Expansion Valve Feedback Control for Air Conditioner Dehumidification
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Solution Overview
Problem
Conventional air conditioners face issues with refrigerant circuit blockage due to full closure of expansion valves, leading to inadequate dehumidification and cooling, and overheating of compressors, as the existing expansion valves lack sufficient control over evaporation temperature and flow rate.
Innovation Solution
An air conditioner design where the evaporation temperature detecting means is placed downstream of the expansion valve in the outdoor unit, allowing for precise control of the flow rate and evaporation temperature, even at low flow rates, and enabling detection of refrigerant circuit blockage before full closure, with a fully closable expansion valve that adjusts flow rate significantly before reaching full closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a fully closable expansion valve is used to sufficiently restrict the flow rate and decrease evaporation temperature for dehumidification, then the evaporation temperature control is improved, but the refrigerant circuit may be blocked due to full closure of the valve
Solution Approach 1:
The patent employs an evaporation temperature detecting means that provides feedback to the control means. The control means adjusts the expansion valve opening degree based on the detected evaporation temperature to maintain it within a predetermined range, preventing both excessive restriction causing blockage and insufficient restriction failing to achieve dehumidification.
Solution Approach 2:
The control means dynamically changes the opening degree parameter of the expansion valve based on the detected evaporation temperature. By adjusting this parameter in real-time, the system achieves sufficient flow restriction for dehumidification while avoiding complete closure that would cause blockage.
2Temperature
If the expansion valve opening degree is reduced to restrict flow rate for dehumidification, then the evaporation temperature decreases, but the flow rate restriction may become excessive causing circuit blockage
Solution Approach 1:
The evaporation temperature detecting means continuously monitors the evaporation temperature and provides feedback to the control means. The control means adjusts the expansion valve opening degree based on this feedback to maintain the evaporation temperature within a predetermined range, ensuring adequate refrigerant flow while achieving dehumidification.
Solution Approach 2:
The expansion valve opening degree is dynamically adjusted by the control means based on real-time evaporation temperature detection. This dynamic control ensures the valve maintains an optimal opening degree that restricts flow sufficiently for dehumidification without closing completely to prevent blockage.
3Measurement precision
If the detecting means is placed in the indoor unit, then the evaporation temperature can be detected, but the refrigerant may completely evaporate before reaching the detecting means making detection impossible
Solution Approach 1:
The patent places the evaporation temperature detecting means in the outdoor unit at a position where refrigerant is supplied from the expansion valve. This preliminary positioning ensures the detecting means is in the refrigerant path before complete evaporation occurs, allowing reliable detection of evaporation temperature and timely control adjustments.
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 design ensures effective dehumidification and cooling by maintaining control over evaporation temperature and flow rate, preventing refrigerant circuit blockage and compressor overheating, and facilitating early detection of potential blockages.
Implementation Method 1
an auxiliary heat exchanger is disposed rearward of a main heat exchanger; and 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
a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected to one another
Implementation Method 4
an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected to one another
Data Source
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.