Air-Conditioner Refrigerant Circuit With Two-Phase Extension Pipe
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Solution Overview
Problem
Existing multi-air-conditioning systems for buildings face challenges in reducing the amount of refrigerant in the refrigerant circuit, particularly due to long extension pipes, which increases the environmental impact in case of leakage and requires more refrigerant during cooling operations.
Innovation Solution
The air-conditioning apparatus incorporates a second expansion device that reduces the pressure of refrigerant flowing into the extension pipe, causing it to enter a two-phase state, thereby reducing the density and amount of refrigerant in the circuit, using a refrigerant mixture of R32 and tetrafluoropropene, and employing a controller to regulate the opening degree of the expansion device based on detected pressure or temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-pressure liquid refrigerant is fed into a long extension pipe during cooling operation, then the refrigerant can reach the indoor unit, but the amount of refrigerant in the entire refrigerant circuit increases significantly
Solution Approach 1:
The patent changes the pressure parameter of the refrigerant by introducing a second expansion device that reduces the pressure of refrigerant before it enters the extension pipe. This pressure reduction causes the refrigerant to transition into a two-phase state, which significantly reduces the density and amount of refrigerant in the extension pipe while still allowing it to reach the indoor unit effectively.
Solution Approach 2:
The patent utilizes phase transition by causing the refrigerant to change from a high-pressure liquid state to a two-phase state (mixture of liquid and vapor) through pressure reduction in the second expansion device. This phase transition reduces the refrigerant density in the extension pipe, thereby reducing the total amount of refrigerant required in the circuit.
2Quantity of substance
If a second expansion device is introduced to reduce refrigerant pressure and create two-phase state, then the amount of refrigerant in the extension pipe decreases, but the device complexity increases
Solution Approach 1:
The second expansion device performs multiple functions: it reduces refrigerant pressure, initiates phase transition to two-phase state, and controls refrigerant flow into the extension pipe. By consolidating these functions into a single device, the patent minimizes the increase in overall system complexity while achieving the goal of reducing refrigerant amount.
3Quantity of substance
If the refrigerant is pressurized to high pressure for efficient heat exchange, then the heat exchange efficiency improves, but the amount of refrigerant required in long extension pipes increases
Solution Approach 1:
The patent applies different pressure conditions to different sections of the refrigerant circuit: high pressure is maintained in the heat exchanger for efficient heat exchange, while reduced pressure (two-phase state) is applied specifically in the extension pipe to reduce refrigerant amount. This localized quality adjustment optimizes both heat exchange efficiency and refrigerant quantity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces the amount of refrigerant in the refrigerant circuit, minimizing environmental impact in case of leakage and optimizing refrigerant usage during cooling operations.
Implementation Method 1
the second expansion device is configured to reduce a pressure of refrigerant flowing into the first extension pipe in the cooling operation to cause the refrigerant to turn into refrigerant having a medium pressure and in a two-phase state
Data Source
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AI summary
An air-conditioning apparatus includes a refrigerant circuit connecting a compressor, a first heat exchanger, a first expansion device, and a second heat exchanger. The compressor and the first heat exchanger are housed in a heat source unit, the first expansion device and the second heat exchanger are housed in a casing, the heat source unit and the casing are connected via a plurality of extension pipes constituting a part of a refrigerant pipe, the heat source unit houses a second expansion device provided at a location on a downstream side with respect to the first heat exchanger and on an upstream side with respect to the first expansion device, and the second expansion device and the first expansion device are connected via a first extension pipe being one of the extension pipes. The second expansion device reduces a pressure of refrigerant flowing into the first extension pipe in cooling operation to cause the refrigerant to turn into refrigerant having a medium pressure and in a two-phase state, and the medium pressure is lower than a refrigerant pressure in a condenser and higher than a refrigerant pressure in an evaporator. In the cooling operation, the refrigerant having the medium pressure and in the two-phase state is caused to flow through the first extension pipe.