Steady-State Modeling and Testing of a Micro Heat Pipe

1990 ◽  
Vol 112 (3) ◽  
pp. 595-601 ◽  
Author(s):  
B. R. Babin ◽  
G. P. Peterson ◽  
D. Wu
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Experimental Results ◽  
State Model ◽  
Operating Characteristics ◽  
Maximum Heat ◽  
Micro Heat Pipe ◽  
Steady State Model ◽  
Micro Heat Pipes

A combined experimental and analytical investigation was conducted to identify and understand better the phenomena that govern the performance limitations and operating characteristics of micro heat pipes—heat pipes so small that the mean curvature of the vapor—liquid interface is comparable in magnitude to the reciprocal of the hydraulic radius of the flow channel. The analytical portion of the investigation began with the development of a steady-state model in which the effects of the extremely small characteristic dimensions on the conventional steady-state heat pipe modeling techniques were examined. In the experimental portion of the investigation, two micro heat pipes, one copper and one silver, 1 mm2 in cross-sectional area and 57 mm in length, were evaluated experimentally to determine the accuracy of the steady-state model and to provide verification of the micro heat pipe concept. Tests were conducted in a vacuum environment to eliminate conduction and convection losses. The steady-state experimental results obtained were compared with the analytical model and were found to predict accurately the experimentally determined maximum heat transport capacity for an operating temperature range of 40° C to 60° C. A detailed description of the methodology used in the development of the steady-state model along with a comparison of the predicted and experimental results are presented.

A One-Dimensional Model of a Micro Heat Pipe During Steady-State Operation

1994 ◽  
Vol 116 (3) ◽  
pp. 709-715 ◽  
Author(s):  
J. P. Longtin ◽  
B. Badran ◽  
F. M. Gerner
Keyword(s):  
Steady State ◽  
Film Thickness ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Dimensional Model ◽  
Pipe Length ◽  
Maximum Heat ◽  
One Dimensional ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

Micro heat pipes are small structures that will be used to cool microscale devices. They function much like their conventional counterparts, with a few exceptions, most notably the absence of a wick. It is expected that water-filled micro heat pipes will be able to dissipate heat fluxes on the order of 10–15 W/cm2 (100,000–150,000 W/m2). This work addresses the modeling of a micro heat pipe operating under steady-state conditions. A one-dimensional model of the evaporator and adiabatic sections is developed and solved numerically to yield pressure, velocity, and film thickness information along the length of the pipe. Interfacial and vapor shear stress terms have been included in the model. Convection and body force terms have also been included in the momentum equation, although numerical experiments have shown them to be negligible. Pressure, velocity, and film thickness results are presented along with the maximum heat load dependence on pipe length and width. Both simple scaling and the model results show that the maximum heat transport capability of a micro heat pipe varies with the inverse of its length and the cube of its hydraulic diameter, implying the largest, shortest pipes possible should be used.

Analytical Modeling of a Loop Heat Pipe at Positive Elevation

2004 ◽  
Author(s):  
Po-Ya Abel Chuang ◽  
John M. Cimbala ◽  
Jack S. Brenizer ◽  
C. Thomas Conroy
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
Experimental Results ◽  
State Model ◽  
Loop Heat Pipe ◽  
Operating Characteristics ◽  
Two Phase ◽  
Steady State Model ◽  
Two Phase Heat Transfer ◽  
Transfer Device

A two-phase heat transfer device, a loop heat pipe (LHP), is studied analytically. It is noted that a LHP behaves differently when it is operated against gravity (adverse elevation) or at gravity assisted (positive elevation) conditions. Steady-state modeling of LHP operating characteristics at adverse or zero elevation was broadly studied in the past. This paper presents a steady-state model of a LHP when it is operated at positive elevation based on experimental results. The effects of elevation on the trend of steady-state operating temperature (SSOT) are then studied using the newly developed steady-state model. Experimental results agree with the model predictions at adverse (88.9mm), zero, and positive (88.9mm) elevations. This steady-state model is the only model known to have the capability to predict the operating characteristics at positive elevation. The model will help to design the LHPs utilized in terrestrial applications.

Steady-State Investigation of Vapor Deposited Micro Heat Pipe Arrays

1995 ◽  
Vol 117 (1) ◽  
pp. 75-81 ◽  
Author(s):  
A. K. Mallik ◽  
G. P. Peterson
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Surface Temperature ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Heat Pipes ◽  
Temperature Gradients ◽  
Bottom Surface ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

An experimental investigation of vapor deposited micro heat pipe arrays was conducted using arrays of 34 and 66 micro heat pipes occupying 0.75 and 1.45 percent of the cross-sectional area, respectively. The performance of wafers containing the arrays was compared with that of a plain silicon wafer. All of the wafers had 8 × 8 mm thermofoil heaters located on the bottom surface to simulate the active devices in an actual application. The temperature distributions across the wafers were obtained using a Hughes Probeye TVS Infrared Thermal Imaging System and a standard VHS video recorder. For wafers containing arrays of 34 vapor deposited micro heat pipes, the steady-state experimental data indicated a reduction in the maximum surface temperature and temperature gradients of 24.4 and 27.4 percent, respectively, coupled with an improvement in the effective thermal conductivity of 41.7 percent. For wafers containing arrays of 66 vapor deposited micro heat pipes, the corresponding reductions in the surface temperature and temperature gradients were 29.0 and 41.7 percent, respectively, and the effective thermal conductivity increased 47.1 percent, for input heat fluxes of 4.70 W/cm2. The experimental results were compared with the results of a previously developed numerical model, which was shown to predict the temperature distribution with a high degree of accuracy, for wafers both with and without the heat pipe arrays.

The Heat Transport Capacity of Micro Heat Pipes

1998 ◽  
Vol 120 (4) ◽  
pp. 1064-1071 ◽  
Author(s):  
J. M. Ha ◽  
G. P. Peterson
Keyword(s):  
Experimental Data ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Pipes ◽  
Original Model ◽  
Semiempirical Model ◽  
Transport Capacity ◽  
Predictive Tool ◽  
Maximum Heat ◽  
Micro Heat Pipes

The original analytical model for predicting the maximum heat transport capacity in micro heat pipes, as developed by Cotter, has been re-evaluated in light of the currently available experimental data. As is the case for most models, the original model assumed a fixed evaporator region and while it yields trends that are consistent with the experimental results, it significantly overpredicts the maximum heat transport capacity. In an effort to provide a more accurate predictive tool, a semi-empirical correlation has been developed. This modified model incorporates the effects of the temporal intrusion of the evaporating region into the adiabatic section of the heat pipe, which occurs as the heat pipe approaches dryout conditions. In so doing, the current model provides a more realistic picture of the actual physical situation. In addition to incorporating these effects, Cotter’s original expression for the liquid flow shape factor has been modified. These modifications are then incorporated into the original model and the results compared with the available experimental data. The results of this comparison indicate that the new semiempirical model significantly improves the correlation between the experimental and predicted results and more accurately represents the actual physical behavior of these devices.

scholarly journals An investigation on effect of EDL on heat transfer of micro heat pipe with square and triangular cross section

2020 ◽  
Vol 21 (3) ◽  
pp. 309
Author(s):  
Maryam Fallah Abbasi ◽  
Hossein Shokouhmand ◽  
Morteza Khayat
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Double Layer ◽  
Electric Double Layer ◽  
Heat Pipes ◽  
The Body ◽  
Working Fluid ◽  
Two Phase ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

Electronic industries have always been trying to improve the efficiency of electronic devices with small dimensions through thermal management of this equipment, thus increasing the use of small thermal sinks. In this study micro heat pipes with triangular and square cross sections have been manufactured and tested. One of the main objectives is to obtain an understanding of micro heat pipes and their role in energy transmission with electrical double layer (EDL). Micro heat pipes are highly efficient heat transfer devices, which use the continuous evaporation/condensation of a suitable working fluid for two-phase heat transport in a closed system. Since the latent heat of vaporization is very large, heat pipes transport heat at small temperature difference, with high rates. Because of variety of advantage features these devices have found a number of applications both in space and terrestrial technologies. The theory of operation micro heat pipes with EDL is described and the micro heat pipe has been studied. The temperature distribution have achieved through five thermocouples installed on the body. Water and different solution mixture of water and ethanol have used to investigate effect of the electric double layer heat transfer. It was noticed that the electric double layer of ionized fluid has caused reduction of heat transfer.

Experimental Investigation of the Maximum Heat Transport in Triangular Grooves

1996 ◽  
Vol 118 (3) ◽  
pp. 740-746 ◽  
Author(s):  
H. B. Ma ◽  
G. P. Peterson
Keyword(s):  
Experimental Investigation ◽  
Heat Transport ◽  
Heat Pipes ◽  
Effective Area ◽  
Experimental Results ◽  
Test Facility ◽  
Working Fluid ◽  
Maximum Heat ◽  
Pressure Losses ◽  
Micro Heat Pipes

An experimental investigation was conducted and a test facility constructed to measure the capillary heat transport limit in small triangular grooves, similar to those used in micro heat pipes. Using methanol as the working fluid, the maximum heat transport and unit effective area heat transport were experimentally determined for ten grooved plates with varying groove widths, but identical apex angles. The experimental results indicate that there exists an optimum groove configuration, which maximizes the capillary pumping capacity while minimizing the combined effects of the capillary pumping pressure and the liquid viscous pressure losses. When compared with a previously developed analytical model, the experimental results indicate that the model can be used accurately to predict the heat transport capacity and maximum unit area heat transport when given the physical characteristics of the working fluid and the groove geometry, provided the proper heat flux distribution is known. The results of this investigation will assist in the development of micro heat pipes capable of operating at increased power levels with greater reliability.

Evaporation, Condensation, and Flow in an Idealized Micro Heat Pipe

2002 ◽  
Author(s):  
Jin Zhang ◽  
Harris Wong
Keyword(s):  
Thermal Conductivity ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Three Dimensional ◽  
Heat Pipes ◽  
Rigorous Analysis ◽  
Evaporation And Condensation ◽  
Micro Heat Pipe ◽  
Complicated Geometry ◽  
Micro Heat Pipes

Micro heat pipes have been used in cooling micro electronic components. However their effective thermal conductivity is low compared with that of conventional heat pipes. Due to the complexity of the coupled heat and mass transport, and to the complicated three-dimensional bubble geometry inside micro heat pipes, there is a lack of rigorous analysis. As a result, the relatively low effective thermal conductivity remains unexplained. We have conceptualized an idealized micro heat pipe that eliminates the complicated geometry, but retains the essential physics. Given the simplified geometry, many effects can be studied, such as thermocapillary flow, and evaporation and condensation physics. In this talk, we will present the flow field induced by evaporation.

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