http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
대류 유동조건에서 Al₂O₃ 나노유체의 유효 열전도율과 비열
나영수(Young Su Na),오동욱(Dong-Wook Oh),이준식(Joon Sik Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
This study aims to figure out the effect of convective flow on the conventional specific heat and the formally reported effective thermal conductivity of Al2O3 nanofluid which has been obtained at a stationary state. The experimental conditions are fully developed laminar flow at a constant heat flux boundary condition through a circular tube. As a result, the Nusselt number of nanofluid is observed lower than the analytic value of 4.36. It implies that the specific heat of nanofluid under convective flow decreases through the increment of the volume flow rate.
대류 유동조건에서 알루미나-물 나노유체의 유효 열확산율에 대한 유동 영향
나영수(Young-Su Na),이준식(Joon Sik Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
This study aims to figure out the effect of convective flow on the effective thermal diffusivity of Al₂O₃-DI water nanofluids. The conventional thermal diffusivity is defined by the thermal conductivity and the heal capacity under a static state. In this study, the thermal diffusivity under convective flow is defined in terms of the temperatures of fluids and heated wall when the velocity and the temperature profiles are assumed fully developed in a circular tube under laminar flow and constant heat flux. The significant distinction between the effective thermal diffusivity under convective flow and that under a static state is observed due to flow dependence at the same thermal condition. The effective thermal diffusivity under convective flow shows stronger dependence on the velocity than the temperature.
알루미나 나노유체의 유효 열확산율에 대한 대류 유동조건의 영향
나영수(Young Su Na),이준식(Joon Sik Lee),김경덕(Kenneth D. Kihm) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
This study compares the effective thermal diffusivities of water-based Alumina nanofluid under convective flow condition with those under static condition. In general, the thermal diffusivity is defined by the thermal conductivity and heat capacity under static condition. In this study, the thermal diffusivities under fully developed laminar flow in a circular tube were calculated by measuring temperatures without using the thermal properties. In contrast with the strong temperature dependence on the effective thermal diffusivities under static condition, those under convective flow condition increased with decreasing mean fluid temperature induced by increasing volume flow rate at constant heat flux. This opposite trend of the temperature dependence on the effective thermal diffusivities under convective flow condition was explained by particle migration due to stronger thermophoresis diffusivity than Brownian diffusivity.
대류유동조건에서 나노입자를 포함한 콜로이드의 유효열전도율
나영수(Young Su Na) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
The effective thermal conductivity of a convective flowing colloidal system, called as the dynamic thermal conductivity, was measured, and it was compared with the effective thermal conductivity of a stationary colloid, called as the static thermal conductivity. Nano-sized alumina particles suspended in water are under the fully developed laminar tube flow with uniformly heating and cooling condition. In the heating condition, the dynamic thermal conductivity is lower than the static thermal conductivity, and it increases with the increment of the Reynolds number. In opposition to the heating condition, the dynamic thermal conductivity in the cooling condition is higher than the static thermal conductivity, and it decreases with the increment of the Reynolds number. This contrary trend of the dynamic thermal conductivity between heating and cooling conditions can be explained by thermophoresis that determines the behavior of nano-sized particles. The concentration of nano-sized particles suspended in water will be coarse or dense locally near the heating or cooling surface, respectively, and the thermophoretic velocity of dispersed particles depends on the temperature regarding the Reynolds number.