• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.4
• /
• pp.497-503
• /
• 1997

In the present study, the cooling package using the heat pipe has been developed to improve the thermal performance in the point of cooling characteristics of the electronic chip placed to the subrack being readily assembled and disassembled in ATM switching system. As the preliminary experiments, the cooling performances between a conventional way using a cooling fin and a proposed method applying the heat pipe are compared and analyzed. The cooling performance at a simulated electronic component packaging a heat pipe module is approximately achieved up to $5.0W/cm^2$ heat flux and the allowable temperature at the heated chip is sustained in the range within $70^{\circ}C$. From the results, it is confirmed that temperature oscillations are also settled by inserted wick in the evaporator section. From the user's viewpoint, the method to assemble and disassemble the heat pipe easily has been devised.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.4
• /
• pp.26-33
• /
• 2019

This study is a thermal and flow analysis of Organic Rankine Cycle (ORC) pipe line for 250 kW grade waste gas heat recovery. We attempted to obtain the boundary condition data through the process design of the ORC, which can produce an electric power of 250 kW through the recovery of waste heat. Then, we conducted a simulation by using STAR-CCM+ to verify the model for the pipe line stream of the 250 kW class waste heat recovery system. Based on the results of the thermal and flow analyses of each pipe line applied to the ORC system, we gained the following conclusion. The pressure was relatively increased at the pipe outside the refracted part due to the pipe shape. Moreover, the heat transfer amount of the refrigerant gas line is relatively higher than that of the liquid line.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.5
• /
• pp.713-723
• /
• 1986

The purpose of this research was to study the heat transfer characteristics of heat pipe which used non-metallic(SiO$_{2}$), circumferential wick and meshed slab wick as ADI method and experimental results. Compared wick experimental data and results by ADI method showed the good agreement and ADI method was utilized in pridicting the performance of heat pipe. Also, ADI method was applied to predict heat pipe performance according to the various volume ratios of metallic bond. The heat transfer characteristics of heat pipe could be predicted by heat flux and superheat term below the maximum heat flux limit. According to the addition ratio of metallic bond, heat transfer ratio could be improved as 2-3 times and when heat conductivity ratio(K$_{b}$/K$_{a}$) was increased at 4-12 ratio, heat transfer was in creased as 1.7-2.4 times, and the prediction of heat transfer could be show as exponential type. In producting non-metallic wick used to low heat pipe, metallic bond which is the conductivity of good quality and enduring for high temperature will be improved as in important problem.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.4
• /
• pp.320-327
• /
• 2006

Numerical analysis and experimental study are performed to investigate the effect of heat load and operating temperature on the thermal performance of several variable conductance heat pipe (VCHP) with screen meshed wick. The heat pipe is designed in 200 screen meshes, 500 mm length and 12.7 mm outer diameter tube of copper, water (4.8 g) is used as working fluid and nitrogen as non-condensible gas (NCG). Heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Analysis values and experimental data of wall temperature distribution along axial length are presented for heat transport capacity, condenser cooling water temperature change, degrees of an inclination angle and operating temperature. These analysis and experiment give the follow findings: For the same charging mass of working fluid, the operating temperature of heat pipe becomes to be high with the increasing of charging mass of NCG. When the heat flux at the evaporator section increases, the vapor pressure in the pipe rises and consequently compresses the NCG to the condenser end part and increases the active length of the condenser. From previous process, it is found out we can control the operating temperature effectively and also the analysis and experimental results are relatively coincided well.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.8 no.1
• /
• pp.1-9
• /
• 1979

Heat transfer characteristics of an annular heat pipe is investigated theoretically and experimentally. An annular heat pipe transports maximum heat which is found to be a cubic polynomial function of the thickness of annulus when the annulus becomes large, maximum heat transfer rate Is limited by boiling criterion. The limit decreases inversely proportional to the thickuess of annulus. Theoretical formula for thermal resistance of annular heat pipe Is proposed. Experimental results on the maximum heat transfer rate satisfactorily agree with theory. Measured thermal resistance is found to be lower than the predicted results as the thickness of annulus becomes large.

• Journal of Energy Engineering
• /
• v.20 no.4
• /
• pp.330-337
• /
• 2011

In these days, the gas or kerosene boiler was usually used as heating system. This study was carried out to investigate the merits of X-L pipe boiler with electric heat line that was specially manufactured. The electric heat line was inserted into inside of X-L pipe and voltage was impressed to electric heat line and, as a result, temperature of X-L pipe filled with heat medium was increased. As changing the number of electric heat line and voltage, the characteristics of X-L pipe boiler and its mechanism on heat generation were studied. Furthermore, the economical efficiency was evaluated by comparing heating cost of X-L pipe boiler with those of kerosene boiler and natural gas boiler, respectively. As the results, it was confirmed that heating cost of X-L pipe boiler was showed as 28% of kerosene boiler and 58% of natural gas boiler.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.19 no.3
• /
• pp.14-22
• /
• 2023

Steel-pipe civil structures, including steel-pipe energy piles and cast-in-place piles (CIPs), utilize steel pipes as their primary reinforcements. These steel pipes facilitate the circulation of a working fluid through their annular crosssection, enabling heat exchange with the surrounding ground formation. In this study, the cooling performance of a ground source heat pump (GSHP) system that incorporated steel-pipe civil structures was investigated to assess their applicability. First of all, the thermal performance test was conducted with steel-pipe CIPs to evaluate the average heat exchange amount. Subsequently, a GSHP system was designed and implemented within an office container, considering the various types of steel-pipe civil structures. During the performance evaluation tests, parameters such as the coefficient of performance (COP) and entering water temperature (EWT) were closely monitored. The outcomes indicated an average COP of 3.74 for the GSHP system and the EWT remained relatively stable throughout the tests. Consequently, the GSPH system demonstrated its capability to consistently provide a sufficient heat source, even during periods of high cooling thermal demand, by utilzing the steel-pipe civil structures.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.1
• /
• pp.64-71
• /
• 2012

An efficient cooling system is an essential part of the electronic packaging such as a high-luminance LED lighting. A special technology, Pulsating Heat Pipe (PHP), can be applied to improve cooling of a sealed, explosion-proof LED light fixture. In this paper, the characteristics of the pulsating heat pipes in the imposed thermal boundary conditions of LED lightings were experimentally investigated and a PHP device that works free of alignment angle was investigated for cooling of explosion-proof LED lights. Five working fluids of ethanol, FC-72, R-123, water, and acetone were chosen for comparison. The experimental pulsating heat pipe was made of copper tubes of internal diameter of 2.1 mm, 26 turns. A variable heat source of electric heater and an array of cooling fins were attached to the pulsating heat pipe. For the alignment of the heating part at bottom, an optimum charging ratio (liquid fluid volume to total volume) was about 50% for most of the fluids and water showed the highest heat transfer performance. For the alignment of the heating part on top, however, only R-123 worked in an un-looped construction. This unique advantage of R-123 is attributed to its high vapor pressure gradient. Applying these findings, a cooling device for an explosion-proof type of LED light rated 30 W was constructed and tested successfully.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.11
• /
• pp.1044-1050
• /
• 2004

The present study has been conducted to develop a heat pipe heat exchanger for middle-high temperature ranged from 300 to $600^{\circ}C$. Heat transfer rate, overall heat transfer coefficient and temperature effectiveness were investigated using a heat pipe heat exchanger with Dowtherm A as working fluid. Theoretical analysis was also conducted, and the followings were obtained: (1) Heat exchange rate increased as waste gas temperature supplied to evaporator and frontal velocity in condenser increased, (2) Overall heat transfer coefficient increased by $3{\sim}7\%$ as frontal velocity in evaporator and condenser increased, (3) Temperature effectiveness was about $30\%$ in evaporator and was about $40\%$ in condenser, (4) Heat recovery rate was about $38\%$, (5) Pressure drop did not exceed $8\;mmH_{2}O$ under the running condition of $1{\sim}3Nm/s$, (6) Simulation results were corresponded with experimental results.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.11
• /
• pp.755-759
• /
• 2016

The use of heat pipes in the electronic telecommunication field is increasing. Among the various types of heat pipes, the thin flat heat pipe has relatively high applicability compared with the circular heat pipe in the electronic packaging application. The thin flat heat pipe based on extrusion fabrication has a simple capillary wick structure consisting of rectangular cross sectional grooves on the inner wall of the pipe. Although the groove serves as a simple capillary wick, and many such grooves are provided on the inner wall, it is difficult for the grooves to realize a sufficiently high capillary force. In the present study, a thin flat heat pipe with a wire bundle was developed to overcome the drawback of poor capillary force in the thin flat heat pipe with grooves, and was evaluated by conducting tests. In the performance test, the thin flat heat pipe with the wire bundle showed a lower thermal resistance of approximately 3.4 times, and a higher heat transfer rate of approximately 3.8 times with respect to the thin flat heat pipe with grooves as the capillary wick respectively. The possibility of using the wire bundle as a capillary wick in the heat pipe was validated in the present study; further study for commercializing this concept will be taken up in the future.