• Journal of the Korean Geotechnical Society
• /
• v.32 no.6
• /
• pp.17-26
• /
• 2016

Characteristic behaviors of geo-structure during freezing and thawing process have to be understood based on fundamental knowledge on phase change in porous soil and interaction between soil and structure. Inversion analysis using published one-dimensional soil freezing tests was conducted to suggest a mechanical model to consider an effect of the ice saturation on Young's modulus. Silty soil was more sensitive to temperature than weathered granite soil and sand, and weathered granite soil was more affected by initial water saturation in stiffness decrease than silty soil. Numerical simulations on chilled gas pipeline showed that shielding effect from surrounding frozen zone around the pipe decreases impact from external load onto the pipe. And a pipe installed in sand backfill showed more heaving due to relatively low stiffness of sand during freezing than that of surrounding in-situ weather granite soil. However, it had more stable stress condition due to effective stress redistribution from external load.

• Food Science of Animal Resources
• /
• v.29 no.1
• /
• pp.55-61
• /
• 2009

The objective of this study was to examine the effects of high and low chilling temperature on the water-holding capacity (WHC) and tenderness of hot-boned breast meat of broiler chickens. Breast meat was obtained from 32 broiler chickens within 15 min post-mortem (PM), and then divided into two groups. One group was chilled at $-1^{\circ}C$ and the other group was stored at $30^{\circ}C$ for 3 hr, and then all the samples were chilled at $2^{\circ}C$ until 24 hr PM. During the storage, their physicochemical characteristics were tested at 15 min, 3 hr and 24 hr PM. These included pH, R-values, cooking losses, sarcomere length, MFI, and shear force of the breast meat, none of which was different (p>0.05) between the two temperature treatments at $-1^{\circ}C$ and $30^{\circ}C$. However, sarcomere length was shortened more at $-1^{\circ}C$ than at $30^{\circ}C$, MFI was larger at $30^{\circ}C$ than at $-1^{\circ}C$, drip loss was greater at $30^{\circ}C$ than at $-1^{\circ}C$, and WHC was lower at $30^{\circ}C$ than at $-1^{\circ}C$(p<0.05). In brief, in terms of yield and tenderness, broiler breast meat stored at $-1^{\circ}C$ was superior to that stored at $30^{\circ}C$.

• Proceedings of the SAREK Conference
• /
• 2007.11a
• /
• pp.352-357
• /
• 2007

The objective of this study is to find the optimal set-point of a hybrid Plant, which is combined by renewable energy plant of the GSHP(Ground Source Heat Pump) and the conventional plant(chiller, boiler). The work presented in this study was carried out by using the EnergyPlus(Version 2.0). In order to validate the simulation model, field data were measured from a building. The GSHP was used as a base plant and the conventional plant as the assistant plant. Various temperatures were controlled (zone summer set-point, zone winter set-point, chilled water temperature, hot water temperature) to find the optimal set-point temperature of the system. The influence of the various set-points were analyzed seasonally.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.1014-1019
• /
• 2009

The optimal control system for heat source and HVAC system has been developed for minimizing energy consumption while maintaining the comfort of indoor thermal environment in terms of the environmental variables such as time varying indoor load and outdoor temperatures. The optimal set-points of control parameters are supply air temperature and chilled or hot water temperatures. The optimal control study has been implemented for biosafety laboratory by using TRNSYS simulation program in order to investigate energy performance for heat source and HVAC system.

• Journal of Advanced Marine Engineering and Technology
• /
• v.21 no.1
• /
• pp.26-36
• /
• 1997

Recently, the new refrigerating system, using non - fluorinated hydrocarbon refrigerants has to be developed for the agricultural fields. One of that kinds of systems is the cooling system using the water vapor and vacuum, in which the water evaporate at the low temperature under vacuum and absorb the large amount of the latent heat. If vapor with large amount of latent heat is removed from the system, the system is cooled accordingly. The characteristics of cooling under the vacuum was observed and measured using experimental apparatus, which is consisted of vacuum chamber, the ejectors, the pumps and the measurement apparatus. As the results of experiments, we know that the evaporation in the vacuum occurs vigorously when the materials to be cooled has more amounts of heat before cooling, and by which effects the materials can be cooled. The cooling vacuum system is more efficient than other methods when the agricultural products is chilled or dried.

• Food Science and Biotechnology
• /
• v.16 no.4
• /
• pp.626-631
• /
• 2007

Pre-rigor bovine sternomandibularis muscles were frozen at 3 hr postmortem thawed at various temperatures (18, 2, and $-2^{\circ}C$), and then meat quality and sensory properties were compared with those in chilled muscle (control). The meat thawed at $18^{\circ}C$ had lower ultimate pH, water holding capacity, and sensory scores and higher muscle shortening, thaw drip loss, and shear values than those of the other samples. The samples thawed at $-2^{\circ}C$ had significantly lower muscle shortening and higher sensory scores in tenderness and juiciness than those thawed at 18 and $2^{\circ}C$. Muscle shortening, pH, WHC, shear values, and sensory properties were not significantly different between control and sample thawed at $-2^{\circ}C$. By holding at $-2^{\circ}C$, thaw shortening was prevented and tender meat comparable to the chilled meat was obtained. These results indicate that thaw shortening can be largely eliminated if the frozen pre-rigor muscle is thawed at $-2^{\circ}C$.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.19 no.2
• /
• pp.207-212
• /
• 2013

In this study, distributed the ship's Centralized Air Conditioning System the way an individual to replace the air conditioning system by using Air-cooled air conditioner. Research results, Individually separated air conditioning system complement the heat source control and thermal efficiency problems and improves the efficiency of the device was confirmed. In addition, under the same conditions refrigeration capacity and coefficient of performance of the device, an average of about 3 %, 23 ~ 26 %, higher, Chilled Water Plants Compressor power consumption is about 12 % lower. Also while heating under the same conditions, power consumption is about 33.5 % lower. Therefore Individually Separated Air Conditioning System greatly contributed to the improved performance of the device and living spaces for comfortable temperature and humidity control as well as heating source could be obtained.

• Solar Energy
• /
• v.19 no.2
• /
• pp.1-8
• /
• 1999

The heat transfer characteristics of ice storage system of falling film type using sprial coil is investigated. The experimental facilities consisted of a water tank, spiral coils located above the tank, an upper water distributor, and a circulating water pump. Water is distributed uniformally over the spiral coils and it forms falling thin films. In the process of freezing, ice is formed on outside of the spiral coils through recirculation of tank water. In the process of melting, ice is melted with return water from the heat load, while the water is chilled again and drops into the tank. The results of falling film type of ice thermal storage system are as follows. The highly efficient shower flowrates for icing is near $3{\ell}/min$. Icing rates on spiral coils is rosed while brine flowrates is increased. Lower brine temperature is not only increased freezing rates but. also become higher total icing weight and overall heat transfer coefficient. Smaller shower flowrates is obtained lower water temperature on outlet for a long time. The amounts of quantity can be detected more accurately by measuring storage tank weight.

• Journal of the Korean Solar Energy Society
• /
• v.27 no.4
• /
• pp.19-26
• /
• 2007

This paper concerns the study of absorption refrigeration and heat pump cycle to use sewage. Simulation analysis on the double-effect absorption refrigeration cycle with parallel and two-stage heat pump cycle has been performed. The working fluid is Lithium Bromide and water solution. The absorption refrigeration cycle use sewage as a cooling water for the absorber and condenser, and absorption refrigeration cycle does that as a chilled water for the evaporator of the first stage cycle. And the two-stage cycle consists of coupling double-effect with parallel and single effect cycle so that the first stage absorber and condenser produces heating water to evaporate refrigerant in the evaporator of the second stage. The effects of operating variables such as a absorber temperature on the coefficient of performance have been studied for absorption refrigeration and heat pump cycle.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.2
• /
• pp.272-280
• /
• 1999

A cycle analysis was achieved to predict the characteristics by comprehensive modeling and simulation of an air-cooled, double-effect absorption system using a new $H_2O/LiBr+HO(CH_2)_3OH$ solution. The simulation results showed that the new working fluid may provide the crystallization limit 8% higher than the conventional $H_2O/LiBr$ solution. With a crystallization margin of 3wt%(weight%), the optimal solution distribution ratio was found in the range of 36 to 40%. Variation of cooling air Inlet temperature has a sensitive effect on the cooling COP and corrosion problem. The simulation of heat exchangers with UA value revealed that the absorber and the evaporator are relatively important for an air-cooled system compared with the condenser and the low temperature generator. The effect of cooling air flow rate, circulation weak solution flow rate and chilled water inlet temperature were also examined. The new working fluid may provide the COP approximately 5% higher than the conventional $H_2O/LiBr$ solution.