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Experimental investigation of non-boiling gas-liquid two-phase flow in helically coiled micro-channel
(2026-05-15)
Benjawun, Phakkhanan
;
Chingulpitak, Sakkarin
;
Pratuyai, Kritsada
;
Wongwises, Somchai
;
Saisorn, Sira
The pressure drop (dP) and flow pattern are presented for two-phase flow in a helical micro-scale channel using an SS-304 tube of 1 mm diameter, having an equal coil pitch of 20 mm, and a coil pitch of 20 mm, all under constant surface heat flux situations. A flow visualization study was conducted, revealing various flow patterns, including bubbly flow, slug flow, churn flow, throat-annular flow, and annular flow. Additionally, the results demonstrated a higher pressure drop (dP) during churn flow in the channel.
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Adiabatic two-phase gas-liquid flow behaviors during upward flow in a vertical circular micro-channel
(2015-12-01)
Saisorn, Sira
;
Wongwises, Somchai
A two-phase air-water flow experiment was carried out to obtain flow pattern, void fraction, and pressure drop data from a vertical micro-channel, which was a fused silica tube with a diameter of 0.53. mm and a length of 320. mm. The adiabatic two-phase flow behaviors during vertical upward direction were experimentally investigated, and consequently, a buoyancy effect can be detected in this work. A flow visualization study was performed, leading to observation of slug flow, throat-annular flow, churn flow, annular flow, and annular-rivulet flow. The shape of the interfacial surface in the slug flow pattern was deformed during vertical upward flow, which was different from the bullet-shaped gas slug observed in the horizontal channel. The flow visualization results also indicate that the flow pattern map for vertical upward flow is not completely compatible with that for horizontal flow. Image analysis was performed to determine the void fraction, which increases linearly with increasing volumetric quality. The vertical upward flow gave a lower void fraction than the horizontal flow. The frictional pressure drop can be increased when the churn flow is formed in the channel. In addition, vertical upward flow can result in higher pressure drop when compared with the horizontal channel.
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Heat transfer characteristics of gas-liquid flow in horizontal rectangular micro-channels
(2014-05-01)
Saisorn, Sira
;
Kuaseng, Piyawat
;
Wongwises, Somchai
An experimental study of heat transfer characteristics of air-water flow in horizontal micro-channels was carried out in this work. The gas-liquid mixture from a y-shaped mixing chamber was forced to pass through a plenum inlet and entered 21 parallel rectangular micro-channels 40. mm long in the direction of flow. Each channel had a width and a depth of 0.45 and 0.41. mm, respectively. The test runs were done at a heat load of 80. W, with superficial Reynolds numbers of gas and liquid ranging between 54-142 and 131-373, respectively. A Stereozoom microscope and camera system were employed to conduct flow visualization. To explore the dependence of a Nusselt number on the flow characteristics, two inlet sections with different designs were used in this work. The experiments revealed that the formation of small gas slugs instead of gas core flow involves an increase in Nusselt numbers. In this work, the gas-liquid flow gave heat transfer enhancement up to 80% over the liquid flow. © 2014 Elsevier Inc.
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A critical review of recent investigations on two-phase pressure drop in flow boiling micro-channels
(2012-01-01)
Saisorn, Sira
;
Wongwises, Somchai
Two-phase pressure drop during flow boiling has been studied for several decades. Obviously, the publications available on micro-channels are relatively small compared with those for ordinarily sized channels. Although the use of micro-channels yields several advantages, the pressure drop taking p lace in these extremely small channels is higher than that in the ordinarily sized channels because of the increased wall friction. The knowledge of the two-phase pressure drop characteristics in addition to heat transfer phenomena is essential to the design and evaluation of the micro-systems. In this paper, recent research on the flow boiling pressure drop in micro-scale channels is reviewed. The experimental results as well as the relevant prediction methods based on different researchers are presented.
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A critical review of recent investigations on flow pattern and heat transfer during flow boiling in micro-channels
(2012-01-01)
Saisorn, Sira
;
Wongwises, Somchai
A summary of recent research on flow boiling in micro-channels is provided in this article. This review aims to survey and identify new findings arising in this important area, which may contribute to optimum design and process control of high performance miniature devices comprising extremely small channels. Several criteria for defining a micro-channel are presented at first and the recent works on micro-scale flow boiling are subsequently described into two parts including flow visualization and two-phase heat transfer. The results obtained from a number of previous studies show that the flow behaviours and heat transfer mechanisms in micro-channels deviate significantly from those in ordinarily sized channels. Future research with numerous aspects of flow boiling phenomena necessary to answer the fundamental questions is still required.
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Two-phase air-water flow in micro-channels: An investigation of the viscosity models for pressure drop prediction
(2011-02-01)
Saisorn, Sira
;
Wongwises, Somchai
Adiabatic two-phase air-water flow is experimentally studied in this work. Two channels, made of fused silica, with different diameters of 0.53 and 0.15. mm are used as test sections. The void fraction data for both tubes are obtained by image analysis. For the larger channel, the void fraction is found to be a linear relationship with the volumetric quality. In the case of the smaller one, however, the non-linear void fraction is obtained. The measured frictional pressure drop data are compared with the predictions regarding the homogeneous flow assumption. Several well-known two-phase viscosity models are subsequently evaluated for applicability to micro-channels. © 2010 Elsevier Ltd.

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