• Journal of the Korean Electrochemical Society
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• v.8 no.4
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• pp.155-161
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• 2005

In this paper, commercial CFD program FLUENT v5.3 is used for simulation of MCFC stack. Besides using conservation equations included in FLUENT by default, mass change, mole fraction change and heat added or removed due to electrochemical reactions and water gas shift reaction are considered by adding several equations using user defined function. The stacks calculated are 6 and 25 kW class coflow stack which are composed of 20 and 40 unit cells respectively. Simulation results showed that pressure drop took place in the direction of gas flow, and the pressure drop of cathode side is more larger than that of anode side. And the velocity of cathode gas decreased along with the gas flow direction, but the velocity of anode gas increased because of the mass and volume changes by the chemical reactions in each electrodes. Simulated temperature profile of the stack tended to increase along with the gas flow direction and it showed similar results with the experimental data. Water gas shift reaction was endothermic at the gas inlet side but it was exothermic at the outlet side of electrode respectively. Therefore water gas shift reaction played a role in increasing temperature difference between inlet and outlet side of stack. This results suggests that the simulation of large scale commercial stacks need to consider water gas shift reaction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1245-1252
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• 2001

The condensation pressure drop for pure refrigerants R-22, R-134a, and a binary refrigerant mixture R-410A flowing in a small diameter tube was investigated. The test section is a counterflow heat exchanger with refrigerant flowing in the inner tube and coolant flowing in the annulus. The test section consists of 1220 [mm] length with horizontal copper tube of 3.38 [mm] outer diameter and 1.77 [mm] inner diameter. The refrigerant mass fluxes ranged from 450 to 1050 [kg/(㎡$.$s)] and the average inlet and outlet qualities were 0.05 and 0.95, respectively. The main experimental results were summarized as follows : In the case of single-phase flow, the pressure drop of R-134a is much higher than that of R-22 and R-410A for the same Reynolds number. The friction factors for small diameter tubes are higher than those predicted by Blasius equation. In the case of two-phase flow, the pressure drop increases with increasing mass flux and decreasing quality. The pressure drop of R-134a is much higher than that of R-22 and R-410A for the same mass flux. Most of correlations proposed in the large diameter tube showed enormous deviations with experimental data. However, the correlation predicted by Honda et al showed relatively good agreement with experimental data for R-134.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.1876-1881
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• 2007

The micro plated heat exchangers were designed to transfer more heat/volume or mass than previous heat exchangers within the context of the design constraints specified. The increase of the surface-to-volume ratio results in an increase of the interfacial area. This enhances considerably the performance of a heat exchanger. This can be an important component in a wide range of applications fuel cell, aerospace, automotive, electronic system and home heating, etc). In this study, the performance evaluation of micro plated heat exchangers under the counter flows with straight and S-shaped channel are carried out. The pressure drop as well as inlet and outlet fluid temperature were measured at steady state under various operating conditions and the total heat transfer rate were also calculated.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1209-1213
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• 2005

It reflects well feature of slope that is characteristic of city river basin of Pusan local. Process various hydrological datas and basin details datas which is collected through basin basis data. weather satellite equipment(EMS-DEU) and automatic water level equipment(AWS-DEU) and use as basin input data of ILLUDAS model, SWMM model and HEC-HMS model In order to examine outflow feature of experiment basin and then use in reservoir design of experiment basin through calibration and verification about HEC-HMS model. Inserted design rainfall for 30 years that is design criteria of creek into HEC-HMS model and then calculated design floods according to change aspect of the impermeable rate. Capacity of reservoir was determined on the outflow mass curve. Designed imagination reservoir(volume $54,000m^3$) at last outlet upper stream of experiment basin, after designing reservoir. It could be confirmed that the peak flow was reduced resulting from examining outflow aspect. Designing reservoir must decrease outflow of urban areas.

• Solar Energy
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• v.10 no.1
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• pp.38-46
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• 1990

For the optimal design and the efficient operation of the double pipe type latent heat storage equipment, the effect of the parameters of the system were analysed. The statistical analysis showed that the theoretical and the experimental results of the volume change rate and the temperature variations were well agreed. Therefore, this theoretical model is reasonable to analyze two dimensional moving boundary problems. In the analysis of the effects of the parameters, the heat extraction fraction and the water outlet temperature of the system as function of the time were analysed depending on the initial temperature of PCM, water inlet temperature, water mass flow rate and the dimension of the inner tube.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.3
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• pp.346-351
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• 1998

The purpose of this study is analyzing the performance of sea water cooling system under various refrigerant pipe length. In sea water cooling system, the increase of refrigerant pipe length cause increases of pressure drops. These pressure drops cause fresh gas in liquid pipe and increase specific volume in gas pipe outlet, so sea water cooling system capacity is decreased by decrease of refrigerant mass flow rate. Sea water cooling system capacity in refrigerant pipe length 70m is decreased more than 30% when compared with pipe length 10m and the decrease of the coefficient of performance is nearly 20%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.7
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• pp.1001-1012
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• 1998

This paper reports the analysis of dynamic characteristics of air-cooled condenser. At first, there is an assumption that the superheated vapor flows into the condenser inlet. And in order to consider the effect of pressure change in the dynamic characteristics of the condenser the combined system of condenser and compressor was used. By using the equation of energy balance and the equation of mass balance, the basic equation for describing the dynamic characteristics of condenser can be derived. The transfer function for describing dynamic response of the condenser to flow rate change outlet can be obtained from using linearizations and Laplace transformations of the equation. From this transfer function, analytical investigation which affects the frequency responses of condenser has been made. Through this study, it became possible that the information about the dynamic characteristics of air-cooled condenser is offered. While the average heat transfer coefficient of the refrigerant side necessary for the theoretical calculation of the dynamic characteristics is given by calculation method for the tube length and pressure drop of air-cooled condenser.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.25-27
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• 2012

In this paper, combustion process in the perforated silicon carbide(SiC) tube using a two dimensional approaches with GRI Mechanism 1.2 was investigated. The computational mesh structure which is divided into $60{\times}15$ and boundary conditions are set to constant mass flow rate at the inlet and constant pressure condition at the outlet respectively. Its result shows that the temperature on this peak was roughly 100K higher than the adiabatic flame temperature of 2223K for a free laminar flame at these conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.10
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• pp.993-1001
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• 2001

Experimental investigation on the performance of dual-evaporator refrigeration system with an ejector has been carried out. In this study, a hydrofluorocarbon (HFC) refrigerant R134a is chosen as a working fluid. The condenser and two-evaporators are made as concentric double pipes with counter-flow type heat exchangers. Experiments were performed by changing the inlet and outlet temperatures of secondary fluids entering condenser, high-pressure evaporator and low-pressure evaporator at test conditions keeping a constant compressor speed. When the external conditions (inlet temperatures of secondary fluid entering condenser and one evaporator) are fixed, results show that coefficient of performance (COP) increases as the inlet temperature of the other evaporator rises. It is also shown that the COP decreases as the mass flaw rate ratio of suction fluid to motive fluid increases. The COP of dual-evaporator refrigeration system with an ejector is superior to that of a single-evaporator vapor compression system by 3 to 6%.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.6 no.4
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• pp.255-261
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• 1977

This study was concerned with the performance of solar air heater using parallel channels. Heat transmission model was developed and fabricated to increase the economic feasibility for solar heating system by using the cheap zinc plate. The prformance was discussed as a function of mass flow rate, and plate, inlet and outlet temperatures. Experimental results show that heat transmission model is sufficient for the analysis of thermal characteristics of air heater and collection efficiency is better than the domestic water heater, as the range 32-49 percent. Collection efficiency in the 2 layers of glass cover is better than that in 1 layer, so it is considered better to use the 2 layers of glass cover during the cold winter season in Korea.