Split Heat Pump Expansion Valve Layout for Low Refrigerant Charge
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Solution Overview
Problem
Existing split heat pumps face challenges in reducing refrigerant fluid mass while maintaining system size, performance, and operating range due to the need for high refrigerant fluid density in transit ducts, especially when using flammable refrigerants like propane, which are restricted by safety regulations.
Innovation Solution
Implementing two expansion valves, one at each end of the transit duct, with one always open and the other adjusted to act as a single expansion valve, to maintain refrigerant fluid in a low-density state throughout the duct, reducing the total mass of refrigerant fluid required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If refrigerant fluid charge is reduced to comply with safety regulations for flammable refrigerants, then safety and regulatory compliance are improved, but operating temperature range and system performance are reduced
Solution Approach 1:
The patent changes the physical state parameter of the refrigerant fluid in the transit duct by introducing a first expansion valve that creates a low-density refrigerant state (through partial expansion or vaporization), allowing the duct to be filled with low-density refrigerant vapor instead of high-density liquid, thereby reducing total refrigerant charge while maintaining system performance and operating range
Solution Approach 2:
The patent segments the refrigerant circuit into distinct zones with different density requirements: the evaporator and condenser maintain high-density liquid refrigerant for efficient heat exchange, while the transit duct uses low-density vapor refrigerant to reduce total charge, allowing each segment to optimize its local refrigerant density for its specific function
2Object-affected harmful factors
If refrigerant fluid charge is reduced to meet safety limits for flammable refrigerants, then safety is improved, but the amount of refrigerant available for heat exchange is reduced, worsening thermal performance
Solution Approach 1:
The patent changes the density parameter of refrigerant in the transit duct from high-density liquid to low-density vapor through the first expansion valve, reducing total refrigerant mass in the duct while ensuring that sufficient high-density liquid refrigerant is maintained in the heat exchangers (evaporator and condenser) to preserve thermal performance
Solution Approach 2:
The first expansion valve acts as an intermediary device that transforms the refrigerant from a high-density state suitable for heat exchange to a low-density state suitable for safe transit duct filling, mediating between the conflicting requirements of safety compliance and thermal performance
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 allows for reduced refrigerant fluid use, compliance with safety regulations, and maintains system performance and operating range, while minimizing environmental impact.
Implementation Method 1
the compressor (5) is operable to suck the refrigerant fluid in the gaseous phase and at low pressure from the evaporator (4), compress the refrigerant fluid
Implementation Method 2
in the condenser (7), the compressed refrigerant fluid releases heat and condensation at high pressure
Implementation Method 3
the refrigerant fluid passes through the expansion device (8) which decompresses it, bringing the refrigerant fluid to a depressurized two-phase state
Implementation Method 4
the refrigerant fluid enters from the transit duct (10) into the evaporator (4) where the refrigerant fluid absorbs heat and evaporates at low pressure
Implementation Method 5
The air or fluid in contact with the evaporator (or, in other words: the space where it is located) is thus cooled, whereas the air or fluid in contact with the condenser (or, in other words: the space where it is located) is heated
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
A heat pump (1) comprising a circuit (2) for circulating a refrigerant fluid, a first heat exchanger (3) placed in the circuit (2) and forming an evaporator (4), a compressor (5) placed in the circuit (2) downstream of the first heat exchanger (3), a second heat exchanger (6) placed in the circuit (2) downstream of the compressor (5) and forming a condenser (7), a transit duct (10) connecting the second heat exchanger (6) to the first heat exchanger (3) downstream of the second heat exchanger (6), an expansion device (8) connected in the transit duct (10) and having a first expansion valve unit (8') and a second expansion valve unit (8") arranged in series in the transit duct (10).