Underfloor Heater Layout for Thermally Isolated Liquid Sensing
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Solution Overview
Problem
Existing underfloor heaters for liquid heating vessels do not provide complete thermal isolation between the thermal sensor and the heating element, as there must always be a connection between the diffuser plate and the heating element, which can affect the accuracy of temperature measurement of the liquid.
Innovation Solution
A separate heat diffuser portion is used for the sensing region, surrounded by a wall that is not connected to the main diffuser portion, allowing the thermal sensor to be in direct contact with the base plate and enhancing thermal isolation from the heating element, with the wall being attached to the base plate to facilitate manufacturing and improve thermal coupling with the liquid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single diffuser plate is used to conduct heat from the heating element, then heat conduction is improved, but thermal isolation between the sensor and heating element deteriorates
Solution Approach 1:
The diffuser plate is divided into two separate portions: a first diffuser portion in thermal contact with the heating element and a second diffuser portion in thermal contact with the sensor. These portions are separated by a gap or channel, preventing direct thermal conduction path between the heating element and sensor while maintaining effective heat distribution to the liquid.
Solution Approach 2:
A channel or gap is introduced as an intermediary barrier between the first and second diffuser portions. This intermediary structure blocks the direct thermal path while allowing both diffuser portions to function independently - one for heat distribution and the other for accurate temperature sensing.
2Reliability
If a separate second diffuser portion is provided for the sensing region, then thermal isolation is improved, but manufacturing complexity increases
Solution Approach 1:
The first and second diffuser portions are manufactured as a single integrated piece with a channel or gap formed between them. This merging approach eliminates the need for separate assembly operations and complex locating mechanisms, while still maintaining the thermal isolation function through the integrated channel design.
Solution Approach 2:
The single diffuser plate structure serves multiple functions: it provides thermal conduction pathways to both the heating element and sensor, maintains structural integrity, and creates the thermal isolation channel - all in one component that simplifies manufacturing.
3Reliability
If the sensor is placed in direct contact with the base plate, then thermal isolation is improved, but heat capacity decreases
Solution Approach 1:
The second diffuser portion is provided locally at the sensor region with sufficient thickness and material properties to provide the required heat capacity for accurate temperature sensing, while the channel ensures this local heat capacity is not compromised by connection to the heating element.
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 allows for accurate temperature measurement of the liquid, reducing the influence of the heating element on the sensor readings and improving thermal sensing capabilities, while also simplifying manufacturing by eliminating the need for separate parts during brazing.
Implementation Method 1
a heat diffuser portion in good thermal contact with the base plate, a heating element in good thermal contact with the diffuser portion
Implementation Method 2
a sensing region for receiving a thermal sensor wherein said sensing region is not directly connected to the diffuser portion and is at least partly surrounded by a wall
Data Source
AI summary
An underfloor heater for a liquid heating vessel comprises a base plate, a heat diffuser portion in good thermal contact with the base plate, a heating element in good thermal contact with the diffuser portion and a sensing region for receiving a thermal sensor. The sensing region is not directly connected to the diffuser portion and is at least partly surrounded by a wall. The sensing region may be provided with a second separate diffuser portion comprising a disc of aluminum brazed to the underside of the base plate.