Supercritical Refrigeration Pressure Control for Maximum COP
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Solution Overview
Problem
Conventional refrigeration systems with supercritical refrigeration cycles using carbon dioxide as a refrigerant face challenges in maintaining an optimum coefficient of performance (COP) due to reliance on single temperature measurements, leading to suboptimal pressure control and COP variations with changing outlet refrigerant and ambient air temperatures.
Innovation Solution
A refrigeration system with a variable throttling expansion mechanism and high pressure control means that adjusts the high pressure refrigerant pressure based on both outlet refrigerant and ambient temperatures, ensuring optimal COP by deriving target values from these temperatures and adjusting throttling accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pressure reduction is controlled based on only one temperature parameter (outlet refrigerant temperature or ambient air temperature), then the control system remains simple, but the coefficient of performance cannot be optimized under varying operating conditions
Solution Approach 1:
The patent applies parameter changes by transitioning from single-parameter temperature control to dual-parameter control (outlet refrigerant temperature and ambient air temperature). The controller adjusts the pressure reduction amount based on combinations of these parameters to maintain optimal high-pressure refrigerant pressure, thereby optimizing COP under varying operating conditions while managing system complexity.
2Productivity
If dual-parameter control is implemented to optimize COP, then the coefficient of performance is maintained under varying conditions, but the control logic becomes more complex
Solution Approach 1:
The patent implements feedback control by continuously monitoring both outlet refrigerant temperature and ambient air temperature, comparing the actual high-pressure refrigerant pressure against target values derived from temperature combinations, and adjusting the pressure reduction amount accordingly. This closed-loop feedback mechanism optimizes COP while managing control logic complexity through systematic parameter management.
3Ease of operation
If high pressure refrigerant pressure is not optimized, then the system operation remains simple, but the coefficient of performance varies and cannot be maintained at optimum levels
Solution Approach 1:
The patent applies dynamics by transitioning from static pressure control to dynamic pressure optimization. The system continuously adjusts the high-pressure refrigerant pressure based on real-time temperature measurements and predefined target pressure relationships, enabling COP optimization while maintaining ease of operation through automated dynamic control.
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
The system operates at an optimized COP by accurately controlling high pressure refrigerant pressure and outlet refrigerant temperature, maintaining refrigerant in optimum states and ensuring consistent performance across varying conditions.
Implementation Method 1
the amount of pressure reduction by at least either one of the first and second pressure reduction units is controlled
Implementation Method 2
the temperature of air around the heat dissipation side heat exchanger, the amount of pressure reduction... is controlled
Data Source
AI summary
A refrigeration system includes a refrigerant circuit performing a vapor compression supercritical refrigeration cycle. The system includes a compression mechanism, a heat source heat exchanger, an expander, and a utilization heat exchanger. The expander includes, for two-stage compression, a high pressure side and a low pressure side throttle mechanism, both variable in the amount of throttling. A controller is configured to derive a target value, providing a maximum COP, for the pressure of high pressure refrigerant in the refrigerant circuit based on the temperature of refrigerant at the outlet of either the heat source side heat exchanger or the utilization side heat exchanger, whichever becomes a heat dissipation side heat exchanger functioning as a heat dissipation unit and on the temperature of a medium exchanging heat with refrigerant in the heat dissipation side heat exchanger, at the inlet of the heat dissipation side heat exchanger.