Freezing device
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The control of refrigeration apparatuses performing supercritical refrigeration cycles faces challenges in settling the control of low pressure and superheat due to the complex interdependencies between compressor capacity, expansion valve opening, and refrigerant circulation state, leading to difficulty in stabilizing the refrigeration cycle, especially with supercritical refrigerants like CO2 which exhibit significant variations in density and enthalpy.
Innovation Solution
The solution involves concurrently controlling multiple objects within the refrigeration apparatus, including the compression mechanism, expansion mechanism, and heat source side fan, by associating the high pressure and predetermined physical values such as enthalpy and superheat, to stabilize the control of the refrigeration cycle, thereby avoiding the vicious loop of interdependent changes that complicate control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the degree of opening of the expansion valve is controlled based on compressor capacity, then the low pressure control is improved, but the control stability deteriorates due to the vicious loop between expansion valve opening, refrigerant circulation state, and compressor capacity
Solution Approach 1:
The patent introduces a correction amount calculation that acts as an intermediary between the expansion valve control and compressor capacity. Instead of directly linking expansion valve opening to compressor capacity, the system calculates a correction amount based on the difference between target and actual low pressure, then applies this correction to the expansion valve control amount. This intermediary step breaks the vicious loop and stabilizes the control system.
Solution Approach 2:
The patent implements a feedback mechanism where the actual low pressure is continuously measured and compared with the target low pressure. The correction amount is calculated based on this pressure difference, and the expansion valve control amount is adjusted accordingly. This closed-loop feedback control ensures that the low pressure is maintained at the target value while avoiding the instability caused by direct coupling between expansion valve and compressor capacity.
2Speed
If concurrent control of multiple objects (compression mechanism, expansion mechanism, heat source side fan) is implemented, then the convergence rate of control is improved, but the device complexity increases
Solution Approach 1:
The patent merges the control of multiple objects (compression mechanism, expansion mechanism, and heat source side fan) into a unified control system. The control amount calculation integrates considerations for all three objects, allowing them to work together to achieve the target low pressure and superheat simultaneously. This merging approach improves the convergence rate by coordinating all control objects rather than adjusting them independently.
Solution Approach 2:
The control system is designed with multi-functionality to handle multiple control objectives simultaneously. The same control amount calculation mechanism manages both low pressure control and superheat control, and can coordinate multiple expansion valves and fans. This universal control approach reduces the need for separate control systems for each function, thereby managing complexity while improving convergence.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present disclosure allows for easy settling of control of capability of an refrigeration apparatus for performing a supercritical refrigeration cycle. An air conditioner (10) includes: a refrigerant circuit (20) sequentially connecting a compressor (21), an outdoor heat exchanger (23), an outdoor expansion valve (24), and an indoor heat exchanger (27), and performing a supercritical refrigeration cycle in which a high pressure is a supercritical pressure or higher; and a controller (40) for controlling a plurality of objects of control including at least the compressor (21) and the outdoor expansion valve (24). The controller (40) concurrently controls the plurality of objects of control, thereby concurrently controlling a predetermined physical value as an index of an ability of the refrigeration apparatus, and the high pressure of the refrigeration cycle.