• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.200-208
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• 2021

Compare to the gaseous hydrogen, liquid hydrogen has various advantages: easy to transport, high energy density, and low risk of explosion. However, the hydrogen liquefaction process is highly energy intensive because it requires lots of energy for refrigeration. On the other hand, the cold energy of the liquefied natural gas (LNG) is wasted during the regasification. It means there are opportunities to improve the energy efficiency of the hydrogen liquefaction process by recovering wasted LNG cold energy. In addition, hydrogen production by natural gas reforming is one of the most economical ways, thus LNG can be used as a raw material for hydrogen production. In this study, a novel hydrogen production and liquefaction process is proposed by using LNG as a raw material as well as a cold source. To develop this process, the hydrogen liquefaction process using hydrocarbon mixed refrigerant and the helium-neon refrigerant is selected as a base case design. The proposed design is developed by applying LNG as a cold source for the hydrogen precooling. The performance of the proposed process is analyzed in terms of energy consumption and exergy efficiency, and it is compared with the base case design. As the result, the proposed design shows 17.9% of energy reduction and 11.2% of exergy efficiency improvement compare to the base case design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4602-4609
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• 2013

In summer and winter, the difference between the temperature during the day and that during the night is high, which leads to various problems during concrete placement, such as cracks and defects in the concrete as well as low durability and strength. Although nuclear power plant concrete is widely used for placement in all seasons, particular attention must be paid to its quality during the summer. Therefore, we evaluated the effects of a cooling method for mixing water, which is a commonly used hot weather precooling method, and the use of a retarder, on the characteristics of Nuclear Power Plant concrete. In the cooling method for mixing water, cold water at 5 was used, with 50% of the water content consisting of ice flakes. The effects of using a retarder were evaluated by reviewing the characteristics of the cement at the unset stage and after hardening. To evaluate the characteristics of the unset cement, we measured the slump, air volumes, setting times, and pressure strengths after hardening. Furthermore, we measured the heat of hydration at different temperatures; the loss of heat was minimized using insulation. Both the slump time and the complete ageing time of the air volume were found to be 120 min at $20^{\circ}C$ and 40 min at $40^{\circ}C$. In the case when the cooling method for mixing water was used and in the case when a retarder was used, the initial and final sets by penetration resistance were delayed, and the delay decreased with increasing air temperature. For the heat of hydration, the cooling method for mixing water not only lowered the maximum temperature but also delayed its attainment. However, the use of a retarder had no effect on the maximum temperature. Moreover, in the early ages (e.g., 3 and 7 days), the pressure strength of the concrete was lower than that of plain cement. However, the strength of 28-day concrete met the standard construction specifications.

• Food Science and Preservation
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• v.24 no.3
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• pp.351-360
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• 2017

We have studied the technology to extend the storage period of 'Seolhyang' strawberries using modified atmosphere package (MAP) and ethyl pyruvate (EP) treatment for domestic distribution and export. The selected ripe strawberries harvested on December 28, 2016 at the Sancheong farmhouse were transported to the laboratory for 2 h and tested. After a day's precooling at $4^{\circ}C$, the strawberries were divided into seven experimental groups. These groups were control, active MAP using low density polyethylene (LDPE), active MAP using polyamide (PA), active MAP using PA with EP treatment, passive MAP using LDPE, passive MAP using PA and passive MAP using PA with EP treatment. Quality analysis was carried out every 4 days during the storage period of 16 days. During the storage period of 16 days, MAP decreased from 3.5% to less than 1.1% in weight loss ratio compared with control, and decreased from 36% to less than 7% in fungal incidence. In the case of fungi in the EP treatment group, hyphae did not grow on the outside of the strawberry but grew to the inside. This tendency was similar to that in the low oxygen and high carbon dioxide environment of the MAP, the mycelium of the fungus did not grow outside of the strawberry. Fungi are the biggest problem in the distribution and export of strawberries, and these results suggest that MAP alone could inhibit mold and increase shelf life.