Heat Pump Tumble Dryer Recirculation for Better Condensation
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Solution Overview
Problem
Condenser tumble dryers have limited energy efficiency due to low condensation efficiency and overheating issues in closed systems, while exhaust air dryers with heat recovery can be less efficient in energy consumption but face challenges with heat recovery in open systems.
Innovation Solution
A condenser tumble dryer with an open air system and a heat pump that incorporates a recirculated air channel to increase the relative air humidity of the process air, enhancing drying efficiency and reducing energy consumption by recovering sensible heat, and potentially eliminating the need for additional coolers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a closed process air circuit is used in a condenser tumble dryer, then condensation efficiency can be improved, but the system overheats due to continuously introduced compressor power
Solution Approach 1:
The air circuit is segmented into a closed loop for heat recovery and an open pathway for heat dissipation. The process air is divided into portions that circulate through the heat pump system and portions that are exhausted to the environment, allowing simultaneous heat recovery and temperature control.
Solution Approach 2:
The system recovers heat from the process air passing through the evaporator and condenser, then discards excess heat through the open air pathway. This allows the system to recover useful energy while preventing overheating by intentionally releasing excess thermal energy to the environment.
2Use of energy by moving object
If an open air system is used in an exhaust air dryer with heat recovery, then energy consumption can be reduced, but condensation efficiency remains limited
Solution Approach 1:
The system merges the advantages of both open and closed air systems by combining an open air pathway for heat dissipation with a closed heat recovery loop. The process air is routed through both pathways, enabling simultaneous heat recovery for energy efficiency and open pathways for maintaining condensation efficiency.
Solution Approach 2:
The process air serves multiple functions: it is used for heat recovery in the evaporator and condenser, for drying the laundry, and for heat dissipation when exhausted to the environment. This multi-functionality allows the system to achieve both energy efficiency and effective condensation.
3Loss of energy
If additional coolers are added to increase condensation efficiency above 80%, then condensation efficiency improves, but device complexity increases
Solution Approach 1:
The excessive heat that would otherwise require additional cooling equipment is extracted and redirected through the open air pathway. By removing the heat dissipation function from the closed heat recovery loop and placing it in a separate open pathway, the system achieves high condensation efficiency without requiring additional coolers or sub-coolers.
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
The solution increases the condensation efficiency, reduces energy consumption, and lowers noise levels by optimizing the air flow through the condenser, allowing for a more efficient and quieter operation with improved heat recovery.
Implementation Method 1
heat is removed from the exhaust air from the drying chamber, generally a drum, by the evaporator of the heat pump
Implementation Method 2
the heat being supplied back to the supply air via the condenser
Implementation Method 3
a heat pump circuit consisting of an evaporator, compressor and condenser
Data Source
AI summary
A dryer has a drum for laundry items to be dried, a supply air channel, an exhaust air channel, a recirculated air channel branching off therefrom and discharging into the supply air channel upstream of a drum inlet, a blower, a heat pump having a condenser disposed in the supply air channel, an evaporator disposed in the exhaust air channel, a throttle, a compressor, a controller and a heater. The dryer is configured such that moist warm air flows out of the drum in an exhaust air channel part, substantially in the same direction as the supply air in an inlet part of the supply air channel containing the condenser. The process air leaving the drum has a relative air humidity Frel, to which Frelmin≤Frel≤Frelmax applies, wherein Frelmin is a predetermined minimum value and Frelmax is a maximum value of the relative air humidity.