Circulating Pump Heater Layout Using a Self-Regulating PTC Resistor
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Solution Overview
Problem
The complexity and high cost of household appliances with integrated heaters and temperature controllers in circulating pumps, such as those in dishwashers, hinder efficient heating due to intricate constructions.
Innovation Solution
Incorporating a PTC resistor within the outer wall of the circulating pump's housing, arranged coaxially around the axis of rotation and radially outside the impeller, which self-regulates temperature by reducing power consumption as it heats, ensuring efficient heat transfer to the liquid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heater with temperature controller or temperature limiter is integrated in the circulating pump, then heating function is achieved, but device complexity and cost increase
Solution Approach 1:
The PTC resistor inherently limits its own temperature through its positive temperature coefficient characteristic, automatically reducing power consumption as temperature increases. This self-regulating property eliminates the need for external temperature controllers or limiters, achieving heating function while reducing device complexity and cost.
Solution Approach 2:
The invention exploits the temperature-dependent electrical resistance parameter of the PTC resistor. As the resistor heats up, its electrical resistance automatically increases, which reduces current flow and power consumption, thereby self-limiting the temperature without requiring additional control components.
2Loss of energy
If the PTC resistor is arranged radially outside the impeller, then heat transfer efficiency to liquid increases, but space utilization becomes constrained
Solution Approach 1:
The PTC resistor is strategically positioned in the region where liquid velocity is highest (radially outside the impeller). This local placement maximizes heat transfer efficiency by exploiting the enhanced convective heat transfer in high-velocity regions, while the housing structure accommodates this arrangement within the available space.
Solution Approach 2:
The heating arrangement utilizes the radial dimension of the pump chamber by placing the PTC resistor in the radial outer region. This spatial arrangement in the radial direction allows efficient heat transfer to the flowing liquid without interfering with the axial dimensions occupied by the impeller and motor components.
3Ease of manufacture
If the PTC resistor is arranged coaxially around the axis of rotation, then manufacturing and assembly are simplified, but heat transfer surface area is reduced
Solution Approach 1:
The housing structure serves multiple functions: it provides mechanical support for the coaxially arranged PTC resistor (simplifying assembly) while simultaneously acting as a heat transfer surface. The housing is thermally coupled to the liquid flow path, allowing heat generated by the PTC resistor to be efficiently transferred to the liquid through the housing walls.
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 achieves efficient heating with inherent temperature limitation, reducing the need for additional controllers and enhancing operational safety, while maintaining cost-effectiveness and simplicity in design.
Implementation Method 1
a PTC resistor (8) is used as the heating element in the heater
Implementation Method 2
Such resistors increase in electrical resistance as their temperature increases. Inherent self-regulation or temperature limitation can thus be achieved since the PTC resistor consumes less power as the temperature increases.
Implementation Method 3
an outlet being provided on a radial outer region of the pump chamber. The PTC resistor is arranged coaxially around the axis of rotation, radially outside the impeller. This achieves an efficient heating effect, since the greatest liquid velocity prevails radially outside of the impeller, which promotes heat transfer to the liquid.
Implementation Method 4
the PTC resistor being arranged within an outer wall of a housing of the circulating pump
Implementation Method 5
the greatest liquid velocity prevails radially outside of the impeller, which promotes heat transfer to the liquid
Data Source
Figure 1~2
Figure 3
AI summary
To heat the water in the fluid circuit of a household appliance, especially a dishwasher, a PTC resistor (8) is provided as a heater on the circulation pump. This heats the water located in the pump chamber (2) of the circulation pump. Thanks to the use of a PTC resistor, there is an inherent overheating protection, and simple temperature control can be achieved without additional components.