Refrigeration system with evaporator temperature sensor failure detection and related methods
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Solution Overview
Problem
Faulty evaporator temperature sensors in refrigeration systems can lead to premature or prolonged defrost operations, resulting in inefficient cooling performance due to incorrect temperature readings, which are not effectively detected by existing technologies.
Innovation Solution
A method involving monitoring the output of the evaporator temperature sensor during defrost operations to identify a rate of change in temperature and compare it to predefined conditions, allowing for adaptive control actions to determine sensor validity and adjust defrost operations accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the evaporator temperature sensor is used to control defrost operations, then the defrost operation can be automated, but the system reliability deteriorates when the sensor degrades over time
Solution Approach 1:
The system performs preliminary validation of the temperature sensor by analyzing its output characteristics before using it to control defrost operations. The controller evaluates whether the sensor reading is consistent with expected physical behavior during defrost, and only accepts the sensor data for control purposes if it passes this preliminary consistency check. This prevents degraded sensor data from compromising system reliability.
Solution Approach 2:
The system implements feedback by continuously monitoring the temperature sensor output during defrost operations and comparing it against expected temperature profiles. When the sensor reading deviates from the expected range or rate of change, the system detects this as sensor degradation and adjusts the defrost control accordingly, using feedback from the sensor validation process to maintain reliable operation.
2Loss of time
If the temperature sensor reading is higher than actual temperature, then the defrost operation terminates prematurely, but this results in partially frosted coil and poor cooling performance
Solution Approach 1:
The system uses feedback from monitoring the temperature sensor output during defrost to detect when the sensor reading is inconsistent with actual temperature behavior. By comparing the sensor reading against the expected temperature profile and rate of change, the system identifies sensor degradation and adjusts the defrost termination decision to account for the faulty reading, preventing premature termination that would leave the coil partially frosted.
3Reliability
If the temperature sensor is faulty and reads lower than actual temperature, then the defrost operation continues longer than necessary, but this raises overall cabinet temperature and causes the refrigeration system to run excessively
Solution Approach 1:
The system implements feedback monitoring of the temperature sensor during defrost operations to detect when the sensor reading is lower than the actual temperature. When such inconsistency is detected, the system adjusts the defrost termination timing to prevent excessive defrost duration, thereby avoiding unnecessary energy consumption by the refrigeration system while still ensuring complete defrosting.
4Device complexity
If no sensor validation is performed, then the system operation is simple, but faulty sensors go undetected and impact system performance
Solution Approach 1:
The system performs a preliminary validation check of the temperature sensor by analyzing its output characteristics during defrost operations. This preliminary action involves comparing the sensor reading against expected temperature profiles and rates of change, and only accepting the sensor data for control purposes if it passes this validation. This adds minimal complexity while significantly improving measurement precision and reliability.
Solution Approach 2:
The system replaces physical inspection or manual validation of the temperature sensor with an automated electronic validation process. The controller electronically analyzes the sensor output signal characteristics and compares them against expected ranges, substituting a simple electronic validation mechanism for more complex physical testing methods, thereby achieving reliable sensor validation with minimal added complexity.
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 enables the refrigeration system to accurately detect faulty temperature sensors, optimizing defrost operations and maintaining efficient cooling performance by adjusting control actions based on sensor reliability, thereby reducing energy consumption and ensuring proper defrosting.
Implementation Method 1
a temperature sensor is placed in the evaporator coil fins. The temperature sensor measures the coil temperature during defrost
Implementation Method 2
a heat source is introduced to raise the temperature of the evaporator above the freezing point of water
Implementation Method 3
to melt frost so it can drip into a catch-pan
Implementation Method 4
a refrigeration system for cooling the space
Data Source
AI summary
A method of automatically controlling a refrigerated device that includes a refrigeration system with an evaporator and an evaporator temperature sensor involves: (a) monitoring an output of the evaporator temperature sensor; (b) based upon monitored temperatures from (a), identifying when a rate of change in temperature indicated by the evaporator temperature sensor satisfies a set rate of change condition and determining if the temperature indicated by the evaporator temperature sensor when the rate of change satisfies to the set rate of change condition is consistent with a predefined expected temperature condition; (c) if the temperature indicated by the evaporator temperature sensor is consistent with the predefined expected temperature condition, taking a first refrigeration control action; and (d) if the temperature indicated by the evaporator temperature sensor is not consistent with the predefined expected temperature condition, taking a second refrigeration control action that is different than the first refrigeration control action.