Multi-Room Air Conditioner Control Using Indoor Air Temperature Difference
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Solution Overview
Problem
Conventional multi-room air conditioners using R32 refrigerant face challenges in controlling the cooling capacity of individual indoor units while suppressing the rise in compressor discharge temperature, as refrigerant superheat degree control is ineffective when the refrigerant at the outlet of the heat exchanger contains liquid refrigerant, leading to reliability issues.
Innovation Solution
A multi-room air conditioner design that connects multiple indoor units to an outdoor unit via liquid and gas pipes, using R32 or a mixed refrigerant with 70% or higher R32 content, incorporates a temperature difference detection device to regulate the indoor expansion mechanism based on air temperature differences between inlet and outlet air in each indoor unit, allowing for independent cooling capacity control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If refrigerant superheat degree control is performed at the outlet of the heat exchanger in each indoor unit, then the cooling capacity of each indoor unit can be controlled, but the refrigerant at the outlet does not contain liquid refrigerant causing abnormal rise in compressor discharge temperature
Solution Approach 1:
The patent introduces a temperature difference detection device as an intermediary to detect the air temperature difference between inlet and outlet of the heat exchanger. This indirect measurement method allows control of cooling capacity without directly measuring refrigerant superheat degree, thereby maintaining liquid refrigerant presence and preventing abnormal compressor discharge temperature rise.
Solution Approach 2:
The patent changes the control parameter from refrigerant superheat degree to air temperature difference. By controlling the indoor expansion mechanism based on air temperature difference rather than refrigerant temperature, the system maintains liquid refrigerant in the heat exchanger outlet while achieving individual cooling capacity control for each indoor unit.
2Reliability
If the vapour quality of refrigerant at compressor inlet is set to be equal to or higher than 0.65 to suppress discharge temperature rise, then compressor reliability improves, but individual cooling capacity control of multiple indoor units becomes difficult
Solution Approach 1:
The patent segments the control of each indoor unit independently by equipping each unit with its own temperature difference detection device and control mechanism. This allows each indoor unit to control its cooling capacity individually based on its own air temperature difference, while the refrigerant vapour quality at compressor inlet is maintained at appropriate levels through coordinated control of multiple expansion mechanisms.
Solution Approach 2:
The patent implements feedback control by using the detected air temperature difference to regulate the indoor expansion mechanism. The control device continuously monitors the air temperature difference and adjusts the expansion mechanism to maintain optimal cooling capacity while ensuring proper refrigerant vapour quality reaches the compressor.
3Reliability
If the superheat degree of refrigerant at heat exchanger outlet is set to 0 to maintain liquid refrigerant and reduce vapour quality, then compressor discharge temperature is suppressed, but refrigerant superheat degree control cannot be performed
Solution Approach 1:
The patent replaces the mechanical/refrigerant-based control system (superheat degree control) with an air-based control system (air temperature difference detection). By substituting refrigerant parameter measurement with air parameter measurement, the system maintains liquid refrigerant while achieving cooling capacity control through air temperature feedback rather than refrigerant superheat control.
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 effectively suppresses the rise in compressor discharge temperature and enables individual control of cooling capacity for each indoor unit, enhancing the reliability and efficiency of the air conditioner.
Implementation Method 1
R32 or mixed refrigerant containing 70 mass % or higher percent of R32 is used as refrigerant circulating through the refrigeration cycle
Implementation Method 2
an indoor unit having an indoor heat exchanger... detects an air temperature difference between inlet-side air and outlet-side air in respective indoor heat exchangers
Data Source
AI summary
It is an object to obtain an air conditioner capable of suppressing rise of compressor discharge temperature and individually controlling cooling capacity of a plurality of respective indoor units. For this purpose, the air conditioner is a multi-room air conditioner, in which a refrigeration cycle is formed by connecting an outdoor unit 100 having an outdoor heat exchanger to the plurality of indoor units 200 and 300 having indoor heat exchangers 201 and 301 and indoor expansion mechanisms 203 and 303 using a liquid pipe 121 and a gas pipe 122. Further, as refrigerant circulating through the refrigeration cycle, R32 or mixed refrigerant containing 70 mass % or higher percent of R32 is used. Further, a temperature difference detection device to detect an air temperature difference between inlet-side air and outlet-side air in the respective indoor heat exchangers of the respective indoor units is provided. The cooling capacity in the respective indoor units is controlled by regulating the indoor expansion mechanisms of the respective indoor units based on the air temperature difference in the indoor units detected with the temperature difference detection device.