Characteristics of Chamber Temperature Change During Vacuum Cooling

Zhao, Rui; Chen, Ertong; Lin, Mei-Ying; Sun, Da‐Wen; Xu, Binkai

doi:10.1111/j.1745-4530.2007.00208.x

Cited by 5 publications

(4 citation statements)

References 7 publications

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“…Considering the power consumption of vacuum pumps and the methane recovery, there is an optimum vacuum level for minimum specific power. 24 According to the first law of thermodynamics, 36 it is expected that the composite temperature would initially decrease as vacuum pressure decreases. As the decrease in vacuum pressure slows down, the surrounding heat (i.e., from column housing) is transferred to the composites, increasing the composite temperature and consequently resulting in temperature minima.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Enrichment of Ventilation Air Methane (VAM) with Carbon Fiber Composites

Bae

2014

Environ. Sci. Technol.

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Treatment of ventilation air methane (VAM) with cost-effective technologies has been an ongoing challenge due to its high volumetric flow rate with low and variable methane concentrations. In this work, honeycomb monolithic carbon fiber composites were developed and employed to capture VAM with a large-scale test unit at various conditions such as VAM concentration, ventilation air (VA) flow rate, temperature, and purging fluids. Regardless of inlet VAM concentrations, methane was captured at almost 100%. To regenerate the composites, the initial vacuum swing followed by combined temperature and vacuum swing adsorption (TVSA) was applied. It was found that initial vacuum swing is a control step for the final methane concentration having 5 or 11 times the VAM enrichment by one-step adsorption, which is, to our knowledge, the best performance achieved in VAM enrichment technologies worldwide. Five-time enriched VAM can be utilized as a principle fuel for lean burn turbine. Also, it can be further enriched by second step adsorption to more than 25% which then can be used for commercially available gas engines. In this way, the final product can be out of the methane explosive range (5-15%).

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Section: ■ Results and Discussionmentioning

confidence: 99%

Enrichment of Ventilation Air Methane (VAM) with Carbon Fiber Composites

Bae

2014

Environ. Sci. Technol.

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“…Typical operational parameters during the initial and final vacuum processes are plotted in Figure 6. As the vacuum pressure decreases, the composite temperature is expected to initially decrease according to the first law of thermodynamics 30 and then the surrounding heat is transferred to the composites, leading to a temperature minimum. 10 Although there is an optimum vacuum pressure for minimum specific power, 31 the initial vacuum pressure (IVP) in this study was controlled between the pressure (P 1 ) at which the temperature minimum appears and the pressure (P 2 ) at which no noticeable desorbed gas flow is detected.…”

Section: Resultsmentioning

confidence: 99%

Site Trials of Ventilation Air Methane Enrichment with Two-Stage Vacuum, Temperature, and Vacuum Swing Adsorption

Bae

et al. 2020

Ind. Eng. Chem. Res.

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Site trials of a two-stage vacuum, temperature, and vacuum swing adsorption (VTVSA) process using carbon fiber composites was, for the first time, carried out at an Australian coal mine to enrich ventilation air methane (VAM) in a safe manner. Four sets of tests were carried out with average inlet VAM concentrations ranging from 0.54 to 0.73 vol %, resulting in 4.34−4.94 vol % CH 4 through the first stage and 27.62−35.89 vol % CH 4 in the final product, which is overall a 44−63 times VAM enrichment. The average CH 4 concentrations after the first stage were successfully maintained to be less than 5 vol % by regulating the initial vacuum pressure in response to the inlet VAM concentrations. The presence of CO 2 in actual ventilation air, specifically the ratio of CO 2 over CH 4 concentrations, was found to associate with the methane recovery of the second stage, and CH 4 and O 2 concentrations in the final product. Compared to our previous results with simulated ventilation air, no effect of the presence of moisture in ventilation air on CH 4 capture performance was found, confirming the adequacy of carbonaceous materials such as carbon fiber composites to be employed for VAM enrichment. In addition, oxygen concentrations in the final product for all tests were less than 10 vol %, enhancing the operational safety at coal mine sites.

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“…However, after cooling the samples for another 420 s, the mean temperature of the petiole reached very close to that of the leaf (Figure 3(d)), indicating thicker structures of the petiole require more time for reducing temperature. When the vacuum was released, the mean temperature of the leaf rose to 23 ∘ C rapidly (Figure 3(e)), because the chamber temperature was always kept at a constant value [18]. However, the temperature of the petiole did not change markedly compared with the leafy part after vacuum was released.…”

Section: Overall Temperature Distribution Of the Whole Brassica Chinementioning

confidence: 97%

“…This occurred in the following manner: firstly, temperatures of all the points were kept unchanged until the vacuum chamber was pumped to the "flash point" when the free water inside the leaf evaporated suddenly; then, after reaching the "flash point," the temperature of each point dropped quickly. But the temperature just dropped down to 11.3 ∘ C, which may have been because (1) the sample was heated in main way of infrared radiation by the vacuum chamber which was hotter than the samples or (2) the sample was heated by the wet air in the vacuum chamber [18].…”

Section: Overall Temperature Distribution Of the Fresh-cut Brassica Cmentioning

confidence: 99%

Temperature Distribution Pattern of Brassica chinensis during Vacuum Cooling

Song

Liu

Jaganathan

2016

Journal of Food Processing

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The temperature distribution of leafy vegetables is often less uniform than that of other vegetables during the vacuum cooling process, a factor that can cause undesired effects such as frostbite. Brassica chinensis, a type of classical leafy vegetable, was used as a model in this paper to optimize vacuum cooling technology for the whole and fresh-cut leafy vegetables. We found that noticeable temperature differences between the leaf and the petiole occurred, which resulted from their structural difference. Temperature variations of different parts of the leaf were also observed, indicating that cooling rate of leaf margin was quicker than the other parts. Our experiments show that using a moderate volumetric displacement of the chamber (0.033 s −1 ) is beneficial for obtaining a relative uniform temperature distribution of the leaf part.

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Characteristics of Chamber Temperature Change During Vacuum Cooling

Cited by 5 publications

References 7 publications

Enrichment of Ventilation Air Methane (VAM) with Carbon Fiber Composites

Enrichment of Ventilation Air Methane (VAM) with Carbon Fiber Composites

Site Trials of Ventilation Air Methane Enrichment with Two-Stage Vacuum, Temperature, and Vacuum Swing Adsorption

Temperature Distribution Pattern of Brassica chinensis during Vacuum Cooling

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