Heat exchanger
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Solution Overview
Problem
The challenge in accurately measuring the temperatures of working fluids in stacked microchannel heat exchangers due to errors from heat conduction, temperature differences, and non-uniform temperature distributions, especially when temperature sensors are not in direct contact with the fluids.
Innovation Solution
The placement of temperature sensors' sensing points within the core region formed downstream of the flow adjustment ring in the inlet and outlet pipes ensures direct contact with the working fluids, allowing for accurate temperature measurement by maintaining constant velocity and uniform temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If temperature sensors are attached to the outer surface of pipes by soldering, then the temperature sensors can be easily installed, but the sensing point is not in direct contact with the working fluid causing measurement errors
Solution Approach 1:
The sensing point is extracted from the pipe wall and placed directly into the working fluid flow. The temperature sensor is positioned such that its sensing point extends into the pipe interior to directly contact the working fluid, separating the measurement function from the pipe wall attachment method.
Solution Approach 2:
The pipe wall acts as an intermediary that transmits thermal energy from the working fluid to the temperature sensor. By having the sensing point directly contact the working fluid, the thermal intermediary path is minimized, reducing measurement errors due to heat conduction through the pipe wall.
2Measurement precision
If the sensing point is placed in the pipe where working fluid flows, then direct contact with working fluid is achieved, but non-uniform temperature distribution and velocity profiles cause measurement errors
Solution Approach 1:
The flow adjustment ring is installed upstream of the temperature sensor to pre-condition the flow before measurement. It creates a flow pattern with a defined core region that has relatively uniform velocity and temperature distribution, preparing the working fluid for accurate temperature measurement.
Solution Approach 2:
The temperature sensor is positioned specifically in the core region of the pipe flow, where the velocity and temperature distribution are more uniform compared to other regions. This localized positioning exploits the favorable flow characteristics of the core region for accurate measurement.
3Reliability
If heat is exchanged between two working fluids, then heat exchange capability is achieved, but temperature differences between inlet and outlet pipes cause heat conduction errors
Solution Approach 1:
The temperature measurement function is extracted from the pipe wall attachment method and placed directly in the working fluid. This eliminates the heat conduction path through the pipe wall that would otherwise be affected by temperature differences between inlet and outlet pipes.
Solution Approach 2:
The temperature difference between inlet and outlet pipes, which normally causes heat conduction errors, is converted into a benefit by using direct immersion measurement. The sensing point directly measures the working fluid temperature without being affected by heat conduction through the pipe wall, turning the temperature gradient into an opportunity for accurate measurement.
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 enables precise temperature measurement of working fluids, reducing measurement errors and improving the accuracy of heat exchange calculations and temperature control in heat exchangers.
Implementation Method 1
the core region with a relatively constant velocity and a uniform temperature distribution is formed
Implementation Method 2
the sensing point of the temperature sensor is arranged in the core region... allowing for accurate temperature measurement by maintaining constant velocity and uniform temperature distribution
Data Source
Figure 1
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Figure 3
AI summary
In order to correctly measure a temperature of a working fluid flowing through an outlet/inlet of a heat exchanger body, a flow adjustment ring is disposed within at least either one of a high-temperature inlet pipe and a low-temperature inlet pipe of the heat exchanger body. In this manner, a core region in which velocity and temperature of the working fluid becomes approximately constant is formed on a downstream side of the flow adjustment ring. A temperature sensor is provided in such a manner that a sensing point is arranged in this core region.