Compressor Injection Bypass Control for Multi-Split Air Conditioning
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Solution Overview
Problem
Air-conditioning apparatuses with multiple indoor units connected to a single outdoor unit face performance issues due to pressure loss and increased valve aperture, leading to reduced cooling and heating performance, especially when using refrigerants like R32, which have higher discharge temperatures and lower suction densities.
Innovation Solution
The air-conditioning apparatus includes a compressor for intermediate-pressure refrigerant injection, an outdoor heat exchanger, flow passage switching devices, injection and outdoor-side flow rate control devices, and bypass flow rate control devices to manage heat exchange and injection efficiently, ensuring stable operation and reliability by lowering discharge temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat exchange amount control devices (solenoid opening and closing valves) are connected in series with the intermediate-pressure control device, then the aperture of valves can be increased to prevent pressure loss, but cooling and heating performance is lowered due to pressure loss
Solution Approach 1:
The patent divides the control function into separate devices: the intermediate-pressure control device (135) controls injection pressure, while the heat exchange amount control devices (132, 133) control heat exchange independently. This segmentation allows each device to operate optimally without compounding pressure losses, resolving the contradiction between valve aperture control and system performance.
2Productivity
If R32 refrigerant is used to downsize the apparatus, then refrigeration capacity per unit mass and volume increases, but discharge temperature rises by about 20 degrees Centigrade compared to R410A
Solution Approach 1:
The patent introduces an intermediate-pressure control device (135) that acts as a mediator by injecting intermediate-pressure refrigerant into the compression process. This intermediary mechanism lowers the discharge temperature of R32 refrigerant while preserving its high refrigeration capacity, resolving the contradiction between productivity and temperature control.
3Productivity
If the flow rate of refrigerant is increased to improve heating capacity, then heating performance improves, but suction density of the compressor decreases
Solution Approach 1:
The patent changes the pressure parameter of the injected refrigerant to intermediate pressure, which optimizes both the flow rate and suction density. By controlling the injection pressure independently through the intermediate-pressure control device (135), the system achieves improved heating capacity while maintaining adequate suction density, resolving the contradiction between productivity and quantity of substance.
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 configuration allows for efficient heat exchange and injection control, maintaining compressor reliability and performance across varying load conditions, even with refrigerants like R32, by reducing pressure loss and optimizing flow rates.
Implementation Method 1
a compressor (1) into which an intermediate-pressure refrigerant is allowed to be injected via an injection pipe (23) in the course of compressing a refrigerant
Implementation Method 2
an outdoor heat exchanger (3)
Implementation Method 3
lowering the discharge temperature by injection is effective
Data Source
AI summary
An air-conditioning apparatus includes an outdoor-side flow rate control device (a fourth flow rate control device) that generates an intermediate pressure for injection into a compressor, and a bypass flow rate control device (a sixth flow rate control device) that is placed at a bypass pipe allowing bypassing of an outdoor heat exchanger in parallel to the outdoor-side flow rate control device and that controls the amount of heat exchange of the outdoor heat exchanger together with the outdoor-side flow rate control device.