Ice Maker Harvest Cycle Control Using Dual Sensor Feedback
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Solution Overview
Problem
Existing grid style ice makers face reliability issues in determining when all ice has been harvested, leading to potential flooding, excessive wear, and 'freeze-up' due to the lack of accurate feedback in the harvest termination process, especially in high water hardness areas and winter months.
Innovation Solution
Incorporating both a harvest sensor and a temperature sensor to confirm that all ice has been harvested, with the temperature sensor providing additional feedback to the controller to ensure accurate termination of the harvest cycle and prevent issues like partial batch weight errors and evaporator damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a harvest sensor is used to detect when ice is harvested, then the harvest cycle can be terminated, but the system may not accurately determine when all ice has been harvested leading to reliability issues
Solution Approach 1:
The system introduces a temperature sensor that provides continuous temperature feedback during the harvest cycle. This feedback mechanism allows the controller to monitor temperature changes and determine when all ice has been harvested, rather than relying solely on the harvest sensor which may trigger prematurely. The temperature feedback creates a more reliable termination condition by monitoring the actual thermal state of the evaporator.
Solution Approach 2:
The temperature sensor acts as an intermediary between the harvest sensor and the controller. While the harvest sensor detects mechanical movement or presence of ice, the temperature sensor provides an intermediate measurement that confirms complete harvest. This intermediary measurement resolves the contradiction by adding a verification layer that ensures reliability before terminating the harvest cycle.
2Device complexity
If the harvest cycle is terminated using only a harvest sensor, then the system operation is simple, but it may cause flooding, excessive wear, and freeze-up due to inaccurate harvest detection
Solution Approach 1:
The system performs a preliminary temperature check before terminating the harvest cycle. The controller monitors temperature trends during the harvest process and uses this preliminary information to predict when complete harvest will occur. This preliminary action prevents premature termination that would cause flooding and wear, while adding minimal complexity to the control system.
Solution Approach 2:
The temperature monitoring provides a cushioning effect by creating a safety margin before harvest termination. Instead of terminating immediately when the harvest sensor triggers, the system continues monitoring temperature to ensure complete harvest, cushioning against the harmful effects of premature termination such as flooding and excessive wear on components.
3Reliability
If temperature monitoring is added to confirm complete harvest, then harvest reliability is improved, but the system complexity increases
Solution Approach 1:
The temperature sensor serves multiple functions: it monitors harvest progression, confirms complete harvest, and provides data for controller decision-making. By making this single component multi-functional, the system achieves improved reliability without proportionally increasing complexity. The same temperature measurement that confirms harvest completion also provides information about the harvest process dynamics.
Solution Approach 2:
The system changes the parameter being monitored from purely mechanical detection (harvest sensor) to thermal detection (temperature sensor). This parameter change enables more accurate harvest determination because temperature changes provide a more definitive indication of complete ice removal. The controller processes temperature parameter changes to determine harvest completion, adding reliability while keeping the added complexity manageable through efficient parameter monitoring.
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
Enhances the reliability of the ice making process by preventing unwanted freeze-ups, potential flooding, and reducing wear on system components, ensuring consistent and accurate ice production.
Implementation Method 1
a temperature sensor for measuring a temperature that indicates that all of the ice has been harvested from the freeze plate
Implementation Method 2
a hot gas valve which is adapted to be opened during a harvest cycle to direct warm refrigerant from the compressor to the evaporator through a hot gas bypass line
Implementation Method 3
an evaporator for receiving the low pressure liquid refrigerant from the thermal expansion valve and discharging low pressure, substantially gaseous refrigerant
Data Source
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AI summary
An ice maker for forming ice having a refrigeration system, a water system and a controller. The refrigeration system includes a freeze plate in which ice is formed and a hot gas valve for harvesting the ice therefrom. A harvest sensor is triggered when at least a portion of the ice is harvested from the freeze plate and at least one temperature sensor measures a temperature that indicates that all of the ice has been harvested from the freeze plate. The temperature sensors may include a temperature sensor for measuring the refrigerant temperature at the evaporator outlet, the refrigerant temperature at the evaporator inlet, and/or the temperature of the freeze plate. The controller closes the hot gas valve in response from the triggering of the harvest sensor and the temperature measured by the temperature sensor(s) indicating that all of the ice has been harvested from the freeze plate.