• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.6
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• pp.449-469
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• 2011

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering during 2010. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends of thermal and fluid engineering have been surveyed as groups of general thermal and fluid flow, fluid machinery, and new and renewable energy. Various topics were presented in the field of general thermal and fluid flow. Research issues mainly focused on the thermal reliability of axial fan and compressor in the field of fluid machinery. Studies on the design of ground source heat pump systems and solar chemical reactors were executed in the field of new and renewable energy. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (3) Refrigeration systems with alternative refrigerants such as hydrocarbons, mixed refrigerants, and CO2 were studied. Performance improvement of refrigeration systems are tried applying various ideas of refrigerant subcooling, dual evaporator with hot gas bypass control and feedforward control. The hybrid solar systems combining the solar collection devices with absorption chillers or compression heat pumps are simulated and studied experimentally as well to improve the understanding and the feasibility for actual applications. (4) Research trend in the field of mechanical building facilities has been found to be mainly focused on field applications rather than performance improvements. Various studies on heating and cooling systems, HVAC facilities, indoor air environments and energy resources were carried to improve the maintenance and management of building service equipments. In the field of heating and cooling systems, papers on a transformer cooling system, a combined heat and power, a slab thermal storage and a heat pump were reported. In the field of HVAC facilities, papers on a cooling load, an ondol and a drying were presented. Also, studies on HVAC systems using unutilized indoor air environments and energy resources such as air curtains, bioviolence, cleanrooms, ventilation, district heating, landfill gas were studied. (5) In the field of architectural environment and energy, studies of various purposes were conducted such as indoor environment, building energy, renewable energy and green building. In particular, renewable energy and building energy-related researches have mainly been studied reflecting the global interest. In addition, many researches which related the domestic green building certification of school building were performed to improve the indoor environment of school.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.119-124
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• 2000

A finite element method is applied to investigate the characteristics of the fluid flow and heat transfer performance in a channel in terms of the various effects of baffle cuts, baffle angles, and leakages. The results show that the decrease of a baffle cut gives a good heat transfer enhancement. However, it also increases pressure drop. In the case of an inclined baffle, the result shows that the pressure drop decreases with a reasonable heat transfer performance. But a steeply inclined baffle gives adverse effects on the performance of the channel. The clearances between baffle-to-shell and tube-to-baffle affect the overall performance. The effects of these parameters are discussed in details.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.101-108
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• 2011

Understanding the exhaust gas recirculation (EGR) cooler fouling in diesel engine is important factor in the durability characteristic of a EGR system. We develope a test rig and PM feeder using carbon black to examine the effect of fouling on EGR cooler devices those were consisted of flat and shell & tube type. The EGR cooler fouling process is a complex interaction involving heat exchanger shape, boundary condition, constitutes, chemistry and operating mode. As the soot deposited to EGR cooler, these formed a thin deposit layer that was less heat exchange than the fresh status of tube enclosing the exhaust gas, resulting in lower heat exchange effectiveness in both type coolers. But these deposits caused different results in pressure drop, it is increased in flat type, but decreased in Shell & tube type of EGR cooler. A cause was estimated from a change of the flow structure and a decrease of contact area as the EGR cooler fouling.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.681-691
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• 2006

Nucleate boiling heat transfer for refrigerants, R113, and R113+wt4% ethanol mixture, an azeotropic mixture under electric field was investigated experimentally in a single-tube shell/ tube heat exchanger. A special electrode configuration which provides a more uniform electric field that produces more higher voltage limit against the dielectric breakdown was used in this study. Experimental study has revealed that the electrical charge relaxation time is an important parameter for the boiling heat transfer enhancement under electric field. Up to 1210% enhancement of boiling heat transfer was obtained for R113+wt4% ethanol mixture which has the electrical charge relaxation time of 0.0053 sec whereas only 280% enhancement obtained for R113 which has relaxation time of 0.97 sec. With artificially machined boiling surface, more enhancement in the heat transfer coefficient in the azeotropic mixture was obtained.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.4
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• pp.483-493
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• 2006

A model for a pressure drop of water vapor flow across tube banks in a horizontal tube absorber of an absorption chiller/heater using LiBr solution as a working fluid has been developed based on a commercial 20RT(70kW) absorption chiller/heater. The numerical results show that the characteristic of the pressure drop in the shell side of the horizontal tube absorber is completely different from that in a conventional shell and tube heat exchanger. Especially, solution film thickness has significant influence on the vapor pressure drop in the horizontal tube absorber. In addition, the effects by the tube diameters, the longitudinal pitch to diameter ratio, and Reynolds number of the vapor flow, on the vapor pressure drop have been studied to evaluate the compactness of tube absorber. It was found that the vapor pressure drop decreases as tube diameter increases, the longitudinal pitch to diameter ratio increases, and Reynolds number of the vapor flow decreases. A comparison of the present study results with well-established experimental and numerical results showed a good overall agreement.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.2
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• pp.167-173
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• 2004

Fouling of heat exchangers is generated by water-borne deposits, commonly known as foulants including particulate matter from the air, migrated corrosion produces; silt, clays, and sand suspended in water; organic contaminants; and boron based deposits in plants. The fouling is known to interfere with normal flow characteristics and reduce thermal efficiencies of heat exchangers. This paper describes the fouling analysis technique developed in this study which can analyze the thermal performance for heat exchangers and estimate the future fouling variations. To develop the fouling analysis technique fur heat exchangers, fouling factor was introduced based on the ASME O&M codes and TEMA standards. For the purpose or verifying the fouling analysis technique, the routing analyses were performed for four heat exchangers in several nuclear power plants; two residual heat removal heat exchangers of the residual heat removal system and two component cooling water heat exchangers of the component cooling water system.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.55-60
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• 2003

As operating time of heat exchangers progresses, fouling generated by water-borne deposits increases and thermal performance decreases. The fouling is known to interfere with normal flow characteristics and reduce thermal efficiencies of heat exchangers. The heat exchangers of nuclear power plants have been analyzed in terms of the heat flux and heat transfer coefficient at test conditions based on the ASME OM-S/G-Part 2 as a means of heat exchanger management. It is hard to estimate the heat performance trend and to establish the future management plan. This paper describes the fouling evaluation method which can evaluate the thermal performance for heat exchangers and estimate the future fouling variations and the plugging margin evaluation method which can reflect the current fouling level developed in this study. To develop the fouling and plugging margin evaluation methods for heat exchangers, fouling factor was introduced based on the ASME O&M codes and TEMA standards. For the purpose of verifying the two evaluation methods, the fouling and plugging margin evaluations were performed for a component cooling heat exchanger in a nuclear power plant.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2298-2314
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• 1996

Electric field effect on boiling of refrigerants R11, R113, and FC72 has been investigated experimentally. One purpose of the experimental investigation is to determine the effects of the electrode arrangements on electrohydrodynamic boiling of the above mentioned liquids. The test equipment employed in the experiment consists of a shell and tube heat exchanger with six or six and twelve rows of electrode wires around the tube. It has been found that the applied voltage promotes the boiling heat transfer coefficient except FC72. Boiling heat transfer enhancement obtained is about 230% for R11, 280% for R113. It has also been observed that bubbles detached from the tube aggregate at the place where the electrical gradient force balances with the buoyancy one. These aggregated bubbles force to decrease the boiling heat transfer coefficient as well as to reduce the voltage needed to the dielectric breakdown.

• Journal of Hydrogen and New Energy
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• v.25 no.1
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• pp.39-46
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• 2014

Our lab designs a heat exchangers for hydrogen gas. Coolant is water, thus it is very difficult to determine heat transfer parameters in this gas-liquid system. Repeated experiments gives overdesign value 6.06%, overall heat transfer coefficient 36.32 ($kcal/m^2-hr-^{\circ}C$) for Hydrogen. Theoretically determined overall heat transfer coefficient is 38.44 ($kcal/m^2-hr-^{\circ}C$). Our lab simulated this system and overdesign 30.4% shows good match with this experiment by HTRI. These parameters are in same range with literature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.4
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• pp.248-257
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• 2010

An exhausted heat recovery system for a small gas engine cogeneration plant was investigated. The system was designed and built in a 300 kW class cogeneration demonstrative system. The basic performance was tested depending on load variation, and installed to a field site as a bottoming heat and power supply system. The exhaust gas heat exchangers (EGHXs) in shell-and-tube type and shell-and-plate type were tested. The entire efficiency of the cogeneration system was estimated between 85 to 90% under the 100% load condition, of which trend appears higher in summer due to the less thermal loss than in winter. Power generation efficiency and thermal efficiency was measured in a range of 31~33% and 54~57%, respectively.