Heat Pump Tumble Dryer Compressor Speed Control for Residual Drying
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Solution Overview
Problem
Conventional tumble dryers with heat pump systems using reciprocating fixed-speed compressors are inefficient due to complex design, large size, and inability to control operating parameters, leading to energy wastage during the drying process.
Innovation Solution
A central processing unit evaluates the time development of physical parameters indicating laundry dryness to gradually reduce the compressor's rotation speed, optimizing energy usage by recognizing the transition to the residual drying phase where water content decreases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reciprocating fixed-speed compressor is used in a heat pump system, then the system can maintain stable operation, but the device complexity increases and the compressor size becomes large
Solution Approach 1:
The patent replaces the mechanical reciprocating compressor with an electric scroll compressor driven by an electric motor. This substitution eliminates the complex reciprocating mechanism while providing variable speed control capability, thus reducing device complexity while maintaining operational stability.
Solution Approach 2:
The patent implements variable speed control of the electric motor driving the scroll compressor, allowing the compression speed to be dynamically adjusted based on drying conditions. This dynamic adjustment reduces the need for oversized components and simplifies the overall system design while maintaining reliable operation across different loading conditions.
2Duration of action of stationary object
If a reciprocating fixed-speed compressor is used, then the compressor can operate continuously, but the loss of energy increases due to on/off operation mode
Solution Approach 1:
The patent employs variable speed control of the electric motor, allowing the compressor to operate continuously at optimized speeds rather than cycling on/off. The control system adjusts the motor speed based on actual drying needs, eliminating energy wastage associated with frequent start-stop operations while maintaining continuous operation for stable performance.
Solution Approach 2:
The patent changes the operating parameters of the compressor by controlling the electric motor speed. By dynamically adjusting the rotation speed according to drying conditions, the system avoids energy wastage from fixed-speed operation and achieves continuous operation at optimal efficiency points.
3Ease of operation
If the compressor operates at fixed speed, then the system is simpler to control, but the productivity decreases due to inability to adapt to changing drying conditions
Solution Approach 1:
The patent implements a control system that monitors drying conditions and provides feedback to adjust the electric motor speed. This feedback mechanism allows the system to automatically adapt to changing drying conditions, improving productivity while maintaining ease of operation through automated control rather than manual intervention.
Solution Approach 2:
The patent makes the compressor speed dynamic rather than fixed, allowing it to adapt to changing drying conditions. The electric motor can be controlled to vary its speed according to the drying phase and moisture content, significantly improving drying efficiency while the automated control keeps the system easy to operate.
4Power
If the compressor size is increased to ensure sufficient compression capacity, then the power output is adequate, but the volume of the stationary object increases
Solution Approach 1:
The patent uses a compact electric scroll compressor with variable speed control, allowing the system to achieve adequate compression power only when needed rather than requiring a large fixed-capacity compressor. The electric motor can be sized smaller since its power output is dynamically adjusted, significantly reducing the volume of stationary objects required.
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 reduces energy consumption by adjusting compressor speed based on laundry dryness, ensuring only necessary energy is used during the final drying stages, thereby saving energy that would otherwise be lost.
Implementation Method 1
a compressor (16) with a variable rotation speed for compressing a refrigerant gas
Implementation Method 2
a first heat exchanger (18) for a first thermal coupling between the air stream circuit (10) and the refrigerant circuit (14)
Implementation Method 3
the first heat exchanger is formed as a condenser of the heat pump system
Implementation Method 4
a second heat exchanger (20) for a second thermal coupling between the air stream circuit (10) and the refrigerant circuit (14)
Implementation Method 5
the second heat exchanger is formed as an evaporator of the heat pump system
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The present invention relates to tumble dryer with at least one heat pump system. The tumble dryer comprises an air stream circuit (10) including at least one drum (12) for receiving laundry to be dried, at least one refrigerant circuit (14) including at least one compressor (16) with a variable rotation speed, a first heat exchanger (18) for a thermal coupling between the air stream circuit (10) and the refrigerant circuit (14) and a second heat exchanger (20) for a further thermal coupling between the air stream circuit (10) and the refrigerant circuit (14). The tumble dryer comprises further a control unit (22) for controlling the rotation speed of the compressor (16) and at least one sensor for detecting at least one physical parameter (TDI, TDO; TEI, TEO; TF; Z; RH) as function of the time of the air stream, the refrigerant ad/or the laundry. A central processing unit is provided, which is arranged to evaluate the time development of the physical parameter (TDI, TDO, TEI, TEO; TF; Z; RH) and which reduces the rotation speed of the compressor (16) according to the evaluation of the time development of the physical parameter (TDI, TDO, TEI, TEO; TF; Z; RH). Further, the present invention relates to a corresponding method for controlling a heat pump system for a tumble dryer.