Heat Source Refrigerant Circuit for Power-Failure Backflow Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing heat source apparatus experiences liquid backflow due to pressure differences in the refrigerant circuit during power failures, leading to undesirable operations when power is restored.
Innovation Solution
The main expansion valve is configured to be fully closed during power outages, and a refrigerant flow control circuit, including sub-expansion valves and a refrigerant tank, regulates the refrigerant flow to prevent backflow by storing or releasing refrigerant, thereby suppressing liquid backflow during restarts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the expansion valve is left open during power failure, then the refrigerant circuit maintains normal flow paths, but liquid refrigerant backflows between heat exchangers due to pressure differences
Solution Approach 1:
The expansion valve is pre-configured to automatically close when power failure is detected, preventing liquid backflow before it can occur. The control unit detects power failure and sends a closing signal to the expansion valve in advance, establishing a protective state before the harmful effect manifests.
Solution Approach 2:
A refrigerant tank is introduced as an intermediary component to receive and store liquid refrigerant that would otherwise backflow. The tank acts as a buffer between the high-pressure and low-pressure sides of the refrigerant circuit, isolating the harmful backflow effect while maintaining system functionality.
2Reliability
If the expansion valve is fully closed during power failure, then liquid backflow is prevented, but the refrigerant flow control capability is reduced
Solution Approach 1:
The refrigerant flow control function is segmented into two independent paths: the main expansion valve for primary flow control, and the refrigerant tank with its own valve for backup flow control. This segmentation allows the system to maintain adaptability through the tank path even when the main valve is closed during power failure.
Solution Approach 2:
The refrigerant tank serves multiple functions: it acts as a surge tank during normal operation, and as an emergency flow control mechanism during power failure. This multi-functionality ensures the system maintains refrigerant flow regulation capability across different operating conditions.
3Reliability
If a refrigerant tank is added to regulate refrigerant flow, then liquid backflow is suppressed, but the device complexity increases
Solution Approach 1:
The refrigerant tank is designed to serve multiple purposes within the refrigerant circuit: it functions as a surge tank during normal operation to accommodate refrigerant volume changes, and as an emergency containment vessel during power failure to prevent liquid backflow. This multi-functionality justifies the added complexity by providing dual benefits from a single component.
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 liquid backflow at power restoration, ensuring stable operation by managing refrigerant flow and pressure differences within the refrigerant circuit.
Implementation Method 1
liquid refrigerant dwelling in the air-cooled heat exchanger flows into the water-cooled heat exchanger due to a pressure difference in the refrigerant circuit
Implementation Method 2
the refrigerant tank is provided between the expansion valve and the water-cooled heat exchanger... to store a surplus amount of refrigerant during the heating operation
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A heat source apparatus including: a compressor; an air-cooled heat exchanger; a load-side heat exchanger configured to exchange heat between a heat medium which flows through a load, and refrigerant; and a main expansion valve which is connected between the air-cooled heat exchanger and the load-side heat exchanger, and has a function of being fully closed when stoppage of power supply from a power supply source is detected, includes a refrigerant flow control circuit connected in parallel to the main expansion valve. The refrigerant flow control circuit includes a first sub-expansion valve configured to regulate a flow rate of the refrigerant, a refrigerant tank configured to store the refrigerant, and a second sub-expansion valve configured to regulate the flow rate of the refrigerant, which are connected in series with one another.