Vapour Compression System Fault Mitigation Using Mass Flow Estimation
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Solution Overview
Problem
Vapour compression systems, such as refrigeration and heat pump systems, become energy inefficient and unstable when a sensor malfunctions, leading to potential shutdown and high maintenance costs.
Innovation Solution
A method that estimates the mass flow of gaseous refrigerant using measurements from functional sensors, derives refrigerant pressure or temperature values, and uses these values to control the system, allowing continued operation even with a malfunctioning sensor, without compromising energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vapour compression system continues operating with a malfunctioning sensor, then system availability is improved, but energy efficiency deteriorates and system stability worsens
Solution Approach 1:
The patent introduces an intermediary estimation mechanism that uses data from functional sensors to derive the missing control parameter. Instead of directly using the malfunctioning sensor's output, the system employs mass flow estimation based on measurements from other sensors (pressure, temperature) to calculate the unavailable parameter, thereby maintaining system operation with reduced energy inefficiency
Solution Approach 2:
The patent creates a virtual copy of the malfunctioning sensor's function by deriving its measurement through calculations based on other sensor data. The system reconstructs the missing control parameter information through mathematical relationships and mass flow estimation, effectively copying the functionality of the failed sensor using available data from other parts of the system
2Reliability
If the vapour compression system continues operating with a malfunctioning sensor, then system availability is improved, but system stability deteriorates
Solution Approach 1:
The patent implements feedback mechanisms where the estimated mass flow and derived parameters are continuously monitored and used to adjust system operation. The controller uses the estimated values to maintain stable control of the vapour compression system, creating a closed-loop system that compensates for the missing sensor input through continuous estimation and adjustment based on available measurements
3Measurement precision
If sensor measurements are used directly for control, then control accuracy is improved, but system vulnerability to sensor failure worsens
Solution Approach 1:
The patent prepares for potential sensor failure by implementing a redundant estimation mechanism that can activate when a sensor malfunctions. The system pre-establishes alternative calculation methods using relationships between different parameters, so that when a sensor fails, the control system can immediately switch to using the estimated values without interruption or significant accuracy loss, thus cushioning against the impact of sensor failure
Data Source
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AI summary
A method for controlling a vapour compression system (1) is disclosed. A mass flow of refrigerant along a part of the refrigerant path is estimated, based on measurements performed by one or more pressure sensors (10, 12, 13) for measuring a refrigerant pressure at selected positions along the refrigerant path and one or more temperature sensors (11, 4) for measuring a refrigerant temperature at selected positions along the refrigerant path. A refrigerant pressure or a refrigerant temperature at a selected position a pressure sensor (10, 12, 13) or temperature sensor (11, 14) along the refrigerant path is derived, based on the estimated mass flow. The vapour compression system (1) is allowed to continue operating, even if a sensor (10, 11, 12, 13, 14) is malfunctioning or unreliable.