Evaporator Defrost Timing With Fan Pre-Warming Control
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Solution Overview
Problem
Current defrost timers in refrigeration systems waste energy by initiating the defrost cycle immediately after the compressor has stopped, as the evaporator coils remain cold and ineffective for defrosting during this period.
Innovation Solution
A refrigeration control system that includes a motor-driven cam-operated switch arrangement to disconnect the compressor from power after the refrigeration cycle, allowing the evaporator fan to continue circulating air and pre-warm the coils, then connects the defrost heater to power only after the coils have warmed, optimizing energy usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the defrost timer initiates a defrost cycle immediately after the compressor run cycle has terminated, then the defrost cycle can be started on schedule, but the defrost heater consumes excess energy without effective defrosting because the evaporator coils are still very cold from coolant evaporation
Solution Approach 1:
The system performs preliminary cooling of the evaporator coils by the evaporator fan before initiating the defrost cycle. This preliminary action ensures that when the defrost heater is activated, the coils are at the optimal temperature for effective defrosting, thereby reducing energy waste and improving defrost efficiency.
Solution Approach 2:
The control system monitors the temperature of the evaporator coils and uses this feedback information to determine the optimal time to initiate the defrost cycle. When the coils reach the predetermined temperature threshold, the system automatically triggers the defrost sequence, ensuring energy-efficient operation while maintaining effective ice removal.
2Productivity
If the defrost heater operates while the evaporator coils are still cold from coolant evaporation, then the defrost cycle can begin immediately, but the heater wastes energy without achieving effective defrosting
Solution Approach 1:
The system performs preliminary cooling of the evaporator coils by the evaporator fan before initiating the defrost cycle. This preliminary action ensures that when the defrost heater is activated, the coils are at the optimal temperature for effective defrosting, thereby reducing energy waste and improving defrost efficiency.
Solution Approach 2:
The control system monitors the temperature of the evaporator coils and uses this feedback information to determine the optimal time to initiate the defrost cycle. When the coils reach the predetermined temperature threshold, the system automatically triggers the defrost sequence, ensuring energy-efficient operation while maintaining effective ice removal.
3Reliability
If the evaporator fan continues to circulate air after the compressor stops, then the coils can pre-warm for more effective defrosting, but the system complexity increases due to coordinated control requirements
Solution Approach 1:
The evaporator fan serves multiple functions: it cools the evaporator coils during the refrigeration cycle and continues to circulate air after compressor shutdown to pre-warm the coils for the upcoming defrost cycle. This multi-functionality reduces the need for separate heating elements and simplifies the overall control logic while improving defrost effectiveness.
Solution Approach 2:
The evaporator fan operates continuously through the transition from refrigeration to defrost mode, eliminating idle time and ensuring uninterrupted preparation of the coils for defrosting. This continuous operation maintains optimal conditions for defrost effectiveness while streamlining the control sequence.
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 reduces energy consumption by allowing the evaporator coils to warm before defrosting, shortening the defrost cycle and minimizing the high-wattage defrost heater's runtime, resulting in net energy savings compared to conventional systems.
Implementation Method 1
an evaporator fan that circulates air over the evaporator coil and into the freezer compartment
Implementation Method 2
a defrost heater that is periodically operated to remove frost build-up from the evaporator coil
Data Source
AI summary
A system and method for refrigeration timer control having an energy efficient defrost cycle are provided. The system and method provide a delay time after the refrigeration cycle and prior to the defrost cycle. During this delay period the evaporator fan may run. The fan circulation and the heat from the fan coil provide a pre-warm cycle to the evaporator prior to the defrost cycle. To further enhance energy efficiency, the system and method may also provide a pre-refrigeration cycle after the defrost cycle. During this pre-refrigeration cycle only the compressor is energized. This prevents warm moist air from being circulated until the evaporator coils are cooled.