Mixed-Refrigerant Air Conditioning with Composition Feedback Control
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Solution Overview
Problem
Existing air-conditioning apparatuses face challenges in efficiently managing the composition of mixed refrigerants, leading to energy inefficiencies and potential safety issues due to varying boiling points and leakage risks, particularly when using environmentally friendly but volatile refrigerants like tetrafluoropropene and R32.
Innovation Solution
An air-conditioning apparatus with a refrigeration cycle incorporating a zeotropic refrigerant mixture of tetrafluoropropene and R32, featuring a compressor, refrigerant flow switching device, heat source side heat exchanger, and a circulating refrigerant composition detection circuit, including pressure and temperature sensors, to accurately detect the composition of the refrigerant and control the expansion device, thereby optimizing energy efficiency and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a zeotropic refrigerant mixture containing tetrafluoropropene and R32 is used, then energy efficiency is improved through optimized heat exchange, but the refrigerant composition varies during circulation due to different boiling points, leading to control difficulties
Solution Approach 1:
The patent implements a feedback control mechanism where the composition detection circuit continuously monitors the refrigerant composition during circulation. The controller receives this detection signal and adjusts the expansion device accordingly to maintain optimal performance despite composition variations caused by different boiling points of tetrafluoropropene and R32
Solution Approach 2:
The system dynamically changes operating parameters based on detected refrigerant composition. The controller modifies expansion device opening, compressor capacity, and heat exchanger operations in response to real-time composition data, allowing the system to adapt to the shifting refrigerant mixture characteristics
2Object-affected harmful factors
If flammable refrigerants with low GWP are used, then environmental friendliness is improved, but safety risks increase due to potential leakage into conditioned spaces
Solution Approach 1:
The patent introduces a heat medium (water or antifreeze) as an intermediary between the refrigerant and the conditioned space. The refrigerant circulates in a closed loop separate from the living space, exchanging heat through the heat medium in heat exchangers, thereby eliminating direct leakage risks to occupants while maintaining environmental benefits
Solution Approach 2:
The system divides the refrigeration cycle into separate loops: a refrigerant loop containing the flammable but environmentally friendly refrigerant, and a heat medium loop that interfaces with the conditioned space. This segmentation isolates the safety risk to a controlled mechanical system away from human occupancy
3Device complexity
If refrigerant composition is not accurately detected, then system complexity is reduced, but energy efficiency deteriorates due to inability to optimize expansion device control
Solution Approach 1:
The patent replaces complex mechanical composition analysis systems with a simplified detection circuit that measures readily available parameters (temperature and pressure). The controller uses these measurements to calculate refrigerant composition, substituting sophisticated mechanical sensors with a more manageable electronic detection and calculation system
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 system achieves high energy efficiency by accurately detecting refrigerant composition and controlling the expansion device, reducing energy consumption and minimizing refrigerant leakage into conditioned spaces, ensuring a safer and more environmentally friendly operation.
Implementation Method 1
a low-pressure side pressure detection device for detecting low-pressure side pressure corresponding to pressure of the refrigerant suctioned by the compressor
Implementation Method 2
a heat exchanger related to heat medium that is capable of exchanging heat between the refrigerant and a heat medium different from the refrigerant
Implementation Method 3
a high-pressure side temperature detection device for detecting high-pressure side temperature corresponding to temperature of the refrigerant flowing into the bypass expansion device
Implementation Method 4
a low-pressure side temperature detection device for detecting low-pressure side temperature corresponding to temperature of the refrigerant discharged from the bypass expansion device
Implementation Method 5
a heat exchanger related to refrigerant that exchanges heat between the refrigerant flowing into the bypass expansion device and the refrigerant discharged from the bypass expansion device
Data Source
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AI summary
An air-conditioning apparatus includes a refrigeration cycle device having a refrigerant circuit A in which a compressor 10 that pressurizes a zeotropic refrigerant mixture containing tetrafluoropropene and R32, a heat source side heat exchanger 12, refrigerant expansion devices 16, and heat exchangers 15 related to heat medium that exchange heat between the refrigerant and a heat medium are connected by pipes, the refrigeration cycle device further including a high-pressure side pressure detection device 32 that detects high-pressure side pressure, a low-pressure side pressure detection device 33 that detects low-pressure side pressure, a high-low pressure bypass pipe 4c connecting a pipe on a discharge side of the compressor 10 and a pipe on a suction side of the compressor 10, a bypass expansion device 14 disposed in the high-low pressure bypass pipe 4c, a high-pressure side temperature detection device 37 that detects high-pressure side temperature, and a low-pressure side temperature detection device 38 that detects low-pressure side temperature; an outdoor unit side controller that detects circulation composition of the refrigerant on the basis of the high-pressure side pressure, the low-pressure side pressure, the high-pressure side temperature, and the low-pressure side temperature; and a relay unit side controller performing at least one of a calculation of evaporating temperature and degree of superheat, and a calculation of condensing temperature and degree of subcooling on the basis of the circulation composition.