Air Conditioning Valve Control During Defrost to Prevent Freezing
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Solution Overview
Problem
Indirect air conditioning systems using water or brine as a heat medium face challenges in defrosting, leading to longer defrosting times and reduced comfort due to heat absorption limitations and potential freezing of the heat exchanger.
Innovation Solution
A controller for an air conditioning apparatus that manages flow rate control valves and fans to direct heat absorption from indoor air to the heat medium, prioritizing heat transfer from rooms with suitable temperatures to prevent freezing and shorten defrosting time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bypass circuit is opened and expansion valve is closed to prevent refrigerant from flowing through the water heat exchanger during defrosting, then the water heat exchanger is protected from freezing, but heat absorption from water to refrigerant does not take place resulting in longer defrosting time
Solution Approach 1:
The system segments the heat exchangers into multiple groups (first group and second group) and controls them differently during defrosting operation. The first group heat exchangers are isolated from refrigerant flow to prevent freezing, while the second group heat exchangers continue to operate and absorb heat from the water heat medium, enabling simultaneous protection and heat absorption functions.
Solution Approach 2:
The second group of heat exchangers serves dual functions: they act as heat absorption paths for the water heat medium during defrosting operation, and can also function as regular heat exchangers during normal heating operation. This multi-functionality allows the system to maintain heat absorption capability while protecting the first group heat exchangers from freezing.
2Reliability
If refrigerant flow through the water heat exchanger is blocked during defrosting, then the heat exchanger is protected from freezing, but heat absorption from the heat medium does not take place reducing room temperature and compromising comfort
Solution Approach 1:
The system segments the heat exchangers into multiple groups (first group and second group) and controls them differently during defrosting operation. The first group heat exchangers are isolated from refrigerant flow to prevent freezing, while the second group heat exchangers continue to operate and absorb heat from the water heat medium, enabling simultaneous protection and heat absorption functions.
Solution Approach 2:
The water heat medium serves as an intermediary that transfers heat from the second group heat exchangers to the first group heat exchangers. During defrosting, the water heat medium absorbs heat from the second group heat exchangers and delivers it to the first group heat exchangers, maintaining room temperature while protecting the first group from freezing.
3Reliability
If the defrosting operation interrupts heating for an extended period, then the outdoor heat exchanger is thoroughly defrosted, but the interruption time increases reducing comfort
Solution Approach 1:
The system maintains continuous useful action during defrosting operation by having the second group heat exchangers continue to absorb heat from the water heat medium and deliver it to the indoor units. This ensures that heating function continues without interruption while the first group heat exchangers are being defrosted, maintaining comfort throughout the operation.
Solution Approach 2:
The system segments the heat exchangers into multiple groups (first group and second group) and controls them differently during defrosting operation. The first group heat exchangers are isolated from refrigerant flow to prevent freezing, while the second group heat exchangers continue to operate and absorb heat from the water heat medium, enabling simultaneous protection and heat absorption functions.
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
The solution effectively shortens defrosting time and improves comfort by ensuring continuous heat absorption from indoor air, preventing freezing and allowing for quicker return to heating operations.
Implementation Method 1
a compressor configured to compress a first heat medium
Implementation Method 2
The first heat exchanger is configured to exchange heat between the first heat medium and outdoor air
Implementation Method 3
The second heat exchanger is configured to exchange heat between the first heat medium and a second heat medium
Implementation Method 4
The plurality of third heat exchangers are each configured to exchange heat between the second heat medium and indoor air
Implementation Method 5
The pump is configured to circulate the second heat medium between the plurality of third heat exchangers and the second heat exchanger
Data Source
AI summary
An air conditioning apparatus includes: a second heat exchanger; a plurality of third heat exchangers; and a plurality of flow rate control valves. In a defrosting mode, when a heat exchanger that is not being requested to perform air conditioning includes a first device having a set temperature lower than or equal to a current room temperature and a second device which is set so as not to perform air conditioning, a controller is configured to control a first flow rate control valve corresponding to the first device and a second flow rate control valve corresponding to the second device such that a degree of opening of the first flow rate control valve is higher than or equal to a degree of opening of the second flow rate control valve.