Expansion Valve Control for Air Conditioner Dehumidification Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In air conditioners, the reduction in cooling capacity leads to decreased refrigerant circulation, causing the expansion valve to partially close, which can result in refrigerant circuit blockage, making it difficult to detect and preventing effective dehumidification and cooling, and potentially leading to compressor overheating.
Innovation Solution
The evaporation temperature detecting means is positioned downstream of the expansion valve in the outdoor unit, allowing for the detection of pressure reduction due to circuit blockage, and the expansion valve is configured to maintain a small flow rate just before full closure, enabling precise control of evaporation temperature and flow rate adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the expansion valve is fully closed to restrict refrigerant flow for dehumidification, then the evaporation temperature can be decreased, but the refrigerant circuit may become blocked
Solution Approach 1:
The patent employs feedback control by detecting evaporation temperature and using it to adjust the expansion valve opening degree. The control unit continuously monitors the evaporation temperature from the detecting means and adjusts the expansion valve to maintain optimal temperature, preventing both excessive closure that causes blockage and insufficient closure that fails to achieve dehumidification.
Solution Approach 2:
The patent places the evaporation temperature detecting means downstream of the expansion valve in the outdoor unit to detect pressure reduction before complete blockage occurs. This preliminary detection allows the control unit to adjust the expansion valve opening degree in advance, preventing circuit blockage while maintaining effective refrigerant flow restriction for dehumidification.
2Temperature
If the expansion valve opening degree is reduced to decrease refrigerant flow for dehumidification, then the evaporation temperature decreases, but the flow rate restriction becomes insufficient with conventional expansion valves
Solution Approach 1:
The patent changes the operational parameters of the expansion valve by controlling its opening degree based on detected evaporation temperature. The control unit adjusts the opening degree to optimize the balance between refrigerant flow restriction and sufficient flow maintenance, enabling effective dehumidification without circuit blockage.
3Temperature
If the refrigerant flow rate is excessively reduced under low load conditions, then dehumidification can be performed, but the detecting means cannot detect evaporation temperature as refrigerant evaporates before reaching it
Solution Approach 1:
The evaporation temperature detecting means is strategically positioned downstream of the expansion valve in the outdoor unit to detect pressure reduction before complete blockage occurs. This preliminary detection ensures that the detecting means can always measure evaporation temperature even when refrigerant flow rate is very small, enabling continuous monitoring and control.
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 setup allows for the detection of refrigerant circuit blockage, enabling effective dehumidification and cooling while preventing compressor overheating by ensuring the expansion valve is not fully closed, thus maintaining efficient operation.
Implementation Method 1
a refrigerant evaporates only in the auxiliary heat exchanger to locally perform dehumidification
Implementation Method 2
the flow rate is restricted just before the expansion valve is fully closed even while the flow rate is very small, to decrease the evaporation temperature
Implementation Method 3
the evaporation temperature detecting means for detecting the evaporation temperature is disposed downstream of the expansion valve in the outdoor unit. This ensures detection of the reduction of the pressure (the reduction of the temperature) due to the blockage of the circuit
Data Source
Figure 1
Figure 2
Figure 3
AI summary
When a fully-closable expansion valve is used, there is a possibility that the expansion valve is fully closed thereby to block a refrigerant circuit. In an air conditioner 1 of the present invention, an indoor heat exchanger 14 includes an auxiliary heat exchanger 20 and a main heat exchanger 21 disposed leeward from the auxiliary heat exchanger 20. In an operation in a predetermined dehumidification operation mode, a liquid refrigerant supplied to the auxiliary heat exchanger 20 all evaporates midway in the auxiliary heat exchanger 20, i.e., before reaching the outlet. Therefore, only an upstream partial area in the auxiliary heat exchanger 20 is an evaporation region, while an area downstream of the evaporation region in the auxiliary heat exchanger 20 is a superheat region. Further, an evaporation temperature sensor 30 which detects an evaporation temperature is disposed downstream of an expansion valve 13 in an outdoor unit 3.