Microfin tubes

Microfin tube data for R-123 are reported by Kedzierski [381], and tests of R-134a are described by Eckels et al. [382], these being the generally accepted, chlorine-free substitutes for R-ll and R-12, respectively. The general conclusion is that the enhancement is generally the same for the new refrigerants as for the traditional ones. 

Microfin tubes are widely used for in-tube convective condensation, as well as the evaporation applications noted in the previous subsection. 

S. Koyama, J. Yu, S. Momoki, T. Fujii, and H. Honda, Forced Convective Flow Boiling Heat Transfer of Pure Refrigerants Inside a Horizontal Microfin Tube, in Convective Flow Boiling, J. C. Chen ed., pp. 137-142, Taylor Francis, Washington, DC, 1996. 

Vibration mills are filled with 60-80 % spheres, cylpebs or rods. The grinding drum is attached to a frame on springs and is driven by an eccentric drive at a frequency of 1000-1500 rpm and amplitudes of approximately 10 mm. The tubes can be up to 4 m in length, with diameters of up to 0.65 m. The continuous operation is performed without classifier at throughputs of up to 15 tonnes per. Vibration mills are use for the microfine grinding of hard material (Fig. 14.9). 

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