Refrigeration system and method for operating same
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Solution Overview
Problem
Current refrigeration systems face inefficiencies and energy consumption issues during the defrosting process, particularly with CO2 refrigerants, as existing methods are either time-consuming, energy-intensive, or risk compressor damage.
Innovation Solution
A CO2 refrigeration system with a closed-loop circuit incorporating a compression stage, cooling stage, reservoir, and evaporation stage, utilizing a defrost line and pressure regulating unit, such as an ejector, to efficiently convey and pressurize refrigerant for defrosting, allowing for a controlled and energy-efficient defrosting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot refrigerant vapor is circulated from the compressor through the evaporator for defrosting, then the evaporator can be defrosted, but liquid refrigerant may be introduced into the compressor which may damage the compressor
Solution Approach 1:
The system divides the refrigerant flow path into separate circuits: a defrost circuit that directs refrigerant from the condenser through the evaporator for defrosting, and a cooling circuit that directs refrigerant from the compressor through the evaporator for cooling. This segmentation prevents liquid refrigerant from the defrost circuit from entering the compressor.
Solution Approach 2:
The system introduces an intermediary component (defrost circuit with separate refrigerant path) between the condenser and evaporator to mediate the defrosting process, ensuring that refrigerant used for defrosting does not directly return to the compressor and potentially cause damage.
2Reliability
If heaters are activated near the evaporator to remove ice build-up, then the evaporator can be defrosted, but the refrigerated area may experience undesirable heating
Solution Approach 1:
The system uses the refrigerant itself to perform the defrosting function by directing it through a separate defrost circuit where it absorbs heat from the evaporator, allowing the evaporator to defrost itself without external heating elements that would warm the refrigerated space.
3Reliability
If the refrigeration cycle is stopped and frost is allowed to melt passively, then the evaporator can be defrosted, but the process is time consuming and inefficient
Solution Approach 1:
The system maintains continuous useful action by implementing an active defrost circuit that continuously directs refrigerant through the evaporator to remove frost, rather than stopping the refrigeration cycle and relying on slow passive melting, thereby significantly reducing defrosting time while maintaining system efficiency.
4Reliability
If heaters are used to defrost the evaporator, then the evaporator can be defrosted, but the method is energy consuming
Solution Approach 1:
The system uses the refrigerant's own thermal properties to perform defrosting by directing it through a separate circuit where it absorbs heat from the evaporator, eliminating the need for external heating elements and associated energy consumption.
Solution Approach 2:
The system exploits phase transitions of the refrigerant (changing from liquid to vapor and back) to transfer heat efficiently during the defrosting process, using the refrigerant's latent heat of vaporization and condensation to absorb and release heat at appropriate stages.
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 solution enables a more efficient and energy-effective defrosting process for CO2 refrigeration systems, reducing time and energy consumption while preventing compressor damage, by using a closed-loop circuit and pressure regulation to manage refrigerant flow during defrosting.
Implementation Method 1
a pressure regulating unit provided in the defrost return line, for pressurizing the CO2 refrigerant having released heat in the evaporation stage
Implementation Method 2
the first portion of the CO2 refrigerant releases heat in the evaporation stage for defrosting the evaporation stage
Implementation Method 3
The pressure regulating unit is an ejector having a nozzle section, a suction section and a pressurizing section
Data Source
AI summary
A refrigeration system operable in cooling mode and defrosting mode is provided. The refrigeration system includes a defrost line connecting a first reservoir to an evaporation stage for conveying at least part of the flash gas from the first reservoir to the evaporation stage when the refrigeration system is operating in defrosting mode. The flash gas thereby releases heat in the evaporation stage for defrosting the evaporation stage. The refrigeration system can also include a discharge line connecting the evaporation stage to a second reservoir.