• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.8 no.2
• /
• pp.299-306
• /
• 1996

This work presents an analytical model, so called modified LMTD method, to predict the thermal performance of finned-tube heat exchanger under frosting conditions. In this model, the total heat transfer coefficient and effective thermal conductivity of the frost layer were defined as a function of frost surface temperature. The surface temperature of the frost layer formed on the heat exchanger was calculated through the analysis of the heat and mass transfer process in the air and frost layer. To examine the validity of this analytical model, the computed results from the present model, such as heat transfer rate, frost mass and thickness of frost, were compared with the ones of the expermental work and LMED method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.10
• /
• pp.724-732
• /
• 2012

The microchannel evaporator with louver fin using carbon dioxide are analyzed according to the frost growth. To predict the performance of microchannel evaporator with the frost growth under low temperature, the simulation condition of previous studies was applied. As a result, the frost thickness increases and its increasing rate is reduced when the operating time increases. Frost thickness increases gradually below the quality of 0.74, and then it decreases rapidly. In addition, the frost growth of present model under same surface temperature is very similar trends with Moallem's test results. In case of low temperature application, the dimensionless frost thickness increases dramatically and it is about 0.86 after 10 minutes.

• Transactions of Materials Processing
• /
• v.21 no.2
• /
• pp.131-137
• /
• 2012

With the advantages of power savings, increased life expectancy and fast response time over traditional incandescent bulb, LEDs are increasingly used for many applications including automotive, aviation, display, and special lighting applications. Since the high heat generation of LED chips can reduce service life, degrade luminous efficiency, and cause variation of color temperature, many studies have been carried out on the optimization of LED packaging and heat sinks. In this study, a fin expansion type cooling device using heat pipe, instead of a solid aluminum heat sink, was designed for LED security lightings based on thermal resistance analysis. Numerical analysis and experimental validation were carried out to evaluate its cooling performance.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.1153-1158
• /
• 2009

The performance of louver-finned flat-tube and fin & tube radiators for computer CPU liquid cooling were experimentally investigated. In this study, 7 samples of radiators with different shape and pass number (1, 2, 10) were tested in a wind tunnel. The experiments were conducted under the different air velocity range from 1 to 4 m/s. The water flow rate through a pass was 1.2 LPM. Inlet temperatures of air and water were $20^{\circ}C$ and $30^{\circ}C$ respectively. It was found that the best performance was observed in the louver-finned flat-tube sample considering pressure drop and heat transfer coefficient.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.3
• /
• pp.417-422
• /
• 2002

The experiments have been carried out to evaluate the cooling performance of a fan-aluminum foam heat sink assembly in comparison with a conventional CPU cooler. In terms of the dimensionless surface temperature of the heater, the cooling performance of the aluminum foam heat sink is similar to that of the conventional one with much reduced weight. The optimum fin height is found to be strongly dependent on the fin height of the heat sink and flow characteristics of the cooling fan.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.17 no.2
• /
• pp.61-67
• /
• 2009

In the present study, an experiment was conducted to investigate the heat and mass transfer performance of heat exchangers used in the condensing gas boiler. Two types of spiral circular fin-tube heat exchangers and a plain tube were tested in the flue gas of propane and dry air. Heat and mass transfer coefficients were measured and compared with the previous correlations. The experimental data for the sensible heat transfer of the plain tube reasonably agreed with the previous correlations for dry air and flue gas. However, the mass transfer coefficient of the plain tube was greater than the previous correlations. The pH, $NO_x$, and $SO_x$ data of condensate were provided.

• Journal of Ocean Engineering and Technology
• /
• v.22 no.3
• /
• pp.58-63
• /
• 2008

A 32-ft class leisure boat was newly developed using statistical analysis of actual ships. Resistance performances were investigated by testing models in a high-speed circulating water channel, and with the CFD method. The effects of a trim tab and of a fin attached at the hull side were studied together. Wave patterns were observed to clarify the relationship between resistance performance and wave characteristics. It was found that a trim tab and a side fin play a role in increasing resistance performance within a certain velocity range.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.11 no.6
• /
• pp.725-732
• /
• 1999

It is usual to use hydrophilic-coated aluminum foil for evaporator fin of air-conditioners to reduce air flow resistance caused by the water droplets condensed on the fin surface. The major effect of a hydrophilic coating is to reduce the contact angle of the condensate and prevent bridging of the condensate between the adjacent fins. The performance of hydrophilic coating generally tends to be degraded as it is used since the coating material is washed down by the condensate. In the present work, several types of hydrophilic coatings were evaluated in terms of durability of hydrophilicity, corrosion resistance and heat resistance. Results showed that an improved hydrophilic coating of resin type presented superb qualify in terms of durability and corrosion resistance while having almost the same level of qualify in heat resistance compared with the others.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.15 no.3
• /
• pp.264-272
• /
• 1986

The performance of vertical and horizontal tubes with multiple fins of rectangular and triangular cross section was investigated theoretically for boiling heat transfer. A simple method for numerical program assuming one-dimensional heat flow was used to predict the performance of these finned tubes and their bundles. The object of the new study was to develop optimum fin design, especially in tube bundles, considering from a viewpoint to minimize the space in which the maximum heat flux density was expected.

• Journal of Power System Engineering
• /
• v.21 no.3
• /
• pp.93-101
• /
• 2017

In conventional adsorption chamber, adsorbent is embedded in between heat exchanger fins by wire mesh. This method impedes heat and mass transfer efficiency. So in this study, to improve the heat transfer performance of heat exchanger, a fin-tube exchanger was coated with FAPO (Ferroaluminophosphate) zeolite adsorbent. The fin-tube heat exchanger has a fin pitch of 1.8 mm with a variation of adsorbent coating thickness of about 0.1 mm, 0.15 mm and 0.2 mm. By varying cooling water temperature and chilled water temperature respecively, heat transfer rate and overall heat transfer coefficient were investigated. As a result, the heat transfer rate and overall heat transfer coefficient increase with decreasing cooling water temperature and increasing chilled water temperature. Under the basic conditions, the heat transfer rate of heat exchanger with 0.2 mm coating thickness is 11% and 43% higher than that of 0.1 mm and 0.15 mm, respectively. The overall heat transfer coefficient is $189.1W/m^2{\cdot}^{\circ}C$, it is two times lager than that of 0.1 mm.