Cascade Refrigeration Receiver Cooling for Defrost Pressure Control
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Solution Overview
Problem
Existing two-stage refrigeration apparatuses face issues with abnormal pressure rise during defrosting in the low-stage refrigeration cycle and require additional refrigeration machines for cooling, leading to increased equipment size and costs.
Innovation Solution
A two-stage refrigeration apparatus with a first and second refrigeration cycle device, a cascade condenser, a receiver heat exchanging portion, defrosting means, and a controller that activates the first compressor to cool the second refrigerant in the receiver heat exchanging portion when the second refrigerant approaches a supercritical state, maintaining pressure below the critical-point pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the low-stage-side condenser is cooled by the cascade heat exchanger during defrosting operation, then the pressure rise inside the low-stage refrigeration cycle is suppressed, but the refrigerant cannot flow through the condenser and cooling becomes insufficient
Solution Approach 1:
The patent divides the condenser into two separate circuits: a cascade heat exchanger for pressure control and a dedicated cooling circuit for maintaining cooling performance. This segmentation allows each circuit to fulfill its specific function independently without interfering with the other.
Solution Approach 2:
The patent introduces an intermediary cooling circuit that acts as a mediator between the cascade heat exchanger and the evaporator. This intermediary circuit allows heat removal from the low-stage refrigerant without requiring it to flow through the cascade heat exchanger, thus maintaining both pressure control and cooling performance.
2Stress or pressure
If a cooling pipe and collector are connected through a refrigerating machine to reduce gas pressure, then the refrigerant pressure is reduced, but the equipment size increases and production cost rises
Solution Approach 1:
The patent makes the cascade heat exchanger serve multiple functions: it acts as both the cascade heat exchanger for pressure control and as the condenser for the low-stage refrigerant. This multi-functionality eliminates the need for separate cooling pipes and collectors, reducing equipment size and cost.
Solution Approach 2:
The patent merges the cooling function with the cascade heat exchanger by allowing the low-stage refrigerant to flow through it. This combines what were previously separate functions (pressure control and cooling) into a single integrated component, simplifying the overall system.
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 effectively suppresses pressure rise in the low-stage refrigeration circuit during defrosting, improving the reliability and reducing equipment size and production costs by utilizing the high-stage refrigeration cycle to cool the low-stage refrigerant.
Implementation Method 1
The receiver heat exchanging portion is configured to cool the receiver by heat exchange with a portion in which the first refrigerant being low-pressure flows in the first refrigerant circuit
Implementation Method 2
The cascade condenser includes the first evaporator and the second condenser and is configured to cause the first refrigerant flowing in the first evaporator and the second refrigerant flowing in the second condenser to exchange heat with each other
Data Source
AI summary
A two-stage refrigeration apparatus includes a high-stage refrigeration cycle including a high-stage-side refrigerant circuit including a high-stage-side compressor, high-stage-side condenser, high-stage-side expansion valve, and high-stage-side evaporator connected by pipes, a low-stage refrigeration cycle including a low-stage-side refrigerant circuit including a low-stage-side compressor, low-stage-side condenser, low-stage-side receiver, low-stage-side expansion valve, and low-stage-side evaporator connected by pipes, a cascade condenser including the high-stage-side evaporator and low-stage-side condenser, a receiver heat exchanging portion configured to cool the low-stage-side receiver, and a high-stage refrigeration cycle controller configured to perform controlling so as to activate the high-stage-side compressor when estimating a low-stage-side refrigerant will reach a supercritical state while the low-stage-side compressor is defrosted on the basis of the pressure of the low-stage-side refrigerant.