Cavity reentrant

One variation in dye laser constmction is the ring dye laser. The laser cavity is a reentrant system, so that the laser light can circulate in a closed loop. The ring stmcture provides a high degree of stabiUty and a narrow spectral width. The spectral width of a conventional dye laser on the order of 40 GH2 is narrowed to a value as small as a few MH2. Such systems offer very high resolution in spectroscopic appHcations. 

Klein D, Hetsroni G, Mosyak A (2005) Heat transfer characteristics of water and APG surfactant solution in a micro-channel heat sink. Int J Multiphase Flow 31 393 15 Kosar, A, Kuo, CJ, Peles, Y (2005) Boiling heat transfer with reentrant cavities. Int. J. Heat Mass Transfer 48 4867-4886... 

Smooth, with artificial reentrant cavities [with diameters of outer circular openings of 0.15-0.20 mm (0.006-0.008 in.)]... 

Goodwin, A.R.H. and Mehl, J.B., Measurement of the dipole moments of seven partially fluorinated hydrocarbons with a radiofrequency reentrant cavity resonator, Int. J. Thermophysics, 18, 795-806, 1997. 

Kubo, H., Takamatsu, H., and Honda, H., 1999, Effeets of Size and Number Density of Miero-Reentrant Cavities on Boiling Heat Transfer from a Silieion Chip Immersed in Degassed and Gas-Dissolved FC-72 , J. Enhanced Heat Transfer, Vol.6, pp.151-160... 

Machined Kun and Czikk [23] Cross-grooved and flattened Regular matrix of reentrant cavities... 

Hwang and Moran [25] Laser drilling Regular matrix of slightly reentrant cavities... 

Formed Webb [26] Standard low-fin tubing with fins bent to reduce gap Helical circumferential reentrant cavities... 

Nakayama et al. [28] Rolled, upset, and brushed Helical circumferential or groove-type reentrant cavities with periodic openings... 

Coated Marto and Rohsenow [31] Poor weld Irregular matrix of surface and reentrant cavities... 

Oktay and Schmeckenbecher [33] Electrolytic deposition Irregular matrix that includes reentrant cavities... 

The heat flux at this condition is referred to as the critical heat flux, or CHF. It depends on the flow conditions, channel geometry, local quality, fluid properties, channel material, and flow history. Bergles and Kandlikar [8] discuss the CHF in microchannels from a systems perspective. It is important to establish CHF condition as a function of the mass flux and quality for a given system to ensure its safe operation. Qu and Mudawar [9] presented CHF data with water in 21 parallel minichannels of 215 x 821 pm cross-section over a range of G = 86—268 kg/(m s) and q" = 264-542 kW/m r = 0.0-0.56, and Fi = 121.3—139.8 kPa. Kosar et al. [5] present low-pressure water data in microchannels enhanced with reentrant cavities. Also, the correlation by Katto [10] developed for large channels may be applied for approximate CHF estimation in the absence of an established CHF correlation for microchannels. 

Kosar A, Kuo C, Peles Y (2005) Reduced pressure boiling heat transfer in rectangtdar microchaimels with interconnected reentrant cavities. J Heat Transf 127 1106-1114... 

We will consider only three types of cavities a crevice (an extended V shape, such as might be produced by a scratch) with a triangular cross section, a conical pit, and a reservoir with an arbitrary, but reentrant shape. These cases are schematically shown in Fig. 15. 

FIG. 15 Three possible gas reservoirs On the left (a), a crevice (extended perpendicular to the plane of the page) or conical pit. On the right (b), a small-mouthed reentrant cavity. In each case, the opening radius is a. 

Of course, both types of cavity can be filled with vapor by a nucleation event followed by growth. In the case of the conical cavity or wedge, it has already been established that such reentrant sites are preferred for bubble nucleation, and with suitable roughness inside the reservoir cavity, this too, would act as a preferred place for nucleation. The chief difference is that nucleation can only fill the cavities with vapor not with noncondensable gases such as N2 or O2. 

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