Multi-Unit Heat Pump Defrosting Control for Stable Heating Capacity
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Solution Overview
Problem
Air-conditioning apparatuses experience a decrease in heating capacity during simultaneous heating and defrosting operations due to the need for outdoor air to be heated by parallel heat exchangers, leading to increased heat transfer from the defrosting heat exchanger, which reduces overall performance.
Innovation Solution
A refrigeration cycle apparatus with multiple heat source units and parallel heat exchangers, where a controller manages the flow of refrigerant to switch between different operation modes, allowing some heat exchangers to defrost while others continue heating, and adjusting suction pressures to maintain optimal heating capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If outdoor fan operates to receive heat from outdoor air by parallel heat exchangers during simultaneous heating and defrosting, then heating operation continues, but heat transfer from defrosting heat exchanger to outdoor air increases, reducing heating capacity
Solution Approach 1:
The outdoor heat exchanger is divided into multiple parallel heat exchangers, allowing selective operation where some units perform defrosting while others perform heating, enabling independent control of each segment's function
Solution Approach 2:
The system dynamically switches between different operational modes (first simultaneous heating and defrosting operation with partial defrosting, second simultaneous heating and defrosting operation with full defrosting) based on outdoor temperature conditions, adapting the defrosting strategy to maintain heating capacity
2Reliability
If refrigerant is supplied to all parallel heat exchangers through defrosting circuit, then defrosting is performed on all units, but heating capacity decreases as all heat exchangers transfer heat to outdoor air
Solution Approach 1:
The system segments the defrosting operation by allowing selective supply of refrigerant to different parallel heat exchangers based on their frosting conditions, rather than uniformly defrosting all units
Solution Approach 2:
The controller adjusts operational parameters (refrigerant flow distribution, suction pressure) based on outdoor air temperature to optimize the balance between defrosting effectiveness and heating capacity maintenance
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 selection of high heating capacity modes, thereby suppressing the decrease in heating capacity during simultaneous heating and defrosting operations by optimizing refrigerant flow and heat exchanger usage based on outdoor air temperature.
Implementation Method 1
a compressor configured to compress and discharge refrigerant
Implementation Method 2
a check valve configured to prevent backflow of the refrigerant discharged from the compressor
Implementation Method 3
a defrosting circuit configured to branch the refrigerant discharged from the compressor on an upstream side of the check valve and supply the refrigerant to at least one or some parallel heat exchangers
Implementation Method 4
a first flow switching device configured to switch a flow passage of refrigerant passing through the plurality of parallel heat exchangers
Implementation Method 5
a plurality of parallel heat exchangers connected in parallel to each other in a flow of refrigerant and configured to operate at least as evaporators
Data Source
AI summary
A controller switches between and performs a first simultaneous heating and defrosting operation of supplying part of refrigerant discharged from a compressor is supplied to one or some parallel heat exchangers among a plurality of parallel heat exchangers through a defrosting circuit and allowing the other one or more parallel heat exchangers to operate as evaporators, and a second simultaneous heating and defrosting operation of, in one or some heat source units among a plurality of heat source units, supplying the refrigerant discharged from the compressor is supplied to all the plurality of parallel heat exchangers through the defrosting circuit, and in the other one or more heat source units, continuing heating by allowing all the plurality of parallel heat exchangers to operate as evaporators.