Microheater

The active micro-channel cooling contains a cooling system centered on a microheat collector that is fabricated much in the same way as the chip. Heat collector usually has a dense amount of micro-channels etched into the surface that works to transfer heat to a fluid, which is circulated through the entire package. 

Khmstalev D, Faghri A (1994) Thermal analysis of microheat pipe. J Heat Transfer ASME... 

Call, C., Microheater, in Proceedings of the 4th International Conference on Microreaction Technology, IMRET 4, pp. 308-313 (5-9 March 2000), AIChE Topical Conf. Proc., Atlanta, USA. 

S. Moller, J. Lin, and E. Obermeier. Material and Design Considerations for Low-Power Microheater Modules for Gas-Sensor Applications , Sensors and Actuators B25 (1995), 343-346. 

C. Rossi, E. Scheid, and D. Esteve. Theoretical and experimental study of silicon micro-machined microheater with dielectric stacked membranes . Sensors and Actuators A63 (1997), 183-189. 

Chemical sensors for mercury vapour, based on QMB, provide sensitivity of 0.7-5 ng/1 [24]. Reversibility is reached by heating the sensor a microheater can be integrated on the sensor surface. This detection principle was also used by several other groups, for example [7,9,25]. Another realization of this transducing principle is based on exploitation of gold-coated microcantilevers for mercury detection [21,22]. 

In a detailed process optimization study, the impact of the type of micromixers and process parameters was determined [56]. As a result, a pilot with a Toray Hi-mixer connected to a shell and tube microheat exchanger was constructed. Continuous operation for 24 h was carried out to obtain pentafluorobenzene (PFB) after protonation (92% yield). In this time, 14.7 kg of the product was produced, that is, about 5 t/a. Thus, the industrial-scale production carried out using a batch reactor (10 m3) can be replaced by adding only four microflow systems of the scale investigated. The pilot plant produces 0.5 kg in 6h continuous operation, thus about 730kg/a (see Figure 5.19). The name of the industrial company was not disclosed. 

Figure 16. (a) SEM of gas microsensor substrate prepared by localized porous-type anodization of Al. (b, c) Optical images of gas microsensor substrate without and with electrodes, (d) Packaged humidity sensor with microheater. Images reproduced from Ref. 7 with permission from ECS - The Electrochemical Society and from Ref. 69 with permission from ASME. 

C) completely refresh and reactivate the alumina surface. As a result, the sensor has the maximum sensitivity to a low humidity level every time humidity is measured. With the integrated microheater, the sensitivity limit was shown to be less than 1 ppm.69,74... 

Microstructured surfaces, as well as micromachined substrates and devices discussed in Sects. II, III, and iy are suitable for a number of applications. They include reflective and absorbing surfaces, wavelength-sensitive filters, multiaperture lens arrays and Fresnel microoptics, field emitter arrays, precision apertures, or molds for microstructured surfaces of other materials. Microstructured alumina ceramics can also be used for tuned broadband infrared emitters. In addition, due to the robustness at high temperatures and well-developed and controlled porosity, the freestanding, heat-treated micromachined anodic alumina substrates can be used for the fabrication of sensors that incorporate a high temperature microheater with low power consumption. 

Figure 7.20 (a) Photograph of the cross flow microheat exchanger and (b) schematic... 

Figure 7.21 Shell and tube microheat exchanger. Copyright 2005 American Chemical Society...

For example, thermally induced radical chlorination of alkanes can be conducted in a microtube reactor having microheat transfer modules. 

It is crucial to increase the capacity of the reactor for industrial applications, and to increase the capacity of a heat exchanger in a microflow system a shell and tube microheat exchanger, which contains 55 microtubes ((f) = 490 /xm) in the shell has been developed (Figure 10.6, see also Chapter 7). This is an example of internal numbering-up. The heat exchanger has only one inlet and one outlet, although it contains 55 microtubes inside. 

A microflow system for relatively large-scale production (i.e., a pilot plant) composed of a Toray Hi-mixer connected to a shell and tube microheat exchanger has been constructed (Figures 10.8 and 10.9). The... 

Fig. 14.6 Schematic diagram showing cross section of microheat exchangers (a) without and (b) with manifold [33. 34]...

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