide/co-fluid mixture is provided for use in a refrigeration cycle in which the carbon dioxide is alternately absorbed and desorbed from the co-fluid. Suitable co-fluids are selected from the class of alkoxylated carboxylic amides, wherein the amides are cyclic or non-cyclic. It has been discovered that N-2,5,8,11-tetraoxadodecyl-2-pyrrolidinone and its homologs exhibit an advantageous property of a high rate of desorption at lower temperatures.

A carbon dioxide/co-fluid mixture is provided for use in a refrigeration cycle in which the carbon dioxide is alternately absorbed and desorbed from the co-fluid. Suitable co-fluids are selected from the class of alkoxylated carboxylic amides, wherein the amides are cyclic or non-cyclic. It has been discovered that N-2,5,8,11-tetraoxadodecyl-2-pyrrolidinone and its homologs exhibit an advantageous property of a high rate of desorption at lower temperatures.