Dual Heat Pump Circuits for Low-Refrigerant Tumble Dryers
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Solution Overview
Problem
Existing heat pump tumble dryers using flammable refrigerants face limitations in refrigerant filling quantity due to safety and normative reasons, which restrict their performance and efficiency.
Innovation Solution
The condenser of the first refrigerant circuit and the evaporator of the second refrigerant circuit are in direct heat transfer connection, arranged outside the process air circuit, allowing for countercurrent or cocurrent flow, and designed as a single structural unit to enhance heat transfer and reduce refrigerant quantity, with optional heat exchanger and coolant connections for further efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If flammable refrigerants are used in heat pump tumble dryers, then cost and environmental friendliness are improved, but refrigerant charge is limited to 150 g for safety reasons
Solution Approach 1:
The single refrigerant circuit is divided into two separate refrigerant circuits, each with its own compressor, evaporator, condenser, and expansion valve. This segmentation allows the system to use flammable refrigerants in each circuit while maintaining safety, as each circuit operates independently with limited refrigerant charge. The two circuits work in parallel to provide sufficient total cooling capacity despite the 150g limit per circuit.
2Reliability
If refrigerant charge is limited to 150 g per circuit for safety, then safety is improved, but drying performance and efficiency deteriorate
Solution Approach 1:
By dividing the system into two independent refrigerant circuits operating in parallel, the total refrigerant charge capacity is effectively doubled while maintaining the 150g safety limit per circuit. Each circuit contributes to the overall drying performance, allowing high-performance operation with flammable refrigerants.
Solution Approach 2:
The two refrigerant circuits are merged in parallel configuration, with both circuits' evaporators working simultaneously to cool the air circulating through the dryer drum. This combination of parallel circuits provides sufficient total cooling capacity to maintain high drying performance despite the refrigerant charge limit in each individual circuit.
3Productivity
If two refrigerant circuits are used to overcome refrigerant charge limits, then productivity is improved, but device complexity increases
Solution Approach 1:
The system is segmented into two identical modular refrigerant circuits, each containing a compressor, evaporator, condenser, and expansion valve. This modular segmentation makes the complexity manageable, as each circuit is a complete independent unit that can be designed and maintained separately, reducing the overall system complexity compared to a single complex circuit.
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 a high-performance tumble dryer with reduced drying time and increased energy efficiency, suitable for both household and commercial use, while minimizing refrigerant usage and simplifying design and operation.
Implementation Method 1
the condenser of the first refrigerant circuit and the evaporator of the second refrigerant circuit are in direct heat transfer connection with each other
Implementation Method 2
the evaporator of the first refrigerant circuit and the condenser of the second refrigerant circuit are each arranged in the process air circuit for heat transfer with the process air
Data Source
Figure 1
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AI summary
The invention relates to a clothes dryer (2) comprising a process air circuit (4), a first refrigerant circuit (6) for a first refrigerant, and a second refrigerant circuit (8) for a second refrigerant, wherein the refrigerant circuits (6, 8) each have an evaporator (10, 12), a compressor (14, 16), a condenser (18, 20), and an expansion valve (22, 24), wherein the evaporator (10) of the first refrigerant circuit (6) and the condenser (20) of the second refrigerant circuit (8) are each arranged in the process air circuit (4) for heat transfer with the process air. The condenser (18) of the first refrigerant circuit (6) and the evaporator (12) of the second refrigerant circuit (8) are in direct heat transfer communication with each other and are arranged outside the process air circuit (4). The invention further relates to a method for operating a clothes dryer (2).