Indoor On-Off Valve Control for Defrost-to-Heating Air Conditioners
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Solution Overview
Problem
In air conditioners installed in intermediate-rise or high-rise buildings, the pressure head difference between the outdoor and indoor units causes refrigerant to flow reversely into the indoor heat exchanger during a defrost operation, leading to refrigerant deficiency and delayed heating operation startup.
Innovation Solution
Incorporating on-off valves in the indoor units and a controller that manages the refrigerant flow by switching the four-way valve to prevent reverse flow, ensuring the refrigerant pressure remains adequate for a smooth transition from defrost to heating operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the outdoor unit is installed above the indoor units in high-rise buildings, then the system can serve multiple floors efficiently, but the pressure head difference causes refrigerant to reverse flow into the indoor heat exchanger during defrost operation
Solution Approach 1:
The on-off valve is activated in advance during the defrost operation to close the liquid refrigerant pipe before the heating operation begins. This preliminary action prevents the pressure head difference from causing reverse flow of refrigerant into the indoor heat exchanger when the heating cycle starts, ensuring reliable refrigerant flow control in multi-floor installations.
2Reliability
If the defrost operation is performed by circulating refrigerant through the outdoor heat exchanger, then the outdoor heat exchanger is defrosted effectively, but the refrigerant pressure difference causes liquid refrigerant to reverse flow into the indoor heat exchanger
Solution Approach 1:
The on-off valve closes the liquid refrigerant pipe in advance during the defrost operation, preventing liquid refrigerant from entering the indoor heat exchanger before the heating operation begins. This ensures that when the heating cycle starts, no reverse flow occurs, maintaining proper refrigerant levels in the system.
Solution Approach 2:
The on-off valve acts as an intermediary device that controls the liquid refrigerant pipe, blocking the path of liquid refrigerant during the transition from defrost to heating operation. This mediator prevents the harmful reverse flow while allowing normal refrigerant circulation during other operations.
3Ease of operation
If the on-off valve remains open during the transition from defrost to heating operation, then the refrigerant can flow freely, but the pressure head difference causes reverse flow and delays heating operation startup
Solution Approach 1:
The on-off valve is closed in advance during the defrost operation to prevent reverse flow of liquid refrigerant into the indoor heat exchanger. By taking this preliminary action, the system avoids refrigerant deficiency and pressure reduction that would otherwise delay the startup of the heating operation, ensuring timely transition to heating mode.
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 solution effectively prevents refrigerant reverse flow and ensures timely and efficient startup of the heating operation by controlling the on-off valves based on pressure differences, maintaining adequate refrigerant pressure and preventing refrigerant deficiency.
Implementation Method 1
a compressor that compresses a refrigerant
Implementation Method 2
a refrigerant pressure at the electronic expansion valve on a side of the outdoor heat exchanger becomes higher than a refrigerant pressure at the electronic expansion valve on a side of the indoor heat exchanger due to a pressure head difference
Implementation Method 3
a refrigerant pressure at the electronic expansion valve on a side of the outdoor heat exchanger becomes higher than a refrigerant pressure at the electronic expansion valve on a side of the indoor heat exchanger due to a pressure head difference
Implementation Method 4
an outdoor heat exchanger gives heat to outdoor air and condenses a high temperature and high pressure gas refrigerant
Implementation Method 5
the indoor heat exchanger draws heat from indoor air and evaporates the refrigerant to change it into a low temperature and low pressure gas refrigerant
Data Source
Figure 1
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AI summary
An air conditioner comprising: a set of outdoor unit 2 having a compressor 21 that compresses a refrigerant, an outdoor heat exchanger 22, and a four-way valve 23; and a plurality of indoor units 3 respectively having indoor heat exchangers 31 connected to the outdoor unit through a liquid refrigerant pipe 5 and a gas refrigerant pipe 6, in which the outdoor unit is arranged above the indoor units. The air conditioner further includes: on-off valves 32 respectively provided in the indoor units 3 on a side of the liquid refrigerant pipe 5; and a controller 72 that performs a defrost operation by switching the four-way valve 23, and the controller once controls the on-off valves 32 in a closing direction when the four-way valve 23 switches the defrost operation to a heating operation.