Air Conditioner Expansion Valve Control for Subcooling Stability
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Solution Overview
Problem
Conventional air conditioners face instability when the refrigerant amount decreases, leading to subcooling issues and improper operation of the expansion valve, resulting in inefficient cooling and potential system impairment.
Innovation Solution
The air conditioner adjusts the degree of opening of the first expansion valve based on a temperature difference and subcooling conditions, using a controller to manage the refrigerant flow and ensure stability by varying the control constants depending on the subcooling state, thereby maintaining optimal operation even when refrigerant is circulated in insufficient amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the expansion valve operates assuming liquid refrigerant when subcooling is insufficient, then the control simplicity is maintained, but the system stability deteriorates due to receiving wet steam instead of liquid refrigerant
Solution Approach 1:
The invention dynamically adjusts the expansion valve opening based on detected refrigerant state (subcooling degree). When subcooling is sufficient, the valve operates with standard control; when subcooling is insufficient, the control system modifies the opening degree to account for wet steam conditions, making the system adaptable rather than static
Solution Approach 2:
The invention implements feedback control by detecting the refrigerant temperature and calculating the subcooling degree, then using this information to adjust the expansion valve opening. This closed-loop feedback ensures the system responds to actual refrigerant conditions rather than operating on fixed assumptions
2Productivity
If the refrigerant amount decreases leading to insufficient subcooling, then the refrigerant circulation efficiency is reduced, but the system can maintain operation with proper control adjustment
Solution Approach 1:
The invention changes the control parameters of the expansion valve based on the detected refrigerant state. When subcooling is insufficient, the system modifies the valve opening degree parameter to compensate for the changed refrigerant conditions, allowing reliable operation even with reduced refrigerant amounts
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 enhances the stability and efficiency of the air conditioner by ensuring proper refrigerant flow and temperature management, reducing the time to reach stability and minimizing the required refrigerant amount, thus improving overall system performance and reducing costs.
Implementation Method 1
a first heat exchanger; a first expansion valve
Implementation Method 2
a degree of subcooling of the refrigerant flowing out of a condenser
Implementation Method 3
a first expansion valve; The controller changes a degree of opening of the first expansion valve
Implementation Method 4
a compressor; the temperature of the refrigerant discharged by the compressor
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An air conditioner according to the present invention allows refrigerant to circulate therethrough. The air conditioner comprises a compressor, a first heat exchanger, a first expansion valve, a second heat exchanger, and a controller. The controller changes an opening degree of the first expansion valve by a first operation amount according to a temperature difference between a target temperature and the temperature of the refrigerant discharged by the compressor. The refrigerant circulates through the compressor, the first heat exchanger, the first expansion valve, and the second heat exchanger. A first ratio when a specific condition is satisfied is larger than a second ratio when the specific condition is not satisfied. The specific condition (S111) indicates that the degree of subcooling of the refrigerant flowing between the first heat exchanger and the first expansion valve is smaller than zero. The first and second ratios are each a ratio of the first operation amount to the temperature difference.