Two-phase flow through a staggered tube bundle of a shell and tube heat exchanger

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Two-phase flow on the shell side of a shell and tube heat exchanger is complex. This paper contributes to the existing data base by presenting data for void fraction and pressure drops for tubes with a diameter of 19 mm. Results for air-water flows near atmospheric pressure are presented. The results were obtained for flows through a column of a thin-slice, staggered tube bundle containing 22 rows. It contained four full columns of tubes and two columns of half tubes placed on the shell walls. The tubes were 19 mm in diameter and 50 mm long with a pitch to diameter ratio of 1.32 and were arranged in a staggered triangular configuration. Previous studies have shown that the void fraction in a shell-side, gas-liquid flow becomes constant after only a few rows. Thus, the void fraction was only measured at one location. A gamma-ray densitometer was used to measure the void fractions. Corresponding pressure drops were obtained between rows 3 and 15. Data are presented for a mass flux range of 25-688 kg/m2s and a gas mass fraction range of 0.0005-0.6. The measurements are shown to compare reasonably well with correlations available in the open literature.cf201

Two-phase flow through a staggered tube bundle of a shell and tube heat exchanger

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Two-phase flow on the shell side of a shell and tube heat exchanger is complex. This paper contributes to the existing data base by presenting data for void fraction and pressure drops for tubes with a diameter of 19 mm. Results for air-water flows near atmospheric pressure are presented. The results were obtained for flows through a column of a thin-slice, staggered tube bundle containing 22 rows. It contained four full columns of tubes and two columns of half tubes placed on the shell walls. The tubes were 19 mm in diameter and 50 mm long with a pitch to diameter ratio of 1.32 and were arranged in a staggered triangular configuration. Previous studies have shown that the void fraction in a shell-side, gas-liquid flow becomes constant after only a few rows. Thus, the void fraction was only measured at one location. A gamma-ray densitometer was used to measure the void fractions. Corresponding pressure drops were obtained between rows 3 and 15. Data are presented for a mass flux range of 25-688 kg/m2s and a gas mass fraction range of 0.0005-0.6. The measurements are shown to compare reasonably well with correlations available in the open literature.cf201

Self-amplification of coherent spontaneous emission in a cherenkov free-electron maser

Ultrashort pulses of microwave radiation have been produced in a dielectric-lined Cherenkov free-electron maser (FEM) amplifier. An intense initial seed pulse, due to coherent spontaneous emission (CSE), arises at the leading edge of the electron pulse. There is evidence to show that 3-4 cycle spikes are produced through the amplification of these seed pulses. A strong dependence of the start-up power on the rise time of the electron pulse has been found. The experimental results are verified by a theoretical analysis. Our study shows that amplification in a FEM amplifier is always initiated by CSE arising from the edge of the electron pulse when the rise time is comparable to the electromagnetic wave period

Psychology and aggression

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68264/2/10.1177_002200275900300301.pd

Flooding in a vertical tube

SIGLEAvailable from British Library Document Supply Centre- DSC:D82947 / BLDSC - British Library Document Supply CentreGBUnited Kingdo