Vacuum Gauge Thermal Management via Chimney Effect
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Solution Overview
Problem
Conventional vacuum gauges face challenges in cooling circuit boards within high-temperature sensor sections, leading to reduced sensitivity and shortened sensor life due to dew condensation and inadequate airflow, which can cause overheating and affect output stability.
Innovation Solution
A vacuum gauge design that utilizes a chimney effect by forming a flow path between the high-temperature sensor section and the circuit board, using an outer case to create a temperature gradient, allowing cold air to be pushed up towards the circuit board without external air application, with a tubular outer case and vents to enhance airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor section temperature is increased to prevent dew condensation, then the sensor sensitivity and life are improved, but the circuit board temperature increases causing overheating of electronic components
Solution Approach 1:
The housing is divided into a first housing accommodating the sensor section and a second housing accommodating the circuit board. This segmentation allows independent thermal management for each component, enabling the sensor section to operate at high temperature while the circuit board is cooled separately through the flow path formed between the two housings.
Solution Approach 2:
A flow path is formed between the first housing and second housing to introduce outside air as an intermediary cooling medium. This flow path allows cold outside air to pass through and cool the circuit board, while the sensor section maintains its high operating temperature, thus mediating the thermal conflict between the two components.
2Temperature
If vents are formed near the circuit board to cool it, then some cooling effect is achieved, but the temperature difference is insufficient and adequate airflow does not occur
Solution Approach 1:
The flow path extends in the vertical dimension from the bottom surface of the first housing to the top surface of the second housing, creating a tall, narrow passage. This vertical arrangement maximizes the temperature difference between the hot sensor section and the cooler outside air, enhancing the chimney effect and driving stronger natural convection currents through the flow path.
Solution Approach 2:
The flow path is positioned asymmetrically between the housings, with the first housing having a larger cross-sectional area than the second housing. This asymmetric configuration optimizes the flow dynamics and temperature gradient, allowing efficient heat transfer from the circuit board to the passing air current.
3Temperature
If outside air is blown into the vacuum gauge using a blower, then the circuit board cooling is improved, but a temperature distribution occurs in the sensor section affecting output stability
Solution Approach 1:
The system uses natural convection (chimney effect) driven by the temperature difference between the hot sensor section and the cooler outside air to generate airflow through the flow path. This self-service cooling mechanism eliminates the need for external blowers, preventing temperature distribution in the sensor section and maintaining output stability while still achieving effective circuit board cooling.
4Ease of operation
If vents are formed at positions slightly lower and higher than the circuit board, then some airflow is generated, but the temperature difference is almost non-existent and sufficient cooling does not occur
Solution Approach 1:
The flow path extends vertically through the housing structure, utilizing the vertical dimension to maximize exposure to the temperature gradient. By positioning the flow path to extend from the bottom to the top of the housing assembly, the design captures the full temperature difference between the hot sensor section and the cooler ambient air, enhancing natural convection without adding complex active cooling components.
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
Effectively cools the circuit board to its heat-resistant temperature or below, even at high sensor section temperatures (up to 200°C), without external air supply, maintaining stability and extending sensor life.
Implementation Method 1
a large temperature difference can be generated between an upstream and a downstream of this flow path. Since an air density gradient is generated between the upstream and the downstream of the flow path, cold air can be pushed up toward the circuit board by utilizing a so-called chimney effect
Data Source
AI summary
In a vacuum gauge that controls a temperature of a sensor section to a high temperature, a circuit board can be sufficiently cooled without applying air to the vacuum gauge from outside. The vacuum gauge includes a sensor section that communicates with a measurement space via a connection port and outputs an output signal according to a pressure in the measurement space, a heater provided around the sensor section to heat the sensor section, a circuit board arranged on a side opposite to the connection port with respect to the sensor section, a first inner case that accommodates the sensor section and the heater, a second inner case that accommodates the circuit board, and an outer case that surrounds the first inner case and the second inner case and forms a flow path, through which outside air flows, together with the first inner case and the second inner case.