Calibration method of refrigerant saturation temperature in a refrigeration system, a controller for applying such a method and a cooling machine
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Solution Overview
Problem
Refrigeration systems face inefficiencies and reliability issues due to uncertainties in refrigerant composition and sensor tolerances, which affect superheat levels and overall performance, especially with the phase-out of high global warming potential refrigerants and unintended mixing of refrigerants.
Innovation Solution
A method to determine and adjust the refrigerant composition in refrigeration systems by running test runs, reading sensor values, and calibrating the system using Antoine equation parameters, ensuring accurate superheat control and system optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard temperature sensors and pressure transmitters are used in the refrigeration system, then the system is cost-effective and easy to manufacture, but measurement inaccuracies due to sensor tolerances affect superheat calculation precision
Solution Approach 1:
The patent changes the parameters of existing sensors and pressure transmitters by applying calibration factors (kT, kP, kSH) to their output signals. Instead of replacing sensors with high-precision instruments, the system adjusts their readings through parameter modification, thereby improving measurement precision while keeping the original cost-effective sensor setup.
Solution Approach 2:
The patent replaces physical mechanical calibration methods with an electronic/software-based calibration system. The calibration factors are determined through a test run and then applied computationally to sensor readings, substituting complex mechanical adjustment procedures with simpler electronic signal processing.
2Reliability
If refrigerant composition is not calibrated, then the system can operate with various refrigerants including environmentally friendly alternatives, but uncertainty in refrigerant composition leads to inaccurate superheat levels and reduced system efficiency
Solution Approach 1:
The refrigeration system performs self-calibration by executing a test run that automatically determines calibration factors specific to the actual refrigerant composition. The system serves itself by adapting to different refrigerants without requiring manual intervention or external calibration equipment, thereby maintaining reliability across various refrigerant types.
Solution Approach 2:
The patent implements a preliminary calibration phase (test run) before normal operation. During this preliminary action, the system determines the actual refrigerant composition and calculates calibration factors that will be used for accurate superheat control throughout subsequent operation, ensuring system efficiency from the start.
3Measurement precision
If a test run is conducted to determine calibration factors, then measurement accuracy is improved, but system downtime and loss of productive operation time occur
Solution Approach 1:
The calibration test run is implemented as a periodic action that occurs once during system commissioning or installation. By concentrating the calibration activity in a single initial period rather than requiring continuous calibration during operation, the system achieves measurement precision while minimizing overall productivity loss.
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 eliminates uncertainties in refrigerant composition and sensor tolerances, enhancing the efficiency, reliability, and environmental sustainability of refrigeration systems by maintaining optimal superheat levels and system performance.
Implementation Method 1
From measurement of the pressure, a saturated temperature of the refrigerant is calculated at dew-point, by use of equations describing relation between vapour pressure and temperature, such as a known Antoine equation
Implementation Method 2
Superheat can be defined as temperature difference between measured temperature at the evaporator outlet and the calculated saturation temperature from the pressure measurement
Implementation Method 3
The expansion valve is set to provide 25% liquid and 75% vapour at an outlet of the expansion valve
Implementation Method 4
an evaporator, one or more evaporator fans, a condenser, one or more condenser fans
Implementation Method 5
a compressor, and a controller for controlling the refrigeration system
Implementation Method 6
a condenser, one or more condenser fans
Data Source
AI summary
A method of determining a refrigerant or a composition of refrigerants in a refrigeration system comprising an expansion valve, an evaporator, one or more evaporator fans, a condenser, one or more condenser fans one or more temperature sensors, one or more pressure sensors, a compressor, and a controller for controlling the refrigeration system, the controller comprising a memory, the expansion valve, the evaporator and the compressor being fluidly interconnected in a refrigerant path having refrigerant flowing therein, comprising the steps of: a) Running a test run and read out values from one or more of the sensors; b) Determining a composition by the result of step a; and c) Adjusting the refrigeration system in relation to the composition determined by step b. Also disclosed is a controller for controlling a refrigeration system and a cooling machine in a reefer container.