Heat Pump Leak Pump-Down Control to Prevent Liquid Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In refrigeration cycle apparatuses, long pipes connecting indoor and outdoor units and multiple indoor units to one outdoor unit can lead to a large amount of refrigerant being sealed, causing the outdoor heat exchanger to enter a liquid sealed state during pump down operations, which may result in damage due to abrupt pressure increases upon temperature changes.
Innovation Solution
A refrigeration cycle apparatus is designed with a four-way valve, compressor, accumulator, indoor and outdoor heat exchangers, expansion valves, and shutoff valves, where the four-way valve is switched between cooling and heating operation positions to redirect refrigerant flow, preventing liquid sealing by moving liquid refrigerant from the outdoor heat exchanger to the accumulator during pump down operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pump down operation is performed when large amount of refrigerant is sealed in the refrigerant circuit, then refrigerant collection is achieved, but outdoor heat exchanger is filled with liquid refrigerant causing liquid sealed state
Solution Approach 1:
The patent segments the refrigerant collection process into two distinct phases: first collecting refrigerant from indoor units to the outdoor unit, then separately handling the liquid refrigerant in the outdoor heat exchanger by switching to heating operation. This segmentation prevents the liquid sealed state by treating the liquid refrigerant issue as a separate step rather than allowing it to accumulate during the initial collection phase.
Solution Approach 2:
The patent performs preliminary action by detecting the liquid sealed state condition before it becomes dangerous, using sensors to monitor the outdoor heat exchanger status. When liquid accumulation is detected, the system proactively switches to heating operation to evaporate the liquid refrigerant, preventing the abrupt pressure increase that would occur if the liquid sealed state were allowed to persist.
2Productivity
If outdoor heat exchanger is filled with liquid refrigerant, then refrigerant collection efficiency is improved, but abrupt pressure increase may damage the heat exchanger
Solution Approach 1:
The patent implements feedback control by continuously monitoring the state of the outdoor heat exchanger during refrigerant collection. When the sensor detects that liquid refrigerant has accumulated to a level that may cause dangerous pressure increase, the system automatically switches to heating operation to evaporate the liquid, thereby maintaining collection efficiency while preventing damage through real-time feedback and automatic correction.
3Reliability
If four-way valve is switched to heating operation position, then liquid refrigerant is moved from outdoor heat exchanger to accumulator, but additional operation time is required
Solution Approach 1:
The patent applies periodic action by implementing intermittent switching between cooling and heating operations during the pump down process. Rather than continuously running in one mode, the system periodically switches to heating operation when liquid accumulation is detected, then returns to cooling operation for continued refrigerant collection. This periodic switching achieves reliable prevention of liquid sealed state while minimizing the total time lost to heating operations.
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 configuration effectively prevents the outdoor heat exchanger from entering a liquid sealed state, ensuring safe and efficient refrigerant collection and reducing the risk of damage from pressure increases during pump down operations.
Implementation Method 1
a four-way valve connected to an outlet of the compressor, an inlet of the accumulator, the outdoor heat exchanger, and an indoor heat exchanger
Implementation Method 2
a compressor configured to compress the refrigerant
Implementation Method 3
an outdoor heat exchanger connected to the four-way valve
Implementation Method 4
an expansion valve connected to the four-way valve
Implementation Method 5
an indoor heat exchanger configured to exchange heat with indoor air
Implementation Method 6
an accumulator configured to store a refrigerant
Data Source
AI summary
A refrigeration cycle apparatus includes a gas leakage sensor and a control device. When refrigerant leakage is detected by the gas leakage sensor, the control device performs a first mode operation to operate a compressor in such a state that a four-way valve is set to a cooling operation state, an expansion valve is opened, and a first shutoff valve is closed. After performing the first mode operation, the control device performs a second mode operation to operate the compressor in such a state that the four-way valve is set to a heating operation state and the first shutoff valve is closed.