• 설비공학논문집
• /
• 제12권9호
• /
• pp.853-859
• /
• 2000

In this study, low temperature waste heat recovery heat exchanger was developed using a principle of self-excited oscillating heat pipe. The heat exchanger of serpentine type was composed of extruded flat aluminum tube with 6 channels (3 nm$\times$ 2.75nm) and louvered fin. The heat transfer area density of heat exchanger was $331.9 m^2/m^3$. Working fluid is R141b and charge ratio was 40% by volume. Heat transfer rate and the effectiveness of heat exchanger was primary concern of this study. As a result, the effectiveness of heat exchanger was about 0.4-0.67, and recovered waste heat rate was about 4.5 kW per one unit of heat exchanger.

• Journal of Advanced Marine Engineering and Technology
• /
• 제40권2호
• /
• pp.96-101
• /
• 2016

The thermal management of high-power LED components in an assembly structure is crucial for the stable operation and proper luminous function. This study employs numerical tools to determine the optimum thermal design in LEDs with a heat sink consisting of a crevice-type vapor-chamber heat pipe. The effects of the MCPCB are investigated in terms of the substrate thicknesses on which the LEDs are mounted. Further, different placement configurations in a system module are considered. This study found that for a confined area, a power of 40 W/LED is applicable to a high-power package. Furthermore, the thermal conductivity of dielectric layer materials should ideally be greater than 0.9 W/m.K. The temperature conditions of the vapor chamber in a heat pipe greatly affect the thermal performance of the system. At an offset distance of 9.0 mm and a $2^{\circ}C$ increase in the temperature of the heat pipe, the resulting maximum temperature increase is approximately $1.9^{\circ}C$ for each heat dissipation temperature. Finally, at a thermal conductivity of 0.3 W/m.K, it was found that the total thermal resistance changes dramatically. Above 1.2 W/m.K, the resistance change reduces exponentially.

• 설비공학논문집
• /
• 제12권7호
• /
• pp.659-666
• /
• 2000

Heat transfer characteristics of a heat exchanger for low temperature waste heat recovery using oscillating capillary tube heat pipe were evaluated against the charge ratio variation of working fluid and various working fluids. R-l42b, R-22 and R-290 were used as working fluids. The heat exchanger was composed of heat pipe with capillary tube bundles, having a 2.6mm in outer diameter, 1.4mm in inner diameter with 101m long, and 40 turns. Charge ratio of working fluid was 40% and 50%. Water was used as secondary fluid. Inlet temperature and mass velocity for each secondary fluid were 297 K, 280 K and9~27 kg /$m^2s$,, respectively. From experimental results, it was found that heat transfer performance of R-22 was higher than those of R-l42b and R-290 and it was proportional to Figure of merit for thermosyphons. As a result, it was thought that R-22 was the most suitable working fluid of waste heat recovery for low temperature waste heat recovery.

• 설비공학논문집
• /
• 제13권5호
• /
• pp.368-376
• /
• 2001

Performance of heat exchanger was evaluated to heat exchanger using oscillating heat pipe for waste heat recovery of low temperature. Oscillating heat pipe used in this study was formed to the closed loop of serpentine shapes using copper tubes. Heat exchanger was formed to shell and tube type and composed of low finned tube. R-22 and R-141b were used to the working fluids of tube side and their charging ratio was 40%. And, water was used to the working fluid of shell side. As the experimental parameters, the inlet temperature difference of heating and cooling part of secondary fluid and the mass velocity of secondary fluid were used. The mass velocity of secondary fluid was changed from 90 kg/$m^2s\; to\;190 kg/m^2$s from the experimental results, heat recovery rate was linearly increased to the increment of the mass velocity of secondary fluid and the inlet temperature difference of secondary fluid. Finally, the performance of heat exchanger was evaluated by using $\varepsilon$-NTU method. It was found that NTU was about 1.5 when effectiveness was decided to 80%.

• 설비공학논문집
• /
• 제13권5호
• /
• pp.363-363
• /
• 2001

• 설비공학논문집
• /
• 제4권3호
• /
• pp.191-203
• /
• 1992

To analyze the unsteady heat transfer phenomena in radiant heating panel, a mathematical model was considered. Numerical analysis for solving the governing equations was conducted by using the finite difference method with boundary-fitted meshes. Transient temperature distributions and thermal responses in heating panel were obtained for various design parameters such as pipe pitches, pipe diameters and pipe depths. Experimental results were also obtained to verify the results of calculation.

• Journal of Advanced Marine Engineering and Technology
• /
• 제40권8호
• /
• pp.686-691
• /
• 2016

This paper employs numerical tools to obtain an optimal thermal design of a heat exchanger with plain-fins. This heat exchanger is located at the condensing section of a crevice-type heat pipe. The plain-fins in the heat exchanger are radically mounted to two tubes in the condensing section. To obtain the optimal design parameters, a computational fluid dynamics technique is introduced and applied to different placement configurations in a system module. Owing to its effects on the heat pipe performance, the temperature difference between the tube surfaces and ambient air is investigated in detail. A greater heat dissipation rate occurs when the plain-fin offsets change from 2 to 3 mm. When this temperature difference is ${\Delta}T=70^{\circ}C$, the upper part of the plain-fins undergoes an accumulation of heat. At below $70^{\circ}C$, the dissipation of heat is accepted. A rectangular plain-fin geometry with varying widths and heights does not have a significant impact on the heat dissipation through-out the overall system. In addition, the temperature distributions between different plain-fin pitches show an equal profile even with different fin pitches.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2006년도 하계학술발표대회 논문집
• /
• pp.333-338
• /
• 2006

This study is a research on Dual Bore heat pipe to investigate the ability of heat transport ability, heat resistance and difference of heat transport ability according to the type of heat pipes. As the result of this research, we got several conclusions. Each pipe of Dual Bore in one section has a similar heat transfer capability. In the range between $-20^{\circ}C$ and $60^{\circ}C$ the heat transfer capability is double than single bore which was analyzed by menas of GAP program. Heat resistance is below $0.05^{\circ}C$/W at every point, and it tells aluminum-ammonia heat pipes are proper for satellite.

• 한국산업융합학회 논문집
• /
• 제24권4_2호
• /
• pp.509-515
• /
• 2021

In this study, a pressure vessel for a heat pipe was fabricated by bonding a metal thin film using a polymer compound sheet. In order to confirm the applicability of the experimentally manufactured copper material thin heat pipe of 0.6 mm or less, the pressure resistance and effective thermal conductivity for pressure generated according to the type of the working fluid of the heat pipe were evaluated to suggest the commercialization potential of the thin heat pipe. As a result of evaluating the pressure resistance and effective thermal conductivity performance of the thin heat pipe, the following conclusions were drawn. 1) Using a PEEK-based polymer compound sheet, it was possible to fabricate a pressure vessel for a thin heat pipe with a pressure resistance of up to 1.0 MPa by bonding a copper thin film, and the possibility of commercialization was confirmed at a temperature below 120 ℃. 2) In the case of the effective thermal conductivity performance evaluation test, the effective thermal conductivity of ethanol was higher than that of FC72 and Novec7000, and in the case of ethanol, the maximum effective thermal conductivity was 2,851 W/mK at 3.0 W of heating.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제12권1호
• /
• pp.21-29
• /
• 2004

This paper is to study the heat transfer performance of the copper-water heat pipe with screen wicks. Recently, the semiconductor capacity of an electronic unit becomes larger, but its size becomes much smaller. As a result, a high- performance cooling system is needed. Experimental variables are inclination angles, temperatures of cooling waters and the mesh number of screen wicks. The distilled water was used as a working fluid. Based on the experimental results, when the copper-water heat pipe of 6mm diameter is used at the top heat mode, the heat transfer performance of 100 mesh 2 layers heat pipe is better than that of 150 and 200 mesh. The thermal resistance of the two layers with the 100-mesh screen was 0.7-$0.8^{\circ}C$/W.