Intermediate-Pressure Injection Control for R32 Heat Pump Heating
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Solution Overview
Problem
Air-conditioning apparatuses with multiple indoor units connected to a single outdoor unit face reduced heating capacity due to decreased suction density and increased discharge temperature when using low GWP refrigerants like R32, leading to pressure loss and efficiency issues in heat exchange control.
Innovation Solution
The air-conditioning apparatus includes a compressor for intermediate-pressure refrigerant injection, an outdoor heat exchanger, flow passage switching devices, and parallel-connected flow rate control devices to manage heat exchange and injection, ensuring efficient operation and reliability by lowering discharge temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If R32 refrigerant is used to reduce GWP, then environmental performance is improved, but discharge temperature increases and suction density decreases
Solution Approach 1:
An intermediate-pressure control device is introduced as a mediator to inject refrigerant at an intermediate pressure stage during compression. This injection process cools the refrigerant, thereby reducing the discharge temperature from the compressor while maintaining the use of R32 refrigerant for environmental benefits.
Solution Approach 2:
The invention changes the pressure parameters during compression by introducing intermediate-pressure injection. By controlling the injection pressure and flow rate through the intermediate-pressure control device, the discharge temperature is adjusted to acceptable levels while preserving the low GWP advantage of R32 refrigerant.
2Ease of operation
If heat exchange amount control devices are connected in series with the intermediate-pressure control device, then heat exchange control is achieved, but pressure loss increases and cooling/heating performance decreases
Solution Approach 1:
The heat exchange control function is segmented from the intermediate-pressure control function. Separate control devices are provided for heat exchange amount control and intermediate-pressure control, allowing each to operate independently without creating series connections that would cause excessive pressure loss.
Solution Approach 2:
The flow rate control devices are designed to perform multiple functions - controlling both heat exchange amount and intermediate-pressure refrigerant injection - thereby eliminating the need for separate series-connected devices and reducing overall pressure loss in the 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
This configuration allows for stable heat exchange control and efficient operation across varying load conditions, maintaining compressor reliability and improving heating capacity by managing discharge temperature effectively.
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
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 3
an outdoor heat exchanger (3)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An air-conditioning apparatus 100 includes an outdoor-side flow rate control device (a fourth flow rate control device 22) that generates an intermediate pressure for injection into a compressor 1, and a bypass flow rate control device (a sixth flow rate control device 26) that is placed at a bypass pipe 25 allowing bypassing of an outdoor heat exchanger 3 in parallel to the outdoor-side flow rate control device and that controls the amount of heat exchange of the outdoor heat exchanger 3 together with the outdoor-side flow rate control device.