Vertical Heat Source Unit Control for Refrigerant Balance
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Solution Overview
Problem
Air-conditioning apparatus with multiple heat source units installed vertically at different heights face refrigerant imbalance due to liquid head differences, affecting system operation, especially in systems with larger diameter return pipes and increased pressure loss.
Innovation Solution
The air-conditioning apparatus includes a controller that regulates the flow rate of refrigerant through the outdoor heat exchanger by controlling the expansion device and flow switching valves, ensuring suction equality between upper and lower heat source units, thereby maintaining refrigerant balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If heat source units are installed vertically at different heights to save installation space, then installation space efficiency is improved, but refrigerant balance between units deteriorates due to liquid head differences
Solution Approach 1:
The invention changes the operating parameters of the outdoor heat exchangers (upper and lower) differently to compensate for the liquid head difference caused by vertical installation. Specifically, the flow rates or heat exchange targets of the outdoor heat exchangers are adjusted so that the suction pressures at both compressors become equal, thereby maintaining refrigerant balance despite the height difference between units
Solution Approach 2:
The control device monitors the suction pressures of both compressors and uses this feedback information to dynamically adjust the operation of the outdoor heat exchangers. By continuously comparing the suction pressures and modifying the heat exchanger performance accordingly, the system maintains equal suction pressures and balanced refrigerant distribution across vertically installed units
2Loss of energy
If the diameter of the return pipe is increased to reduce pressure loss, then pressure loss is reduced, but the system becomes more sensitive to liquid head effects causing refrigerant imbalance
Solution Approach 1:
By adjusting the operating parameters of the outdoor heat exchangers (such as flow rate or heat exchange target), the invention compensates for the increased sensitivity to liquid head effects. The control device modifies these parameters to ensure that despite the larger pipe diameter and reduced pressure loss, the liquid head differences do not cause significant refrigerant imbalance between vertically installed units
3Reliability
If heat source units are arranged horizontally in a row, then refrigerant balance is maintained, but installation space efficiency deteriorates when installation area is constrained
Solution Approach 1:
The invention enables vertical installation by changing the operating parameters of the outdoor heat exchangers to compensate for height differences. This allows the heat source units to be arranged vertically rather than horizontally, significantly improving installation space efficiency while maintaining refrigerant balance through parameter adjustment
Solution Approach 2:
The invention transitions from horizontal arrangement (two-dimensional plane) to vertical arrangement (three-dimensional space utilization). By exploiting the vertical dimension and compensating for height differences through parameter changes in the outdoor heat exchangers, the system achieves space-efficient installation without sacrificing refrigerant balance
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 effectively suppresses refrigerant imbalance between heat source units, even when installed vertically, ensuring stable operation and allowing for vertical installation in constrained spaces.
Implementation Method 1
an outdoor heat exchanger configured to function at least as an evaporator
Implementation Method 2
a liquid head generated by a difference in height between the heat source units
Data Source
AI summary
An air-conditioning apparatus includes two heat source units, each including a compressor, an outdoor heat exchanger functioning as an evaporator, an accumulator connected to a suction side of the compressor, and at least one of an outdoor air-sending device configured to supply air corresponding to a heat exchange target for refrigerant to the outdoor heat exchanger or a flow control device (bypass and expansion device for bypass) configured to regulate a flow rate of the refrigerant flowing through the outdoor heat exchanger. A controller is configured to control at least one of the outdoor air-sending device or the flow control device so that a suction quality of the compressor of an upper heat source unit installed on an upper side and a suction quality of the compressor of a lower heat source unit installed on a lower side become the same.