Micro scale heat transfer

Kakac S, Vasiliev LL, Bayazitoglu Y, Yener Y (2005). Micro-scale heat transfer. Springer, Berhn Heidelberg. 

Zhang Z (2007) Nano/Micro-scale Heat Transfer. McGraw-Hill... 

Bayazitoglu, Y., and Tunc, G., (2002) Extended Boundary Condition for Micro-Scale Heat Transfer, AIAA/ASME Thermophysics Conference, in St Eouis, June 2002, Also published in Proceedings of theAlAA J. of Thermophysics and Heat Transfer, Vol.16 no. 3, pp.472-474. 

Mishan Y, Mosyak A, Pogrebnyak E, Hetsroni G (2007) Effect of developing flow and thermal regime on momentum and heat transfer in micro-scale heat sink. Int J Heat Mass Transfer 50 3100-3114... 

Celata GP, Cumo M, Marcom V, McPhail SJ, Zummo Z (2005) Micro-tube heat transfer scaling effects an experimental validation. In Proceedings of ECI International Conference on Heat Transfer and Fluid Flow in Microchannels, Caste/Vecchio PascoU, Italy, 25-30 September 2005... 

New questions have arisen in micro-scale flow and heat transfer. The review by Gad-el-Hak (1999) focused on the physical aspect of the breakdown of the Navier-Stokes equations. Mehendale et al. (1999) concluded that since the heat transfer coefficients were based on the inlet and/or outlet fluid temperatures, rather than on the bulk temperatures in almost all studies, comparison of conventional correlations is problematic. Palm (2001) also suggested several possible explanations for the deviations of micro-scale single-phase heat transfer from convectional theory, including surface roughness and entrance effects. 

Guo ZY, Li ZX (2002) Size effect on micro-scale single phase flow and heat transfer. In Proceedings of the 12th International Heat Transfer Conference, Grenoble, France, 18-23 August 2002... 

In our analysis, we discuss experimental results of heat transfer obtained by previous investigators and related to incompressible fluid flow in micro-channels of different geometry. The basic characteristics of experimental conditions are given in Table 4.1. The studies considered herein were selected to reveal the physical basis of scale effect on convective heat transfer and are confined mainly to consideration of laminar flows that are important for comparison with conventional theory. 

Gao P, Le Person S, Favre-Marinet M (2002) Scale effects on hydrodynamics and heat transfer in two-dimensional mini and micro-channels. Int J Themial Sci 41 1017-1027 Garimella SV, Sobhan CB (2003) Transport in micro-channels - a critical review. Ann Rev Heat Transfer 13 1-50... 

The solid-liquid two-phase flow is widely applied in modern industry, such as chemical-mechanical polish (CMP), chemical engineering, medical engineering, bioengineering, and so on [80,81]. Many research works have been made focusing on the heat transfer or transportation of particles in the micro scale [82-88], In many applications, e.g., in CMP process of computer chips and computer hard disk, the size of solid particles in the two-phase flow becomes down to tens of nanometres from the micrometer scale, and a study on two-phase flow containing nano-particles is a new area apart from the classic hydrodynamics and traditional two-phase flow research. In such an area, the forces between particles and liquid are in micro or even to nano-Newton scale, which is far away from that in the traditional solid-liquid two-phase flow. 

The last category is the pressure-driven gas flows, which are typical in micro gas fluidic and micro heat transfer systems. Because the channel diameter or width in micro gas fluidic systems is in the scale of sub-micrometer or less, ultra-thin gas lubrication theory plays an important role in... 

This paper describes work on equipment and instrumentation aimed at a computer-assisted lab-scale resin prep, facility. The approach has been to focus on hardware modules which could be developed and used incrementally on route to system integration. Thus, a primary split of process parameters was made into heat transfer and temperature control, and mass transfer and agitation. In the first of these the paper reports work on a range of temperature measurement, indicators and control units. On the mass transfer side most attention has been on liquid delivery systems with a little work on stirrer drives. Following a general analysis of different pump types the paper describes a programmable micro-computer multi-pump unit and gives results of its use. 

During the time the process gas spends in a micro channel, heat is transferred from the gas to the channel walls or vice versa. If in an exothermic reaction the time-scale for heat conduction in the channel walls is larger than the residence time of the fluid, considerable temperature gradients will build up along the walls... 

Worz et al. give a numerical example to illustrate the much better heat transfer in micro reactors [110-112]. Their treatment referred to the increase in surface area per unit volume, i.e. the specific surface area, which was accompanied by miniaturization. The specific surface area drops by a factor of 30 on changing from a 11 laboratory reactor to a 30 m stirred vessel (Table 1.7). In contrast, this quantity increases by a factor of 3000 if a 30 pm micro channel is used instead. The change in specific surface area is 100 times higher compared with the first example, which refers to a typical change of scale from laboratory to production. 

A detailed characterization of micro mixing and reaction performance (combined mixing and heat transfer) for various small-scale compact heat exchanger chemical reactors has been reported [27]. The superior performance, i.e. the process intensification, of these devices is evidenced and the devices themselves are benchmarked to each other. 

This is explained by a possible higher activity of pure rhodium than supported metal catalysts. However, two other reasons are also taken into account to explain the superior performance of the micro reactor boundary-layer mass transfer limitations, which exist for the laboratory-scale monoliths with larger internal dimensions, are less significant for the micro reactor with order-of-magnitude smaller dimensions, and the use of the thermally highly conductive rhodium as construction material facilitates heat transfer from the oxidation to the reforming zone. 

The main driver was to develop a laboratory-scale micro-channel process and transfer it to the pilot-scale, aiming at industrial fine-chemical production [48, 108]. This included fast mixing, efficient heat transfer in context with a fast exothermic reaction, prevention offouling and scale-/numbering-up considerations. By this means, an industrial semi-batch process was transferred to continuous processing. 

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