• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.80-92
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• 1998

A third-order simulation model of a Vuilleumier{VM) heat pump has been developed. This model takes into account the major losses such as the heat conduction losses through regenerators and displacers, the pumping losses and the wall-to-gas heat transfer losses in active volumes, in addition to the heat exchanger and regenerator losses. The working volume was divided into 12 control volumes and the conservation equations of mass and energy were applied to each control volume. Pressure drops were considered in regenerators only. Thermodynamic behavior of the working gas in a VM heat pump was investigated and effects of the major losses and operating conditions on the performance of a VM heat pump were shown.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.6
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• pp.534-539
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• 2009

One of the most efficient techniques improving the heat transfer performance of a diesel electric generation is a corrosion control in jacket cooling water system. The environmental parameters most affecting corrosion are dissolved salt concentration, temperature, and pH of cooling water. No corrosion occurs in carbon steel probe at pH 11 in normal operating condition of diesel electric generation cooling water. pH control agent in this study is trisodium phosphate. pH control appears to be the most convenient way to enhance the thermal performance of a diesel electric generation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.8
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• pp.2681-2692
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• 1996

The finite-volume method for radiation in a three-dimensional non-orthogonal gas turbine combustion chamber with absorbing, emitting and anisotropically scattering medium is presented. The governing radiative transfer equation and its discretization equation using the step scheme are examined, while geometric relations which transform the Cartesian coordinate to a general body-fitted coordinate are provided to close the finite-volume formulation. The scattering phase function is modeled by a Legendre polynomial series. After a benchmark solution for three-dimensional rectangular combustor is obtained to validate the present formulation, a problem in three-dimensional non-orthogonal gas turbine combustor is investigated by changing such parameters as scattering albedo, scattering phase function and optical thickness. Heat flux in case of isotropic scattering is the same as that of non-scattering with specified heat generation in the medium. Forward scattering is found to produce higher radiative heat flux at hot and cold wall than backward scattering and optical thickness is also shown to play an important role in the problem. Results show that finite-volume method for radiation works well in orthogonal and non-orthogonal systems.

• Solar Energy
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• v.17 no.1
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• pp.103-111
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• 1997

The purpose of this research is the study of characteristics of heat transfer in a heat pipe controlled by solenoid valve. A solenoid valve located to the adiabatic section between evaporator and condenser of heat pipe was used to control the valve action for effective energy transfer of the industrial exchanger machine. By the results presented in this study temperature difference between evaporator and condenser increases with increasing the temperature frequency and with decreasing the temperature amplitude. When inclination angle and flow rate of cooling water increases, the temperature amplitude is reached to the steady state rapidly with increasing the temperature frequncy.

• The KSFM Journal of Fluid Machinery
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• v.18 no.6
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• pp.37-44
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• 2015

Conjugate heat analysis on a high pressure turbine stage including secondary flow paths has been carried out. The secondary flow paths were designed to be located in front of the nozzle and between the nozzle and rotor domains. Thermal boundary conditions such as empirical based temperature or heat transfer coefficient were specified at nozzle and rotor solid domains. To create heat transfer interface between the nozzle solid domain and the rotor fluid domain, frozen rotor with automatic pitch control was used assuming that there is little temperature variation along the circumferential direction at the nozzle solid and rotor fluid domain interface. The simulation results showed that secondary flow injected from the secondary flow path not only prevents main flow from penetrating into the secondary flow path, but also effectively cools down the nozzle and rotor surfaces. Also thermal barrier coating with different thickness was numerically implemented on the nozzle surface. The thermal barrier coating further reduces temperature gradient over the entire nozzle surface as well as the overall temperature level.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.133.2-133.2
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• 2010

Fischer-Tropsch synthesis (FTS) was carried out in heat-exchanger typed reactor with cobalt metallic foam catalyst. Considering the heat and mass transfer limitations in the cobalt catalyst, a Co-foam catalyst with an inner metallic foam frame and an outer cobalt catalyst was developed. The Co-foam catalyst was highly selective toward liquid hydrocarbon production and the liquid hydrocarbon productivity at $203^{\circ}C$ reached to $52.5ml/(kg_{cat}{\cdot}h)$, which was higher than that obtained by the Co-pellet. Furthermore, the heat-exchanger typed reactor was developed to efficiently control the highly exothermic reaction heat. The reaction heat generated in the FTS reaction on the cobalt active site was easily transferred to reactor wall by the metallic foam in the catalyst and the transferred reaction heat was directly removed by the hot oil which circulated the wall side of the heat-exchanger typed reactor.

• Journal of Bio-Environment Control
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• v.28 no.3
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• pp.204-211
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• 2019

The purpose of this study is to provide basic data for setting environmental design standards for domestic greenhouses. We conducted experiments on thermal environment measurement at two commercial greenhouses where hot water heating system is adopted. We analyzed heat transfer characteristics of hot water heating pipes and heat emission per unit length of heating pipes was presented. The average air temperature in two greenhouses was controlled to $16.3^{\circ}C$ and $14.6^{\circ}C$ during the experiment, respectively. The average water temperature in heating pipes was $52.3^{\circ}C$ and $45.0^{\circ}C$, respectively. Experimental results showed that natural convection heat transfer coefficient of heating pipe surface was in the range of $5.71{\sim}7.49W/m^2^{\circ}C$. When the flow rate in heating pipe was 0.5m/s or more, temperature difference between hot water and pipe surface was not large. Based on this, overall heat transfer coefficient of heating pipe was derived as form of laminar natural convection heat transfer coefficient in the horizontal cylinder. By modifying the equation of overall heat transfer coefficient, a formula for calculating the heat emission per unit length of hot water heating pipe was developed, which uses pipe size and temperature difference between hot water and indoor air as input variables. The results of this study were compared with domestic and foreign data, and it was found to be closest to JGHA data. The data of NAAS, BALLS and ASHRAE were judged to be too large. Therefore, in order to set up environmental design standards for domestic greenhouses, it is necessary to fully examine those data through further experiments.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2315-2324
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• 2023

Space nuclear reactors are becoming popular in deep space exploration owing to their advantages of high-power density and stability. Following the fourth-generation nuclear reactor technology, a conceptual design of the dual drum-controlled space molten salt reactor (D²-SMSR) is proposed. The reactor concept uses molten salt as fuel and heat pipes for cooling. A new reactivity control strategy that combines control drums and safety drums was adopted. Critical physical characteristics such as neutron energy spectrum, neutron flux distribution, power distribution and burnup depth were calculated. Flow and heat transfer characteristics such as natural convection, velocity and temperature distribution of the D²-SMSR under low gravity conditions were analyzed. The reactivity control effect of the dual-drums strategy was evaluated. Results showed that the D²-SMSR with a fast spectrum could operate for 10 years at the full power of 40 kWth. The D²-SMSR has a high heat transfer coefficient between molten salt and heat pipe, which means that the core has a good heat-exchange performance. The new reactivity control strategy can achieve shutdown with one safety drum or three control drums, ensuring high-security standards. The present study can provide a theoretical reference for the design of space nuclear reactors.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2946-2951
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• 2008

Combustion instability is a major issue in design of gas turbine combustors for efficient operation with low emissions. Combustion instability is induced by the interaction of the unsteady heat release of the combustion process and the change in the acoustic pressure in the combustion chamber. In an effort to develop a technique to predict self-excited combustion instability of gas turbine combustors, a new stability analysis method based on the transfer matrix method is developed. The method views the combustion system as a one-dimensional acoustic system with a side branch and describes the heat source as the input to the system. This approach makes it possible to use the advantages of not only the transfer matrix method but also well-established classic control theories. The approach is applied to a simple gas turbine combustion system to demonstrate the validity and effectiveness of the approach.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.6
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• pp.526-533
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• 2006

The prediction of heat-up time of an LCD glass plate in LCD glass pre-treatment process has been implemented in the present study. Firstly, the analytical solution for one-dimensional radiation heat transfer from IR heaters to a LCD glass plate is obtained. When the surface temperature of the IR heaters is set at 473 K, the heat-up time of LCD glass to averaged temperature of 383K is 28 seconds. In addition, a three dimensional full CFD analysis using STAR-CD is implemented in an effort to consider the effect of 3-D heat loss through the furnace walls. From the results of the 3-D CFB analysis, the heat-up time increases up to 32.5 seconds under the same conditions. When the IR heater temperature in creases up to 573 K, the heat-up time decreases to 12 seconds for the one-dimensional analytical solution and to 13.5 seconds for the 3-D CFD analysis, respectively.