Dynamic Thermal Conductivity Measurement for Micro-Structure Fluids
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Solution Overview
Problem
Existing methods for measuring dynamic thermal conductivity of micro-structure fluids are inaccurate due to convection caused by centrifugal force, concentration, and temperature gradients, especially when the fluid amount is small, and they cannot maintain steady-state temperature conditions.
Innovation Solution
A device comprising an upper and lower fixing plate with a rotating plate in between, a heater, and thermocouples, which maintains micro-structure fluid in a dynamic state while minimizing heat loss and convection by controlling temperature differences between the plates, allowing for accurate measurement of thermal conductivity under steady-state conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a probe is immersed into micro-structure fluid for thermal conductivity measurement, then thermal conductivity can be measured, but convection is caused by centrifugal force and concentration gradients leading to measurement inaccuracy
Solution Approach 1:
The patent extracts the harmful probe immersion method and replaces it with a non-contact measurement approach. The measurement system is separated from the fluid by placing the measurement cell on a rotating platform, eliminating the direct probe immersion that causes convection while maintaining measurement capability through thermal coupling with the fluid in the cell.
Solution Approach 2:
The patent applies equipotentiality by rotating the entire measurement cell assembly at the same angular velocity as the fluid. This creates a co-rotating reference frame where centrifugal forces are balanced, eliminating relative motion between the measurement system and fluid that would otherwise generate convection currents and measurement errors.
2Loss of time
If the amount of micro-structure fluid is small, then measurement time is reduced, but maintaining steady-state temperature conditions becomes difficult
Solution Approach 1:
The patent uses a nested structure where the measurement cell is placed inside a temperature-controlled chamber or water bath. This nested configuration allows the small volume of fluid in the measurement cell to benefit from the thermal mass and temperature stability of the surrounding larger volume, maintaining steady-state conditions while using minimal fluid.
Solution Approach 2:
The patent implements a pre-conditioning step where the measurement system and fluid are brought to thermal equilibrium before the actual measurement begins. This skipping of the transient heating phase and direct transition to steady-state measurement reduces total measurement time while ensuring accurate temperature conditions are met.
3Ease of operation
If conventional hot-wire method is used, then measurement is simple and quick, but convection from density difference prevents accurate measurement
Solution Approach 1:
The patent eliminates convection by rotating the measurement cell and fluid together at the same angular velocity, creating a co-rotating reference frame. This equipotential approach balances centrifugal forces throughout the system, preventing density-driven convection currents that would otherwise disrupt the thermal field and compromise measurement accuracy.
Solution Approach 2:
The patent replaces the conventional stationary hot-wire probe with a rotating measurement cell system. Instead of using a mechanical probe that disturbs the fluid, the measurement is performed through thermal coupling with the rotating cell walls, substituting direct mechanical probe contact with a distributed thermal measurement approach that avoids localized convection.
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 precise measurement of dynamic thermal conductivity of micro-structure fluids even with small amounts, preventing convection and minimizing heat loss, thus providing accurate results under controlled temperature conditions.
Implementation Method 1
the heater is operated and a constant heat flux is applied
Implementation Method 2
thermocouples installed in each of the upper and lower fixing plates
Implementation Method 3
The micro-structure fluid sensitively varies depending on shear stress applied to the fluid
Data Source
AI summary
A device and method for measuring dynamic thermal conductivity of micro-structure fluid. The device includes an upper fixing plate (110a) and a lower fixing plate (110b) which are vertically spaced apart from each other, a lower body (150b) which defines a side surface of a separation space formed between the upper fixing plate and the lower fixing plate, a rotating plate (120) which is disposed in the separation space in such a way that gaps are respectively formed among the rotating plate and the upper and lower fixing plates, a shaft (140) which passes through the upper fixing plate and is coupled to the rotating plate, a heater which installed on an upper portion of the upper fixing plate, and thermocouples (118a) and (118b) which are respectively installed in the upper and lower fixing plates.