Receiver Fill Valve Control for Heat Pump Mode Transitions
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Solution Overview
Problem
Compression refrigerant heat pumps face issues with refrigerant pressure faults and liquid slugs entering the compressor when switching between operating modes, particularly during defrosting, which can damage the compressor and disrupt heating and cooling functions.
Innovation Solution
A heat pump system that includes a compressor, indoor and outdoor heat exchangers, a receiver, and a valve system comprising a check valve and a two-position valve, which manages refrigerant flow to prevent pressure faults and liquid slugs by adjusting the refrigerant charge and flow rates during heating, cooling, and defrost modes, using a directional valve to control the flow between the indoor and outdoor heat exchangers and the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the heat pump transitions between operating modes (heating, cooling, defrost), then the system can provide versatile climate control functions, but refrigerant pressure faults and liquid slugs may enter the compressor causing damage
Solution Approach 1:
The valve system performs preliminary action by closing the receiver valve before mode transitions occur, preventing liquid refrigerant from entering the compressor during upcoming transitions. The system proactively manages refrigerant charge by opening the receiver valve during defrost mode to store excess refrigerant, thereby preventing pressure faults and liquid slug formation before they can harm the compressor.
Solution Approach 2:
The receiver acts as an intermediary component that buffers refrigerant between the outdoor heat exchanger and the rest of the system. The valve system mediates refrigerant flow by selectively opening or closing the receiver valve to control when refrigerant enters or leaves the receiver, thereby preventing harmful pressure fluctuations and liquid slugs during mode transitions while maintaining system versatility.
2Quantity of substance
If the receiver valve remains closed during defrost mode, then refrigerant charge is maintained in the system, but liquid slugs may form and enter the compressor causing damage
Solution Approach 1:
The system applies preliminary action by closing the receiver valve before defrost mode begins, preventing refrigerant from leaving the system. During defrost mode, the valve remains closed to maintain refrigerant charge, but the outdoor heat exchanger still receives sufficient refrigerant through the expansion valve to prevent liquid slug formation and compressor damage.
Solution Approach 2:
The valve system changes the operational parameter of the receiver valve from fully open to fully closed during defrost mode, thereby controlling refrigerant charge distribution. This parameter change allows the system to retain refrigerant in the system while preventing liquid slugs from forming in the compressor by adjusting the refrigerant flow dynamics through the closed valve configuration.
3Stress or pressure
If the receiver valve is opened during mode transitions, then excess refrigerant can be stored to prevent pressure faults, but refrigerant flow instability may occur
Solution Approach 1:
The valve system performs preliminary action by opening the receiver valve in advance of mode transitions to store excess refrigerant before pressure faults can occur. This proactive approach allows the receiver to act as a buffer, absorbing pressure fluctuations and maintaining stable refrigerant flow to the compressor, thereby preventing both pressure faults and flow instability.
Solution Approach 2:
The receiver serves as an intermediary that stabilizes refrigerant pressure and flow. By selectively opening or closing the receiver valve, the system uses the receiver as a buffer zone to absorb pressure fluctuations during mode transitions, thereby maintaining stable refrigerant composition and flow to the compressor while preventing pressure faults.
4Ease of operation
If the valve system uses complex multi-valve configuration, then refrigerant flow can be precisely controlled during mode transitions, but device complexity and cost increase
Solution Approach 1:
The valve system achieves multi-functionality by using a single receiver valve that performs multiple functions: controlling refrigerant charge during heating mode, preventing liquid slugs during defrost mode, storing excess refrigerant during cooling mode, and stabilizing pressure during transitions. This universal valve replaces what would otherwise require multiple specialized valves, thereby maintaining precise refrigerant flow control while reducing device complexity and cost.
Solution Approach 2:
The check valve and receiver valve work together as a unified system where the check valve provides automatic one-way flow control and the receiver valve provides manual or controlled flow regulation. This combination achieves precise refrigerant flow control during all mode transitions while maintaining relatively simple device architecture, avoiding the need for complex multi-valve configurations.
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
The system effectively prevents refrigerant pressure faults and liquid slugs from entering the compressor, ensuring smooth transitions between operating modes and maintaining efficient refrigerant flow, thereby protecting the compressor and optimizing heat pump performance across different modes.
Implementation Method 1
a valve system connected in fluid communication between the indoor line-A and the receiver, wherein the valve system comprises a check valve and a receiver valve that are in parallel flow relationship with each other
Implementation Method 2
a directional valve connected in fluid communication with the suction line, the discharge line, the outdoor line-A, and the indoor line-B, wherein the directional valve is movable to selectively direct refrigerant flow through the heat pump
Implementation Method 3
an outdoor heat exchanger installed between an outdoor line-A and an outdoor line-B; an indoor heat exchanger installed between an indoor line-A and an indoor line-B
Implementation Method 4
a compressor connected to convey the refrigerant from a suction line to a discharge line
Implementation Method 5
a heating expansion valve connected in fluid communication between the receiver and the outdoor line-B; a cooling expansion valve connected in fluid communication between the outdoor line-B and the indoor line-A
Data Source
AI summary
A heat pump includes a valve system that connects a receiver tank in fluid communication with an indoor heat exchanger, wherein the valve system, operating under a novel control scheme, works in conjunction with the receiver to control the heat pump's effective refrigerant charge. To avoid suction or discharge pressure faults and to help prevent slugs of liquid refrigerant from entering the heat pump's compressor as the heat pump switches between heating and cooling modes or switches between heating and defrost modes, the control scheme provides momentary periods of transition between those modes of operation. In some embodiments, the valve system comprises a check valve connected in parallel flow relationship with a two-position receiver valve, wherein the check valve has an appreciably higher flow coefficient than that of the receiver valve.