Method for controlling a vapour compression system in ejector mode for a prolonged time
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Vapor compression systems with ejectors face inefficiencies at low ambient temperatures, as the ejector's performance decreases, leading to reduced energy efficiency and increased power consumption.
Innovation Solution
A method that controls the vapor compression system by adjusting the pressure of refrigerant leaving the heat rejecting heat exchanger based on ambient temperature, using a derived reference pressure value when the ejector operates efficiently and a fixed reference pressure value when it does not, to maintain efficient operation and improve energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the ejector operates at low ambient temperatures, then the energy efficiency of the vapor compression system is improved, but the coefficient of performance decreases slightly
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the reference pressure value based on ambient temperature conditions. When ambient temperature is low, the system switches from a derived reference pressure value (optimized for COP) to a fixed reference pressure value that maintains ejector operation. This parameter switching enables the ejector to continue operating at low temperatures, improving energy efficiency while accepting a slight COP trade-off.
Solution Approach 2:
The system implements dynamics by making the reference pressure value adaptive rather than fixed. The control method dynamically selects between derived and fixed reference pressure values based on real-time ambient temperature conditions, allowing the ejector to transition between different operational states. This dynamic adjustment optimizes the balance between energy efficiency and coefficient of performance across varying environmental conditions.
2Use of energy by moving object
If the ejector is operated in summer mode with all refrigerant from evaporator supplied to secondary inlet, then energy efficiency is maximized, but the system cannot operate efficiently at low ambient temperatures
Solution Approach 1:
The patent extends the operating temperature range by introducing a fixed reference pressure value that can be applied when ambient temperatures are low. This parameter option allows the ejector to maintain operation in summer mode across a broader temperature spectrum, improving the system's adaptability while preserving energy efficiency benefits.
Solution Approach 2:
The control method achieves multi-functionality by enabling the ejector to operate effectively in both high-temperature summer mode and low-temperature conditions. The system universally applies energy-efficient ejector operation across different ambient temperature ranges by selecting appropriate reference pressure values, making the summer mode configuration versatile across seasonal variations.
3Loss of energy
If a derived reference pressure value is used to optimize coefficient of performance, then energy efficiency is improved, but the ejector cannot operate at lower ambient temperatures
Solution Approach 1:
The patent resolves this contradiction by implementing a dual-parameter strategy: using derived reference pressure values when ambient temperature is high (to optimize COP) and switching to a fixed reference pressure value when ambient temperature is low (to enable ejector operation). This parameter switching mechanism maintains adaptability across temperature ranges while preserving energy efficiency where possible.
Solution Approach 2:
The system dynamically adjusts the reference pressure value selection based on ambient temperature conditions. The control method transitions between derived and fixed reference pressure values, enabling the ejector to adapt to varying environmental conditions. This dynamic approach expands the operational temperature range while maintaining optimal performance characteristics in each regime.
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 allows the ejector to operate at lower ambient temperatures, enhancing the energy efficiency of the vapor compression system by maintaining efficient operation even at low temperatures, albeit with a slight decrease in coefficient of performance.
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 a vapour compression system having an ejector includes, in the case that a pressure difference between a pressure prevailing in the receiver and a pressure of refrigerant leaving the evaporator decreases below a first lower threshold value, the pressure of refrigerant leaving the heat rejecting heat exchanger is kept at a level which is slightly higher than the pressure level providing optimal coefficient of performance.