Heat Pump Dryer Phase Detection for Dynamic Fan and Compressor Control
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Solution Overview
Problem
Energy-intensive drying processes in heat pump dryers result in unnecessary energy consumption due to the transport of dry or insufficiently moist air, as the relative humidity of the process air decreases, leading to inefficient energy use.
Innovation Solution
A method for operating a dryer with a heat pump that involves a variable-speed compressor and sensors to detect transitions from quasi-steady-state to non-steady-state drying phases, reducing fan speed and compressor power consumption when relative humidity decreases, ensuring high relative humidity is maintained in the process air to minimize energy waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the blower continues to operate at constant speed during the transient drying phase, then the process air circulation is maintained, but unnecessary energy is consumed by transporting dry or insufficiently moist air
Solution Approach 1:
The blower speed is dynamically adjusted based on the drying phase. During the transient drying phase when relative humidity decreases, the blower speed is reduced compared to the quasi-steady-state drying phase. This dynamic adaptation allows the system to maintain adequate air circulation while reducing energy consumption during periods when the drying demand is lower.
Solution Approach 2:
The system uses humidity sensors to continuously monitor the relative humidity of the process air and provides feedback to the control unit. Based on this feedback, the control unit determines the drying phase and adjusts the blower speed accordingly. This closed-loop control ensures that the blower operates at optimal speed to match the actual drying needs, avoiding unnecessary energy consumption.
2Reliability
If the compressor operates at constant power, then the heat pump provides stable heating, but the system cannot adapt to changing drying conditions and may overheat
Solution Approach 1:
The compressor power is dynamically adjusted based on the drying phase and temperature conditions. During the transient drying phase or when temperature limits are approached, the compressor power is reduced. This dynamic adjustment allows the heat pump to provide stable heating during high-demand phases while preventing overheating during lower-demand phases, ensuring both reliability and temperature control.
Solution Approach 2:
Temperature sensors monitor the heat pump circuit temperature and provide feedback to the control unit. When the temperature approaches the maximum limit or during the transient drying phase when less heating is needed, the control unit reduces the compressor power. This feedback mechanism ensures the system maintains stable operation while adapting to changing conditions to prevent overheating.
3Loss of energy
If the system operates without phase detection, then the control is simpler, but energy is wasted by not reducing fan and compressor power during the transient drying phase
Solution Approach 1:
The control system uses feedback from humidity sensors and temperature sensors to detect the drying phase. By monitoring the relative humidity and temperature of the process air, the system can determine when it transitions from quasi-steady-state to transient drying phase. This feedback enables automatic adjustment of fan and compressor power without requiring complex manual control, reducing energy waste while maintaining acceptable control system complexity.
Solution Approach 2:
The system automatically detects the drying phase and adjusts its own operation without external intervention. The control unit monitors sensor data, determines the drying phase, and autonomously adjusts the fan and compressor power settings. This self-service capability allows the system to optimize energy consumption based on actual drying conditions without requiring complex external control mechanisms.
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 optimizes energy use by maintaining high relative humidity in the process air, reducing unnecessary energy consumption and preventing overheating of the heat pump circuit, thereby enhancing the energy efficiency and safety of the drying process.
Implementation Method 1
The heat pump can be used to extract heat from the process air flowing off the moist objects, which is applied to a corresponding heat sink for this purpose, and to conduct this heat by means of a suitable pump device to a heat source, from which it reaches the process air before it reaches the process air to be dried Objects
Implementation Method 2
the warm, moisture-laden process air is essentially cooled in an evaporator of the heat pump, which acts as a heat sink
Implementation Method 3
The water condensed in the evaporator is then generally collected in a suitable container
Implementation Method 4
The vaporized refrigerant goes to the compressor (also called 'compressor') and is compressed there. The refrigerant circulating in the refrigerant circuit is driven by the compressor, so that the compressor supplies the energy required to operate the pumping process
Implementation Method 5
From the compressor it goes to the condenser, where it is liquefied with the release of heat. The released heat heats the process air
Implementation Method 6
The liquefied refrigerant flows through a throttle, where its internal pressure is reduced, back to the evaporator
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a method for operating a dryer 1 with a drum 2 for laundry items to be dried, a process air circuit 3 in which a blower 12 for conveying process air is arranged, a control unit 4, a heat pump circuit 8,9,10,11 an evaporator 8, a condenser 9, a throttle 10 and a variable-performance compressor 11, and at least one sensor 5, 6, 22, 23, with a heating phase, a quasi-stationary drying phase and a non-stationary drying phase being run through one after the other, and with evaluation of Sensor signals of the sensor 5, 6, 22, 23 determine a transition from the quasi-stationary to the transient drying phase, and when a transition is detected, a speed u of the fan 12 is reduced and a power consumption p of the compressor 11 is reduced. The invention also relates to a dryer 1 suitable for carrying out this method.