• Journal of Biosystems Engineering
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• v.8 no.2
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• pp.49-61
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• 1983

U shape multitube heat exchanger was equipped in the flue to recover the exhaust heat from the boiler system. The fluids of the exhaust heat recovery equipment were the flue gas as the hot fluid, and the water as the cold fluid. The flow geometry of the fluids was cross flow - two pass, the hot fluid being mixed and the cold fluid unmixed. The results of the theoretical and the experimental analysis and the economic evaluation are summarized as follows. 1) The heat exchanger effectiveness and the temperature efficiency of the hot fluid were about 35% when the fuel consumption rate was 140 - 150 L/15min. The temperature efficiency for the cold fluid ranged from 3.0% to 4.5%. The insulation efficiency ranged from 85% to 98%, which was better than the KS air preheater insulation efficiency of 90%. 2) The relationship between the fuel consumption rate, F, and the outlet temperature, $T_{h2}$, of the flue gas from the heat exchanger was $T_{h2}$ = 0.927F + 110. In order to prevent the low temperature corrosion from the coagulation of $SO_3$, it is necessary to maintain the fuel consumption rate above 82 L/15min. 3) The ratio of the exhaust heat from the boiler system to the total energy consumption was about 14.5%. With the installation of the exhaust heat recovery equipment, the energy recovery ratio to the exhaust heat was about 25%. Accordingly, about 3.6% of the total fuel consumption was estimated to be saved. 4) Economic analysis indicated that the installation of the exhaust heat recovery equipment was feasible to save the energy, because the capital reocvery period was only 10 months when the fuel consumption rate was 80 L/15min. 4 months when it was 160 L/15min. 5) Based on the theoretical and the experimental analysis, it was estimated to save the energy of about 18 million Won per year, if four heat exchangers are installed in a factory. 6) A further study is recommended to identify the relationship among the flow rate of the exhaust gas, the size of the heat exchanger and the capacity of the air preheater. For a maximum heat recovery from the exhaust gas an automatic control system is required to control the flow rate of the cold fluid depending on the boiler load.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1603-1605
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• 1997

$LiNiO_2$ is prepared by heating LiOH $H_2O$ and $Ni(OH)_2$ (mole ratio 1:1). In this study, we investigated X-ray diffraction, and charge/discharge property heat treatment condition and conductive agent sort and volume of $LiNiO_2$ prepared at various temperature and time. All $LiNiO_2$ prepared at this study showed hexagonal structure. In charge/discharge capacities, heated at $O_2$ than air and $750^{\circ}C$ than $700^{\circ}C$, specific capacity is higher. Therefore, when preliminary heat at $650^{\circ}C$ $O_2$ and heat at $750^{\circ}C$ carried out, charge/discharge property is best.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.9
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• pp.719-726
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• 2015

One method of increasing the heat-transfer rate is to increase the heat-transfer area. In this study, we test a wide louver fin-and-tube heat exchanger with $P_t/P_l$ = 1.03, and we compare the results with those of a louver fin-andtube heat exchanger with $P_t/P_l$ = 0.6. The results obtained show that the heat-transfer capacities of the wide louver samples are larger (16% in one row, 29% in two rows, and 38% in three row samples) than those of the louver samples. Considering the area ratio of 2.17, the increase in the heat-transfer capacity is somewhat small. The reason for this may be due to the smaller heat-transfer coefficient and fin efficiency of the wide louver sample. The effect of the fin pitch on the j and f factors are not profounded. The j and f factors decreased as the number of tube rows increased. We compare the data obtained with existing correlations.

• Journal of Electrochemical Science and Technology
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• v.7 no.3
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• pp.206-213
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• 2016

Transition metal oxide-based electrodes for lithium ion batteries have recently attracted much attention because of their high theoretical capacity. Here we report the electrochemical behavior of cobalt oxide nanorods as anodes, prepared by a template-free, one-step electrochemical deposition of cobalt nanorods, followed by an oxidation process. The as-deposited cobalt has a slightly convex columnar structure, and controlled thermal oxidation produces cobalt oxides of different Co/O ratios, while the original shape is largely preserved. As an anode in a rechargeable lithium battery, the Co/O ratio has a strong effect on initial capacity and cycling stability. In particular, the one-dimensional Co@Co_xO_y core shell structure obtained from a mild heat-treatment results in superior cycling stability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4721-4726
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• 2010

The performance characteristics of water-chilling heat pump using CO2 for the control of inverter frequency was investigated experimentally. An experimental apparatus is consisted of a compressor, a gas cooler, an expansion valve, an evaporator and a liquid receiver. All heat exchangers used in the test rig are counter flow type heat exchangers with concentric dual tubes, which are made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2.4m length. The experimental results summarize as the following: for constant inlet temperature of evaporator and gas cooler, as mass flow rate, compression ratio and discharge pressure increases with the inverter frequency. And heating capacity and compressor work increases, but coefficient of performance(COP) decreases with the inverter frequency of compressor. As inlet temperature of secondary fluid in the evaporator increases from $15^{\circ}C$ to $25^{\circ}C$, compression ratio and compressor work decreases, but mass flow rate, heating capacity and COP increases with the inverter frequency of compressor. The above tendency is similar with performance variation with respect to the variation of inverter frequency in the conventional vapor compression refrigeration cycle.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.171-176
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• 2008

As one way of design optimization of two-stage two-cylinder rotary compressor used for R410A heat pump application, displacement volume ratio, being defined by the ratio of the second stage cylinder volume to that of the first stage, has been varied and its effect on the compressor performance has been investigated by a computer simulation program. For simplicity, only the cylinder height of the second stage was varied to change the volume ratio. With increasing the volume ratio in the range of VR=$0.55{\sim}0.9$, volumetric efficiency increased monotonically, but adiabatic efficiency showed a maximum at around VR=0.6. Mechanical efficiency was little influenced by the volumetric ratio. As a consequence, maximum improvement of the compressor performance was found at around VR=0.7. Compared to a one-stage two-cylinder rotary compressor with about the same cooling capacity, COP improvement was about 6.96%.

• Korean Journal of Food Science and Technology
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• v.19 no.6
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• pp.486-491
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• 1987

The performance and applicability to food concentration of heat pump were investigated. During heating the water of spa from $43^{\circ}C$ to $51^{\circ}C$, COP's of heat pump (R-12, 150 HP) were 4.03 at heating part and 3.5 at cooling part. And, the efficiency of compressor (${\alpha}$) was 0.477 While the city water was heated to $39^{\circ}C$ by heat pump (R-22, 10 HP), its COP's were 3.0 at heating part and 1.87 at cooling part. During concentrations sucrose solution by centrifugal evaporator (ALFA-LAVAL CO, CTIB) with heat pump, heat capacity for condensating water vapor was required greater 15% than the latent heat for concentrating and then the overall heat transfer coefficient was $1196\;Kcal/m^{2}.\;h.\;^{\circ}C$. When low temperature concentration ($30-35^{\circ}C$, 28-40 Torr) of garlic extract was carried out by the water of $60^{\circ}C$ and $15^{\circ}C$ adjusted by heat pump, the ratio of heat capacity for concentrating vs. that for condensating of water vapor was 0.961.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.219-224
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• 1997

A transient short-hot-wire technique has been presented for simultaneous measurements of the thermal conductivity and diffusivity of fluids under the microgravity condition. Two-dimensional heat conduction equations for concentric cylinders with various radius ration and length-diameter ratio have been solved numerically by taking account of the heat capacity of the inner cylinder. A unique relation between the non-dimensional temperature of inner cylinder and Fourier number is obtained for a wide range of thermal properties of the fluids, because the relation if found to be almost independent of these properties. Then the characteristic could be utilized as a masterplot to evaluate both the thermal conductivity and diffusivity. In principle, this method is proved to have an error within 1% for both of these properties.

• Elastomers and Composites
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• v.28 no.4
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• pp.274-282
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• 1993

Resorcinol-tannin-formaldehyde-latex(RTFL) adhesive was prepared to bond SBR to nylon in reinforced rubber composites. A key factor of adhesive contributes to the adhesion strength between SBR and nylon was the toughness of adhesive itself. Although the stiffness and strength of adhesive film decreased slightly with increasing level of tannin substitution for resorcinol in a standard RFL adhesive, the maximum toughness of adhesive film, which showed yield behavior and high dissipative capacity, was obtain by 60% tannin substitution. However, a marked softening and reduction in toughness occurred at sufficiently high substitution. Also, the adhesive film, which was heat-treated to simulate cure, showed higher strength than the unheated film. Thus, the properties of tannin containing adhesives could be optimized by using 40/60 weight ratio of the resorcinol/tannin in RTFL adhesive composition as well as heat treatment of adhesive film.

• Journal of Aerospace System Engineering
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• v.14 no.4
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• pp.32-39
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• 2020

A technological review and analysis were performed on thermal cracking of aviation hydrocarbon fuels that circulate as coolants in regenerative cooling systems of hypersonic flights. Liquid hydrocarbons decompose into low-carbon-number hydrocarbons when they absorb a considerable amount of energy at extremely high temperatures, and these thermal cracking behaviors are represented by heat sink capacity, conversion ratio, reaction products, and coking propensity. These parameters are closely interrelated, and thus, they must be considered for optimum performance in terms of the overall heat absorption in the regenerative cooling system and supersonic combustion in the scramjet engine.