Ceramic Heater Resistance Feedback for Thermal Shock Protection
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Solution Overview
Problem
Ceramic heaters used for liquid heating are prone to cracking due to thermal shock caused by boiling liquids, which occurs when the liquid flow rate decreases or stagnates, leading to excessive heating and uneven cooling.
Innovation Solution
A ceramic heater control apparatus that monitors the electrical resistance of the resistive heating element and stops energization when the resistance exceeds a predetermined upper limit, set by adding an allowable resistance to a reference resistance, to prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the liquid flow rate decreases or the liquid stagnates on the ceramic heater surface, then the heating efficiency increases, but the liquid may boil and cause thermal shock to the ceramic heater
Solution Approach 1:
The control apparatus continuously monitors the electrical resistance of the resistive heating element and uses this feedback to detect changes in liquid flow conditions. When electrical resistance exceeds a predetermined threshold, it indicates the liquid may be boiling, and the control apparatus responds by reducing or stopping power supply to prevent thermal shock and cracking.
2Speed
If the ceramic heater operates at high power to heat the liquid quickly, then the heating speed increases, but the risk of thermal shock and cracking increases
Solution Approach 1:
The control apparatus performs preliminary monitoring of electrical resistance during the heating process to detect early signs of boiling before thermal shock can occur. By detecting electrical resistance changes in advance and taking preventive action to reduce power supply, the system avoids the harmful effects of thermal shock and cracking.
3Use of energy by stationary object
If the liquid flow rate is reduced to save energy, then the energy consumption decreases, but the liquid stagnation causes excessive heating and boiling
Solution Approach 1:
The control apparatus uses electrical resistance monitoring as feedback to detect when liquid stagnation causes excessive heating. Even at reduced power levels, the system continuously monitors resistance changes and can identify when the liquid is about to boil, allowing the system to adjust power supply accordingly to prevent harmful effects.
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
Prevents cracking of ceramic heaters by accurately detecting thermal shock through electrical resistance changes, ensuring safe operation even in varying liquid flow conditions.
Implementation Method 1
a resistive heating element (201) which generates heat when energized
Implementation Method 2
the ceramic heater is heated by the heat generated by the resistive heating element, while it is cooled by the liquid
Implementation Method 3
When cracking occurs in the ceramic heater, the electrical resistance of the resistive heating element tends to increases
Data Source
AI summary
A ceramic heater control apparatus controls a ceramic heater including a resistive heating element which generates heat when energized and a ceramic base body in which the resistive heating element is embedded. The control apparatus energizes the resistive heating element, and stops the energization of the resistive heating element when the electrical resistance of the resistive heating element has exceeded an upper limit electrical resistance during the energization of the resistive heating element. The upper limit electrical resistance is obtained by adding a predetermined allowable electrical resistance to a reference electrical resistance.