Expansion Valve Control for Multi-Room Temperature Deviation Minimization
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Solution Overview
Problem
Existing air-conditioning systems fail to minimize room temperature deviations from target temperatures due to differences in indoor heat exchanger types and installation conditions, leading to deteriorated control performance and energy efficiency when the driving range of electric expansion valves is limited.
Innovation Solution
An air-conditioning apparatus and method that utilize room temperature sensors, a variable displacement compressor, and a controller with units for calculating required capacities, total opening degrees, and optimization problems to determine optimal electric expansion valve opening degrees, ensuring the room temperature deviation is minimized while maintaining high-efficiency operation within the allowable driving range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional control methods are used to determine electric expansion valve opening degrees, then the control system is simple, but the room temperature deviation from target temperature cannot be minimized due to differences in heat exchanger types and installation conditions
Solution Approach 1:
The control system continuously monitors room temperature deviations and uses this feedback to dynamically adjust electric expansion valve opening degrees. The required capacity calculation unit integrates temperature deviations over time to determine the necessary cooling/heating capacity, creating a closed-loop feedback mechanism that minimizes room temperature deviations while adapting to different heat exchanger types and installation conditions.
Solution Approach 2:
The system transitions from static, predetermined valve opening control to dynamic control where opening degrees are continuously adjusted based on real-time room temperature measurements. The optimization unit dynamically calculates optimal opening degrees by solving quadratic programming problems that consider current temperature deviations, ensuring adaptive control performance across varying operational conditions.
2Reliability
If the driving range of electric expansion valves is limited, then the system operates within safe boundaries, but control performance for room temperature and discharge temperature deteriorates
Solution Approach 1:
The system changes the control parameter from direct valve opening degree specification to required capacity calculation based on integrated temperature deviations. By formulating the control problem as a quadratic programming optimization with constraints on valve opening ranges, the system finds optimal opening degrees that maximize control performance while respecting the limited driving range constraints, thereby maintaining both reliability and productivity.
Solution Approach 2:
The control system performs preliminary calculation of required capacities by integrating temperature deviations before determining valve opening degrees. This preliminary action allows the optimization unit to pre-calculate optimal opening degrees that satisfy both performance requirements and driving range limitations, preventing performance deterioration before it occurs.
3Adaptability or versatility
If multiple indoor heat exchangers with different types and installation conditions are connected, then the system covers more application scenarios, but uniform control strategies fail to minimize temperature deviations
Solution Approach 1:
The control system segments the overall control problem into individual required capacity calculations for each indoor heat exchanger. Each heat exchanger's required capacity is calculated independently based on its specific room's temperature deviation, allowing customized control strategies for each unit while maintaining system-wide coordination through the optimization unit that distributes total opening degrees appropriately.
Solution Approach 2:
The system applies local quality control by calculating required capacities and optimal opening degrees specific to each indoor heat exchanger's local conditions (room temperature deviation, heat exchanger type, installation conditions). This localized approach ensures that each heat exchanger receives tailored control parameters that minimize its specific temperature deviations, rather than applying uniform control strategies.
4Productivity
If optimization calculations are performed in real-time, then optimal valve opening degrees are achieved, but computational complexity and processing time increase
Solution Approach 1:
The control system extracts the core optimization problem from complex multi-variable control and formulates it as a standardized quadratic programming problem with clear objective functions (minimizing opening degree deviations from target values) and constraints (valve driving ranges). This extraction simplifies the computational task while maintaining optimization effectiveness, making real-time solution feasible.
Solution Approach 2:
The system changes the mathematical formulation of the control problem into a quadratic programming format with quadratic objective functions and linear constraints. This parameter transformation allows the use of efficient quadratic programming algorithms that can solve the optimization problem rapidly in real-time, reducing computational complexity while achieving optimal control results.
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 solution effectively reduces room temperature deviations to a minimum value while ensuring high-efficiency operation by optimizing electric expansion valve opening degrees, even when the driving range is limited, and varying installation conditions are considered.
Implementation Method 1
a variable displacement type compressor that causes refrigerant to sequentially circulate through an outdoor heat exchanger, electric expansion valves, and indoor heat exchangers
Implementation Method 2
electric expansion valves, each of which is connected to an associated one of the indoor heat exchangers
Implementation Method 3
indoor heat exchangers provided in respective rooms
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An air-conditioning apparatus includes: room temperature sensors (106); room temperature setting units (107); a variable displacement type compressor (101) that causes refrigerant to circulate through an outdoor heat exchanger (103), electric expansion valves (104), and indoor heat exchangers (105); a required-capacity calculation unit (4) including an integrator for a temperature deviation; an electric expansion-valve total opening degree output unit (2) that outputs a total opening degree; a temporary electric expansion-valve opening degree calculation unit (5) that uses a required capacity and the total opening degree; an evaluation function derivation unit (201) that obtains a distance function with a valve opening degree and a temporary valve opening degree as an evaluation function; an equality constraint derivation unit (202) that obtains equality constraints for equalizing the sum of opening degrees as a variable to the total opening degree; a valve opening degree upper/lower limit calculation unit (3) that calculates upper and lower limits of each opening degree; an inequality constraint derivation unit (203) that obtains inequality constraints in which each opening degree falls within the range between the upper and lower limits; and an optimization problem calculation unit (204) that calculates the opening degrees from the evaluation function and the equality and inequality constraints, whereby the room temperature deviation can be made to approach the minimum value.