Refrigerant Charge Determination Using Flow Meter and Pressure Cycling
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Solution Overview
Problem
Current methods for determining refrigerant charge in a cooling circuit are expensive, time-consuming, and require additional equipment, affecting the temperature stability of the cargo being cooled.
Innovation Solution
A method that uses a Coriolis flow meter to measure refrigerant flow through the expansion device in the cooling circuit, with the expansion device in a fully open state, allowing for refrigerant charge determination without additional equipment, by controlling pressure and flow characteristics to ensure accuracy and minimize temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the known method of pumping down the cooling circuit with a vacuum pump is used to determine refrigerant charge, then accurate measurement of refrigerant amount is achieved, but additional equipment and time are required, increasing cost and affecting cargo temperature stability
Solution Approach 1:
The cooling circuit's own components (compressor, expansion device, heat exchangers) are utilized to perform the refrigerant charge determination. The system serves itself by using its operational cycles (loading, unloading, pressure equalizing) to gather necessary data without external intervention, eliminating the need for vacuum pumps and external measurement equipment.
Solution Approach 2:
The method monitors changes in pressure and temperature parameters within the cooling circuit during controlled operational phases. By tracking how these parameters evolve during loading, unloading, and pressure equalizing steps, the system calculates refrigerant charge based on the relationship between pressure differential, temperature, and refrigerant mass, replacing physical evacuation with parameter-based calculation.
2Measurement precision
If the known method of pumping down the cooling circuit is used, then refrigerant charge can be determined, but the process is time consuming, but cargo temperature stability is compromised
Solution Approach 1:
The system performs preliminary controlled operations (loading step, unloading step, pressure equalizing step) that prepare the refrigerant in specific states and locations within the circuit. These preliminary actions organize the refrigerant phases and pressures in advance, enabling rapid calculation of charge based on pre-established relationships between operational parameters and refrigerant mass.
Solution Approach 2:
The determination process utilizes continuous monitoring of pressure and temperature throughout the loading, unloading, and pressure equalizing phases. Rather than interrupting the system for separate measurement, the useful action of refrigerant circulation and phase change continues throughout, with data collected continuously to enable real-time charge calculation without stopping the cooling function.
3Measurement precision
If the known method is used to determine refrigerant charge, then measurement is possible, but additional equipment and time are required, increasing operational cost
Solution Approach 1:
The cooling circuit components perform multiple functions: they not only provide cooling but also serve as the measurement system for refrigerant charge determination. The compressor, expansion device, and heat exchangers are used both for their primary cooling function and for creating the controlled conditions necessary to measure refrigerant charge through pressure and temperature monitoring during operational phases.
Solution Approach 2:
The system determines its own refrigerant charge using its existing components and operational cycles, eliminating the need for external service equipment and specialized measurement tools. This self-determination capability allows rapid assessment without removing the system from service or requiring expensive external equipment, thereby improving operational efficiency and reducing costs.
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 method reduces costs and time, ensuring accurate refrigerant charge determination without affecting the cargo's temperature, as it allows for precise measurement of refrigerant flow and phase detection, enabling efficient operation of the cooling circuit.
Implementation Method 1
a heat releasing heat exchanger in said high pressure section for cooling, in particular condensing, compressed refrigerant
Implementation Method 2
a heat absorbing heat exchanger in said low pressure section for vaporizing said expanded refrigerant
Implementation Method 3
a flow meter, in particular a Coriolis flow meter, would be used in order to detect the amount of refrigerant flowing from that high pressure section to said low pressure section during said unloading step
Data Source
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AI summary
Method for refrigerant charge determination in a cooling circuit (40), comprising the following steps a loading step comprising loading essentially all refrigerant from the low pressure section (72) into the high pressure section (74) of the circuit by reducing the expansion flow (100), an unloading step admitting the expansion flow (100) of the refrigerant loaded in said high pressure section (74) into said low pressure section (72) and determining the amount of refrigerant flowing in said unloading step from said high pressure section (74) to said low pressure section (72), and calculating on the basis of said amount of refrigerant flowing in said unloading step from said high pressure section (74) to said low pressure section (72) the refrigerant charge in said cooling circuit (40).