Method for controlling a fan of a vapour compression system in accordance with a variable temperature setpoint
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Solution Overview
Problem
Existing methods for controlling fans in vapor compression systems, such as refrigeration and air conditioning, lead to increased energy consumption and noise due to continuous fan speed increases in response to small deviations in temperature measurements, even when the refrigerant temperature is already near ambient temperature, causing inefficient operation.
Innovation Solution
A method that adjusts the temperature setpoint value for the fan speed, allowing a larger temperature difference at higher fan speeds to prevent further increases in fan speed, thereby minimizing energy consumption and noise by stabilizing the fan operation when the refrigerant temperature is close to ambient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the fan speed is continuously increased to reduce the temperature difference between refrigerant leaving the heat rejecting heat exchanger and ambient temperature, then the temperature control precision is improved, but the energy consumption and noise level increase
Solution Approach 1:
The patent applies dynamics by making the temperature setpoint variable rather than fixed. The setpoint dynamically adjusts based on the relationship between fan speed and temperature difference, allowing the system to adapt to changing operating conditions. This resolves the contradiction by preventing continuous fan speed increases when temperature measurements are uncertain, thereby reducing energy consumption while maintaining acceptable temperature control.
Solution Approach 2:
The patent changes the parameter of temperature setpoint from a constant value to a variable value that depends on fan speed. By implementing a setpoint that increases with fan speed, the system accounts for measurement uncertainties and avoids unnecessary fan operation, thus reducing energy consumption while maintaining temperature control within acceptable ranges.
2Measurement precision
If the fan speed is continuously increased in response to small temperature deviations, then the temperature control responsiveness is improved, but the noise level and wear on the fan increase
Solution Approach 1:
The dynamic adjustment of the temperature setpoint based on fan speed creates a responsive yet stable control system. The setpoint adapts to the current operating conditions, allowing the system to respond appropriately to temperature deviations without overreacting to measurement uncertainties, thereby reducing noise and wear.
Solution Approach 2:
The patent applies beforehand cushioning by pre-adjusting the temperature setpoint based on fan speed before control actions are taken. This anticipatory adjustment cushions against the harmful effects of continuous fan speed increases by establishing a higher tolerance threshold when fan speed is already high, thus reducing noise and wear.
3Device complexity
If a fixed temperature setpoint is used for fan control, then the control algorithm simplicity is maintained, but the system cannot distinguish between measurement deviations and actual temperature differences
Solution Approach 1:
The patent changes the temperature setpoint parameter from fixed to variable, making it dependent on fan speed. This enhancement adds only one functional relationship while significantly improving the system's ability to distinguish between measurement deviations and actual temperature differences, maintaining relative simplicity while improving measurement precision.
Solution Approach 2:
The patent implements feedback by using the fan speed information to adjust the temperature setpoint. This feedback mechanism allows the control algorithm to adapt to the current operating state, improving its ability to accurately distinguish between measurement deviations and actual temperature differences without substantially increasing complexity.
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 ensures energy-efficient operation of vapor compression systems by preventing unnecessary fan speed increases, reducing energy consumption and noise, and maintaining efficient fan operation by allowing a higher temperature difference at higher fan speeds.
Implementation Method 1
the fan being arranged to provide a secondary fluid flow across the heat rejecting heat exchanger
Implementation Method 2
In the heat rejecting heat exchanger, heat exchange takes place between the refrigerant flowing through the heat rejecting heat exchanger and the ambient
Implementation Method 3
heat exchange takes place between the refrigerant flowing through the heat rejecting heat exchanger and the ambient, e.g. in the form of a secondary fluid flow across the heat rejecting heat exchanger
Data Source
AI summary
A method for controlling a fan (6) of a vapour compression system (1) is disclosed, the fan (6) being arranged to provide a secondary fluid flow across a heat rejecting heat exchanger (3). A temperature difference, ΔT=Tout−Tamb, between a temperature, Tout, of refrigerant leaving the heat rejecting heat exchanger (3) and a temperature, Tamb, of ambient air of the heat rejecting heat exchanger (3) is established. A setpoint value, ΔTsetp, for the temperature difference, ΔT, is obtained, the setpoint value, ΔTsetp, being dependent on the fan speed of the fan (6) in such a manner that the setpoint value, ΔTsetp, increases as the fan speed increases. The fan speed of the fan (6) is controlled in order to control the temperature difference, ΔT, in accordance with the obtained setpoint value, ΔTsetp.