Refrigerant vapor compression system with flash tank receiver
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Solution Overview
Problem
Refrigerant vapor compression systems, especially those operating in transcritical cycles, face complexity in controlling refrigerant charge due to the absence of distinct liquid or vapor phases, making it challenging to maintain equilibrium and respond to system requirements effectively.
Innovation Solution
A refrigerant vapor compression system incorporating a flash tank receiver and a controller that uses sensors to monitor operating characteristics like temperature and pressure, adjusting the secondary expansion device to maintain a consistent refrigerant charge, with an economizer line for vapor refrigerant flow to an intermediate pressure stage of the compression device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flash tank receiver is used in a transcritical refrigerant vapor compression system, then refrigerant charge control is improved, but device complexity increases
Solution Approach 1:
The flash tank receiver serves as an intermediary device between the condenser and expansion device, providing a controlled environment for refrigerant phase separation and charge regulation. This mediator component enables precise charge control in transcritical systems where direct control would be complex due to the absence of distinct liquid-vapor phases throughout the cycle.
Solution Approach 2:
The system utilizes parameter changes by controlling pressure and temperature conditions within the flash tank receiver to achieve desired refrigerant charge states. By adjusting operating parameters such as the degree of superheat at compressor inlet and pressure differential across the expansion device, the system optimizes refrigerant charge distribution while managing the added device complexity.
2Measurement precision
If sensors and controllers are added to monitor and adjust refrigerant charge, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The control system implements feedback mechanisms where sensors continuously monitor operating characteristics such as temperature, pressure, and refrigerant charge levels. This feedback information is processed by the controller to automatically adjust expansion device positioning and superheat control, maintaining optimal refrigerant charge without requiring complex manual intervention or overly sophisticated control architecture.
Solution Approach 2:
The refrigerant charge control system operates with a degree of autonomy where the controller automatically adjusts system parameters based on sensor inputs. The system self-regulates refrigerant distribution and phase separation in the flash tank receiver, reducing the need for external monitoring and manual adjustment while maintaining measurement precision through integrated sensing.
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 solution enables precise control of refrigerant charge, ensuring optimal operating conditions by maintaining a desired liquid level in the flash tank receiver, thereby improving system efficiency and stability in both subcritical and transcritical cycles.
Implementation Method 1
Liquid refrigerant from the condenser enters the receiver tank and settles to the bottom of the tank. As this liquid will be at saturated temperature, refrigerant vapor will fill the space in the tank not filled by liquid refrigerant.
Implementation Method 2
a secondary expansion device operative to expand the high pressure refrigerant flowing therethrough to a liquid/vapor refrigerant mix at a lower pressure intermediate the high pressure and the low pressure
Implementation Method 3
a refrigerant compression device for compressing refrigerant to a high pressure
Implementation Method 4
a refrigerant cooling heat exchanger for passing refrigerant received from said compression device at a high pressure in heat exchange relationship with a cooling medium
Implementation Method 5
a refrigerant heating heat exchanger for passing refrigerant at a low pressure in heat exchange relationship with a heating medium
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A refrigerant vapor compression system includes a flash tank receiver (20) disposed in the refrigerant circuit intermediate the refrigerant cooling heat exchanger (40) and the refrigerant heating heat exchanger (50). The flash tank receiver, which receives a liquid/vapor refrigerant mix, also functions as a receiver. A refrigerant charge control apparatus (70) includes a liquid level sensing device (25) disposed in operative association with the flash tank receiver for sensing the level of liquid refrigerant within the flash tank receiver, at least one sensor (72) for sensing a system operating parameter, and a controller operative to determine a desired liquid refrigerant level within the flash tank receiver and to selectively adjust a secondary expansion device (75) to increase or decrease the flow of refrigerant passing into the flash tank receiver to provide a circulating refrigerant charge consistent with maintaining a desired system operating parameter.