Refrigeration apparatus with defrost operation for parallel outdoor units
Solution Overview
Problem
In refrigeration apparatuses with multiple outdoor units connected in parallel to an indoor unit, defrosting operations often result in excess refrigerant accumulation, leading to inefficiencies and risks such as overflow and compressor contamination, due to the indoor expansion valve being fully closed during defrosting, restricting refrigerant flow to the indoor unit.
Innovation Solution
A refrigeration apparatus with a control unit that enables a partial defrost mode, where outdoor heat exchangers function as both evaporators and condensers, allowing refrigerant to flow to the indoor heat exchanger and other outdoor units, ensuring continuous refrigerant circulation and reducing excess refrigerant accumulation by directing refrigerant flow through the indoor expansion valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the indoor expansion valve is fully closed during defrosting, then defrosting can be performed in outdoor heat exchangers, but excess refrigerant accumulates in the outdoor heat exchangers making defrosting inefficient and creating risk of liquid refrigerant overflow to the compressor
Solution Approach 1:
The patent introduces the accumulator as an intermediary component between the outdoor heat exchangers and the compressor. During defrosting, the accumulator receives and holds the excess refrigerant that flows back from the defrosted heat exchangers, preventing it from directly entering the compressor. This mediator component resolves the contradiction by allowing the indoor expansion valve to remain closed (maintaining defrosting effectiveness) while providing a safe destination for excess refrigerant.
Solution Approach 2:
The system performs beforehand cushioning by pre-positioning the accumulator in the refrigerant circuit to cushion against the harmful effect of excess refrigerant. The accumulator is designed with sufficient capacity to hold the expected volume of excess refrigerant during defrosting operations, creating a buffer that prevents liquid refrigerant from reaching the compressor. This prior cushioning approach allows aggressive defrosting without risking compressor damage.
2Reliability
If the accumulator size is increased to suppress liquid refrigerant overflow, then compressor protection is improved, but device complexity and size increase
Solution Approach 1:
The patent optimizes the accumulator size by changing the parameter of refrigerant flow control. Instead of simply increasing accumulator size, the system adjusts the opening degree of the indoor expansion valve during defrosting to regulate the amount of refrigerant flowing toward the accumulator. This parameter change allows a smaller accumulator to effectively handle excess refrigerant, reducing device complexity while maintaining compressor protection.
Solution Approach 2:
The system applies partial action by controlling the indoor expansion valve to allow only the necessary amount of refrigerant to flow to the accumulator during defrosting, rather than allowing all refrigerant to pass through. This controlled partial flow reduces the burden on the accumulator, enabling a compact design that provides adequate protection without excessive size or complexity.
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 effectively suppresses adverse events caused by excess refrigerant, enhances defrosting efficiency, and prevents compressor issues by ensuring refrigerant flow to the indoor unit and other outdoor units, reducing the need for large accumulators and minimizing temperature fluctuations.
Implementation Method 1
the outdoor heat exchangers of some of the plurality of outdoor units are caused to function as evaporators
Implementation Method 2
the outdoor heat exchangers of the rest of the plurality of outdoor units are caused to function as condensers
Implementation Method 3
the outdoor heat exchangers functioning as the evaporators while the outdoor heat exchangers of the rest of the plurality of outdoor units are caused to function as condensers
Data Source
AI summary
Provided is a refrigeration apparatus in which adverse events caused by excess refrigerant can be suppressed even when defrosting is performed with some of a plurality of outdoor units designated as units to be defrosted. An air-conditioning apparatus is configured from a parallel connection of a first outdoor unit and a second outdoor unit, wherein when a second outdoor heat exchanger of the second outdoor unit is caused to function as an evaporator while a first outdoor heat exchanger of the first outdoor unit is caused to function as a condenser to defrost the first outdoor heat exchanger, a refrigerant circuit has a flow channel that supplies some of the refrigerant flowing out of the first outdoor heat exchanger to the second outdoor heat exchanger and a flow channel that supplies the rest of the refrigerant flowing out of the first outdoor heat exchanger to an indoor heat exchanger.