Cascade refrigeration system
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Solution Overview
Problem
The conventional cascade refrigeration system faces challenges with slow start-up times, decreased compressor reliability, and increased power consumption due to the alternating operation of compressors in the low-side and high-side refrigerant circuits.
Innovation Solution
The proposed cascade refrigeration system incorporates a high-side and low-side refrigerant circuit with a cascade heat exchanger, where the high-side refrigerant circuit includes a bypass path and a switching device to control the circulation path, allowing for efficient heat exchange and reduced pressure differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the low-side and high-side refrigerant circuits are simultaneously activated, then the system can operate both circuits, but the refrigerant circulation amount cannot be sufficiently ensured leading to low-pressure cutoff and high-pressure cutoff abnormalities
Solution Approach 1:
The system activates the high-side refrigerant circuit first before activating the low-side refrigerant circuit. The controller monitors the discharge temperature of the high-side compressor and only activates the low-side circuit when the discharge temperature reaches a predetermined value, ensuring sufficient refrigerant circulation is established in the high-side circuit before the low-side circuit begins operation.
2Reliability
If the low-side refrigerant circuit is stopped and restarted repeatedly to prevent high-pressure abnormality, then pressure abnormalities are avoided, but the start-up time increases and compressor reliability decreases
Solution Approach 1:
The high-side refrigerant circuit is activated in advance before the low-side refrigerant circuit. By establishing proper refrigerant circulation and pressure conditions in the high-side circuit first, the system prevents pressure abnormalities when the low-side circuit is activated, eliminating the need for repeated stopping and starting of compressors.
3Reliability
If the compressors are alternately operated to prevent pressure abnormalities, then system stability is improved, but power consumption increases due to repeated activation and stop
Solution Approach 1:
The high-side compressor is activated in advance and maintained in operation while the low-side circuit is activated. This sequential activation approach allows both circuits to operate simultaneously without repeated compressor shutdowns, reducing power consumption while maintaining system stability through proper pressure and temperature 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
This configuration enables a prompt start-up operation, maintains compressor reliability, and reduces power consumption by optimizing refrigerant circulation and heat exchange processes.
Implementation Method 1
the high-side refrigerant and the low-side refrigerant exchange heat in the cascade heat exchanger
Data Source
AI summary
There is provided a cascade refrigeration system that promptly performs a start-up operation and suppresses a decrease in reliability of a compressor and suppresses an increase in power consumption. The cascade refrigeration system includes: a high-side refrigerant circuit (2) having a high-side first circulation path (17) containing a high-side compressor (10), a high-side heat exchanger (11), a high-side expansion valve (12), and a cascade heat exchanger (13) where a high-side refrigerant and a low-side refrigerant exchange heat, sequentially connected; and a low-side refrigerant circuit (3) containing a low-side compressor (20), the cascade heat exchanger (13), a low-side expansion valve (21), and a heat source-side heat exchanger (22) sequentially connected, in which the high-side refrigerant circuit (2) includes: a high-side second circulation path (18) in which a discharge side and a suction side of the high-side compressor (10) are connected by a high-side bypass path (15) and through which the high-side refrigerant discharged from the high-side compressor (10) circulates to the suction side of the high-side compressor (10) through the high-side bypass path (15); and a high-side opening and closing valve (16) performing switching between the high-side first circulation path (17) and the high-side second circulation path (18).