Water Refrigeration Cycle Backflow Path for Pump Cavitation Control
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Solution Overview
Problem
The existing refrigeration cycle apparatus using water as a refrigerant requires a high-precision expansion valve and complex control due to the low pressure difference between high and low-pressure sides, leading to increased size and complexity.
Innovation Solution
Incorporating a condensation-side circulation path with a pump upstream of a heat exchanger and a back-flow path that directs refrigerant liquid to prevent cavitation, reducing the required net positive suction head and allowing for size reduction by mixing cooled liquid with high-temperature liquid entering the pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If water is used as a refrigerant, then environmental friendliness is improved, but the pressure difference between high and low-pressure sides is reduced, requiring high-precision expansion valves and complicated control
Solution Approach 1:
The refrigeration cycle is divided into two separate circulation paths: a high-temperature-side circulation path for heat release and a low-temperature-side circulation path for heat absorption. This segmentation allows independent optimization of each path, eliminating the need for complex expansion valve control while maintaining environmental friendliness through water as refrigerant.
Solution Approach 2:
A level difference Δh is introduced as an intermediary mechanism between the high-temperature-side condenser and low-temperature-side evaporator. This level difference automatically generates the required pressure difference, serving as a passive mediator that eliminates the need for high-precision expansion valves and complex active control systems.
2Device complexity
If a level difference is used to ensure pressure difference, then control complexity is reduced, but the apparatus size increases
Solution Approach 1:
The high-temperature-side and low-temperature-side circulation paths are merged into a single integrated system where the condenser and evaporator share a common structural space. This merging allows the level difference to be minimized while maintaining pressure difference, thereby reducing apparatus size while keeping control simple.
Solution Approach 2:
The system changes the operating parameters by using water as refrigerant with specific thermodynamic properties, allowing the pressure difference to be maintained through a smaller level difference Δh compared to traditional refrigerants. This parameter change enables both simplified control and reduced apparatus size.
3Device complexity
If the condensation path is configured without backflow control, then the structure is simpler, but cavitation occurs in the pump
Solution Approach 1:
A backflow path is introduced that allows refrigerant liquid to flow back from the downstream side to the upstream side of the heat exchanger for heat release. This feedback mechanism prevents pressure drop and cavitation in the pump while maintaining relatively simple structure, thereby improving pump reliability.
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 reduces the size of the refrigeration cycle apparatus while preventing cavitation and allowing for easier control, enhancing system reliability and efficiency.
Implementation Method 1
an evaporator that retains a refrigerant liquid and that evaporates the refrigerant liquid therein
Implementation Method 2
a compressor that draws the refrigerant vapor from the evaporator, compresses the refrigerant vapor, and discharges the compressed refrigerant vapor to the condenser
Implementation Method 3
a condenser that condenses the refrigerant vapor and that retains the refrigerant liquid
Implementation Method 4
a condensation-side circulation path that allows the refrigerant liquid retained in the condenser to circulate via a heat exchanger for heat release
Implementation Method 5
a condensation-side pump at a position upstream of the heat exchanger for heat release
Data Source
AI summary
A refrigeration cycle apparatus (1A) includes: an evaporator (23) that retains a refrigerant liquid and that evaporates the refrigerant liquid therein; a condenser (22) that condenses a refrigerant vapor therein and that retains the refrigerant liquid; a vapor channel (2A) that is provided with a compressor (21) and that directs the refrigerant vapor from the evaporator (23) to the condenser (22); a liquid channel (2B) that directs the refrigerant liquid from the condenser (22) to the evaporator (23); a condensation-side circulation path (4) that allows the refrigerant liquid retained in the condenser (22) to circulate via a heat exchanger for heat release (41) and that is provided with a condensation-side pump (45) at a position upstream of the heat exchanger for heat release (41); and a back-flow path (7) that directs a portion of the refrigerant liquid flowing in a section downstream of the heat exchanger for heat release (41) in the condensation-side circulation path (4) to a section upstream of the condensation-side pump (41) in the condensation-side circulation path (4) or to a bottom of the condenser (22).