Hot Gas Bypass Ejector for Compressor Capacity Control
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Solution Overview
Problem
Existing refrigerant vapor compression systems, particularly those using centrifugal compressors, face inefficiencies in capacity control due to limitations in inlet vane usage and energy inefficiencies in hot gas bypass methods.
Innovation Solution
A refrigerant vapor compression system incorporating an ejector in the hot gas bypass line, controlled by a controller that adjusts the hot gas bypass valve and flow control valve based on temperature and pressure ratios, and presence of pressure pulsations, to optimize energy recovery and compressor suction pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hot gas bypass is used to control compressor capacity, then capacity control is achieved, but energy efficiency deteriorates
Solution Approach 1:
The patent converts the harmful hot gas bypass flow, which normally represents energy waste, into a beneficial resource by routing it through an ejector. The hot gas from the bypass line provides motive force to drive the ejector, creating a vacuum effect that enhances refrigerant flow and improves overall system efficiency while maintaining capacity control.
Solution Approach 2:
The ejector serves as an intermediary device between the hot gas bypass line and the compressor suction port. It mediates the interaction by using the hot gas flow to create a vacuum effect that draws refrigerant vapor from the evaporator, thereby improving the efficiency of both the bypass function and the refrigerant circulation.
2Productivity
If inlet guide vanes are used for capacity control, then capacity control is achieved, but device complexity increases due to sizing limitations
Solution Approach 1:
The patent extracts the capacity control function from the inlet guide vane system and relocates it to the hot gas bypass valve. By removing the dependency on inlet guide vanes, the system simplifies the overall device structure while maintaining effective capacity control through the bypass mechanism combined with the ejector.
3Productivity
If hot gas bypass valve is opened to control capacity, then capacity reduction is achieved, but compressor suction pressure stability deteriorates
Solution Approach 1:
The patent merges the hot gas bypass function with the ejector vacuum generation function. The hot gas bypass valve controls capacity by regulating hot gas flow to the ejector, which simultaneously maintains stable compressor suction pressure through the vacuum effect created by the ejector, thereby stabilizing the suction pressure despite capacity changes.
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 recovers energy through the use of an ejector in the hot gas bypass line, reducing the work needed by the compressor and improving energy usage by dynamically controlling the flow of refrigerant.
Implementation Method 1
an ejector in communication with the hot gas bypass line, the compressor suction port and the outlet of the heat absorption heat exchanger
Implementation Method 2
a heat absorption heat exchanger fluidly coupled to the expansion device
Data Source
Figure 1
Figure 2
AI summary
A refrigerant vapor compression system 10 includes a compressor 12 having a compressor suction port and a compressor discharge port; a heat rejection heat exchanger 14 fluidly coupled to the compressor discharge port; an expansion device 16 fluidly coupled to an outlet of the heat rejection heat exchanger 14; a heat absorption heat exchanger 18 fluidly coupled to the expansion device 16; a hot gas bypass line 24 fluidly coupled to the compressor discharge port; an ejector 30 comprising a motive port 32 fluidly coupled to the hot gas bypass line 24, a suction port 34 fluidly coupled to an outlet of the heat absorption heat exchanger 18 and a discharge port 38 fluidly coupled to the compressor suction port; a hot gas bypass valve 26 positioned between the compressor discharge port and the motive port 32 of the ejector 30; a flow control valve 36 fluidly coupled to the outlet of the heat absorption heat exchanger 18, and fluidly coupled to the suction port 34 of the ejector 30 and the compressor suction port.