Refrigerant Charging Method for Variable-Density Two-Phase Pipe Flow
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Solution Overview
Problem
In air conditioners, determining the appropriate refrigerant amount for a refrigerant circuit with a gas-liquid two-phase state flowing through the liquid-side connection pipe is challenging, as the constant refrigerant amount per unit length assumption fails due to increased pressure loss and limited regions of liquid and gas-liquid two-phase states, especially with longer pipes.
Innovation Solution
A method and device that adjust the refrigerant amount per unit length of the liquid-side connection pipe based on its length, using a compressor, condenser, expansion valves, and evaporators, where the refrigerant is decompressed before entering the evaporator, allowing for a variable refrigerant amount that increases with pipe length, and considering the number and lengths of branch pipes and the refrigeration apparatus's horsepower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the refrigerant amount per unit length is kept constant regardless of pipe length, then the calculation is simple, but the refrigerant charging amount becomes inaccurate for longer pipes due to increased pressure loss
Solution Approach 1:
The patent applies dynamics by making the refrigerant amount per unit length variable rather than constant. Specifically, it sets different refrigerant amounts per unit length for different pipe length ranges (e.g., 0.5g/m for 3-5m, 0.6g/m for 6-8m, 0.7g/m for 9-11m, 0.8g/m for 12-14m). This dynamic adjustment compensates for the increasing pressure loss in longer pipes, ensuring accurate refrigerant charging across various installation conditions while maintaining simple calculation methodology.
2Ease of operation
If the liquid-side connection pipe is filled with liquid refrigerant, then the refrigerant amount can be calculated by simple multiplication, but this assumption fails when gas-liquid two-phase state exists in the pipe
Solution Approach 1:
The patent applies parameter changes by adjusting the refrigerant amount per unit length parameter based on the actual refrigerant state in the pipe. Instead of assuming constant liquid fill, it modifies the charging density parameter to account for gas-liquid two-phase conditions. This allows the simple multiplication method to remain valid while adapting to different refrigerant states by changing the per-unit-length parameter according to pipe length ranges.
3Adaptability or versatility
If the connection pipe length is increased to accommodate installation requirements, then the installation flexibility improves, but the pressure loss increases and limits the region where liquid refrigerant can flow
Solution Approach 1:
The patent compensates for increased pressure loss in longer pipes by changing the refrigerant amount per unit length parameter. For pipes in the range of 3-5m, it uses 0.5g/m; for 6-8m, 0.6g/m; for 9-11m, 0.7g/m; and for 12-14m, 0.8g/m. This parameter adjustment ensures that sufficient refrigerant is charged to maintain proper circulation and heat exchange performance despite the increased pressure loss, thereby supporting installation flexibility without sacrificing system efficiency.
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 approach ensures an appropriate refrigerant cycle can be maintained despite longer pipe lengths and increased pressure loss, allowing for accurate refrigerant charging that corresponds to the pipe length and apparatus capacity.
Implementation Method 1
a first expansion valve, an evaporator, a liquid-side connection pipe that feeds the refrigerant, which has passed through the condenser and then has been decompressed by the first expansion valve, to the evaporator
Data Source
AI summary
In a refrigeration apparatus including a refrigerant circuit in which a refrigerant in a gas-liquid two-phase state flows through a liquid-side connection pipe, a refrigerant-amount determining method and a refrigerant-amount determining device capable of grasping an appropriate refrigerant charging amount corresponding to the length of the connection pipe is provided. Provided is a refrigerant-amount determining method for a refrigerant to be charged to a refrigeration apparatus including a refrigerant circuit in which a compressor, an outdoor heat exchanger that functions as a condenser, an outdoor expansion valve, indoor heat exchangers that function as evaporators, a liquid-side connection pipe that feeds the refrigerant, which has passed through the outdoor heat exchanger and then has been decompressed by the outdoor expansion valve, to each of the indoor heat exchangers, and a gas-side connection pipe that feeds the refrigerant, which has passed through each of the indoor heat exchangers, to a suction side of the compressor, are connected to one another. The method determines a refrigerant amount of the refrigerant to be charged to the refrigerant circuit such that a refrigerant amount per unit length of the liquid-side connection pipe increases as a length of the liquid-side connection pipe is larger.