Constant-Volume Refrigerant Charging for Accurate CO2 Mass Transfer
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Solution Overview
Problem
Conventional refrigerant charging systems face inaccuracies due to vibration sensitivity and high costs, particularly when using load cells and mass flow technology, especially with carbon dioxide as refrigerant, which is stored at higher pressures and in a gaseous state, requiring a more accurate and cost-effective solution.
Innovation Solution
A refrigerant charging system utilizing a constant volume tank with temperature and pressure sensors to calculate the mass of refrigerant, allowing precise determination and transfer of refrigerant without relying on load cells or expensive mass flow technology, using a controller to manage valves and a heater for pressure adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a load cell is used to measure refrigerant mass, then the measurement is obtained, but the system becomes sensitive to vibration and loses precision
Solution Approach 1:
The patent replaces the mechanical load cell system with a thermodynamic calculation system. Instead of mechanically weighing the refrigerant, the system uses temperature and pressure sensors combined with thermodynamic property data to calculate refrigerant mass. This substitution eliminates vibration sensitivity while maintaining measurement capability through the relationship between thermodynamic state and mass in a constant volume tank.
2Measurement precision
If mass flow technology is used to measure refrigerant flow, then flow rate measurement is achieved, but the system becomes expensive and less accurate with gaseous refrigerants
Solution Approach 1:
The patent replaces expensive mass flow technology with a thermodynamic calculation approach. Instead of using complex flow sensors that are costly and less accurate with gases, the system uses simple temperature and pressure sensors with thermodynamic property data to calculate mass flow rate. This approach is particularly effective for gaseous refrigerants like carbon dioxide, providing accurate measurement at lower cost.
3Productivity
If carbon dioxide is used as refrigerant, then refrigeration efficiency is improved, but the tank weight increases due to thicker walls
Solution Approach 1:
The patent addresses the tank weight issue by replacing mechanical weighing with thermodynamic calculation. Since the tank weight is constant and known, the system subtracts this from the total weight calculation derived from thermodynamic properties, allowing accurate refrigerant mass measurement despite the heavy tank walls required for high-pressure carbon dioxide storage.
4Quantity of substance
If the tank weight is several hundred pounds, then sufficient refrigerant storage capacity is achieved, but load cell sensitivity is reduced
Solution Approach 1:
The patent eliminates the sensitivity problem by replacing the load cell with thermodynamic calculation. The system determines refrigerant mass from temperature and pressure measurements combined with thermodynamic property data for the specific refrigerant. This approach maintains measurement precision regardless of the large tank weight, as the calculation is based on the refrigerant's thermodynamic state rather than the total system weight.
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 accurate refrigerant charging with reduced vibration sensitivity and lower costs, ensuring efficient operation and precise mass transfer, even with carbon dioxide, by using temperature and pressure sensors to calculate and control the refrigerant mass within a constant volume tank.
Implementation Method 1
A refrigerant charging system utilizing a constant volume tank with temperature and pressure sensors to calculate the mass of refrigerant
Implementation Method 2
A refrigerant charging system utilizing a constant volume tank with temperature and pressure sensors to calculate the mass of refrigerant
Implementation Method 3
A heater may optionally be connected to the refrigerant source for raising the temperature of refrigerant within the refrigerant source
Implementation Method 4
transferred refrigerant from a refrigerant source to a storage vessel... The refrigerant is then transferred from the storage vessel to the refrigeration system
Data Source
AI summary
A refrigerant charging system for charging a refrigeration system with refrigerant includes a refrigerant source, a storage vessel, input and output lines, and a device for detecting mass of refrigerant within the storage vessel. The input line fluidly connects the refrigerant source to the storage vessel, and the output line extends from the storage vessel and is adapted to connect to the refrigeration system. The system also includes an input control valve disposed between the storage vessel and the refrigerant source, and an output control valve disposed between the storage vessel and the refrigeration system. A heater is connected to the refrigerant source for raising the temperature of refrigerant within the refrigerant source. A method of charging a refrigeration system is also disclosed. The system and method are useful to charging the refrigerant system of an automotive vehicle, among others.