Ejector Capacity Control for Liquid Refrigerant Return
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Solution Overview
Problem
Vapour compression systems face challenges in efficiently managing ejector capacity and handling liquid refrigerant flow, leading to suboptimal energy efficiency and potential compressor damage due to improper ejector selection and capacity adjustment.
Innovation Solution
A method that adjusts ejector capacity based on real-time parameter values representing liquid refrigerant flow rates, shifting between low and high pressure ejectors to match system requirements and operating conditions, ensuring efficient operation and effective liquid refrigerant removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a liquid ejector is used, then the pressure lift for liquid refrigerant is high when the pressure difference is small, but the ejector cannot operate efficiently when the pressure difference is large
Solution Approach 1:
The system dynamically switches between liquid ejector and gas ejector based on real-time pressure difference conditions. The control unit monitors the pressure difference across the ejector and activates the appropriate ejector type, making the system adaptable rather than static, thereby resolving the contradiction between pressure lift capability and energy efficiency across varying operating conditions.
Solution Approach 2:
The invention changes the operational parameter (pressure difference threshold) to determine which ejector type should be active. By monitoring pressure difference values and switching ejector types based on whether the pressure difference is small or large, the system optimizes performance across different operating ranges, addressing the contradiction between high pressure lift at low pressure differences and energy efficiency at high pressure differences.
2Use of energy by moving object
If a gas ejector is used, then the energy efficiency is high when the pressure difference is large, but the ejector cannot provide sufficient pressure lift when the pressure difference is small
Solution Approach 1:
The system dynamically switches between liquid ejector and gas ejector based on real-time pressure difference conditions. The control unit monitors the pressure difference across the ejector and activates the appropriate ejector type, making the system adaptable rather than static, thereby resolving the contradiction between pressure lift capability and energy efficiency across varying operating conditions.
Solution Approach 2:
The invention changes the operational parameter (pressure difference threshold) to determine which ejector type should be active. By monitoring pressure difference values and switching ejector types based on whether the pressure difference is small or large, the system optimizes performance across different operating ranges, addressing the contradiction between high pressure lift at low pressure differences and energy efficiency at high pressure differences.
3Use of energy by moving object
If ejector capacity is not adjusted based on liquid refrigerant flow rate, then the system structure is simple, but energy efficiency is suboptimal and compressor damage may occur
Solution Approach 1:
The control unit receives feedback about the operating conditions (pressure difference, refrigerant flow rate) and adjusts the ejector capacity accordingly. This feedback mechanism enables the system to optimize energy efficiency by matching ejector capacity to actual liquid refrigerant removal needs, while avoiding unnecessary complexity through rule-based control logic.
Solution Approach 2:
The system uses the ejector's own performance characteristics and the measured operating conditions to automatically determine the appropriate ejector capacity. The control unit monitors pressure difference and refrigerant flow parameters, and the ejector system self-adjusts its operation mode without requiring external intervention, achieving energy optimization through self-monitoring and self-adjustment.
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 method enhances energy efficiency by optimizing ejector capacity distribution, preventing liquid refrigerant from reaching the compressor and improving system performance by selecting the most suitable ejector type based on current conditions.
Implementation Method 1
An ejector is a type of pump which uses the Venturi effect to increase the pressure energy of fluid at a suction inlet (or secondary inlet) of the ejector by means of a motive fluid supplied to a motive inlet (or primary inlet) of the ejector.
Data Source
AI summary
A method for controlling ejector capacity in a vapour compression system (1) is disclosed. A parameter value being representative for a flow rate of liquid refrigerant from the evaporator(s) (8, 10) and into a return pipe (12, 13) is obtained, and the capacity of the ejector(s) (6) is adjusted based on the obtained parameter value. Ejector capacity may be shifted between low pressure ejectors (liquid ejectors) (6a, 6b, 6c, 6d) and high pressure ejectors (gas ejectors) (6e, 6f).