Expansion Valve Coordination for Multi-Unit Air Conditioner Heating
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Solution Overview
Problem
Conventional air conditioning apparatuses with two expansion valves in series face challenges in accurately controlling refrigerant depressurization, leading to surplus refrigerant, wet compression, and inefficient energy use, especially when handling varying heat loads across multiple indoor units.
Innovation Solution
An air conditioning apparatus with a controller that regulates the opening degree of the heat-source-side expansion valve based on the opening degrees of usage-side expansion valves, ensuring balanced depressurization and preventing surplus refrigerant, while also incorporating an accumulator to manage excess refrigerant during air-warming operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the outdoor expansion valve and indoor expansion valve are controlled separately to reach target values, then the total depressurization reaches the target pressure, but the refrigerant in the liquid refrigerant communication tube readily goes into a gas-liquid two-phase state and surplus refrigerant accumulates
Solution Approach 1:
The patent combines the control of outdoor and indoor expansion valves into a unified control system. The controller coordinates both valves to work together, ensuring that the sum of their depressurization effects reaches the target while maintaining proper refrigerant phase and preventing surplus refrigerant accumulation.
Solution Approach 2:
The patent dynamically adjusts the opening degrees of expansion valves based on operating conditions (air-cooling vs. air-warming mode). By changing the control parameters (opening degrees) according to different operational states, the system prevents refrigerant from entering a two-phase state and avoids surplus refrigerant accumulation.
2Reliability
If the opening degree of the indoor expansion valve is set to slightly open to prevent liquid refrigerant accumulation during thermo-off state, then liquid refrigerant accumulation is prevented, but when heat loads differ among indoor units, it is difficult to create a difference in opening degrees and energy efficiency decreases
Solution Approach 1:
The patent implements dynamic control of expansion valve opening degrees based on real-time heat load detection. When indoor units are in thermo-off state, the system dynamically adjusts opening degrees to maintain slight openness for preventing liquid accumulation, while simultaneously responding to varying heat loads to optimize energy efficiency.
Solution Approach 2:
The controller uses feedback from heat load detection to adjust the opening degrees of expansion valves. By continuously monitoring the thermal state of indoor units and adjusting valve openings accordingly, the system prevents liquid refrigerant accumulation while maintaining optimal energy efficiency for each unit's actual heat load.
3Measurement precision
If the opening degrees of indoor expansion valves are extremely small or nearly closed in low opening degree state, then depressurization amount is ensured, but it is difficult to accurately control the amounts of depressurization and much refrigerant flows through indoor units with small heat loads
Solution Approach 1:
The patent applies partial action by adjusting expansion valve opening degrees to appropriate levels rather than extreme positions. By avoiding extremely small or fully closed states, the system maintains sufficient depressurization control accuracy while preventing excessive refrigerant flow to units with small heat loads, thereby optimizing energy utilization.
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 solution allows for precise control of refrigerant flow, preventing wet compression and surplus refrigerant, enabling efficient energy use and balanced operation across indoor units with varying heat loads.
Implementation Method 1
the degree of depressurization in the refrigeration cycle is established by the total amount of depressurization achieved by the outdoor expansion valve and the indoor expansion valve together
Implementation Method 2
the refrigerant in a liquid refrigerant communication tube flowing from the indoor unit to the outdoor unit readily goes into a gas-liquid two-phase state
Data Source
AI summary
An air conditioning apparatus includes a heat source unit, usage units, and a controller. The heat source unit has a compression mechanism, a heat-source-side heat exchanger operable at least as an evaporator, and a heat-source-side expansion valve. The usage units have usage-side heat exchangers operable at least as condensers, and usage-side expansion valves. The controller regulates the opening degree of the heat-source-side expansion valve based on the opening degrees of the usage-side expansion valves.