Device for drying laundry and method for operating a heat pump of such a device
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Solution Overview
Problem
Open process air systems in laundry dryers face inefficiencies due to high energy consumption and reduced dehumidification capacity, especially when operating in closed rooms, as they struggle to maintain condensation efficiency above 80% without excessive thermal losses.
Innovation Solution
A cooling unit is thermally coupled to the refrigerant line between the compressor and condenser of the heat pump, cooled by process air from the evaporator, which leads to stronger subcooling of the refrigerant, increasing condensation efficiency and reducing energy input, allowing the dryer to operate effectively in closed rooms with an open process air system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an open process air system is used with a heat pump for heat recovery, then energy consumption is reduced compared to condensation dryers, but condensation efficiency cannot be maintained above 80% in closed rooms due to thermal losses
Solution Approach 1:
The refrigerant is cooled in advance in the refrigerant line between the compressor and condenser, before entering the condenser. This preliminary cooling action ensures that the refrigerant temperature is sufficiently low to maintain condensation efficiency above 80% even when operating in closed rooms with thermal losses, while still benefiting from the energy efficiency of the open process air system
Solution Approach 2:
A cooling unit is introduced as an intermediary component in the refrigerant line to provide the necessary cooling. This cooling unit acts as a mediator that enables the system to maintain condensation efficiency without requiring the process air to be cooled, thus preserving the energy efficiency benefits of the open process air system while achieving reliable condensation performance
2Productivity
If compressor power is continuously supplied to maintain drying speed, then drying performance is improved, but the heat pump overheats reducing efficiency in closed process air systems
Solution Approach 1:
The cooling unit in the refrigerant line serves as an intermediary that removes excess heat from the refrigerant without affecting the process air temperature. This allows the compressor to continue operating at full power for high drying speed while the refrigerant is actively cooled to prevent heat pump overheating and maintain efficiency
3Reliability
If process air is cooled to maintain condensation efficiency in open systems, then condensation efficiency increases, but energy consumption increases due to the cooling requirement
Solution Approach 1:
Instead of cooling the process air, the invention introduces a cooling unit as an intermediary that cools the refrigerant directly in the refrigerant line. This approach maintains condensation efficiency by lowering refrigerant temperature while avoiding the energy penalty of cooling the large volume of process air, thus resolving the contradiction between condensation efficiency and energy consumption
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 solution enhances condensation efficiency to over 80%, reduces energy consumption, and maintains dehumidification performance, enabling the dryer to operate efficiently in closed rooms while minimizing thermal losses and energy input.
Implementation Method 1
at least one cooling unit thermally coupled to a refrigerant line between a compressor and a condenser of the heat pump for cooling a refrigerant flowing through the refrigerant line
Implementation Method 2
heat is extracted from the exhaust air exiting the drying chamber by means of an evaporator of the heat pump
Implementation Method 3
heat is extracted from the exhaust air exiting the drying chamber by means of an evaporator of the heat pump, which is then transferred back to the process air entering the process air system via a condenser in a refrigerant circuit of the heat pump
Data Source
Figure 1
AI summary
The invention relates to a device (1, 14) for drying laundry, comprising at least one open process air system (3, 15) with at least one drying chamber (4) for receiving laundry to be dried and at least one heat pump (7) thermally coupled to the process air system (3, 15). In order to reduce the energy content of process air at an outlet of the open process air system (3, 15) and to increase the dehumidification capacity of the device (1, 14), the device (1, 14) comprises at least one cooling unit (13) thermally coupled to a refrigerant line (12) between a compressor (10) and a condenser (8) of the heat pump (7) for cooling a refrigerant flowing through the refrigerant line (12).