Air-Conditioner Injection Circuit Control for Heating Refrigerant Balance
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Solution Overview
Problem
In air-conditioning apparatuses, the difference in refrigerant amount required during cooling and heating operations is not effectively managed, especially with long extension pipes, leading to difficulties in maintaining the necessary refrigerant ratio and increasing manufacturing costs due to the need for additional sensors.
Innovation Solution
An air-conditioning apparatus with a refrigeration cycle that includes a compressor with an injection port, an indoor heat exchanger, first and second pressure reducing devices, an injection circuit, and an internal heat exchanger, where the controller adjusts the opening degree of the second pressure reducing device to satisfy the relation A+C=B×Gr, allowing for efficient refrigerant accumulation during heating operations without requiring an intermediate-pressure sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a main circuit expansion valve is added in the outdoor unit to accumulate liquid-phase refrigerant in the extension pipe during heating operation, then the difference in necessary refrigerant amount between cooling and heating operations can be absorbed, but the device complexity and manufacturing cost increase due to additional components and sensors
Solution Approach 1:
The injection circuit expansion valve in the injection circuit is made to serve dual purposes: its primary function of controlling refrigerant flow to the injection compressor, and a secondary function of enabling liquid-phase refrigerant accumulation in the extension pipe during heating operation by controlling its opening degree to create appropriate pressure differential. This eliminates the need for a separate main circuit expansion valve.
Solution Approach 2:
The functions of the injection circuit expansion valve and the hypothetical main circuit expansion valve are merged into a single component. The injection circuit expansion valve simultaneously performs refrigerant injection control and heating mode refrigerant accumulation, reducing the total number of components needed in the system.
2Manufacturing precision
If an intermediate-pressure sensor is added to detect refrigerant pressure between the first pressure reducing device and the second pressure reducing device for precise control, then the opening degree of the second pressure reducing device can be accurately controlled, but the manufacturing cost increases
Solution Approach 1:
The system uses existing sensors (discharge pressure sensor and suction pressure sensor) to self-determine the opening degree of the second pressure reducing device through calculation, rather than relying on a dedicated intermediate-pressure sensor. The controller calculates the required opening degree based on the detected discharge and suction pressures, eliminating the need for additional sensing hardware.
Solution Approach 2:
The physical intermediate-pressure sensor is replaced with a computational approach using existing sensor data. Instead of directly measuring intermediate pressure with a sensor, the system substitutes this mechanical measurement with a calculation based on discharge and suction pressure readings, achieving the same control objective without additional hardware.
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 enables a larger refrigerant accumulation in the pipe during heating operations while keeping manufacturing costs low by controlling the second pressure reducing device's opening degree, thus effectively managing the refrigerant ratio and reducing the need for additional sensors.
Implementation Method 1
an internal heat exchanger configured to exchange heat between refrigerant flowing between the branching portion and the second pressure reducing device and refrigerant depressurized by the third pressure reducing device
Implementation Method 2
a first pressure reducing device, a second pressure reducing device, and an injection circuit expansion valve (third pressure reducing device)
Data Source
AI summary
An air-conditioning apparatus includes: a refrigeration cycle; an injection circuit for connecting between an injection port and a branching portion arranged between an indoor expansion valve and a main circuit expansion valve; an injection circuit expansion valve arranged in the injection circuit; an internal heat exchanger for exchanging heat between refrigerant flowing between the branching portion and the main circuit expansion valve and refrigerant depressurized by the injection circuit expansion valve; and an outdoor unit control device, the outdoor unit control device being configured to control an opening degree A of the main circuit expansion valve so as to satisfy Relation A+C=B×Gr, where A represents the opening degree of the main circuit expansion valve, C represents an opening degree of the injection circuit expansion valve, B represents a coefficient, and Gr represents a refrigerant circulating amount in the refrigeration cycle.