Stored-Heat Air Conditioner Control for Defrost Heat Retention
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Solution Overview
Problem
Conventional air conditioning apparatuses face challenges in maintaining the quantity of heat stored for defrosting operations due to heat release from the heat storage material after heating, especially when using phase-change materials, and determining the optimal timing for ending heat storage operations is difficult.
Innovation Solution
The air conditioning apparatus employs a refrigerant circuit with a stored-heat heat exchanger that ends the heat storage operation based on cumulative time criteria and performs a heat retention operation by slightly opening the heat storage expansion valve to minimize heat loss, allowing for proper judgment of heat storage completion and maintaining heat quantity for defrosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the heat storage operation ends simply by switching to heating operation only, then the operation control is simplified, but heat release from the heat storage material occurs due to outdoor temperature effects, causing a decrease in the quantity of heat available for defrosting
Solution Approach 1:
The control unit performs a heat retention operation after the heat storage operation ends, before switching to heating operation only. This preliminary action maintains the heat quantity in the heat storage material by causing the stored-heat heat exchanger to exchange heat with the heat storage material, preventing heat release due to outdoor temperature effects and ensuring sufficient heat is available for subsequent defrosting operations
2Quantity of substance
If heat storage material undergoing phase change is used, then the heat storage capacity is improved, but determining the timing of heat storage completion becomes difficult due to little temperature difference during phase change
Solution Approach 1:
The control unit determines the timing of heat storage completion based on the elapsed time of the heat storage operation and the refrigerant temperature. This feedback mechanism uses measurable parameters (time and temperature) to accurately determine when heat storage is sufficient, overcoming the difficulty of detecting phase change completion through temperature alone
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 approach effectively suppresses the decrease in usable heat during defrosting operations by ensuring sufficient heat retention and accurately determining the end of heat storage, thereby maintaining the efficiency of the stored-heat usage operation.
Implementation Method 1
a stored-heat heat exchanger that exchanges heat between a refrigerant and a heat storage material
Implementation Method 2
when heat storage material that undergoes phase change is used
Implementation Method 3
a condensation temperature of the refrigerant in the refrigerant circuit
Implementation Method 4
releases heat from the heat storage material by causing the stored-heat heat exchanger to function as an evaporator of the refrigerant
Data Source
Figure 1
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AI summary
An air conditioning apparatus (1) is provided with a refrigerant circuit (10) further provided with a compressor (21), an outdoor heat exchanger (23), an indoor heat exchanger (42a, 42b), and a stored-heat heat exchanger (28) that exchanges heat between a refrigerant and a heat storage material, and is capable of performing a heat storage operation during a heating operation and a stored-heat usage operation during a defrosting operation. This air conditioning apparatus, in the heat storage operation during the heating operation, ends the heat storage operation if a heat storage cumulative time that is an integrated value for the time at which a condensation temperature of the refrigerant is greater than or equal to a heat storage completion condensation temperature, is greater than or equal to a heat storage completion cumulative time, and after the heat storage operation ends, while the heating operation is performed, a heat retention operation is performed for retaining heat of the heat storage material.