Heat Pump Dryer Air Loop With Integrated Pre-Cooling Heat Exchanger
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Solution Overview
Problem
Existing clothes dryers with closed-loop heat pump systems face inefficiencies due to higher construction costs and complexity when additional air/air heat exchangers are added to enhance dehumidification, leading to suboptimal energy use and longer drying cycles.
Innovation Solution
A clothes dryer design incorporating a closed loop with a drum, a first air-air heat exchanger, a second heat exchanger (evaporator), and a third heat exchanger (condenser), where the process air is cooled, further cooled, and then warmed before re-circulating back into the drum, with a controllable air guidance device to adapt flow volumes between heat exchangers, optimizing energy input for faster drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If additional air/air heat exchangers are added to enhance dehumidification, then dehumidification rate is improved, but device complexity and construction costs increase
Solution Approach 1:
The patent combines the first air/air heat exchanger and second air/air heat exchanger into a single integrated heat exchanger unit. This merging maintains the dual-function capability of pre-cooling process air and cooling ambient air while reducing device complexity and construction costs compared to using separate heat exchangers.
Solution Approach 2:
The integrated heat exchanger serves multiple functions: it pre-cools process air before it enters the evaporator, cools ambient air for discharge, and enables heat recovery between process air and ambient air. This multi-functionality achieves enhanced dehumidification without proportionally increasing device complexity.
2Productivity
If additional air/air heat exchangers are added to enhance dehumidification, then dehumidification rate is improved, but construction costs increase
Solution Approach 1:
The patent combines the first air/air heat exchanger and second air/air heat exchanger into a single integrated heat exchanger unit. This merging maintains the dual-function capability of pre-cooling process air and cooling ambient air while reducing device complexity and construction costs compared to using separate heat exchangers.
3Productivity
If process air is cooled more extensively before entering the condenser, then dehumidification rate is improved, but energy input requirements increase
Solution Approach 1:
The first air/air heat exchanger pre-cools the process air before it enters the evaporator, performing cooling action in advance. This preliminary cooling reduces the energy input required by the heat pump system to achieve the same dehumidification rate, as the evaporator operates with air that is already partially cooled.
Solution Approach 2:
The system uses the temperature difference between process air and ambient air to drive heat exchange in the air/air heat exchangers. This self-service heat recovery mechanism enhances dehumidification without requiring additional energy input from external sources.
4Speed
If process air temperature at condenser outlet is increased, then drying speed is improved, but energy input requirements increase
Solution Approach 1:
The control unit monitors the temperature of process air at the condenser outlet and adjusts the flow volumes through the air/air heat exchangers accordingly. This feedback control optimizes the balance between achieving high drying speed and minimizing energy input by dynamically adjusting heat exchange parameters.
Solution Approach 2:
The system dynamically adjusts the flow volumes of process air and ambient air through the air/air heat exchangers based on operating conditions. This dynamic adjustment allows the system to optimize drying speed while minimizing energy input requirements by adapting heat exchange rates to actual drying needs.
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 achieves a 10% increase in dehumidification rate and a 5°C increase in process air temperature at the condenser outlet, resulting in a 10% faster drying cycle with energy savings, while maintaining moderate complexity and cost.
Implementation Method 1
a first air/air heat exchanger (8) for pre-cooling the process air (P) before the process air (P) enters the evaporator (4)
Implementation Method 2
the process air P is cooled down below its dew point such that condensate C is generated, in particular by getting the process air P in contact with surfaces of the evaporator 4
Implementation Method 3
When being discharged through an air outlet 5b (working point p5), its temperature has been increased to a high temperature level T5 of about 73 °C
Data Source
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AI summary
A clothes dryer 31 comprises a closed loop L for process air P, the loop L comprising a drum 2, a first heat exchanger 8, a second heat exchanger 4, and a third heat exchanger 5, wherein the first heat exchanger 8 has a first air channel 9 and a second air channel 11 for transferring heat between them, an air outlet 9b of the first air channel 9 being connected to an air inlet 4a of the second heat exchanger 4, an air outlet 4b of the second heat exchanger 4 being connected to an air inlet 11a of the second channel 11 of the first heat exchanger 8, and an air outlet 11b of the second channel 11 being connected to an air inlet 5a of the third heat exchanger 5. A method for operating a clothes dryer 21; 31 is also disclosed. The invention is particularly useful for closed-loop heat pump clothes dryers.