Domestic appliance, in particular a clothes drier, with a heat pump comprising an expansion device
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Solution Overview
Problem
The use of electronically controlled expansion valves in heat pumps with flammable working fluids requires additional safety measures and increased manufacturing costs, making it economically unviable, and there is a need for a cost-effective and fail-safe solution to prevent compressor malfunctions due to uncontrolled pressure increases.
Innovation Solution
Incorporating a static expander in parallel with the controllable valve ensures a fail-safe flow path for the working fluid, allowing continued operation even if the controllable valve closes, using a capillary as the static expander to maintain pressure differences within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electronically controlled expansion valve is used in a heat pump with flammable working fluid, then the pressure control precision and reliability are improved, but the manufacturing cost increases and additional safety measures are required
Solution Approach 1:
The expansion device is segmented into two independent parallel paths: an electronically controllable valve for precise pressure control during normal operation, and a static expander (capillary) as a fail-safe backup. This segmentation allows the system to achieve both precise control and cost-effectiveness by using the simple capillary when the electronic valve fails or is not needed.
Solution Approach 2:
The system changes the flow resistance parameter dynamically by switching between the electronically controllable valve (variable resistance) and the static expander (fixed resistance). The control device adjusts the valve opening to maintain pressure within a predetermined range, or switches to the capillary when pressure control is not required or fails.
2Ease of manufacture
If a static expander is used instead of an electronically controlled valve, then the manufacturing cost is reduced and the system is simpler, but the pressure control precision and ability to prevent compressor damage is reduced
Solution Approach 1:
The system prepares a fail-safe static expander in advance that automatically takes over if the electronically controlled valve fails. This prior cushioning ensures that even if the complex electronic control fails, the simple capillary provides a backup pressure control mechanism that prevents compressor damage.
Solution Approach 2:
The control device acts as an intermediary that monitors the pressure and switches between the electronically controlled valve and the static expander. When pressure is within the predetermined range, the electronic valve is used; when pressure deviates or the electronic valve fails, the control device switches to the capillary to maintain safe operation.
3Reliability
If parallel configuration of static expander and controllable valve is implemented, then the fail-safe operation is achieved, but the device complexity increases
Solution Approach 1:
The static expander and electronically controllable valve are merged into a single expansion device with parallel flow paths. Both components work together in the same housing, sharing common connections to the evaporator and working fluid circuit, thereby reducing overall system complexity despite having two expansion paths.
Solution Approach 2:
The expansion device achieves multi-functionality by combining both a statically controlled expander and an electronically controllable valve in parallel. This universal design allows the single expansion device to provide both precise pressure control (via the electronic valve) and fail-safe operation (via the capillary), eliminating the need for separate systems.
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 configuration enables the use of flammable working fluids in heat pumps with electronically controllable expansion valves, ensuring safe and cost-effective operation by maintaining intended pressure differences and preventing compressor failures.
Implementation Method 1
using a capillary as the static expander to maintain pressure differences within a predetermined range
Implementation Method 2
a heat source for emitting heat
Implementation Method 3
a heat sink for absorbing heat
Implementation Method 4
a working fluid circulating in the heat pump between the heat sink and the heat source, which is also referred to as a 'refrigerant' according to common practice in the technology, is cyclically and repeatedly evaporated and condensed
Implementation Method 5
a working fluid circulating in the heat pump between the heat sink and the heat source, which is also referred to as a 'refrigerant' according to common practice in the technology, is cyclically and repeatedly evaporated and condensed
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a household appliance 1 comprising a heat pump, the heat pump comprising a heat source 2 for emitting heat, a heat sink 3 for absorbing heat and a working fluid circuit 4, 5, 6, 7 for pumping heat from the heat sink 3 to the heat source 2, which working fluid circuit 4, 5, 6, 7 comprises a compressor 4, an expansion device 5, 6 and a self-contained first piping system 7 for circulating a working fluid from the compressor 4 to the heat source 2, from the heat source 2 to the expansion device 5, 6, from the expansion device 5, 6 to the heat sink 3 and from the heat sink 3 to the compressor 4 as well as a control device 8, and the expansion device 5, 6 comprises a valve 5 controllable by the control device 8. The expansion device 5, 6 has a static expander 6, which can be flowed through by the working medium in parallel with the controllable valve 5.The household appliance 1 is specifically designed as a clothes dryer 1.