Ejector Refrigeration Pressure Control at Low Ambient Temperatures
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Solution Overview
Problem
Vapor compression systems face inefficiencies at low ambient temperatures due to the ejector's reduced performance, leading to decreased energy efficiency and increased power consumption.
Innovation Solution
A method that adjusts the pressure of refrigerant leaving the heat rejecting heat exchanger by comparing the pressure difference between the receiver and evaporator to threshold values, using either a derived or fixed reference pressure value to maintain efficient operation of the ejector, even at lower ambient temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the ejector operates at low ambient temperatures using conventional control methods, then the system switches to winter mode with reduced ejector operation, but energy efficiency deteriorates and power consumption increases
Solution Approach 1:
The control method dynamically adjusts the reference pressure value based on the pressure difference between receiver and evaporator. When the pressure difference indicates deteriorating ejector performance, the reference pressure is increased to maintain ejector operation, allowing the system to adapt to low ambient temperature conditions while preserving energy efficiency.
Solution Approach 2:
The invention changes the pressure parameter (reference pressure value) of the refrigerant leaving the heat rejecting heat exchanger based on operating conditions. By adjusting this parameter in response to pressure difference measurements, the system maintains optimal ejector performance across a wider temperature range, preventing the energy efficiency deterioration that occurs in conventional winter mode operation.
2Use of energy by moving object
If the ejector operates at low ambient temperatures with increased reference pressure, then energy efficiency is maintained, but the complexity of the control system increases
Solution Approach 1:
The control method employs feedback by continuously measuring the pressure difference between the receiver and evaporator, comparing it to threshold values, and adjusting the reference pressure value accordingly. This closed-loop feedback mechanism maintains energy efficiency through automated adjustments without requiring complex manual intervention or additional hardware components.
Solution Approach 2:
The control system performs self-service by automatically monitoring its own operating conditions through pressure difference measurements and autonomously adjusting the reference pressure value to maintain optimal ejector performance. This self-regulating capability maintains energy efficiency without requiring external complex control systems or manual operation.
3Reliability
If the reference pressure value is increased to maintain ejector operation at low temperatures, then the ejector operates more effectively, but the pressure of refrigerant leaving the heat rejecting heat exchanger increases
Solution Approach 1:
The reference pressure value is dynamically adjusted based on real-time pressure difference measurements between receiver and evaporator. This dynamic adjustment allows the system to increase pressure only when and where needed to maintain ejector performance, rather than maintaining high pressure continuously, thereby balancing reliability improvement with pressure management.
Solution Approach 2:
The invention changes the reference pressure parameter in response to measured pressure difference conditions. By selectively adjusting this parameter only when the pressure difference indicates deteriorating ejector performance, the system maintains reliable ejector operation while minimizing unnecessary pressure increases that would occur with constant high-pressure operation.
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 approach enhances energy efficiency by allowing the ejector to operate effectively at lower temperatures, reducing energy consumption and maintaining optimal coefficient of performance (COP) by adjusting the refrigerant pressure accordingly.
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
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AI summary
A method for controlling a vapour compression system (1) comprising an ejector (6) is disclosed. In the case that a pressure difference between a pressure prevailing in the receiver (7) and a pressure of refrigerant leaving the evaporator (9) decreases below a first lower threshold value, the pressure of refrigerant leaving the heat rejecting heat exchanger (5) is kept at a level which is slightly higher than the pressure level providing optimal COP. Thereby the ejector (6) can operate at lower ambient temperatures, and the energy efficiency of the vapour compression system (1) is improved.