A Design for Loop Thermosyphon Including Effect of Non-Condensable Gas

2011 ◽  
Author(s):  
Hiroyuki Toyoda ◽  
Tadakatsu Nakajima ◽  
Yoshihiro Kondo ◽  
Akio Idei ◽  
Shigemasa Sato
Keyword(s):  
Thermal Resistance ◽  
Ambient Temperature ◽  
Partial Pressure ◽  
Total Pressure ◽  
Air Cooling ◽  
Total Thermal Resistance ◽  
Cooling Performance ◽  
Design Information ◽  
Cooling Part

We have developed a loop thermosyphon for cooling electronics devices. Its cooling performance changes with the ambient temperature and amount of input heating. Especially it deteriorates with non-condensable gas (NCG) increase. NCG leakage of thermosyphon cannot detect below under 10−10 Pa-m3/s, though we have to design the thermosyphon considering these characteristics to provide guaranteed performance for 5–10 years. In this study, the effect of the amount of NCG in each component of a thermosyphon was measured while changing the amount of heater input, and the amount of NCG. As a result, we obtained some useful design information. The performance of air cooling part does not depend on the NCG amount in this case. The performance of evaporation part depends on the total pressure that includes the partial pressure of vapor and the partial pressure of NCG. The performance of condensation part is deteriorated strongly by NCG amount increase. Additionally, we expressed these performances as approximations. These expressions let us predict the total thermal resistance of this thermosyphon by the NCG amount and the input heating amount. Then, using the leakage of a thermosyphon and the amount of dissolved NCG in water, we predicted the amount of NCG that will be in the thermosyphon after 10 years. These results also let us predict the thermosyphon’s total thermal resistance after 10 years. Though there is a slight leakage on thermosyphon, using this technique, we are able to design a thermosyphon that is guaranteed the cooling performance for a long term.

A Novel Electronics Cooling System Using Water Heat Pipes Under Freezing Conditions

2003 ◽  
Author(s):  
Osamu Suzuki ◽  
Atsuo Nishihara
Keyword(s):  
Prediction Model ◽  
Thermal Resistance ◽  
Ambient Temperature ◽  
Cooling System ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
System Model ◽  
Cooling Performance ◽  
Temperature Range ◽  
Metal Block

A novel electronics cooling system that uses water heat pipes under an ambient temperature range from −30°C to 40°C has been developed. The system consists of several water heat pipes, air-cooled fins, and a metal block. The heat pipes are separated into two groups according to the thermal resistance of their fins. One set of heat pipes, which have fins with higher thermal resistance, operates under an ambient temperature range from −30°C to 40°C. The other set, which have lower resistance, operates from 0°C to 40°C. A prediction model based on the frozen-startup limitation of a single heat pipe was first devised and experimentally verified. Then, a prediction model for the whole-system was formulated according to the former model. The whole-system model was used to design a prototype cooling system, and it was confirmed that the prototype has a suitable cooling performance for an environmentally friendly electronics cooling system.

Variation of thermal resistance with input current and ambient temperature in low-power SMD LED

2018 ◽  
Vol 35 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Muna E. Raypah ◽  
Dheepan M.K. ◽  
Mutharasu Devarajan ◽  
Shanmugan Subramani ◽  
Fauziah Sulaiman
Keyword(s):  
Low Power ◽  
Thermal Resistance ◽  
Ambient Temperature ◽  
Light Emitting Diode ◽  
Operating Conditions ◽  
Input Current ◽  
Junction Temperature ◽  
Total Thermal Resistance ◽  
Content Type ◽  
Thermal Transient

Purpose Thermal behavior of light-emitting diode (LED) device under different operating conditions must be known to enhance its reliability and efficiency in various applications. The purpose of this study is to report the influence of input current and ambient temperature on thermal resistance of InGaAlP low-power surface-mount device (SMD) LED. Design/methodology/approach Thermal parameters of the LED were measured using thermal transient measurement via Thermal Transient Tester (T3Ster). The experimental results were validated using computational fluid dynamics (CFD) software. Findings As input current increases from 50 to 90 mA at 25°C, the relative increase in LED package (ΔRthJS) and total thermal resistance (ΔRthJA) is about 10 and 4 per cent, respectively. In addition, at 50 mA and ambient temperature from 25 to 65°C, the ΔRthJS and ΔRthJA are roughly 28 and 22 per cent, respectively. A good agreement between simulation and experiment results of junction temperature. Originality/value Most of previous studies have focused on thermal management of high-power LEDs. There were no studies on thermal analysis of low-power SMD LED so far. This work will help in predicting the thermal performance of low-power LEDs in solid-state lighting applications.

An Analytical Convergence Study of the Forced Air Cooling in Electronic Packaging

2016 ◽  
Vol 819 ◽  
pp. 34-41 ◽  
Author(s):  
K.A. Ong ◽  
Mohd Zulkifly Abdullah
Keyword(s):  
Thermal Resistance ◽  
Air Flow ◽  
Simulation Method ◽  
Input Power ◽  
Junction Temperature ◽  
Air Cooling ◽  
Element Analysis ◽  
Total Thermal Resistance ◽  
Minimum Number ◽  
Forced Air

A forced air thermal cooling model has been developed by using Ansys software, to study at each step of the input power, what will be the corresponding junction temperature? Few approaches were used to ensure the accuracy of the thermal simulation method, ranging from the minimum number of simulation iterations required in the finite element analysis, to the residuals target in terms of the momentum, continuity and energy equations, the objective is to ensure the simulations are converged and provide the reasonable results, which is also an indication of how the partial equations have successfully been solved with analytic method. The thermal resistance network in the model has also been established, mainly to understand the next level details in this thermal model by analyzing the correlation between the air flow and the thermal resistance at each junction, and also to understand the effect of the air flow with respect to the total thermal resistance. The thermal analytic model that built has proven to be healthy and it requires 200 iterations to achieve steady state with the reasonable temperature output, and there is no convergence issue in which the continuity, momentum and energy graphs showed the healthy trend, it achieved 10-7 for continuity, energy and momentum equations. it shows that when the air flow reduces the overall thermal resistance increases, in other word, reducing the air flow will increase the thermal resistance

scholarly journals INFLUENCE OF THERMAL RESISTANCE OF AIR CONDENSER TUBES ON STEAM COOLING EFFICIENCY

2020 ◽  
Author(s):  
J. Jianguo ◽  
G. Varlamov ◽  
K. Romanova ◽  
L. Suxiang ◽  
L. Zhigang
Keyword(s):  
Mathematical Model ◽  
Thermal Resistance ◽  
Ambient Temperature ◽  
Cooling System ◽  
Steam Pressure ◽  
Operating Conditions ◽  
Air Cooling ◽  
Cooling Unit ◽  
Air Condenser ◽  
Working Bodies

The research is carried out using a mathematical model of conditions and features of condensation processes with the influence of changes in internal and external thermal resistances of working bodies, which occur during contamination of outside and inside metal pipes of heat exchange surfaces of air condenser. capacitor. Particular attention is paid to the selection, detailing and determination of more than twenty basic parameters that characterize the operation of the direct cooling unit of the condensing unit for the summer, the conditions of heat transfer processes between the working bodies taking into account the finned outer surface of elliptical condenser tubes. The results of experiments on the mathematical model are analyzed and the influence of the incoming air velocity and ambient temperature on the output steam pressure in the condenser direct air cooling system within the change of internal and external thermal resistances in the range 0-0.001(m2·K)/W due to cooling tube contamination is determined. air condenser steam turbine installation. Conditions, character and features of influence of thermal resistance of pollution in cooling tubes on steam pressure at an exit from them are defined, the basic factors defining steam pressure at an exit, necessity of the organization of control of thermal resistance of pollution in a pipe during unit operation at variable operating conditions and expediency is substantiated. conducting test studies of operating modes while taking into account the influence of thermal resistance of external and internal pollution on the thermal efficiency of the cooling unit. Studies have shown that at a fixed value of the heat load of the exhaust steam, the pressure of the steam outlet increases with increasing ambient temperature and decreasing the speed of the incoming air.

Heat Transfer Characteristics and Cooling Performance of Microchannel Heat Sinks With Nanofluids

2009 ◽  
Author(s):  
Chien-Hsin Chen ◽  
Chang-Yi Ding
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Thermal Resistance ◽  
Inertial Force ◽  
Fluid Phase ◽  
Inertial Effect ◽  
Microchannel Heat Sink ◽  
Heat Transfer Characteristics ◽  
Total Thermal Resistance ◽  
Cooling Performance

This paper presents a numerical study on the heat transfer characteristics and cooling performance of a microchannel heat sink with water-γAl2O3 nanofluids having different nanoparticle volume fraction. In view of the small dimensions of the microstructures, the microchannel heat sink is modeled as a fluid-saturated porous medium in the simulation. The Forchheimer-Brinkman-extended Darcy equation is used to describe the fluid flow and the two-equation model with thermal dispersion is utilized for heat transfer. Typical results for the temperature distributions of the fin and fluid phase are presented for various values of the inertial force parameter. It is found that the fin temperature distribution is practically not sensitive to the inertial effect, while the fluid temperature distribution and the total thermal resistance change significantly due to the inertial force effect. In general, the effect of fluid inertia is to reduce the total thermal resistance and the temperature difference between the fin and the fluid phase. The total thermal resistances obtained from the present model with inertial effect match well with the available experimental results, whereas the thermal resistance is overestimated as the inertial effect is neglected.

Comprehensive Reduction of Thermal Resistance in Air Cooled Condensers

2015 ◽  
Author(s):  
Ahmad Saleh ◽  
Jayanta Kapat
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Transfer Process ◽  
Cooling System ◽  
Ambient Air ◽  
Heat Transfer Process ◽  
Air Cooling ◽  
Total Thermal Resistance ◽  
Fin Efficiency

Restriction on water consumption is becoming an increasing problem for the power generation industry. As an alternative both to once-through cooling and to surface condenser/wet-cooling tower combination, utility companies and equipment manufacturers are considering, and even implementing, air-cooled condenser (ACC). However, the industry is quite reluctant to switch over to ACC for three important reasons: (a) lower power output, (b) higher capital cost, and (c) larger physical foot-print, all because of the same reason — it is not as efficient to transfer heat from condensing steam to air as it is to transfer to water. In other words, overall thermal resistance from condensing steam to the ambient air is significantly higher than to cooling water. To get a clear and full understanding of the heat transfer process occur in air-cooling condenser, Detailed mathematical equations were derived to model the heat transfer process through the fined-tubes of the ACC. The total thermal resistance model was analyzed and investigated to identify the design components with highest affect in the process. The paper proposes a viable cooling system based on novel heat pipe technology which addresses these problems. This technology employs boiling as the means to store and transfer heat energy. A detailed mathematical set of equations was derived to model the heat pipe thermal resistance. A comparison of the heat transfer performances of the ACC technology and the proposed method is presented. The proposed cooling system suggests a solution for each of the three components of the thermal resistance, the super-hydrophobic coating of the steam ducts internal surfaces increased the condensing heat transfer rate by an order of magnitude, the proposed design of the heat pipes improved the external heat transfer, and the installation mechanism improves the fin efficiency by eliminating the contact resistance between steam duct and the heat pipe.

scholarly journals Integration of a Multiple-Condenser Loop Heat Pipe in a Compact Air-Cooled Heat Sink

2013 ◽  
Author(s):  
H. Arthur Kariya ◽  
Daniel F. Hanks ◽  
Wayne L. Staats ◽  
Nicholas A. Roche ◽  
Martin Cleary ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Sink ◽  
High Performance ◽  
Ambient Air ◽  
Optimal Operation ◽  
Working Fluid ◽  
Air Cooling ◽  
Loop Heat Pipe ◽  
Total Thermal Resistance

We present the characterization of a compact, high performance air-cooled heat sink with an integrated loop heat pipe. In this configuration, heat enters the heat sink at the evaporator base and is transferred within the heat pipe by the latent heat of vaporization of a working fluid. From the condensers, the heat is transferred to the ambient air by an integrated fan. Multiple condensers are used to increase the surface area available for air-cooling, and to ensure the equal and optimal operation of the individual condensers, an additional wick is incorporated into the condensers. We demonstrated with this design (10.2 cm × 10.2 cm × 9 cm), a total thermal resistance of less than 0.1 °C/W while dissipating a heat load of 500 W from a source at 75 °C. Furthermore, constant thermal resistance was observed in the upright as well as sideways orientations. This prototype is a proof-of-concept demonstration of a high performance and efficient air-cooled heat sink design that can be readily integrated for various electronics packaging and data center applications.

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