Parallel Outdoor Heat Exchangers for Continuous Heating Defrost
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Solution Overview
Problem
Existing air-conditioning systems face challenges in efficiently defrosting outdoor heat exchangers during heating operations, leading to reduced heating capacity and comfort due to heat leaks and the formation of root ice, especially when the outdoor temperature is low.
Innovation Solution
The system incorporates a main circuit with a compressor, indoor heat exchanger, parallel heat exchangers, a defrost pipe, and an interface heat exchanger, along with bypass pipes to efficiently direct refrigerant flow, ensuring continuous heating during defrosting by preventing heat leakage and enhancing defrosting effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the outdoor heat exchanger is divided into parallel heat exchangers for simultaneous defrosting and heating, then heating can continue during defrosting, but heat leaks from the defrosted heat exchanger to the evaporator reduce defrosting effectiveness
Solution Approach 1:
The outdoor heat exchanger is divided into multiple parallel heat exchangers (first outdoor heat exchanger and second outdoor heat exchanger), allowing independent control and operation of each unit. This segmentation enables one heat exchanger to perform defrosting while the other maintains heating, resolving the conflict between heating continuity and defrosting effectiveness by isolating thermal interactions between the two units.
Solution Approach 2:
A hot pipe is introduced as an intermediary component that receives high-temperature refrigerant from the compressor discharge and directs it to the heat exchanger requiring defrosting. This intermediary system provides a dedicated defrosting heat source independent of the evaporator operation, preventing heat leakage from affecting defrosting effectiveness while maintaining heating continuity through the other heat exchanger.
2Reliability
If high-temperature refrigerant is supplied to defrost the heat exchanger, then defrosting effectiveness improves, but heating capacity declines due to heat leakage to the evaporator
Solution Approach 1:
The system segments the heating function across two parallel outdoor heat exchangers. While one heat exchanger receives high-temperature refrigerant for defrosting, the other heat exchanger simultaneously provides heating to the indoor unit. This segmentation ensures that heating capacity is maintained through the non-defrosted heat exchanger, eliminating the trade-off between defrosting effectiveness and heating power.
Solution Approach 2:
The system maintains continuous heating action by switching between two outdoor heat exchangers. When one heat exchanger is undergoing defrosting, the other continues to provide heating without interruption. This continuity of useful action ensures that heating capacity is sustained throughout the defrosting cycle, resolving the contradiction between effective defrosting and maintained heating power.
3Reliability
If the refrigeration cycle is reversed for defrosting, then the frost melts effectively, but the heating operation is suspended causing comfort impairment
Solution Approach 1:
The outdoor heat exchanger system is segmented into multiple independent units that can operate in different modes simultaneously. One heat exchanger can be dedicated to defrosting while another maintains heating operation, allowing both functions to occur concurrently without requiring cycle reversal. This segmentation eliminates the need to suspend heating for defrosting, maintaining heating comfort throughout the defrosting process.
Solution Approach 2:
A hot pipe system acts as an intermediary that provides a dedicated defrosting pathway independent of the main heating cycle. High-temperature refrigerant is diverted through the hot pipe to the defrosted heat exchanger, while the main heating cycle continues uninterrupted through the other heat exchanger. This intermediary defrosting system allows effective frost melting without suspending the heating operation, preserving indoor comfort.
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 efficient defrosting without suspending heating operations, maintaining indoor comfort and heating capacity even at low outdoor temperatures by effectively managing refrigerant flow and preventing root ice formation.
Implementation Method 1
receiving heat from air in the evaporator
Implementation Method 2
heat from the air can be utilized
Implementation Method 3
a part of high-temperature refrigerant discharged from the compressor is alternately supplied to each of the parallel heat exchangers to thereby alternately defrost the parallel heat exchangers
Implementation Method 4
outdoor heat exchanger serving as evaporator
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An air-conditioning apparatus is capable of efficiently performing defrosting operation without suspending a heating operation of an indoor unit. The air-conditioning apparatus includes a main circuit (50) sequentially connecting, via a pipe, a compressor (1), indoor heat exchangers (3b and 3c), first flow control devices (4b and 4c), and a plurality of parallel heat exchangers (5-1 and 5-2) connected in parallel to each other to allow refrigerant to circulate, first defrost pipes (39-1 and 39-2) branching a part of the refrigerant discharged from the compressor 1 and causing the part of the refrigerant to flow into one of the plurality of parallel heat exchangers (5-1 and 5-2) to be defrosted, an interface heat exchanger (11) located between the plurality of parallel heat exchangers (5-1 and 5-2), a first bypass pipe (37) branching a part of the refrigerant discharged from the compressor (1) and causing the part of the refrigerant to flow into the interface heat exchanger (11), and a second bypass pipe (38) causing the part of the refrigerant flowing out of the interface heat exchanger (11) to flow into the main circuit (50).