Heat Pump Defrost Circuit for Continuous Indoor Heating
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Solution Overview
Problem
Air-conditioning apparatuses that use heat-pump technology struggle to perform defrosting without stopping heating operations, leading to reduced heating capacity and compromised comfortability in indoor spaces due to limitations in refrigerant pressure adjustment during defrosting.
Innovation Solution
An air-conditioning system with a main circuit including a compressor, indoor heat exchangers, pressure reducing devices, and an outdoor heat exchanger with parallel heat exchangers, featuring defrosting pipes and expansion devices to adjust refrigerant pressure, allowing for continuous heating during defrosting by switching the connection of heat exchangers and controlling the flow of refrigerant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If refrigerant pressure is set to high pressure during defrosting, then defrosting capacity is improved, but heating capacity is reduced due to insufficient refrigerant for heating
Solution Approach 1:
The outdoor heat exchanger is divided into multiple parallel heat exchangers, allowing separate control of refrigerant flow to defrosting and heating circuits. This segmentation enables independent optimization of defrosting capacity and heating capacity without mutual interference.
Solution Approach 2:
The refrigerant pressure and flow rate are made dynamically adjustable through expansion devices that can change their opening degree based on operational requirements. This allows the system to optimize refrigerant distribution between defrosting and heating circuits in real-time, preventing the static pressure setting problem.
2Productivity
If refrigerant flow rate to defrosting heat exchangers is increased, then defrosting effectiveness is improved, but heating capacity is reduced due to insufficient refrigerant flow for heating
Solution Approach 1:
The refrigerant circuit is segmented into defrosting circuit and heating circuit with separate flow control. The defrosting circuit receives refrigerant through the first expansion device while the heating circuit receives refrigerant through the second expansion device, allowing independent optimization of flow rates for each function.
Solution Approach 2:
The system changes the opening degree parameter of expansion devices to control refrigerant flow rates dynamically. By adjusting these parameters, the system can optimize defrosting effectiveness while maintaining sufficient refrigerant flow for heating capacity.
3Power
If refrigerant pressure is set to low pressure during defrosting, then heating capacity is maintained, but defrosting cannot be performed with latent heat reducing efficiency
Solution Approach 1:
The expansion devices enable dynamic pressure adjustment, allowing the system to set high pressure during defrosting to utilize latent heat for efficient frost melting, then switch to normal operating pressure for heating. This dynamic control eliminates the need to choose between high pressure (efficient defrosting) and low pressure (heating capacity).
Solution Approach 2:
The segmented circuit architecture allows the defrosting circuit to operate independently at high pressure for efficient latent heat defrosting, while the heating circuit maintains its own refrigerant flow and pressure settings, preventing the pressure compromise in conventional systems.
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
Enables defrosting without stopping heating operations, improving comfortability by maintaining heating capacity and adjusting refrigerant pressure to ensure efficient latent heat usage during defrosting.
Implementation Method 1
a first expansion device provided on the first defrosting pipe to adjust a pressure of the refrigerant supplied through the first defrosting pipe to the parallel heat exchanger to be defrosted; a second expansion device provided on a return pipe returning the refrigerant from the parallel heat exchanger to be defrosted to the main circuit; and a third expansion device which is provided between a connection point between an outlet of the second defrosting pipe and one of the indoor heat exchangers
Implementation Method 2
when the saturation temperature of the refrigerant for defrosting is lower than the melting temperature of frost, defrosting cannot be performed with latent heat of the refrigerant
Implementation Method 3
an outdoor heat exchanger that receives heat from air; a plurality of indoor heat exchangers
Data Source
AI summary
An air-conditioning apparatus includes: a first defrosting pipe branching from a main circuit to supply a portion of refrigerant discharged from a compressor to one of plural parallel heat exchangers to be defrosted; a second defrosting pipe which returns, to the main circuit, the refrigerant supplied through the first defrosting pipe to the one parallel heat exchanger; a first expansion device provided on the first defrosting pipe; a second expansion device provided on the second defrosting pipe to adjust a pressure of the refrigerant in the one parallel heat exchanger; and a third expansion device provided between a connection point between an outlet of the second defrosting pipe and the main circuit and one of plural indoor heat exchangers functioning as an evaporator, to adjust a pressure of the refrigerant in the one of the indoor heat exchangers; and a controller that controls the second and third expansion devices individually.