Heat Pump Dryer Heater Layout to Prevent Compressor Liquid Suction
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Solution Overview
Problem
Tumble dryers with heat pump circuits face inefficiencies due to additional heaters causing flow resistance, susceptibility to dirt, and risk of fluff ignition, which complicates heating and can lead to clogged systems.
Innovation Solution
Incorporating a heater within the heat pump circuit, specifically between the condenser and evaporator, to supply energy efficiently and prevent liquid medium suction by the compressor, with an additional heat exchanger for controlled heat extraction, and a controller to manage the heater's operation based on temperature thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an additional heater is installed in the process circuit to rapidly raise temperature, then heating speed is improved, but flow resistance increases and the system becomes susceptible to dirt and fluff accumulation
Solution Approach 1:
The heater is extracted from the process circuit and relocated to the heat pump circuit. This removes the source of flow resistance and contamination issues from the process air path while preserving the heating function. The heater now operates on the refrigerant side where it does not interfere with air flow or contribute to fluff accumulation problems.
Solution Approach 2:
The heat pump circuit acts as an intermediary medium between the heater and the process circuit. Instead of heating process air directly (which causes flow resistance and contamination), the heater warms the refrigerant, which then transfers heat to the process air through the heat exchanger, eliminating direct contact between the heater and process air.
2Temperature
If a heater is installed in the process circuit to provide heating, then heating function is improved, but the system becomes prone to clogging from fluff and dirt
Solution Approach 1:
The heater is extracted from the process circuit environment where fluff and dirt are present. By relocating it to the heat pump circuit, the heater operates in a clean refrigerant environment that does not contain lint or fluff, eliminating the clogging problem while maintaining heating capability through thermal transfer.
Solution Approach 2:
The heat pump refrigerant serves as an intermediary that transfers thermal energy from the heater to the process air without carrying fluff or contaminants. This mediation prevents contamination transfer while achieving the desired heating effect in the drying chamber.
3Productivity
If heating is provided in the process circuit, then drying capability is improved, but the heating system becomes more expensive and less compact
Solution Approach 1:
The heat pump circuit is given a dual function: it not only cools the process air during the drying cycle but also serves as the heating medium when the electric heater is activated. This eliminates the need for separate heating and cooling systems, reducing overall system cost and improving compactness while maintaining full drying capability.
Solution Approach 2:
The heating function is merged with the existing heat pump circuit rather than being implemented as a separate process circuit heater. The refrigerant loop serves both thermal management functions, consolidating components and reducing system complexity, cost, and space requirements.
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 enhances heating efficiency, reduces the risk of system clogging, and allows for quicker drying times while maintaining optimal compressor operation, ensuring efficient heat transfer and preventing compressor damage from liquid suction.
Implementation Method 1
a heater (9) is provided in the heat pump circuit, by means of which energy can be supplied to the system
Implementation Method 2
The evaporator (6) is used to cool the process air and in this way remove water from it, while the condenser (3) is used to reheat the process air
Implementation Method 3
The medium is conveyed from a compressor (2) to a condenser (3)
Implementation Method 4
then via a throttle element (5), e.g. in the form of a capillary or an expansion valve, to an evaporator (6)
Implementation Method 5
The evaporator (6) is used to cool the process air and in this way remove water from it
Implementation Method 6
the condenser (3) is used to reheat the process air so that it can absorb new water
Data Source
Figure 1
Figure 2
AI summary
A tumble dryer is equipped with a heat pump cycle to cool and heat the process air. A heater (9) and an additional heat exchanger (4) are provided in the heat pump circuit. Heat can be supplied to the system efficiently and easily with the heater (9), e.g. in a start-up phase of operation or when there is a risk that the compressor (2) will suck in liquid medium. The heater (9) is advantageously arranged between the throttle element (5) and the evaporator (6), since that is where the heat can be introduced most efficiently.