Heat Pump Switchable Cascade Control for CoP Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Heat pumps face challenges in efficiently controlling multiple temperature levels and dynamic operating conditions due to complex coupling effects between compressors and expansion valves, leading to limited control ranges and reduced coefficient of performance (CoP) in both SISO and MIMO control systems.
Innovation Solution
A method that integrates SISO control for compressor regulation using heat flow as a reference variable and switchable cascade control for electronically controlled expansion valves, with mass flow difference as a reference variable, allowing for decoupling of refrigeration circuit dynamics and optimizing CoP through a physical model-based estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If SISO control is used for compressor and expansion valve regulation, then the control structure is simple, but the control range is limited and coupling effects between components cannot be optimized
Solution Approach 1:
The patent implements a dynamic control strategy where the controller adapts its control parameters based on operating conditions. The system transitions from fixed SISO control to a more flexible control approach that accounts for coupling effects between compressor and expansion valve, allowing the control characteristics to change dynamically with system state while maintaining reasonable structural simplicity.
Solution Approach 2:
The patent changes control parameters dynamically based on system operating conditions. By adjusting control parameters such as reference values and control characteristics according to measured system states, the system expands its effective control range without requiring a complete redesign of the control structure, thus resolving the contradiction between simplicity and adaptability.
2Loss of energy
If MIMO control is used to optimize system efficiency and decouple system states, then CoP is improved, but the mathematical complexity and personnel costs increase significantly
Solution Approach 1:
The patent extracts and addresses only the most critical coupling effects between the compressor and expansion valve rather than implementing a full MIMO control system. By focusing on the dominant interaction mechanisms and applying targeted control adjustments, the system achieves significant CoP improvement without the excessive mathematical complexity and personnel costs associated with complete MIMO control.
Solution Approach 2:
The patent applies enhanced control measures locally at the most critical interfaces where coupling effects occur, particularly between the compressor and expansion valve. Rather than uniformly complexifying the entire control system, the patent introduces sophisticated control logic only where needed to address dominant coupling effects, thus improving efficiency while limiting overall system complexity.
3Ease of manufacture
If classic SISO control with single variable reference is used, then calibration effort is reduced, but intermediate physical variables such as refrigerant temperature and heat flow cannot be directly influenced
Solution Approach 1:
The patent introduces intermediate control variables and reference values that serve as mediators between the simple SISO control structure and the complex physical processes. By using measured physical variables such as refrigerant temperatures and heat flows as intermediate references, the system maintains calibration simplicity while gaining the ability to directly influence intermediate physical variables through the control loop.
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 minimizes overheating, ensures only vaporized working fluid enters the compressor, and optimizes CoP by dynamically adjusting control parameters, expanding the control range and improving efficiency while reducing electrical energy consumption.
Implementation Method 1
The term heat pump is used extensively for devices in which a left-handed Clausius-Rankine cycle is to take place
Implementation Method 2
at least one electronically controlled expansion valve
Implementation Method 3
at least one evaporator
Implementation Method 4
The heat pump extracts heat from a colder medium
Implementation Method 5
at least one condenser
Implementation Method 6
the use of the heating circuit flow temperature as a reference variable
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Method for controlling a heat pump in which a left-handed thermodynamic Clausius-Rankine cycle is operated and in which a working fluid is circulated in a closed, hermetically sealed working fluid circuit (1), wherein the heat pump has at least one compressor, at least one electronically controlled expansion valve, at least one condenser and at least one evaporator, wherein useful heat is supplied to a heating circuit, wherein a SISO control method is used for controlling the compressor, the reference variable for the compressor control is the heat flow that is transferred from the working fluid in the condenser through the heat exchanger wall to the heating circuit water, the control of the electronically controlled expansion valve is carried out by a switchable cascade control, wherein the first of the cascade controls uses the temperature value of the superheat in the evaporator as the reference variable,and wherein the second of the cascade controls uses the working fluid mass flow difference between the compressor and the electronically controlled expansion valve (4) as a reference variable, and switches from the first to the second of the cascade controls as soon as a steady state has been established during the control of the first cascade control.