Double slug interaction in downward-facing nucleate boiling was studied to investigate its effect on boiling performance. Two heating surfaces were individually controlled to apply heat flux while their boiling performance were measured. A slug generated from upper heater affect on lower heater to make convectional flow by suction following departure of slug. Moreover, it showed to reduce hovering time of slug bubble on lower heater because it could help bubble departure on lower heater. Meanwhile, a slug generated from lower heater affected on upper heater to make convectional flow by sweeping. However, it showed to increase hovering time of slug bubble on upper heater, because they collapsed to each other. So, the slugs from lower heater enhanced the boiling performance of upper heater with low heat flux condition, but reduced the performance of it with high heat flux condition.

This paper reports slug bubble dynamics on modified surface with two-dimensional graphene film in downward-facing nucleate boiling. Behaviors of slug bubbles were observed with high speed camera, and post-processing was followed to measure departing speed, frequency, and diameter of slug bubbles, which were important to analyze boiling performance change. The graphene-modified surface showed enhanced boiling heat transfer coefficient (BHTC) and critical heat flux (CHF). The effect of surface modification on slug bubble dynamics was quantitatively analyzed; bigger slugs departed from the modified surface with faster speed but same frequency, compared with the bare. It seems that the BHTC enhancement is caused by increase of bubble diameter, resulting in increase of its departing speed. The higher speed of departing bubble could extend the hydrodynamic limit of vapor removal from downward-facing surface, so that CHF performance could be enhanced.

A two-phase flow in mini-channels is consist with various flow regimes (such as bubble slug, annular, churn flow) according to gas and liquid phase flow rates. A previous researches revealed that in a case of slug flow in hydrophobic mini-channels, gas and liquid phase are perfectly separated by interfaces and triple contact line. In this study, the single dry slug flow experiments in circular mini-channel (D = 1.018 mm) are conducted to observe interfacial break-up phenomena in high capillary number range (Ca < 0.02). The slug is consist with D.I. water or D.I. water-ethanol binary mixtures (5% and 10%, mole fraction). On the base of previous researches, we calculate the pressure drop at moving triple contact line. In an addition, a single dry slug flow is visualized by using high-speed camera. Through the experiment, three regimes of pressure drop are observed; steady, loss, separation. As a result, criteria between steady and loss regimes is closely related to capillary number, and criteria between loss and separation regimes is related to surface tension.

This paper reports an uncertainty analysis of quantitative visualization methodology for slug bubble dynamics in downward-facing nucleate boiling condition. Measurement of dynamics of slug bubble, i.e. departing speed, frequency, and diameter, is very important to predict safety margin of thermal systems in moving vehicle. By employing high speed visualization and post-processing, we quantitatively measured the volume and location of slug bubble, so that vapor generation rate and departing speed data were derived from their time differentiation. As a visualization methodology, its reliability was evaluated via uncertainty analysis. For 95% confidence interval, uncertainty of vapor generation rate and departing speed were 3% and 2%, respectively, and which were one order lower than standard deviation of those data.

At a two phase flow, according to gas and liquid phase flow rates, various flow regimes are developed such as bubbly, slug/plug, churn, annular, droplet flow and so on. At a two phase flow in small scaled channels, among various flow regimes, the intermittent flows such as bubbly, slug/plug flow are developed in the broad regions of two phase flow pattern map. In particular, the flow regimes are influenced by surface wettability. In a case of slug flow in hydrophobic small scaled channels, gas and liquid phases are perfectively separated by interfaces and contact line. The pressure drop of the two-phase flow is largely generated at moving contact line. Therefore, to well design two-phase flow system with small scales, it is important to estimate the pressure drop at moving contact line. In this study, on the basis of previous research, the pressure drop at moving contact line is experimentally measured for a various fluids (0-40% water-ethanol mixtures). And, the previous correlation to estimate pressure drop at moving contact line is verified by experimental data. In an addition, we discuss interfacial broken phenomena of slug flow in a minichannel. (D=1.555mm).

The volume of fluid method is used to investigate the behavior of a liquid water slug in a PEMFC trapezoidal gas channel(GC) with a open angle of 60 degrees. To evaluate the effect of the contact angle of the top and side walls, the gas diffusion layer water coverage ratio(GWCR) and water volume fraction(WVF) in a inspection control volume are analyzed. As the contact angle increases, GWCR increases and WVF decreases. The cases with the GC contact angle of 60 and 80 degrees show the more favorable water removal characteristics compared to the other cases in a GC flooding condition.

 ,  , This study was conducted to investigate food preference and developmental characteristics of the gray field slug, Deroceras reticulatum Muller (Stylommatophora: Limacidae) using various foods. The food preference of D. reticulatum was most highest on Chinese cabbage (Brassica campestris L.), followed on cucumber (Cucumis sativus L.), and significantly low on beet (Beta vulgaris var. Ruba), kale(Brassica oleracea L. var. acephala D.C), carrot (Daucus carota L.) and Chinese cabbage (Brassica campestris L.) which were not different significantly. The total number of eggs laid by D. reticulatum was the highest (n = 109.6) on cucumber and the lowest (n = 10.1) on leaf perilla (Perilla frutescens var. japonica Hara). Hatchability was the highest (92.4%) on cucumber and the lowest (62.5%) on leaf perilla. The egg developmental period was not significantly different from 12 days to 13 days among host plants. Juvenile period and adult longevity ranged from 75 days to 111 days and 66 days to 187 days, respectively. Thereby, life span from egg to adult longevity of D. reticulatum was the longest on cucumber with 273 days and the shortest on 190 days on leaf perilla.

The egg size and weight of the gray field slug, Deroceras reticulatum Müller, was 1.91×2.19 ㎜ and 3.3 ㎎ at 24℃, respectively. Its weight increased from newly laid eggs to adults for 17 weeks at four temperature regimes and was heaviest at 20℃, followed by 24, 16 and 28℃. Likewise, hatching rate of the egg batches was highest with 95% at 20℃, followed by 24, 16 and 28℃ with significant differences. The number of eggs in the batches was increased with 20 at 20℃ while it was only 10 at 28℃. The average accumulated egg-laying days was longest with 15 days at 20℃ while shortest with 9 days at 24℃. The range of egg-laying period was shortest with 84-134 days at 16℃ and longest at 20℃. Thus, the total number of eggs laid by adult D. reticulatum was highest with 217 at 20℃ and lowest with 105 at 16℃. The egg period was 12-19 days while the juvenile period and adult longevity were 51-68 days and 85-134 days, respectively. The life span of D. reticulatum from egg to adult was longest with 216 days at 20℃, followed by 193 days at 24℃, 170 days at 16℃ and 151 days at 28℃. Accordingly, the most favorable temperature for the oviposition, development and longevity of D. reticulatum is 20℃.

Grey field slug, Deroceras reticulatum Muller, is one of the major pests of chinese cabbage, Brassica campestris. To determine the economic thresholds of grey field slug on chinese cabbage, the slugs were inoculated after planting 1 week into chinese cabbages with a density of 0, 2, 4, 8, 16 slugs per 16 chinese cabbages(1㎡) at the plastic house in the spring and autumn of 2008. The rates of damaged cabbages by slug inoculation were 10.7% at 2 slugs and 42.7% at 16 slugs in the spring, and 20.3% at 2 slugs and 59.2% at 16 slugs in the autumn. The linear relationships between the initial slugs density and yield reduction of chinese cabbage were as following ; Y = 286.07x + 548.62, R2=0.9524(in the spring cultivation), Y = 318.91x + 998.05, R2=0.9323(in the autumn cultivation). Based on these results, the economic threshold of grey field slug per 16 chinese cabbages(1㎡) was 2.52 slugs in the spring and 0.86 slugs in the autumn.

Among various food base baiting materials, beer and macerated cucumber were the most effective to induce slug that is a troublesome pest on leafy vegetables, especially on lettuce. However, the baits attracted only but did not kill the pest. When the baits were combined with various insecticidal organic materials, a few combinations such as beer and cigarette mixture successfully induced and killed the slug in the field test. The most effective combination of beer 50 ㎖ and a cigarette contained in a small plastic box killed 25 slugs per night. While macerated cucumber 50 ㎖ and a cigarette mixture killed only 4.3 slugs. The bait of beer and cigarette mixture revealed 68.4% control value against slug damage when treated for 3 consecutive days in a lettuce cultivation greenhouse. The bait also effectively reduced the slug damage in a lettuce nursery showing 58.3% control value. The method seemed highly useful for the control of slug in the organic farming system in which application of pesticides are strictly prohibited.