Thermal characterization of convective heat transfer in microwires based on modified steady state "hot wire" method

TL;DR

This paper introduces a modified steady state hot wire method that simplifies measuring convective heat transfer coefficients of microwires without needing thermal conductivity data, validated through experiments with various materials and diameters.

Contribution

A novel MSSHW method for measuring microwire convection heat transfer coefficients without thermal conductivity knowledge, verified against traditional methods and empirical data.

Findings

MSSHW method accurately measures convection heat transfer coefficients.

Convection coefficient increases as microwire diameter decreases.

Material type has little effect on convection coefficient.

Abstract

The convection plays a very important role in heat transfer when MEMS work under air environment. However, traditional measurements of convection heat transfer coefficient require the knowledge of thermal conductivity, which makes measurements complex. In this work, a modified steady state "hot wire" (MSSHW) method is proposed, which can measure the heat transfer coefficient of microwires' convection without the knowledge of thermal conductivity. To verify MSSHW method, the convection heat transfer coefficient of platinum microwires was measured in the atmosphere, whose value is in good agreement with values by both traditional measurement methods and empirical equations. Then, the convection heat transfer coefficient of microwires with different materials and diameters were measured by MSSHW. It is found that the convection heat transfer coefficient of microwire is not sensitive on materials, while it increases from 86 W/(m$^2$K) to 427 W/(m$^2$K) with the diameter of microwires decreasing from 120 ${\mu}$m to 20 ${\mu}$m. Without knowing thermal conductivity of microwires, the MSSHW method provides a more convenient way to measure the convective effect.