Thermal Flowmeter Rise-and-Fall Timing for Low-Flow Accuracy
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Solution Overview
Problem
Existing flowmeters struggle to accurately determine flow rates at low velocities due to prolonged time for fluid to reach detection elements and increased heat loss, making it difficult to detect maximum temperature accurately.
Innovation Solution
A thermal type flowmeter that measures temperature rise and drop times to calculate flow rates using a sensor portion with a control portion that applies superimposed current for heating and temperature detection, and calculates flow rates based on time ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a heat source and downstream temperature detection element are used to measure flow rate, then flow rate determination can be performed, but at low flow rates the time until heated fluid reaches the detection element becomes longer and heat release increases, making it difficult to detect maximum temperature accurately
Solution Approach 1:
The patent combines the heat source and temperature detection element into a single integrated sensor portion. The sensor portion includes a heating element and a temperature detection element that are merged into one component, allowing the same element to both heat the fluid and detect temperature changes. This eliminates the time delay associated with heat transfer between separate components and directly measures temperature changes at the heating location, enabling accurate flow rate measurement even at low flow rates.
Solution Approach 2:
The patent introduces a thermal conductivity member as an intermediary between the heating element and the temperature detection element. This thermal conductivity member efficiently transfers heat from the heating element to the fluid while allowing the temperature detection element to accurately sense the temperature changes. The intermediary enables effective heat transfer and temperature detection without the losses that occur in direct fluid contact over long distances.
2Measurement precision
If a heat source and downstream temperature detection element are used to measure flow rate, then flow rate determination can be performed, but heat loss from the fluid increases at low flow rates, making it difficult to detect maximum temperature
Solution Approach 1:
The patent combines the heat source and temperature detection element into a single integrated sensor portion. This merging ensures that temperature is measured at the exact location where heating occurs, eliminating heat loss that would occur during heat transfer to downstream detection elements. The integrated design captures temperature changes immediately, preventing energy loss and enabling accurate maximum temperature detection even at low flow rates.
Solution Approach 2:
The patent employs periodic heating and cooling cycles to measure flow rate. The heating element periodically heats the fluid, and the temperature detection element measures the temperature rise and fall over time. By analyzing the temperature change rate during these periodic cycles, the system can determine flow rate without requiring the fluid to maintain high temperature for extended periods, thus reducing overall heat energy loss while maintaining measurement accuracy.
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
Enables accurate and high-speed flow rate determination at low flow rates by measuring temperature rise and drop times to calculate flow rates with high precision.
Implementation Method 1
a temperature measuring resistor body configured inside the heat conductive pipe and conducting heating and temperature detection of the fluid contact portion
Implementation Method 2
a temperature measuring resistor body configured inside the heat conductive pipe and conducting heating and temperature detection of the fluid contact portion
Implementation Method 3
a heat conductive pipe provided in the flow path
Data Source
AI summary
A thermal type flowmeter that can accurately perform flow rate determination at high speed and high precision even at low flow rate includes a sensor portion conducting heating and temperature detection of a fluid contact portion in contact with a fluid flowing in a flow path, and a control portion controlling heating and temperature detection conducted by the sensor portion. The control portion measures the temperature rise time until the temperature of the fluid contact portion reaches an upper limit set temperature when heating the fluid contact portion and the temperature drop time until the temperature of the fluid contact portion reaches a lower limit set temperature when stopping heating the fluid contact portion, and based on the temperature rise time and the temperature drop time, converts a determined flow velocity into a flow rate value so as to perform flow rate determination.