Cascade Refrigeration Circuit Using Two-Phase Refrigerant Expansion
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Solution Overview
Problem
Refrigerating apparatuses face challenges in reducing the design pressure of the low-temperature side circuit while minimizing costs, as increasing the design pressure requires stronger components and larger expansion tanks, and lowering it necessitates larger expansion tanks, making it difficult to achieve both simultaneously.
Innovation Solution
The refrigerating apparatus incorporates a second flow control valve to turn the refrigerant in the liquid pipe into a gas-liquid two-phase state, reducing the capacity and cost of the expansion tank by adjusting the internal volume and pipe diameters, and using a tank electromagnetic valve to manage pressure during non-operation periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the design pressure of the low-temperature side circuit is lowered to reduce cost, then the cost of components is reduced, but the expansion tank capacity must be increased to prevent pressure buildup during non-operation
Solution Approach 1:
The patent changes the physical state parameter of the refrigerant from liquid to gas-liquid two-phase by adjusting the degree of opening of the second flow control valve. This parameter change allows the refrigerant to occupy larger volume in the same space, effectively reducing the required expansion tank capacity while maintaining lower design pressure
Solution Approach 2:
The patent dynamically adjusts the refrigerant state by controlling the second flow control valve during non-operation periods. The valve opening degree is adjusted to achieve the desired gas-liquid two-phase state, making the system adaptable to different operational conditions and optimizing the expansion tank size requirement
2Volume of stationary object
If the design pressure of the low-temperature side circuit is increased to reduce expansion tank capacity, then the expansion tank size and cost are reduced, but the withstand pressure of all low-temperature side circuit components must be increased, leading to higher overall cost
Solution Approach 1:
Instead of changing the design pressure parameter, the patent changes the refrigerant state parameter to gas-liquid two-phase. This alternative parameter change achieves the same goal of reducing expansion tank capacity without requiring increased withstand pressure of other components, thereby avoiding the associated cost increase
3Stress or pressure
If the expansion tank capacity is increased to maintain lower design pressure, then the design pressure can be kept low, but the cost of the expansion tank and overall system increases
Solution Approach 1:
The patent changes the refrigerant state from liquid to gas-liquid two-phase, which fundamentally alters the volume characteristics of the refrigerant. This parameter change allows the system to maintain low design pressure while using a smaller expansion tank, breaking the direct correlation between low design pressure and large expansion tank capacity
Solution Approach 2:
The patent applies partial gasification of the refrigerant rather than complete gasification. By achieving a gas-liquid two-phase state with appropriate gas fraction, the system obtains sufficient volume expansion effect to reduce tank size while avoiding the excessive action of complete gasification which would require even larger tanks
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 a reduced capacity and cost of the expansion tank, enabling a lower design pressure without increasing the size or cost of other components, while maintaining efficient operation and preventing pressure buildup.
Implementation Method 1
a second flow control valve provided at an outlet of the receiver to depressurize the refrigerant flowing out of the receiver and supply the refrigerant to the liquid pipe in a gas-liquid two-phase state
Implementation Method 2
an expansion tank connected to a suction side of the low-temperature circuit compressor in the low-temperature side circuit via a tank electromagnetic valve and configured to suppress an increase in pressure in the low-temperature side circuit during a non-operation period
Implementation Method 3
an expansion tank connected to a suction side of the low-temperature circuit compressor in the low-temperature side circuit via a tank electromagnetic valve
Data Source
AI summary
A refrigerating apparatus includes a high-temperature side circuit and a low-temperature side circuit connected to each other via a cascade condenser, a low-temperature side second flow control valve that turns a refrigerant, passing through a liquid pipe connecting between a cooling unit and other circuit parts in a low-temperature side circuit b, into a gas-liquid two-phase refrigerant, and an expansion tank connected to the suction side of a low-temperature circuit compressor via a tank electromagnetic valve.