Experimental study on spray flash evaporation under high temperature and pressure

Cai, Benan; Zhang, Qi; Yang, Jin Long; Gu, Hongfang; Wang, Haijun

doi:10.1016/j.ijheatmasstransfer.2017.06.017

Cited by 17 publications

(9 citation statements)

References 33 publications

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“…There was a small change in the volume size of the jujube slices because FD freezes the water into ice crystals, and the ice is directly removed by vaporization under high vacuum (Yang et al., 2019). HD causes a slow evaporation of water and serious volume shrinkage of the jujube slices because of the high temperatures involved were observed (Cai et al., 2017). PPD volatilizes water rapidly using a pressure difference, thus, the shrinkage of the jujube slices was better than that of the hot‐air dried samples.…”

Section: Resultsmentioning

confidence: 99%

Effect of different drying methods on the quality and microstructure of fresh jujube crisp slices

Wang

Gao

Zhao

et al. 2020

J. Food Process. Preserv.

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This study investigated the effects of different drying methods, including hot‐air drying (HD), freeze drying (FD), and pressure‐differential puffing drying (PPD), on the quality and microstructure of fresh jujube crisp slices. Our data confirmed that PPD has the best effect, followed by FD and HD. Crisps dried using FD had good color and the best rehydration rate, shrinkage volume rate, and apparent density. The color, rehydration, and hardness of fragile chips by PPD and FD were similar; jujube slice volume shrinkage and density increase were due to water evaporation during drying. The bioavailability and microstructure of PPD was the best. Polysaccharide and total phenol bioavailability was the highest in PPD samples and remained stable, with clear porous structure and a smaller folding structure, indicating that PPD maintains the porous cell structure. Thus, PPD provides high quality fresh jujube crisp slice products due to uniform honeycomb network and less collapsed structure. Practical applications Jujube is a fruit grown in China. This study provides technical information and theoretical basis for the production of puffed dry food, which is widely used in food production. First, the crisps obtained can be directly graded, packaged, sold, and transformed into green snack food; these techniques can be applied to other fruits, such as cantaloupe, apricot, and carrot. Second, dried fruits and vegetables were directly processed into ultra‐micro nutrient powder, which retains its flavor to a large extent. Furthermore, the dried powder may be used as auxiliary materials or seasoning in the processing of other foods to improve the color and flavor of the product. Processing fresh jujube into crisps can widen its industrial applications and add value to its products.

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Section: Resultsmentioning

confidence: 99%

Effect of different drying methods on the quality and microstructure of fresh jujube crisp slices

Wang

Gao

Zhao

et al. 2020

J. Food Process. Preserv.

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“…If the liquid is exposed to a sudden pressure reduction it becomes superheated and starts to evaporate, as the vapor pressure of the liquid exceeds the ambient pressure 4. In static flash evaporation, a vacuum is applied to a steam boiler 15, while dynamic flash evaporators use an orifice to eject a liquid into a vacuum chamber 6, 10. Dynamic flash evaporation starts with bubble nucleation at the orifice exit, as the liquid rapidly approaches boiling conditions with the release in pressure.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…A dynamic flash evaporation generates a spray of very small and fast droplets, predominantly in the two‐digit µm and m s −1 ‐scale, respectively 5–7. A variety of articles studies flash evaporation directly at the point of origin near the nozzle exit in order to elucidate the impact of several parameters like initial liquid temperature, pressure gradient and degree of superheat on the jet formation, shattering and atomization for evaluation of the evaporation process 8–10. Studies focusing on the impact of flashing jets in a spatially larger scale as for instance on entrainment in separation plants are rare.…”

Section: Introductionmentioning

confidence: 99%

Droplet Entrainment Analysis in a Flash Evaporator with an Image‐Based Measurement Technique

Jasch

Schulz

Bart

et al. 2021

Chemie Ingenieur Technik

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Local droplet sizes and volumes of entrained liquid are captured with an image-based measurement technique for comparison with a conventional, integral method for entrainment analysis. Experiments in a forced circulation flash evaporation were performed for different operating conditions and with two different chemical systems. Droplet size and frequency rise with an increase in thermal energy input. The local readings confirm the trends found by the integral measurement method. The modification of the image-based probe enables the detection of small ( 10 mm) and at the same time fast droplets under challenging operating conditions, such as vacuum and superheated feed similar to industrial process conditions.

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“…To assess the effect of the ambient 235 pressure, experiments have been performed in vacuum (Kurschat et al, 1992;Lecourt et al, 2009;Vetrano et al, 2013;Du et al, 2013;Xu et al, 2013;Lamanna et al, 2014;Luo and Haidn, 2016;Guo et al, 2018) as 240 well as in high pressure chambers Cai et al, 2017). Water has been commonly used as a test liquid (Park and Lee, 1994;Du et al, 2013;Günther and Wirth, 2013;Pavlenko et al, 2013;Cai et al, 2017;Sinha et al, 2018).…”

Section: Experimental Studies and Measurementsmentioning

confidence: 99%

“…Flash-boiling water has been used to increase the relative humidity (Cai et al, 2017). Other experimental investigations have used common organic solvents such as acetone (Lamanna et al, 2014), EtOH (Vetrano et al, 2013;Lamanna 250 et al, 2014;Lecourt et al, 2009;Xu et al, 2013) and MeOH (Xu et al, 2013;Zhang et al, 2015;Thompson and Heister, 2016).…”

mentioning

confidence: 99%

Ultra-high speed visualization of a flash-boiling jet in a low-pressure environment

Alghamdi

Thoroddsen

Hernández-Sánchez

2019

International Journal of Multiphase Flow

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Highlights• We visualized flash-boiling jets at an unprecedented frame rate of 5 Million frames per second. At such high frame rate we observed for the first time the evolution of the bubble expansion and the burst mechanisms, responsible for the jet atomization.• For developed flash-boiling conditions, minimum pixel intensity profiles revealed that droplets are ejected in all directions from the nozzle. This crucial fact was translated into spray angles larger than 300• .• The detailed close up to the nozzle revealed that the droplet size distribution of the spray is wide, contrary to the common belief. Using a simple argument we infer that the smallest droplets are on the hundreds of nanometer range. This means that the drop size distribution extends trough almost four orders of magnitude.• We measured velocities up to 140 m/s during the expansion of bubbles from the core of the jet. Such velocity is a bit less than half of the speed of a 0.22 bullet, an unprecedented velocity for expanding bubbles. AbstractWe visualize the flash-boiling atomization of liquid jets released into a low-pressure environment at frame rates of up to five million frames per second using a long distance microscope. Such temporal resolution allowed us to capture the details of the bubble expansion mechanism, responsible for the jet atomization, for the first time. We document an abrupt transition from a laminar to a fully external flashing jet by systematically reducing the ambient pressure. We perform experiments with different volatile liquids, ejected through micro-nozzles with different inner diameters. Surprisingly, minimum pixel intensity projections revealed spray angles close to θ s ∼ 360• and speeds of bubble expansion up to 140 m/s. Particle tracking shows that ejected droplets achieve speeds much larger than the jet velocity and drop sizes order of magnitude smaller than the diameter of the nozzle. Furthermore, hole growth speeds measured on the bubbles film in combination with to Taylor-Culick predictions suggests that the smallest droplet sizes are on the hundreds of nanometer or submicron range, which contravenes the general belief that flash-boiling atomization results in uniform drop sizes.

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Experimental study on spray flash evaporation under high temperature and pressure

Cited by 17 publications

References 33 publications

Effect of different drying methods on the quality and microstructure of fresh jujube crisp slices

Effect of different drying methods on the quality and microstructure of fresh jujube crisp slices

Droplet Entrainment Analysis in a Flash Evaporator with an Image‐Based Measurement Technique

Ultra-high speed visualization of a flash-boiling jet in a low-pressure environment

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