Relay Refrigerant Control for Multi-Unit Heating and Freeze Prevention
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Solution Overview
Problem
Air-conditioning apparatuses with multiple heat source units face issues with uneven refrigerant distribution, leading to degraded cooling capacity and potential freezing of indoor units during heating operations, due to excessive narrowing or opening of flow control valves.
Innovation Solution
An air-conditioning apparatus with a relay device that includes a gas-liquid separator, separate pipes for gas and liquid refrigerant, a bypass pipe, and a controller that adjusts the outdoor expansion device opening degrees based on detected temperatures to maintain optimal refrigerant distribution and prevent freezing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flow control valves are narrowed excessively to control refrigerant distribution, then refrigerant equalization among heat source apparatuses is improved, but the evaporating temperature of evaporators in cooling indoor units rises and cooling capacity is degraded
Solution Approach 1:
The patent divides the refrigerant flow control into separate paths: a first flow control valve for controlling total refrigerant flow to maintain equalization, and a second flow control valve for adjusting bypass flow to maintain cooling capacity. This segmentation allows independent optimization of both refrigerant distribution and cooling performance without mutual interference.
2Productivity
If flow control valves are opened excessively to maintain discharge temperature, then cooling capacity is maintained, but the temperature of liquid pipes in cooling indoor units falls below freezing point causing protection control mode activation
Solution Approach 1:
The patent introduces a bypass pipe with a second flow control valve as an intermediary path that allows precise adjustment of refrigerant flow. By controlling the bypass flow independently, the system can maintain liquid pipe temperature above freezing point while preserving cooling capacity, avoiding protection control mode activation.
3Power
If multiple heat source apparatuses are used to increase capacity, then system capacity is improved, but refrigerant distribution becomes uneven among heat source apparatuses
Solution Approach 1:
The patent employs a control unit that monitors refrigerant conditions and dynamically adjusts the opening degrees of flow control valves based on detected parameters. This feedback mechanism ensures uniform refrigerant distribution among multiple heat source apparatuses while maintaining optimal system capacity and preventing abnormal operating conditions.
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 controlled refrigerant distribution among heat source units, maintaining the cooling capacity and preventing freezing of indoor units by regulating the superheat degrees and liquid pipe temperatures within prescribed ranges.
Implementation Method 1
a gas-liquid separator configured to separate the refrigerant flowing from the high pressure pipe into gas refrigerant in a gas state and liquid refrigerant in a liquid state
Data Source
AI summary
The air-conditioning apparatus includes the plurality of heat source apparatuses; a plurality of indoor units each including an indoor heat exchanger and each configured to perform one of cooling and heating operations; a relay device connected to the heat source apparatuses by a high pressure pipe and a low pressure pipe and configured to distribute refrigerant flowing therein from the heat source apparatuses to the plurality of indoor units; and a controller configured to control operations of the heat source apparatuses. The relay device includes a relay device temperature detecting unit configured to detect a temperature of the refrigerant flowing through the bypass pipe. During the heating main operation, the controller changes an opening degree of each of the outdoor side expansion devices based on the temperature detected by the relay device temperature detecting unit.