Household Dryer Exhaust Temperature Control for Shorter Drying Cycles
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Solution Overview
Problem
Existing tumble dryer control methods, relying on fixed exhaust air temperature set points and hysteresis or PI control, lead to inefficient energy use and prolonged drying cycles due to temperature oscillations and dependence on operational conditions, potentially damaging clothes.
Innovation Solution
An adaptive temperature control method that dynamically adjusts the set point based on real-time exhaust temperature, derivative analysis, and simplified thermodynamic modeling to optimize energy consumption, drying time, and fabric care, avoiding excessive temperature swings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed exhaust air temperature set point is used with hysteresis or PI control, then the control system is simple to implement, but the drying cycle is prolonged and energy consumption increases due to temperature oscillations
Solution Approach 1:
The patent implements dynamic set point adjustment where the target exhaust air temperature is not fixed but adapts during the drying cycle. The set point is modified based on the difference between current and target temperature, allowing the system to respond dynamically to changing drying conditions and reduce oscillations, thereby shortening drying time without requiring complex additional hardware.
Solution Approach 2:
The patent changes the temperature parameter dynamically by adjusting the set point based on the temperature difference (dT) between current and target exhaust air temperature. This parameter adaptation allows the control system to optimize drying efficiency at different stages of the cycle, reducing overall drying time while maintaining simplicity in the control architecture.
2Device complexity
If a fixed exhaust air temperature set point is used, then the control algorithm is simple, but energy consumption increases due to temperature oscillations and inability to adapt to varying operational conditions
Solution Approach 1:
The patent dynamically adjusts the temperature set point parameter based on the difference between current and target exhaust air temperature. This adaptive parameter modification enables the system to reduce energy losses by avoiding unnecessary heating when the temperature is close to target, while maintaining a relatively simple control algorithm structure.
Solution Approach 2:
The patent implements a feedback mechanism where the current exhaust air temperature is continuously monitored and compared with the target temperature. The difference (dT) is used to adjust the set point, creating a closed-loop control that reduces energy consumption by adapting to actual operating conditions without requiring complex algorithms or additional sensors.
3Ease of operation
If hysteresis control is used to switch the heater, then the control implementation is simple, but temperature oscillations occur around the upper temperature limit causing undesired effects
Solution Approach 1:
The patent replaces static hysteresis control with a dynamic control approach where the set point adjusts based on the temperature difference (dT). This dynamic adaptation smooths temperature transitions and reduces oscillations around the upper temperature limit while maintaining ease of implementation through straightforward set point modification in the existing control logic.
4Ease of operation
If the heater is cycled on and off to maintain set point temperature, then the control is straightforward, but drying time is prolonged due to repeated temperature adjustments
Solution Approach 1:
The patent modifies the temperature set point parameter dynamically during the drying cycle based on the difference between current and target temperature. This parameter adaptation reduces the frequency and magnitude of heater cycling, allowing the drying process to proceed more continuously and efficiently, thereby shortening overall drying time while maintaining straightforward control implementation.
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 approach results in shorter drying cycles, reduced energy consumption, and improved fabric care by setting the optimal temperature set point according to the dryer's steady-state conditions, reducing temperature fluctuations and heat losses.
Implementation Method 1
at least a temperature sensor for monitoring the temperature of the exhaust air
Implementation Method 2
the control of the heating element used for heating air entering the drying chamber
Implementation Method 3
heating air entering the drying chamber
Implementation Method 4
a closed loop control system for maintaining the drying temperature close to a set point temperature
Data Source
Figure 1~5
Figure 3~4
Figure 6
AI summary
A method for drying clothes in a household dryer having a drying chamber (1), at least a temperature sensor (5a) for monitoring temperature at the air exhaust from the chamber, and a control system for maintaining temperature in the drying chamber close to a set point temperature (ST) comprises an assessment of an optimum set point temperature on the basis of at least said air exhaust temperature (E).