• Journal of Mechanical Science and Technology
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• 제16권3호
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• pp.344-353
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• 2002

A reliable computational heat transfer model has been investigated to define the heat transfer characteristics of a spray column direct contact heat exchanger, which is often utilized in the process involving counterflows for heat and mass transfer operations. Most of the previous studies investigated are one-dimensional unsteady solutions based on rather fragmentary experimental data. Development of a multidimensional numerical model and a computational algorithm are essential to analyze the inherent multidimensional characteristics of a direct contact heat exchanger. The present study has been carried out numerically and establishes a solid simulation algorithm for the operation of a direct contact heat exchanger. Operational and system parameters such as the speed and direction of working fluid droplets at the injection point, and the effects of aspect ratio and void fraction of continuous fluid are examined thoroughly as well to assess their influence on the performance of a spray column.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1272-1276
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• 2009

The purpose of this study is to introduce wasted heat recovery heat exchanger for different kind of material in HVAC systems in field. For the purpose of estimating the large volume rotary heat exchanger and cross flow plate heat exchanger in heat recovery ventilator.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.149-152
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• 2007

The numerical simulations on the heat transfer and flow field were carried out for the improvement of the performance of the shell and tube heat exchanger. The steady incompressible 3-D Navier-Stokes solution is obtained with the actual operational condition and geometry of the heat exchanger. The present geometry of the heat exchanger causes poor heat transfer since the air inside shell dose not flow through the tube bundle, but around it. The enhancement of the heat transfer can be achieved by the variation of the design factor like the sealing strip located on the top/bottom and middle of the baffle.

• Journal of Advanced Marine Engineering and Technology
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• 제28권1호
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• pp.39-45
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• 2004

The commercial viability of heat exchanger is mainly dependent on their long-term fouling characteristics because the fouling increases the pressure loss and degrades the thermal Performance of a heat exchanger. An experimental study was performed to investigate the characteristics of fluid flow and heat transfer in a fluidized bed heat exchanger with circulating various solid particles. The Present work showed that the flow velocity range for Possible collision between the tube wall and the particles was higher with heavier density solid particles. in audition. the solid particle periodically hitting the tube wall broke the thermal boundary laver. and increased the rate of heat transfer.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3142-3147
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• 2008

A simple transient simulation of ground source heat pump system was carried out to investigate the effects of ground thermal conductivity on its performance. The TRNSYS code with a simple water to water heat pump model was used to compare the COP variation of the system. A new ground heat exchanger called by semi-closed loop was proposed and constructed in the real site. The effective thermal conductivity was measured using the test equipment developed by according to the line source model. The simulation results showed that highly efficient thermal conductivity of the grout material could increase the performance of the heat pump system very well. And the new ground heat exchanger showed the increased effective thermal conductivity as the penetration water flow rate(PWFR) was increased. Therefore, the performance improvement of the heat pump system using the proposed ground heat exchanger can be expected.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2328-2333
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• 2008

The experimental study was carried out to evaluate the heat transfer performance on the shell side of shell-and-plate finned tube heat exchanger with three different tube numbers(9, 13 and 19). Oil flowing on the shell side was cooled by cold water flowing inside the tubes. A shell-and-tube heat exchanger of an oil cooler consisted of one shell pass and two tube passes with the inner tube diameter of 8.82 mm and the tube length of 575 mm. Mass flow rate was varied from 1.2 to $6.0\;m^3/h$ for oil and from 0.6 to $3.0\;m^3/h$ for cold water, respectively. From the experiment of shell-and-plate finned tube heat exchanger, the shell side heat transfer coefficient of heat exchanger with 9 tubes was compared with that of 13 and 19 tubes. It was found that the heat exchanger with 9 plate finned tubes showed more performance of heat transfer than that of 13 and 19 tubes.

• 대한기계학회논문집B
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• 제32권10호
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• pp.769-775
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• 2008

In this study, the investigations on the dimpled type Exhaust Gas Recirculation (EGR) cooler have been focused on the high heat exchanger efficiency. To overcome low heat exchanger efficiency of general EGR cooler, the dimpled type EGR cooler was developed. It was ensured the improvement of the performance of the dimpled type EGR cooler related to the heat exchange based on a series of the experiment. These results were caused by the increase of thermal surface area in accordance with the dimple's one. The estimation model of the heat exchanger efficiency using the Effectiveness-NTU method was also developed in order to verify the validity of experimental result. Also, the program for the estimation of the heat exchanger efficiency on the EGR cooler with regard to the dimpled tube shape was developed. Resultantly, it was confirmed that the dimpled type EGR cooler could be served better performance than the conventional one in view of the heat exchanger efficiency.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.9-16
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• 2004

Close-coupled catalyst (CCC) can reduce the engine cold-start emissions by utilizing the energy in the exhaust gas. However, in case the engine is operated at high engine speed and load condition, the catalytic converter may be damaged and eventually deactivated by thermal aging. Excess fuel is sometimes supplied intentionally to lower the exhaust gas temperature avoiding the thermal aging. This sacrifices the fuel economy and exhaust emissions. This paper describes the results of an exhaust heat exchanger to lower the exhaust gas temperature mainly under high load conditions. The heat exchanger was installed between the exhaust manifold and the inlet of close-coupled catalytic converter. The exhaust heat exchanger successfully decreased the exhaust gas temperature, which eliminated the requirement of fuel enrichment under high load conditions. However, the cooling of the exhaust gas through the heat exchanger may cause the deterioration of exhaust emissions at cold start due to the increment of catalyst light-off time.

• Advances in aircraft and spacecraft science
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• 제2권4호
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• pp.469-482
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• 2015

This study has the aim to develop a numerical design regarding the position and the inner performances of a heat exchanger in a light helicopter. the problem was to find first of all the best position of the heat exchanger inside the engine vane in order to maximize the air flow rate capable to pass through the heat exchanger section. It is to be said that the only air contribution in the vane comes from the opening present in the roof under the main rotor. The design has been performed by means of the commercial code Fluent and using the well known grid generator ICEM CFD. Different positions are first investigated so to establish the best one. Subsequently, different areas of the opening on the roof have been considered in order to maximize even more the flow rate in the heat exchanger that was not sufficient based on the first guess of velocity, as aforementioned. At the end interesting design results are presented and discussed by contours of fields and values.

• 설비공학논문집
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• 제22권10호
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• pp.657-664
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• 2010

The theoretical analysis of performance characteristics in a $CO_2$ cycle with the heat exchanger type was carried out. The size and performance of the fin-tube and microchannel heat exchanger were compared with operating conditions. As a result, the performance of the fin-tube gascooler and evaporator were more sensitive to the variation of operating condition compared to that of the microchannel gascooler and evaporator. Beside, the sizes of microchannel gascooler and evaporator could be decreased by 73% and 76%, respectively, compared to those of the fin-tube type gascooler and evaporator with the similar capacity. The COP and reliability of the $CO_2$ system can be increased by using a microchannel heat exchanger.