Air conditioner

An air conditioner, comprising:

• a refrigeration circuit formed by sequentially connecting a compressor, a condenser, an electronic expansion valve capable of controlling an opening degree thereof, and an evaporator by pipes;
• a compressor bypass pipe connecting an outlet of said evaporator and an inlet of said condenser interposing a first on-off valve;
• the air conditioner is switched to a forced circulation operation in which said first on-off valve is closed and said compressor is in a running state or to a natural circulation operation in which said first on-off valve is opened and said compressor is in a stopping state, and the opening degree of said electronic expansion valve is controlled respectively in accordance with said forced circulation operation and said natural circulation operation;
• wherein said first on-off valve is a check valve for allowing a flow of refrigerant from said outlet of said evaporator to said inlet of said condenser and prohibiting a back flow flowing.

An air conditioner comprising:

• a refrigeration circuit formed by sequentially connecting a compressor, a condenser, an expansion valve, and an evaporator by pipes;
• a compressor bypass pipe for connecting an outlet of said evaporator and an inlet of said condenser interposing a first on-off valve;
• an other on-off valve provided in a pipe between an outlet of said compressor and an outlet of said compressor bypass pipe;
• and
• a controller for switching to one of:
• a forced circulation operation in which said first on-off valve is closed and said other on-off valve is opened to render said compressor in a running state, and
• a natural circulation operation in which said first on-off valve is opened and said other on-off valve is closed to render said compressor in a stopping state,
• wherein the on-off valves are automatically closed in response to pressure differences within the air conditioner, and
• wherein the controller controls an opening degree of the expansion valve.

An air conditioner comprising:

• a refrigeration circuit formed by sequentially connecting a compressor, a condenser, an expansion valve, and an evaporator by pipe;
• a compressor bypass pipe for connecting an outlet of said evaporator and an inlet of said condenser interposing a first on-off valve;
• another on-off valve provided in a pipe between an outlet of said compressor and an outlet of said compressor bypass pipe;
• and
• wherein said air conditioner is selectively switchable to one of:
• a forced circulation operation in which said first on-off valve is closed and said other valve is opened to render said compressor in a running state, and
• a natural circulation operation in which said first on-off valve is opened and said other on-off valve is closed to render said compressor in a stopping state,
• wherein a refrigerant which flows into said condenser flows downward in said condenser,
• further including:
• a plurality of refrigerant paths in said condenser formed by dividing refrigerant pipes in a vertical direction of said condenser;
• and
• a subcooling portion formed in a lower portion of said condenser,
• wherein branched flows of said refrigerant respectively pass through said refrigerant paths downward and join at an outlet of said condenser.

An air conditioner comprising:

• a refrigeration circuit formed by sequentially connecting a compressor, a condenser, an expansion valve, and an evaporator by pipe;
• a compressor bypass pipe for connecting an outlet of said evaporator and an inlet of said condenser interposing a first on-off valve;
• another on-off valve provided in a pipe between an outlet of said compressor and an outlet of said compressor bypass pipe;
• and
• wherein said air conditioner is selectively switchable to one of:
• a forced circulation operation in which said first on-off valve is closed and said other valve is opened to render said compressor in a running state, and
• a natural circulation operation in which said first on-off valve is opened and said other on-off valve is closed to render said compressor in a stopping state,
• wherein:
• a plurality of refrigerant paths are provided in said condenser by dividing refrigerant pipes in a vertical direction of said condenser to form an upper refrigerant path and a lower refrigerant path,
• wherein branches of said refrigerant respectively flow through said refrigerant paths in a downward direction and join at the outlet of said condenser, and
• wherein the length of said upper refrigerant path is longer than the length of said lower refrigerant path.

An air conditioner comprising:

• a refrigeration circuit formed by sequentially connecting a compressor, a condenser, an expansion valve, and an evaporator by pipes;
• a compressor bypass pipe for connecting an outlet of said evaporator and an inlet of said condenser interposing a first on-off valve;
• an other on-off valve provided in a pipe between an outlet of said compressor and an outlet of said compressor bypass pipe;
• and
• a controller for switching to one of:
• a forced circulation operation in which said first on-off valve is closed and said other on-off valve is opened to render said compressor in a running state and;
• a natural circulation operation in which said first on-off valve is opened and said other on-off valve is closed to render said compressor in a stopping state,
• wherein the on-off valves are automatically closed in response to pressure differences within the air conditioner;
• and
• wherein a tube diameter of a pipe between said outlet of said evaporator and said inlet of said condenser is larger than the tube diameter of a pipe between an outlet of said condenser and an inlet of said evaporator.

An air conditioner, comprising:

• a refrigeration circuit formed by sequentially connecting a compressor, a condenser, an electronic expansion valve capable of controlling an opening degree thereof, and an evaporator by pipes;
• a compressor bypass pipe connecting an outlet of said evaporator and an inlet of said condenser interposing a first on-off valve;
• the air conditioner is switched to a forced circulation operation in which said first on-off valve is closed and said compressor is in a running state or to a natural circulation operation in which said first on-off valve is opened and said compressor is in a stopping state, and the opening degree of said electronic expansion valve is controlled respectively in accordance with said forced circulation operation and said natural circulation operation;
• wherein the height of an outlet of refrigerant pipe of said condenser is higher than the height of an outlet of refrigerant pipe of said evaporator by a distance of between 0.5 m and 2 m.

A process using an air conditioner, the air conditioner comprising a refrigeration circuit formed by sequentially connecting a compressor, a condenser, an electronic expansion valve capable of controlling an opening degree thereof, and an evaporator by pipes, the air conditioner further including a compressor bypass pipe connecting an outlet of the evaporator and an inlet of the condenser and interposing a first on-off valve, the process comprising the steps of:

• instructing said air conditioner to switch to a forced circulation operation or a natural circulation operation;
• in response to an instruction to switch to the forced circulation operation, closing the first on-off valve, opening the expansion valve to a first degree of opening to allow refrigerant to pass therethrough, and operating the compressor in a running state;
• and
• in response to an instruction to switch to the natural circulation operation, opening the first on-off valve, opening the expansion valve to a second degree, different from the first degree, to allow refrigerant to pass therethrough, and stopping the compressor.