• International Journal of Air-Conditioning and Refrigeration
• /
• v.17 no.2
• /
• pp.52-60
• /
• 2009

The purpose of this research is to develop high efficiency plastic plate heat exchangers which can be substituted for conventional aluminum plate heat exchangers. Four simulation models of plastic plate heat exchangers are designed and simulated: that is, flat plate type, turbulent promoter type, corrugate type and dimple type heat exchanger. The flat plate type is designed as the reference model in order to evaluate how much thermal performance increases. The turbulent promoter type is fabricated with cylindrical-type vortex generators and rib-type turbulent promoters. The corrugate type is obtained from the conventional stainless steel compact heat exchangers, which are called the herringbone-type compact heat exchangers. The dimple type has a number of dimples on its surface. In this study, the flow and heat transfer characteristics of the plastic plate heat exchanger are investigated using numerical simulation and compared with experimental results. Numerical simulation is carried out using the FLUENT code. The flows are assumed as a three-dimensional, incompressible and turbulent model. The computational analysis and experimental results both show that the friction coefficient and Nu number is highest in the corrugate type. The tendency of numerical simulation results is in good agreement with that of the experimental results.

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

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.3
• /
• pp.1111-1116
• /
• 2011

Heat exchangers have been used for the automotive, HVAC systems, and other various industrial facilities, so the market is very wide. In general, high-efficiency heat exchangers with louver fins are used in the dust-free environment while heat exchangers with wavy fins are used for dusty environment such as construction site, etc. In this study, numerical analysis has been performed for typical heat exchangers, used as oil coolers or fuel coolers, with dual cell model that can handle different grids for the air-side and oil-side of heat exchangers. First wind tunnel tests were conducted to obtain one-dimensional thermal performance data of heat exchangers. Then, heat release rates with varying air flows were numerically predicted using the three-dimensional dual-cell model. The model can greatly enhance the accuracy of thermal design since it includes the effects of nonuniformity of air flows across heat exchangers.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.11
• /
• pp.1492-1499
• /
• 2001

In order to develop the compact and flexible heat exchangers, we made the helically coiled heat exchangers. They can be manufactured with small diameter copper tubes without the need for fins; inner diameter=1.0 mm, straight tube length=1.5 m. The experiments were carried out with the following conditions; evaporation pressure=0.6 MPa, air velocity=0.7 ∼ 1.7 m/s, and working fluid=R-22. Pressure drop and heat transfer coefficient of heat exchangers were experimented according to the air velocity. The results of heat transfer coefficient show a 35% beneficial increase fur these heat exchangers over the other covered fin-tube heat exchangers. A cooling capacity of about 3 kW was obtained with an air velocity of 1.5 m/s. The distribution header has also been designed fur efficient distribution of refrigerant flow.

• Journal of Power System Engineering
• /
• v.17 no.6
• /
• pp.54-62
• /
• 2013

A numerical analysis is performed to evaluate mass flow balance in the heat exchanger for the dehumidifier. To improve the mass flow balance for maximum heat transfer performance, inlet, outlet and baffle are changed. Mass flow balance is evaluated by non-uniformity of flow which is the same concept with the standard deviation. Usually, there will occur many paths between the inlet and the outlet, however, it will follow shortest and low resistance ways. The uniform distribution of flow is numerically analyzed for several types of heat exchangers. Making the shortest way between the inlet and the outlet is most important factor. Two types of heat exchangers are installed in the dehumidifier and 4 cases of Type A heat exchangers and 3 cases of Type B heat exchangers are evaluated and optimized. The result of this research is applied to design heat exchanger for commercial dehumidifiers.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.2
• /
• pp.222-229
• /
• 2009

This study presents comparison of heat transfer and air side friction characteristics in a condenser condition of air conditioner between Louver fin-tube heat exchangers and aluminum parallel heat exchangers. All experiments are performed using an air-enthalpy type calorimeter, which is designed based on the method described in ASHRAE standards. The air velocities crossing the heat exchanger tubes are varied from 0.7 to 1.6 m/s with 0.3 m/s interval, maintaining air dry temperature and relative humidity at $20^{\circ}C$ and 60% respectively. Water temperature and flow rate inside the tube are $70^{\circ}C$ and 10 LPM, respectively. Experimental results show that the heat transfer performances of aluminum heat exchangers are 17-163% higher than those of Louver fin-tube heat exchangers based on the data per unit volume, mass, and heat transfer area, whereas air side pressure drops of aluminum heat exchangers are 19-81% lower.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.1
• /
• pp.53-59
• /
• 2009

The objectives of this paper are to study the characteristics of heat transfer and pressure drop of the micro channel heat exchangers using diffusion bonding technology. Four types of heat exchangers are designed and manufactured, which are straight type, long dot type, splited wavy type and straight double side type. Heat transfer and pressure drop performance of each heat exchangers are measured in various operating conditions, and compared each other. The results show that the $(j/f)^{1/3}$ performance of splited wavy type and long dot type increases about 10.3% and 6.1% at the Reynolds number 470 compared to that of straight type, respectively. On the other hand, $(j/f)^{1/3}$ performance of straight double side type decreases 19.7%.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2304-2309
• /
• 2008

The objectives of this paper are to study the characteristics of heat transfer and pressure drop of the micro channel heat exchangers using diffusion bonding technology. Four types of heat exchangers are designed and manufactured, which are straight type, long dot type, splited wavy type and straight double side type. Heat transfer and pressure drop performance of each heat exchangers are measured in various operating conditions, and compared each other. The results show that the $(j/f)^{1/3}$ performance of splited wavy type and long dot type increases about 10.3% and 6.1% at the Reynolds number 470 compared to that of straight type, respectively. On the other hand, $(j/f)^{1/3}$ performance of straight double side type decreases 19.7%.

• Nuclear Engineering and Technology
• /
• v.52 no.1
• /
• pp.51-58
• /
• 2020

Despite the recent growth of interest in molten salt reactor technology and the crucial role which heat transfer plays in the design of power reactors, specific studies on the design of heat exchangers for the Molten Salt Fast Reactor have not yet been performed. In this work we deliver a preliminary but quantitative analysis of the intermediate heat exchangers, based on reference design data from the SAMOFAR H2020-Euratom project. Two different promising reference technologies are selected for study thanks to their compactness features, the Printed Circuit and the Helical Coil heat exchangers. We present preliminary design results for each technology, based on simplified design tools. Results highlight the limiting effects of the compactness constraints imposed on the fuel salt inventory and the allowed size. Large pressure drops on both flow sides are to be expected, with negative consequences on pumping power and natural circulation capabilities. The small size required for the flow channels also represents possible fabrication issues and safety concerns regarding channel blockage.

• Proceedings of the SAREK Conference
• /
• 2006.06a
• /
• pp.627-632
• /
• 2006

An experimental study is conducted to investigate the effect of the tube row and fin spacing on the air-side heat transfer and friction characteristics of fin-tube heat exchangers with slit fin pattern. A total of twelve samples of fin-tube heat exchangers with the nominal tube diameter of 7 mm, transverse tube pitch of 19 mm and longitudinal tube pitch of 12.5 mm are tested. The thermal fluid measurements are made using a psychometric calorimeter. The raw data are reduced to the desired heat transfer coefficient in terms of j-factor and friction factor of f for various frontal air velocities, fin pitches and number of tube rows.