Method for operating a vapour compression system with a receiver
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Vapour compression systems using transcritical refrigerants like CO2 face inefficiencies due to varying ambient temperatures, which affect the optimal pressure inside the receiver, leading to suboptimal energy usage and system performance.
Innovation Solution
A method that measures parameters such as enthalpy of refrigerant leaving the heat rejecting heat exchanger to calculate a setpoint value for the receiver pressure, allowing the compressor unit to adjust and maintain an optimal pressure level, balancing compressor work and system requirements across a wide range of ambient temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the pressure inside the receiver is increased to reduce compressor work, then the work required by the compressor is reduced, but the liquid/gas ratio in the receiver becomes unbalanced with more liquid refrigerant, forcing the heat rejecting heat exchanger pressure to be even higher and decreasing system efficiency
Solution Approach 1:
The invention applies dynamics by making the receiver pressure adjustable rather than fixed. The system dynamically adapts the receiver pressure setpoint based on ambient temperature conditions through the control unit, which selects from multiple predetermined setpoints. This allows the system to optimize compressor work at different operating conditions without permanently forcing the heat rejecting heat exchanger pressure to excessive levels.
Solution Approach 2:
The invention changes the pressure parameter of the receiver based on ambient temperature. The control unit stores multiple predetermined pressure setpoints corresponding to different ambient temperature ranges and selects the appropriate setpoint based on current conditions. This parameter adaptation resolves the contradiction by allowing high receiver pressure (reducing compressor work) only when ambient temperature justifies it, while maintaining lower pressure setpoints when ambient temperature is low to preserve system efficiency.
2Productivity
If a fixed pressure level is selected in the receiver to balance compressor work and system requirements, then the system operates efficiently under common conditions, but the pressure level becomes unsuitable when operating conditions change, particularly ambient temperature
Solution Approach 1:
The control system transitions from a static fixed pressure level to a dynamic adaptive pressure level. The control unit continuously monitors ambient temperature and adjusts the receiver pressure setpoint accordingly by selecting from multiple predetermined setpoints. This dynamic adaptation ensures the system maintains optimal efficiency across varying operating conditions while preserving the benefit of balanced compressor work and system requirements.
Solution Approach 2:
The invention implements feedback by using the control unit to monitor ambient temperature conditions and adjust the receiver pressure setpoint in response. The control unit compares current ambient temperature with stored setpoint conditions and selects the appropriate pressure level. This feedback mechanism ensures the system adapts to changing operating conditions while maintaining optimal performance.
3Use of energy by moving object
If the pressure inside the heat rejecting heat exchanger is increased to maintain high receiver pressure, then compressor work is reduced, but the efficiency of the vapour compression system decreases
Solution Approach 1:
The invention changes the operating parameters of both the receiver and heat rejecting heat exchanger based on ambient temperature. By storing multiple predetermined pressure setpoints in the control unit and selecting appropriate combinations, the system can reduce compressor work through higher receiver pressure only when ambient temperature conditions permit, without permanently increasing heat rejecting heat exchanger pressure to levels that would cause energy losses.
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 enables the vapour compression system to operate in an energy-efficient manner by dynamically adjusting the receiver pressure based on current operating conditions, improving energy conservation and system efficiency regardless of ambient temperature fluctuations.
Implementation Method 1
a compressor unit (2) comprising one or more compressors (11), the compressor unit being configured to compress refrigerant
Implementation Method 2
a heat rejecting heat exchanger (3) arranged to receive compressed refrigerant from the compressor unit and to cool the refrigerant
Implementation Method 3
a high pressure valve (4) arranged in a refrigerant path, at a position downstream relative to the heat rejecting heat exchanger... the pressure of the refrigerant is thereby reduced
Implementation Method 4
a receiver (5) arranged between the high pressure valve and an expansion device... In the receiver, liquid refrigerant is separated from gaseous refrigerant
Implementation Method 5
an expansion device (6) arranged to supply refrigerant to an evaporator... the pressure of the refrigerant is thereby reduced
Implementation Method 6
an evaporator (7) arranged to receive refrigerant from the expansion device and to evaporate the refrigerant
Data Source
AI summary
A method for controlling a vapour compression system, the vapour compression system including a compressor unit with one or more compressors. At least one of the compressors is connectable to a gaseous outlet of a receiver, and at least one of the compressors is connectable to an outlet of an evaporator. A parameter of the vapour compression system is measured, an enthalpy of refrigerant leaving the heat rejecting heat exchanger being derivable from the measured parameter. A setpoint value for a pressure inside the receiver is calculated, based on the measured parameter, and the compressor unit is operated in accordance with the calculated setpoint value, and in order to obtain a pressure inside the receiver which is equal to the calculated setpoint value. The vapour compression system is operated in an energy efficient manner over a wide range of ambient temperatures.