Refrigerant Pressure Ratio Control for AC Mode Switching Vibration
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Solution Overview
Problem
Air-conditioning apparatuses experience pipe vibration due to the abrupt flow of high-pressure refrigerant when switching from heating to cooling operation modes, caused by the simultaneous switching of four-way and expansion valves in the refrigerant cycle circuit.
Innovation Solution
Incorporating a controller that uses pressure sensors to determine the ratio of high-pressure to low-pressure refrigerant pressures, adjusting the opening degrees of expansion devices to manage the flow and reduce pressure differences, and controlling the second refrigerant flow switching devices to perform mode switching operations, thereby minimizing pipe vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the four-way valve and expansion valve switch their flow passages simultaneously when changing operation mode, then the switching operation is completed quickly, but high-pressure refrigerant abruptly flows into low-pressure pipe causing pipe vibration
Solution Approach 1:
The control device performs preliminary action by controlling the expansion valve to adjust refrigerant flow before the simultaneous switching of valves, thereby preventing abrupt pressure changes and pipe vibration during mode transition
Solution Approach 2:
The expansion valve opening degree is dynamically adjusted as a control parameter during mode switching. By changing the opening degree from fully open to a controlled position, the refrigerant flow rate is regulated to prevent abrupt pressure differential changes that cause pipe vibration
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 pipe vibration during operation mode switching by managing the flow of refrigerant, ensuring stable operation and extending the lifespan of refrigerant pipes.
Implementation Method 1
Each of the heat-medium heat exchangers is configured to cause heat exchange to be performed between the heat-source-side refrigerant and the heat medium
Implementation Method 2
a low-pressure-side pressure sensor configured to detect a pressure of the heat-source-side refrigerant that flows into the compressor and output the pressure as a first detection value; a high-pressure-side pressure sensor configured to detect a pressure of the heat-source-side refrigerant discharged from the compressor
Implementation Method 3
The controller is configured to adjust opening degrees of the expansion devices... such that an associated one of the heat-medium heat exchangers operates as a condenser or an evaporator
Data Source
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AI summary
An air-conditioning apparatus includes a low-pressure-side pressure sensor that detects the pressure of heat-source-side refrigerant that flows into a compressor and outputs it as a first detection value and a high-pressure-side pressure sensor that detects the pressure of heat-source-side refrigerant discharged from the compressor and outputs it as a second detection value. When switching the operation mode of the apparatus, a controller determines whether the ratio of the first detection value to the second detection value is higher than a first threshold. When the ratio is higher than the threshold, the controller causes a second refrigerant flow switching device to perform a switching operation. When the ratio is less than or equal to the threshold, the controller makes an adjustment such that an opening degree of an expansion device is less than a second threshold, and then causes the second refrigerant flow switching device to perform the switching operation.