Refrigeration Cycle Control Using Quasi-Subcooling Degree
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Solution Overview
Problem
Conventional refrigeration apparatuses require time to achieve high-efficiency operation when the high-pressure side pressure exceeds the critical pressure of the refrigerant, due to the need for repeated control of the pressure reducing means to maintain optimal refrigerant pressure.
Innovation Solution
Control the quasi-subcooling degree, which is the temperature difference between the quasi-condensation temperature and the cooler outlet refrigerant temperature, within a predetermined range of 5° C. to 12° C., using the expansion mechanism to enhance control convergence and achieve rapid high-efficiency operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refrigerant pressure on the high-pressure side is controlled to conform to a set value by adjusting the pressure reducing means, then the refrigerant pressure can be maintained at the optimal value, but the coefficient of performance takes time to approach the maximum value due to repeated control adjustments needed when refrigerant temperature changes
Solution Approach 1:
The invention changes the controlled parameter from refrigerant pressure to quasi-subcooling degree (temperature difference between quasi-condensation temperature and cooler outlet refrigerant temperature). By controlling this temperature parameter instead of pressure, the system achieves faster convergence to optimal operation because temperature responds more directly and predictably to expansion mechanism adjustments, eliminating the repeated oscillations seen in pressure-based control
Solution Approach 2:
The invention implements feedback control by continuously monitoring the quasi-subcooling degree and adjusting the expansion mechanism accordingly. The control unit compares the actual quasi-subcooling degree with the target value and modifies the expansion mechanism's degree of opening to minimize the difference, ensuring the system rapidly converges to and maintains optimal coefficient of performance
2Reliability
If the degree of opening of the pressure reducing means is repeatedly adjusted to maintain refrigerant pressure at the set value after refrigerant temperature changes, then the refrigerant pressure can be kept at the optimal value, but the control process becomes complex and time-consuming
Solution Approach 1:
The invention simplifies the control process by changing from pressure control to temperature-based quasi-subcooling degree control. This parameter change reduces control complexity because temperature measurements and adjustments are more straightforward than pressure control, and the relationship between expansion mechanism opening and quasi-subcooling degree is more direct and less prone to oscillations
Solution Approach 2:
The invention replaces the mechanical pressure control system with a thermal parameter control system. Instead of using pressure sensors and pressure-based control algorithms, the system uses temperature sensors and temperature-based control logic, which simplifies the overall control architecture and reduces the complexity of the control process
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 allows for rapid achievement of high-efficiency operation by maintaining the coefficient of performance near its maximum value, providing satisfactory responsiveness and efficiency in refrigeration cycle operations.
Implementation Method 1
a quasi-subcooling degree, which is the temperature difference between a quasi-condensation temperature and a cooler outlet refrigerant temperature, is within a predetermined temperature range
Implementation Method 2
a refrigeration cycle operation in which the high-pressure side attains a pressure that exceeds the critical pressure of the refrigerant
Data Source
AI summary
A refrigeration apparatus is configured to perform a refrigeration cycle operation in which a high-pressure side attains a pressure that exceeds the critical pressure of a refrigerant used in the refrigeration cycle operation. The refrigeration apparatus includes a refrigerant circuit and a control unit. The refrigerant circuit has a plurality of constituent components including a compressor, a cooler, an expansion mechanism, and a heater. The control unit is operatively coupled to control at least one of the constituent components such that a quasi-subcooling degree is within a predetermined temperature range, the quasi-subcooling degree being a temperature difference between a quasi-condensation temperature and a cooler outlet refrigerant temperature, with the quasi-condensation temperature being the refrigerant temperature at which isobaric specific heat capacity of the refrigerant at the refrigerant pressure on the high-pressure side of the refrigeration cycle is at a maximum.