Ice Machine Refrigerant Charge Detection Using Freeze Time
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Solution Overview
Problem
Conventional compressor protection systems in refrigeration systems rely on discrete temperature and pressure sensors, which are costly, complex, and inaccurate in detecting refrigerant charge levels, especially under severe undercharge or overcharge conditions, due to variability in manufacturing and refrigerant volume changes.
Innovation Solution
A diagnostic system using sensors to monitor current, power, discharge line temperature, and pressure, with processing circuitry that determines the refrigerant charge level by calculating freeze time and processing signals from multiple sensors, including those positioned at the compressor and condenser, to accurately assess the charge level and trigger alarms or power interruptions as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple discrete temperature and pressure sensors are used to monitor compressor operation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces physical temperature and pressure sensors with a computational model that uses electrical parameters (current, voltage, frequency) to infer refrigerant charge levels. This substitution eliminates the need for multiple discrete sensors throughout the system, reducing device complexity while maintaining measurement capability through electrical measurements that are already taken for compressor control.
Solution Approach 2:
The patent introduces an intermediary computational approach that translates easily measurable electrical parameters into indirect indicators of refrigerant charge. Instead of directly measuring temperature and pressure with physical sensors, the system uses current and voltage measurements as intermediaries to calculate charge levels, avoiding the need for complex sensor networks.
2Measurement precision
If discrete sensors are placed throughout the system, then measurement coverage is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces multiple physical sensors with electrical measurements taken at the compressor motor terminals. This substitution dramatically simplifies manufacturing and installation, as the electrical parameters can be measured using existing motor control circuitry without requiring additional sensor placement throughout the refrigeration system.
3Measurement precision
If traditional sensors are used to detect refrigerant charge, then detection capability is improved, but reliability decreases under severe undercharge or overcharge conditions
Solution Approach 1:
The patent changes the measurement parameters from direct temperature and pressure sensing to electrical parameter analysis (current, voltage, frequency). This parameter change allows the system to detect refrigerant charge levels through the electrical characteristics of the compressor motor, which remain reliable even under severe undercharge or overcharge conditions where traditional sensors may fail or provide inaccurate readings.
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 provides accurate and efficient detection of refrigerant charge levels, reducing system inefficiencies and failures by using multiple sensors and processing circuitry to calculate charge levels, thus enhancing compressor protection and system reliability.
Implementation Method 1
A processing circuitry processes the first signal and the second signal to determine a freeze time
Data Source
AI summary
A system includes a compressor driven by a motor. A condenser receives working fluid from the compressor. An evaporator is in fluid communication with the condenser and the compressor. A first sensor produces a first signal indicative of one of current and power drawn by the motor. A second sensor produces a second signal indicative of a discharge line temperature. A processing circuitry processes the first signal and the second signal to determine a freeze time. The processing circuitry processes the freeze time, the current signal, and the discharge line temperature signal to determine a working fluid charge level.