Refrigerant Charging Control for Low-Temperature Heat Pump Systems
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Solution Overview
Problem
In air conditioning apparatuses with interconnected outdoor and indoor units via liquid and gas refrigerant communication pipes, the challenge is to perform refrigerant charging without excessively lowering indoor temperatures, especially when the total volume of indoor heat exchangers is smaller than the outdoor heat exchanger, ensuring the circuit is charged with the prescribed quantity of refrigerant, especially at low outdoor temperatures.
Innovation Solution
The air conditioning apparatus employs a control component that switches between heating and cooling refrigerant charging operations based on the volume relationship between indoor and outdoor heat exchangers, starting with a heating operation to prevent temperature drops and then switching to a cooling operation to ensure the circuit is fully charged with the prescribed quantity of refrigerant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the cooling refrigerant charging operation is performed to charge the refrigerant circuit with the prescribed quantity of refrigerant, then the refrigerant circuit can be charged with the required quantity, but the indoor temperature is excessively lowered
Solution Approach 1:
The control component performs a heating refrigerant charging operation before the cooling refrigerant charging operation. This preliminary heating operation accumulates refrigerant in the indoor heat exchangers and prevents excessive indoor temperature lowering during the subsequent cooling charging operation, while still enabling the circuit to be charged with the prescribed quantity of refrigerant.
2Temperature
If the heating refrigerant charging operation is performed to avoid lowering indoor temperatures, then the indoor temperature is maintained, but the refrigerant circuit cannot be charged with the prescribed quantity of refrigerant when the total volume of indoor heat exchangers is smaller than the outdoor heat exchanger volume
Solution Approach 1:
The heating refrigerant charging operation is performed first to accumulate refrigerant in the indoor heat exchangers and maintain indoor temperature. After this preliminary operation, the cooling refrigerant charging operation is then performed to charge the circuit with the remaining required quantity of refrigerant, achieving both temperature maintenance and proper refrigerant charging.
Solution Approach 2:
The refrigerant charging process is divided into two periodic stages: first a heating charging operation, then a cooling charging operation. This periodic alternation allows the system to achieve refrigerant accumulation in indoor units while maintaining temperature stability, and then complete the prescribed quantity charging without excessive temperature drop.
3Quantity of substance
If the prescribed quantity of refrigerant is determined by the cooling operation when the outdoor heat exchanger volume is large, then the cooling operation can be properly charged, but the heating operation cannot accumulate sufficient refrigerant in the indoor heat exchangers
Solution Approach 1:
The heating refrigerant charging operation is performed first to accumulate refrigerant in the indoor heat exchangers according to heating operation requirements. This preliminary action ensures that indoor units have sufficient refrigerant for heating, and then the cooling charging operation adds the remaining quantity needed for cooling operation, achieving adaptability to both modes.
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 allows for reliable refrigerant charging without excessively lowering indoor temperatures and ensures the refrigerant circuit is appropriately charged, even at low outdoor temperatures, by using a combination of heating and cooling charging operations tailored to the volume relationship between indoor and outdoor heat exchangers.
Implementation Method 1
an outdoor unit having an outdoor heat exchanger and plural indoor units having indoor heat exchangers
Implementation Method 2
causes the outdoor heat exchanger to function as a radiator of refrigerant and causes the indoor heat exchangers to function as evaporators of the refrigerant
Implementation Method 3
a refrigerant circuit switchable to a cooling cycle state, which causes the outdoor heat exchanger to function as a radiator of refrigerant and causes the indoor heat exchangers to function as evaporators of the refrigerant, and a heating cycle state, which causes the outdoor heat exchanger to function as an evaporator of the refrigerant and causes the indoor heat exchangers to function as radiators of the refrigerant
Data Source
AI summary
In a case where the total volume of plural indoor heat exchangers is smaller than the volume of an outdoor heat exchanger, a control component performs a heating refrigerant charging operation until a heating refrigerant charging completion condition is met, and thereafter performs a cooling refrigerant charging operation until a refrigerant charging completion condition where a refrigerant circuit is charged with a prescribed quantity of refrigerant is met.