Supercritical Refrigeration System Pressure Control for Optimized COP
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Solution Overview
Problem
Conventional refrigeration systems with supercritical refrigeration cycles using carbon dioxide struggle to maintain an optimal coefficient of performance (COP) due to reliance on single temperature or pressure parameters, leading to suboptimal operation.
Innovation Solution
A refrigeration system with a vapor compression supercritical refrigeration cycle that includes a high pressure control mechanism to adjust the high pressure refrigerant pressure based on both outlet refrigerant temperature and ambient air temperature, using variable throttling mechanisms to optimize COP, and an outlet temperature control mechanism to adjust refrigerant temperatures for maximum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pressure reduction amount is controlled based on single temperature or pressure parameter, then control simplicity is maintained, but coefficient of performance (COP) optimization is compromised
Solution Approach 1:
The control method changes from using single temperature or pressure parameter to using multiple parameters (outlet refrigerant temperature and ambient air temperature) simultaneously. The controller calculates pressure reduction amount based on the combination of these parameters, enabling optimal COP while maintaining control simplicity through automated calculation.
Solution Approach 2:
The control method implements feedback by continuously monitoring both outlet refrigerant temperature and ambient air temperature, then adjusting the pressure reduction amount based on the relationship between these parameters and COP. This closed-loop control ensures optimal performance while simplifying operator intervention.
2Loss of energy
If outlet refrigerant temperature is adjusted to optimize COP, then energy efficiency improves, but refrigerant pressure control becomes more complex
Solution Approach 1:
The controller performs multiple functions: it monitors outlet refrigerant temperature, monitors ambient air temperature, calculates the optimal pressure reduction amount, and controls the expansion valve. By consolidating these functions in a single control device, the system achieves energy efficiency without proportionally increasing overall system complexity.
Solution Approach 2:
The control system replaces complex mechanical pressure control mechanisms with electronic sensing and calculation. The controller uses temperature sensors and computational algorithms to determine optimal pressure reduction, substituting mechanical complexity with electronic control that achieves the same goal more efficiently.
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 achieves optimized COP by dynamically adjusting refrigerant pressures and temperatures, ensuring optimal performance in both cooling and heating modes, maintaining high and low pressure refrigerants in their respective optimum states.
Implementation Method 1
an expansion mechanism (40) including, for two-stage expansion of refrigerant in the refrigerant circuit (20), a high pressure side throttle mechanism (41, 42) variable in the amount of throttling and a low pressure side throttle mechanism (42, 41) variable in the amount of throttling
Implementation Method 2
a heat source side heat exchanger (21), an expansion mechanism (40), and a utilization side heat exchanger (23)
Implementation Method 3
a compression mechanism (30)
Data Source
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AI summary
A refrigerant circuit (20) includes, in order to perform a vapor compression supercritical refrigeration cycle, a compression mechanism (30), an outdoor heat exchanger (21), an expansion mechanism (40), and an indoor heat exchanger (23). The expansion mechanism (40) includes, for the two-stage expansion of refrigerant in the refrigerant circuit (20), a first throttle mechanism (41) variable in the amount of throttling and a second throttle mechanism (42) variable in the amount of throttling. In the cooling operation mode, there is derived a target value for the pressure of high pressure refrigerant in the refrigerant circuit (20), from the temperature of refrigerant at the outlet of the outdoor heat exchanger (21) and the temperature of air at the inlet of the outdoor heat exchanger (21). In the heating operation mode, there is derived a target value for the pressure of high pressure refrigerant in the refrigerant circuit (20), from the temperature of refrigerant at the outlet of the indoor heat exchanger (23) and the temperature of air at the inlet of the indoor heat exchanger (23). The amount of throttling of either the first throttle mechanism (41) or the second throttle mechanism (42) is adjusted so that the high pressure refrigerant pressure becomes the target value.