Air-Conditioner Pressure Control for Stable Heating Capacity
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Solution Overview
Problem
Conventional air-conditioning apparatuses face challenges in maintaining maximum heating capacity due to issues like refrigerant leakage, insufficient charging, and limitations in compressor operation, which affect the control of subcooling and high-pressure side pressure, leading to inefficient heating performance.
Innovation Solution
The air-conditioning apparatus controls the high-pressure side pressure of the load-side heat exchanger and the degree of suction superheat of the compressor by adjusting the flow rate of refrigerant, using a load-side expansion device to ensure the pressure at the compressor outlet matches a target pressure, thereby optimizing heating capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the degree of subcooling is increased to raise high-pressure side pressure and suppress reduction in heating capacity, then heating capacity is improved, but the control becomes impossible when refrigerant leakage or insufficient charging occurs, leading to excessive throttling
Solution Approach 1:
The patent changes the control parameter from degree of subcooling to degree of suction superheat. By controlling the suction superheat instead of subcooling, the system can reliably control high-pressure side pressure even when refrigerant charge is insufficient or leakage has occurred, avoiding excessive throttling while maintaining heating capacity.
2Productivity
If refrigerant is injected into the compressor to increase circulation amount and heating capacity, then heating capacity is improved, but liquid compression operation occurs with large amount of injection, limiting the improvement
Solution Approach 1:
The patent changes the control parameter from degree of subcooling to degree of suction superheat. By controlling the suction superheat degree, the system can increase refrigerant circulation amount and heating capacity without causing liquid compression operation in the compressor, as the superheat control ensures refrigerant enters the compressor in vapor phase.
3Productivity
If the flow rate of refrigerant is reduced to control high-pressure side pressure and suction superheat, then heating capacity is maximized, but the system becomes sensitive to refrigerant charge conditions
Solution Approach 1:
The patent changes the control parameter from degree of subcooling to degree of suction superheat. This parameter change makes the control system adaptable to various refrigerant charge conditions, as suction superheat can be controlled and measured reliably regardless of whether refrigerant charge is sufficient or deficient, allowing the system to maintain optimal heating capacity across different charge conditions.
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 allows the air-conditioning apparatus to consistently achieve maximum heating capacity, even under conditions of refrigerant shortage or aged system deterioration, by controlling high-pressure side pressure and suction superheat, enhancing indoor comfort and operational reliability.
Implementation Method 1
controls an opening degree of the load-side expansion device, based on a discharge pressure of the compressor, so that pressure of refrigerant at an outlet of the compressor becomes equal to a target pressure
Implementation Method 2
heat-source-side unit including a heat-source-side heat exchanger and a compressor
Implementation Method 3
load-side heat exchanger and a load-side expansion device with a heat-source-side unit including a heat-source-side heat exchanger
Data Source
AI summary
An air-conditioning apparatus including a refrigeration cycle configured by connecting one or more load-side units including a load-side heat exchanger and a load-side expansion device with a heat-source-side unit including a heat-source-side heat exchanger and a compressor and by causing refrigerant to circulate through a refrigerant circuit including the load-side heat exchanger, the load-side expansion device, the heat-source-side heat exchanger, and the compressor, controls, during a heating operation, the opening degree of the load-side expansion device, based on the discharge pressure of the compressor, so that the pressure of refrigerant at the outlet of the compressor becomes equal to a target pressure, in the case where the operation capacity of the compressor is approximately at the maximum value of the operation capacity of the compressor.