Refrigerant Charging Pressure Conditioning for Accurate Fill Measurement
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Solution Overview
Problem
Conventional refrigerant filling systems in refrigeration systems, such as air conditioning systems, face accuracy issues due to the distance between the charging valve and the charging hose, leading to variations in refrigerant amount caused by ambient temperature changes, resulting in reduced accuracy in determining the filled amount.
Innovation Solution
A method and system that pressurize the refrigerant tank to a differential pressure above the saturation pressure of the ambient temperature, using a compressor and temperature/pressure sensors to ensure the inlet line is filled with liquid refrigerant, vaporizing the majority of the refrigerant to reduce density variations and improve charging accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the charging valve is placed inside the machine at a distance of a couple of meters from the charging hose, then the system structure is simplified and easier to operate, but the ambient temperature variations greatly affect whether the charging line and hose are filled with liquid or vaporized refrigerant, resulting in reduced measurement precision
Solution Approach 1:
The system performs preliminary heating of the refrigerant in the tank before charging to ensure complete vaporization. This preliminary action eliminates the uncertainty of liquid vs vapor state during charging, thereby maintaining measurement precision despite the long distance between charging hose and valve.
Solution Approach 2:
The system changes the temperature parameter by heating the refrigerant tank to a predetermined temperature higher than ambient temperature. This parameter change ensures the refrigerant remains in vapor phase throughout the charging line, eliminating the measurement precision issue caused by temperature variations.
2Measurement precision
If the charging valve is placed close to the charging adapter to minimize dead volume, then the measurement precision of refrigerant amount is improved, but the device complexity increases and the ease of operation deteriorates
Solution Approach 1:
The system introduces an intermediary heating mechanism (heat exchanger or heating element) between the refrigerant source and the charging valve. This intermediary ensures the refrigerant is fully vaporized before reaching the charging line, allowing the valve to be positioned conveniently while maintaining measurement precision.
Solution Approach 2:
The system replaces the mechanical solution of placing the valve close to the adapter with a thermal field solution (heating the refrigerant). This substitution allows the valve to be positioned at a convenient distance while maintaining vapor phase refrigerant for accurate charging measurements.
3Measurement precision
If the refrigerant is kept in liquid state in the charging line, then the amount of refrigerant leaving the tank matches the amount leaving the tank with high accuracy, but the ambient temperature variations cause uncertainty about whether the line is filled with liquid or vapor, reducing measurement precision
Solution Approach 1:
The system deliberately induces a phase transition from liquid to vapor by heating the refrigerant in the tank before charging. This controlled phase transition ensures the refrigerant is in a stable vapor state throughout the charging process, eliminating the instability caused by ambient temperature variations and improving measurement precision.
Solution Approach 2:
The system changes the temperature parameter of the refrigerant by heating it to a predetermined temperature higher than ambient temperature. This parameter change stabilizes the refrigerant composition by ensuring complete vaporization, thereby improving measurement precision despite ambient temperature variations.
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
The system achieves high accuracy in determining the refrigerant amount filled into the refrigeration system by minimizing variations in the refrigerant left in the hose, with an accuracy of +/-15 grams, by ensuring the refrigerant is vaporized, which has a density more than 40 times lower than liquid refrigerant.
Implementation Method 1
a compressor, which is configured for compressing the refrigerant from an external reservoir to a filling pressure
Implementation Method 2
The conditioning process further causes a large portion, in particular the majority, of the refrigerant to be vaporized
Implementation Method 3
As the density of vaporized refrigerant is more than 40 times lower than the density of the liquid refrigerant
Implementation Method 4
a pressure sensor, which is configured for measuring the pressure of the refrigerant in the tank
Implementation Method 5
at least two temperature sensors, which are respectively configured for measuring the ambient temperature and the temperature of the refrigerant collected in the tank
Data Source
AI summary
A method of filling refrigerant into a refrigeration system by means of a filling system comprising a tank includes the step of pressurizing the tank by means of a conditioning process to a predetermined differential pressure above the saturation pressure of the actual ambient temperature before the refrigerant is filled into the refrigeration system.