Flow dependence of interfacial thermal resistance in nanochannels

Abstract

In nanochannel flows, the thermal resistance at the fluid-solid interface may depend on the flow scenario. In this work, we study the interfacial thermal resistance R th in nanoscale force-driven flows at different temperatures and fluid-wall interactions. For Ar flows in Cu and Ag channels, the fluid-wall binding energy is strong and it is found that R th assumes a maximum value as the external force is varied. The maximum value is caused by the fluid adsorption on the solid surfaces and the temperature increase in the fluid due to viscous frictions. However, when the fluid-wall interaction is weak, the maximum value is not observed and the interfacial thermal resistance decreases monotonously with increasing external force. With the presence of fluid adsorption, it is also found that the peak in R th is more detectable at low temperature than high temperature. © 2010 American Institute of Physics. ͓doi:10.1063/1.3327931͔ Thermal management is a key issue in the design of electronic devices. Among the available techniques, the liquid-based cooling methods are quite promising in removing the heat in high-power devices. [1][2][3][4] In certain liquid-based cooling systems, liquid coolants are circulated through micro-or nanoscale channels, which are attached to the heat sources, such as chips. The cooling capacity of such methods depends on the flow rate and thermal resistance at the liquidsolid interface. The flow rate can be controlled by a pump and a high flow rate is usually desired to enhance the cooling capacity. The interfacial thermal resistance R th depends on many parameters, such as the fluid-wall interaction, surface structure, and temperature. 5-10 Our recently work indicates that R th is also associated with the flow rate and the effect of flow rate on the thermal resistance is coupled with the fluidwall interaction and temperature. 11 However, the detailed information about the dependence of R th on the flow rate is unavailable. The coupling of the flow rate, fluid-wall interaction, and R th could be nonlinear and may defy our intuitive understanding that high flow rate improves the cooling capacity. Therefore, it is necessary to explore the relationship between the flow rate and R th under various conditions. This is also important in the design and optimization of liquidbased cooling techniques.Compared with experiments, molecular dynamics ͑MD͒ simulations offer an easy way to investigate the effects of various parameters on the thermal resistance at the fluidsolid interface. 5-15 Most of the previous MD studies are mainly focused on how the surface wettability ͑or fluidsurface binding energy͒ and structure are related to R th . Little work has been carried out to understand the effect of flow rate on R th . In addition, how the thermal resistance is coupled with the flow rate may be affected by the fluid-surface interaction parameters and the fluid heating due to various sources of friction. 11 Although the relationship between the thermal and velocity slips has been numerically investigated, 7 ...

On the validity of the Navier-Stokes equations for nanoscale liquid flows: The role of channel size

“…For large channels, the temperature of the fluid can be much higher than the thermostat applied to the wall due to viscous frictions. 37,38 To maintain a uniform temperature in the whole system, the external force applied on the fluid molecules are carefully controlled. In nanoscale flows, fluid adsorption on solid surfaces is a popular phenomenon, which leads to new flow behaviors.…”

Molecular dynamics modeling of thermal resistance at argon-graphite and argon-silver interfaces

“…Torii et al showed that the energy transfer in directions parallel to the interface are governed by surface corrugations at the molecular-scale, and energy transfer in the direction perpendicular to the surface is governed by the molecular number density on solid surfaces [10]. More recently, Liu et al investigated flow dependence of the interface thermal resistance of argon in copper and silver channels, and found "solid like" behavior of argon near the walls [11]. These authors reported increased thermal resistance due to adsorption of argon on the walls.…”

Dependence of nanoconfined liquid behavior on boundary and bulk factors

“…Boundary factors originate from the solid-liquid interface, and the influence extends into the liquid bulk. These include the solid-liquid interaction [2][3][4][5][6][7][8][9][10][11][12][13][14], the commensurability of solid and liquid densities [3,4], solid structure [6,15], surface geometry [16], surface temperature [2], and so on. Bulk factors exist in the liquid bulk and the influence spreads to the boundary.…”

“…Bulk factors exist in the liquid bulk and the influence spreads to the boundary. These include the driving force [5,[7][8][9]14], shear rate [11,13], flow rate [5,7,8], dissipation heat [10,11], liquid temperature [7], temperature gradient [2], and so on. Generally speaking, competition exists between the two types of factors at all scales, and confined liquid behavior is the consequent balance of the combined effect.…”