• Solar Energy
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• v.17 no.3
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• pp.23-33
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• 1997

The theory on phase change temperature control and nucleation of PCM was suggested in this research. The crystallization model of PCM was established. And H2O-NaCl mixtures were selected as cold storage materials for agricultural products and thermo-physical properies of the PCM were analyzed with experimental processes including freeze-thaw cycles.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.173-178
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• 2010

The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity are increased and COP are decreased due to supercooling of water in the course of phase change from liquid to solid. This study investigates the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, $(CH_3)_3N$) of 20~25 wt% as a low temperature latent heat storage material. The results showed that the phase change temperature are increased and the supercooling degree and the specific heat are decreased according to the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25wt% has the average phase change temperature of $5.8^{\circ}C$ and the supercooling degree of $8.0^{\circ}C$, retention time of liquid phase for 651sec and specific heat of 3.499 kJ/kgK in the cooling process. This expressed good than different concentration of TMA cooling characteristic. Like this, to apply TMA 25wt%-water clathrate compound is determined by advantageous as the low temperature latent heat storage material.

• Food Science and Preservation
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• v.15 no.1
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• pp.15-20
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• 2008

By considering the storage temperatures of agricultural products, three types of PCMs $(K_1$, $K_2$, $K_3$) were developed to be used in temperature ranges of $0{\sim}5^{\circ}C$, $5{\sim}10^{\circ}C$ and $10{\sim}15^{\circ}C$, $K_1$ PCM for $0{\sim}5^{\circ}C$ was developed by mixture of $C_{14}H_{30}$ and soduim polyacrylate, and $K_2$ PCM for $5{\sim}10^{\circ}C$ and $K_3$ PCM for $10{\sim}15^{\circ}C$ were mixture of $C_{14}H_{30}$, $C_{18}H_{38}$ and soduim polyacrylate with different composition ratio. 'The target temperatures of cold chain system were set at $7^{\circ}C$, $13^{\circ}C$, and $17^{\circ}C$ with $K_{1-3}$, $K_{2-3}$ and $K_{3-1}$ PCMs, respectively. The times to reach the target temperatures in the storage chamber were 21 hours, 18 hours, and 61 hours with $K_1$, $K_2$, and $K_3$ PCMs, respectively. The performances of natural convection type and forced convection of the temperature controlled portable container were analyzed Apples were stored in the portable container of $5^{\circ}C$, and temperatures at surface and center were measured. The initial temperature of the apple was $25^{\circ}C$. The temperatures of apple at the surface and the center were $15^{\circ}C$ and $16^{\circ}C$, respectively, after 5 hours with natural convection type. However, the temperatures at the surface and the center were already reached to $7^{\circ}C$ within 1 hour with forced convection type. The forced convection type showed the better performance and the temperatures of portable container were maintained more than 15 hours.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2471-2475
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• 2007

Clathrate compound is the material that host in hydrogen bond forms cage and guest is included into it and combined. Crystallization of hydrate is generated at higher temperature than that of ice from pure water. And physical properties according to temperature are stable and congruent melting phenomenon is occurred without phase separation. But clathrate compound still had supercooling problem occurred in the course of phase change and supercooling should be minimized because it affects efficiency of equipment very much. Therefore, various studies on additives to restrain this or heat storage methods are needed. In this study was investigated the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, $(CH_3)_3N)$ of 20${\sim}$25 wt% as a low temperature latent heat storage material. And ethanol$(CH_3CH_2OH)$ was added and its cooling characteristics were studied experimentally to restrain supercooling of TMA-water clathrate compound.

• Journal of Institute of Convergence Technology
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• v.2 no.1
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• pp.1-6
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• 2012

The cold chain system in South-East Asia is requiring to maintain freshness of refrigerated or frozen food. In this study, Thermal storage system using Phase change material (PCM) was developed and evaluated its performance about temperature and cold keeping time. For various application of cold chain system, we developed portable cold box, cold roll container and freezing station. Keeping time on laboratory tests of portable cold box in case of refrigeration and freezing were 6 hours and 4 hours, respectively. Cold container was developed to 2.5 ton scale. Evaluation in Indonesia, it was showed to keep the setting temperature of $-10^{\circ}C$ over 40 hours at $30^{\circ}C$ of ambient air. Freezing station using PCM was kept over 24 hours under $-20^{\circ}C$.

• Food Science and Preservation
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• v.23 no.4
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• pp.471-478
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• 2016

For the distribution of fresh produce, the thermoelectric cooling system combined with thermo electric materials (TEM) and phase change material (PCM) was studied. The PCM used this study was produced by in-situ polymerization technology which referred microencapsulation of hydrocarbon (n-tetradecane and n-hexadecane). In this study, quality characteristics of bell peppers in thermoelectric cooling system combined with TEM and PCM were analyzed and control was placed in an EPS (expanded polystyrene) box. As a result of quality characteristics analysis, weight of bell peppers decreased and moisture content of bell peppers was 90.96~94.43% during storage. Vitamin C content of bell pepper decreased during storage and reduction ratio of control was higher than that of BPT-5 treatment(bell pepper in thermoelectric cooling system with PCM which is kept the temperature at $5^{\circ}C$). The result of color value, on 21 day, ${\Delta}E$ value of BPT-5 treatment was 5.05 while that of control was 41.8. On 21 day, total bacteria count of BPT-5 treated bell pepper shown less than that of control. In conclusion, it suggested that the thermoelectric cooling system combined with PCM improved quality of fresh produce during transportation and storage.

• Food Science and Preservation
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• v.9 no.3
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• pp.261-266
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• 2002

A transpiration model was selected and tested experimentally to predict transpiration into of Fuji apple stored in a normal air and controlled atmospheres (l∼3% O$_2$+ l∼3% CO$_2$) at 0$\^{C}$ and 98% RH for 6weeks. CA storage decreased the respiration rate of Fuji apple by 50% when compared with normal air storage. The transpiration rates of apple showed 50∼70% higher in normal air storage than those in CA storage and were decreased by increasing CO$_2$concentration under same concentration of O$_2$. The transpiration rates estimated by the selected model were in good agreement with experimental data for Fuji apples under controlled atmosphere conditions and normal air. When the respiratory heat generation rate u of Fuji apple increased with storage conditions, the evaporating surface temperature and transpiration rate also increased. But since some portion of respiratory heat was used as latent heat in the evaporating surface, the change of u value had a little effect on the determination of the evaporation temperature and the transpiration rate.

• Journal of the Korean Solar Energy Society
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• v.24 no.1
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• pp.7-12
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• 2004

Mixtures type PCM, $H_2O$-NaOH that has relatively large capacity of the latent heat and long duration of phase change temperature was developed and experimentally analyzed for the low temperature storage of the food and medical products. The results could be summarized as follows; 1. Borax as nucleating agent and acrylic polymer as thickening agent were added to $H_2O$ to prevent the supercooling and phase separation. 2. Phase change (solid$\leftrightarrows$liquid) duration of $H_2O$ added with NaOH was prolonged longer 50% than that of pure $H_2O$. 3. Phase change temperature of the latent heat material, $H_2O$-NaOH was $1.5\sim2^{\circ}C$ the maximum latent Heat was 279 kJ/kg at the NaOH addition of 1.3 wt.%. 4. The specific heat of $H_2O$-NaOH at the solid and liquid state was increased in proportion to the wt.% of NaOH, when NaOH of $1.15\sim1.60$ wt.% was added to $H_2O$, the specific heat of the solid state was increased from 3.19 kJ/kg to 5.84 kJ/kg and that of liquid state from 7.8 kJ/kg to 10.28 kJ/kg. 5. When NaOH of $1.15\sim1.60$ wt.% was added to $H_2O$, the total heat storage capacity composed of sensible and latent heat was $313\sim331.3$ kJ/kg and the maximum heat storage capacity was occurred at NaOH addition of 1.30 wt. %.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.216-224
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• 1997

In the recent 10 years the protected cultivation area in Korea has been increased rapidly, and now it is very important issue to develop the heating and cooling system using the renewable energy, because the greenhouse heating and cooling cost is increased with the fossil fuel price rises. Actually the development of the cooling system is more difficult than that of the heating system, since the cooling load of greenhouse in the summer season is 2―3 times larger than the heating load in the winter season. In this study low temperature phase change materials (LTPCM) for the cold storage system were selected and developed. The theoretical and experimental analysis of thermal characteristics of LTPCM makes it possible to control the phase change temperature and stabilize the thermo-physical properties. LTPCM developed in this study has good advantages to be used as the cold storage not only for the house and working space in factory but also for the cold storage of agricultural and live-stock products.

• Korean Journal of Food Science and Technology
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• v.20 no.6
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• pp.820-826
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• 1988

The freezing point$(t_f)$, latent heat of freezing$({\triangle}\;H_f)$ and kinetic constant of fleering$(k_f)$ were determined from DSC thermogram at cooling rate $-2.5^{\circ}C/min{\sim}-10.0^{\circ}C/min$. The freezing point of various starches was decreased with an increase in cooling rate, and that of whole starches were lower than defatted starches. Changes of the latent heat of freezing was not observed at above cooling rate $-2.5^{\circ}C/min$. The latent heat of freezing$({\triangle}\;H_f)$ could be deduced as a function of water content(W) as follows: ${\triangle}\;H_f=0.700W-13.048$, (Kcal/kg) $(35%{\leqq}W{\leqq}70%)\;{\triangle}\;H_f=1.569W-73.861,\;(Kcal/kg)\;(W{\geqq}70%$) In the water content range $35{\sim}90$(wt %), the activation energy of various starches in freezing process was determined $126{\sim}270$ Kcal/mol.