Microwave heating: an evaluation of power formulations

Ayappa, K. G.; Davis, H. T.; Crapiste, Guillermo Hector; Davis, Elizabeth E.; Gordon, Joan

doi:10.1016/0009-2509(91)85093-d

Cited by 264 publications

(180 citation statements)

References 16 publications

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“…The slab was located in free space, so no other waves than the incident one would be involved. Solving Maxwell's equations ͑see, e.g., Stratton 7 or Ayappa et al 8 ͒ yields the classical wave equation in one dimension…”

Section: Theorymentioning

confidence: 99%

Thermal profiles and thermal runaway in microwave heated slabs

Vriezinga

1999

Journal of Applied Physics

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Asymptotic expressions describing radiative heat transfer between polar materials from the far-field regime to the nanoscale regime J. Appl. Phys. 111, 014311 (2012) Penetration depth in near-field radiative heat transfer between metamaterials Appl. Phys. Lett. 99, 143107 (2011) Near-surface silica does not increase radiative heat dissipation from plant leaves Appl. Phys. Lett. 99, 024104 (2011) Maximum near-field radiative heat transfer between thin films Appl. Phys. Lett. 98, 243120 (2011) Cryogenic apparatus for study of near-field heat transfer Rev. Sci. Instrum. 82, 055106 (2011) Additional information on J. Appl. Phys. The microwave heating of slabs of water bound with a gel is modeled and analyzed without any restriction to the Biot number regime. Despite the fact that the temperature distribution over the slab is not uniform at all, the phenomenon of thermal runaway is basically caused by resonance of the electromagnetic waves within the object, combined with heat loss. A plot of the steady-state temperature at any position within the slab, versus the microwave power, is an S-shaped or a multi S-shaped curve. With respect to thermal runaway there is a strong similarity between isothermal and nonisothermal slabs. Using the average temperature of the nonisothermal slab, regardless of its Biot number, yields a reasonable approximation to describe the runaway. This is caused by the specific characteristic of the dielectric loss factor of water, which decreases with increasing temperature. This results in an almost constant absorption of energy over the whole slab without disturbing the wave character of the absorption. It turned out that this smoothing of the absorbed power plays a dominant role in the calculations of the temperature profiles. Any calculation where the temperature dependence of the permittivity is omitted, will not only pass the phenomenon of thermal runaway, but its temperature profiles will differ substantially from the ones where the temperature dependence has been taken into account.

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Section: Theorymentioning

confidence: 99%

Thermal profiles and thermal runaway in microwave heated slabs

Vriezinga

1999

Journal of Applied Physics

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“…The volumetric heating term (q) in equation (2) is strongly influenced by the geometry of the heated material. Ayappa et al [2] demonstrate that the equation for electromagnetic power distribution generated in a slab of thickness (W) can be described by:…”

Section: A Brief Review Of Microwave Heating In Moist Materialsmentioning

confidence: 99%

“…All these frequencies interact to some degree with moist materials. The major advantages of microwave heating are its short startup, precise control, and volumetric heating [2]. In industry, microwave heating is used for drying [2][3][4][5], oil extraction from tar sands, cross-linking of polymers, metal casting [2], medical applications [6], pest control [7], enhancing seed germination [8], and solvent free chemistry [9].…”

Section: Introductionmentioning

confidence: 99%

Applications of Microwave Heating in Agricultural and Forestry Related Industries

Brodie¹

2012

The Development and Application of Microwave Heating

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“…Although in some cases, thermal and dielectric properties may be assumed to be temperature-independent [78], the knowledge of the function * (,) r T εω of a material is a necessary and key condition to implement the numerical simulation of interaction between microwave and the material. There is a lot of basic work that has been done for this area [66] reaction to determine the complex permittivity of the reactant, because it varies not only with temperature, but also with reaction duration time.…”

Section: Txy Zt T Xy Zmentioning

confidence: 99%