A duct is provided and includes a tubular member having an inlet portion, an outlet portion and a central portion interposed between the inlet and outlet portions and a tributary tubular member fluidly coupled to the tubular member at the central portion. The tributary tubular member includes first and second torus sectors defining first and second apertures, respectively, through which an upstream end of the central portion extends. The second torus sector is disposed within the first torus sector to define a sectioned toroidal annulus about the first and second apertures and between an exterior surface of the second torus sector and an interior surface of the first torus sector.

A duct is provided and includes a tubular member having an inlet portion, an outlet portion and a central portion interposed between the inlet and outlet portions and a tributary tubular member fluidly coupled to the tubular member at the central portion. The tributary tubular member includes first and second torus sectors defining first and second apertures, respectively, through which an upstream end of the central portion extends. The second torus sector is disposed within the first torus sector to define a sectioned toroidal annulus about the first and second apertures and between an exterior surface of the second torus sector and an interior surface of the first torus sector.

A heat pump system includes a first bypass pipe provided with a first bypass valve and connecting a liquid refrigerant pipe and a low-pressure refrigerant pipe, a refrigerant heat exchanger configured to cause a heat-exchange between refrigerant flowing in the liquid refrigerant pipe and refrigerant flowing in first bypass pipe, a second bypass pipe provided with a second bypass valve and connecting the liquid refrigerant pipe and the low-pressure refrigerant pipe, and a controller. The controller is configured to control opening degree of the first bypass valve based on detected superheated temperature of refrigerant flowing in the first bypass pipe, and detected discharge temperature of a compressor and control opening degree of the second bypass valve based on the detected discharge temperature.

A heat pump system includes a first bypass pipe provided with a first bypass valve and connecting a liquid refrigerant pipe and a low-pressure refrigerant pipe, a refrigerant heat exchanger configured to cause a heat-exchange between refrigerant flowing in the liquid refrigerant pipe and refrigerant flowing in first bypass pipe, a second bypass pipe provided with a second bypass valve and connecting the liquid refrigerant pipe and the low-pressure refrigerant pipe, and a controller. The controller is configured to control opening degree of the first bypass valve based on detected superheated temperature of refrigerant flowing in the first bypass pipe, and detected discharge temperature of a compressor and control opening degree of the second bypass valve based on the detected discharge temperature.

A compressor includes a housing having a suction inlet, at least one economizer inlet, and an outlet. A first cylinder arranged within the housing includes a first suction valve arranged in fluid communication with the suction inlet and a first discharge valve fluidly connected to the outlet. At least one second cylinder is arranged within the housing. The at least one second cylinder has a second suction valve in fluid communication with the at least one economizer inlet and a second discharge valve fluidly connected to the outlet. A first piston is arranged within the first cylinder and a second piston is arranged within the at least one second cylinder.

A compressor includes a housing having a suction inlet, at least one economizer inlet, and an outlet. A first cylinder arranged within the housing includes a first suction valve arranged in fluid communication with the suction inlet and a first discharge valve fluidly connected to the outlet. At least one second cylinder is arranged within the housing. The at least one second cylinder has a second suction valve in fluid communication with the at least one economizer inlet and a second discharge valve fluidly connected to the outlet. A first piston is arranged within the first cylinder and a second piston is arranged within the at least one second cylinder.

There is provided a HVAC system comprising: a fluid circuit for conveying a refrigerant; a compressor for compressing the refrigerant; three heat exchangers defining an evaporator, an outdoor exchanger and a heat recovery exchanger provided along the fluid circuit; an expansion valve provided along the fluid circuit; and a receiver connected in parallel to the expansion valve, wherein a fill valve is located between the receiver and a connection upstream of the expansion valve and a drain valve is located between the receiver and a connection downstream of the expansion valve; wherein the fluid circuit comprises a plurality of valves which are configured to be controlled based on a selected operating mode such that at least one of the outdoor exchanger and the heat recovery exchanger is connected to a discharge line of the compressor and in series with one of the other heat exchangers which is connected to a suction line of the compressor, with the expansion valve disposed between the heat exchangers; wherein the fill and drain valves are configured to be controlled to store a volume of refrigerant in the receiver so as to provide an effective refrigerant charge in the fluid circuit that corresponds to the selected operating mode.

There is provided a HVAC system comprising: a fluid circuit for conveying a refrigerant; a compressor for compressing the refrigerant; three heat exchangers defining an evaporator, an outdoor exchanger and a heat recovery exchanger provided along the fluid circuit; an expansion valve provided along the fluid circuit; and a receiver connected in parallel to the expansion valve, wherein a fill valve is located between the receiver and a connection upstream of the expansion valve and a drain valve is located between the receiver and a connection downstream of the expansion valve; wherein the fluid circuit comprises a plurality of valves which are configured to be controlled based on a selected operating mode such that at least one of the outdoor exchanger and the heat recovery exchanger is connected to a discharge line of the compressor and in series with one of the other heat exchangers which is connected to a suction line of the compressor, with the expansion valve disposed between the heat exchangers; wherein the fill and drain valves are configured to be controlled to store a volume of refrigerant in the receiver so as to provide an effective refrigerant charge in the fluid circuit that corresponds to the selected operating mode.

A vapor compression system includes a first conduit fluidly coupling a liquid collection portion of a condenser and an evaporator, where the first conduit is configured to direct a first flow of refrigerant from the condenser to a first inlet of the evaporator and a second conduit fluidly coupling the liquid collection portion of the condenser and the evaporator, where the second conduit is configured to direct a second flow of refrigerant from the condenser to a second inlet of the evaporator via gravitational force, and where the first inlet is disposed above the second inlet relative to a vertical dimension of the evaporator.

A vapor compression system includes a first conduit fluidly coupling a liquid collection portion of a condenser and an evaporator, where the first conduit is configured to direct a first flow of refrigerant from the condenser to a first inlet of the evaporator and a second conduit fluidly coupling the liquid collection portion of the condenser and the evaporator, where the second conduit is configured to direct a second flow of refrigerant from the condenser to a second inlet of the evaporator via gravitational force, and where the first inlet is disposed above the second inlet relative to a vertical dimension of the evaporator.