A method for controlling operation of a vapour compression system in a subcritical and a supercritical mode
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Solution Overview
Problem
Vapour compression systems, such as refrigeration and air conditioning systems, require different control strategies for subcritical and supercritical regimes, making it complex to operate near the transitional point and necessitating separate control formulas, which complicates system management.
Innovation Solution
A method and system that use a single calculation formula to control vapour compression systems in both subcritical and supercritical regimes by measuring the refrigerant's temperature and calculating a pressure reference, allowing the controllable valve to adjust the pressure, ensuring seamless operation across regimes without distinguishing between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different control strategies are used for subcritical and supercritical regimes, then the system can be controlled in both regimes, but the device complexity and ease of operation deteriorate due to requiring separate control formulas and regime tracking
Solution Approach 1:
The patent applies universality by developing a single control formula that functions for both subcritical and supercritical regimes. The controller uses one unified calculation method (Eq. 1) that automatically adapts to either regime based on operating conditions, eliminating the need for separate control strategies and regime tracking logic.
Solution Approach 2:
The patent uses parameter changes by deriving a control formula where the pressure reference is calculated as a function of temperature and regime type. The formula P_GC,Ref = f(T_GC, regime) changes its calculation approach based on the operational regime, allowing a single unified formula structure to handle both subcritical and supercritical conditions without requiring separate control logic.
2Adaptability or versatility
If different control strategies are used for subcritical and supercritical regimes, then the system can be controlled in both regimes, but the ease of operation worsens due to the need to track operating regime and switch between control methods
Solution Approach 1:
The unified control formula serves multiple functions simultaneously - it calculates the pressure reference for both subcritical and supercritical regimes using the same mathematical structure. The controller automatically determines which regime is active and applies the appropriate calculation within the single formula, making operation simple without requiring manual regime tracking or switching.
Solution Approach 2:
The control system performs self-service by automatically determining the operating regime and selecting the appropriate calculation method within the unified formula. The system monitors temperature and pressure conditions, autonomously identifies whether it is in subcritical or supercritical mode, and adjusts the pressure reference calculation accordingly without requiring external intervention or complex switching logic.
3Adaptability or versatility
If separate control formulas are used for subcritical and supercritical regimes, then each regime can be optimized, but the loss of time increases due to regime tracking and control switching requirements
Solution Approach 1:
The unified control formula enables continuous operation without interruption for regime switching. The controller continuously calculates the pressure reference using the single formula, which automatically adapts as the system transitions between subcritical and supercritical regimes. This eliminates dead time associated with detecting regime changes and switching between separate control strategies.
Solution Approach 2:
The single control formula provides regime-specific optimization while maintaining a unified structure. The formula P_GC,Ref = f(T_GC, regime) incorporates both subcritical and supercritical calculation approaches within one mathematical framework, allowing the system to maintain optimized control for each regime while eliminating the time required for switching between separate control systems.
Data Source
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Figure 3a~3c
AI summary
A method for controlling operation of a vapour compression system ( 1), and a vapour compression system ( 1) are disclosed. The vapour compression system (1) comprises a compressor (2), a heat rejecting heat exchanger (3), a controllable valve (4), a receiver (5), at least one expansion device and at least one evaporator arranged along a refrigerant path having refrigerant flowing therein. The vapour compression system (1) is capable of being operated in a subcritical control regime as well as in a supercritical control regime. The method comprises the steps of measuring a temperature, TGC, of refrigerant leaving the heat rejecting heat exchanger; calculating a pressure reference, PGC,Ref, based on the measured temperature, TGC, and using a calculation formula being applicable to the subcritical control regime as well as to the supercritical control regime; and controlling an opening degree of the controllable valve in order to obtain a pressure of refrigerant leaving the heat rejecting heat exchanger which is equal to the calculated pressure reference, PGC, Ref. Since the calculation formula is applicable to the subcritical control regime as well as to the supercritical control regime, only one calculation formula is necessary, and the vapour compression system (1) can thereby be controlled in a very easy manner.