Experimental Investigation of Micro Heat Pipe Radiators in Radiation Environment

2001 ◽  
Author(s):  
Y. X. Wang ◽  
G. P. Peterson
Keyword(s):  
Experimental Investigation ◽  
Heat Pipe ◽  
Heat Transport ◽  
Radiation Efficiency ◽  
Wire Diameter ◽  
Radiation Environment ◽  
Transport Capacity ◽  
Maximum Heat ◽  
Micro Heat Pipe

Abstract A flexible micro heat pipe radiator, fabricated by sintering an array of aluminum wires between two thin aluminum sheets, was developed as part of a program to conceptulize, develop, and test lightweight, flexible radiator fin structures for use on long-term spacecraft missions. A detailed experimental investigation was conducted to determine the temperature distribution, maximum heat transport capacity, and radiation efficiency of these micro heat pipe radiators in a radiation environment. Experimental results from three Aluminum-Acetone micro heat pipe radiators with wire diameters of 0.635 mm, 0.813 and 1.016 mm are presented, evaluated and discussed. The results of the experimental program indicted that the maximum heat transport capacity and radiation efficiency, both increased with increasing wire diameter. The maximum heat transport capacity of the micro heat pipe radiator utilizing a wire diameter of 0.635 mm was 15.2 W. The radiators utilizing wire diameters of 0.813 mm and 1.016 mm never reached the maximum heat transport capacities for the given test conditions. In the tests, temperature distributions were recorded for several sink temperatures and indicated that as the sink temperature decreased the radiation efficiency decreased for a given heat input. The maximum heat transport capacity increased with increasing evaporating temperature for the micro heat pipe radiator utilizing a wire diameter of 0.635 mm. Comparison of micro heat pipe radiators with and without working fluid, indicated that significant improvements in temperature uniformity and radiation efficiencies could be obtained, especially at high heat fluxes. A maximum radiation efficiency of 0.95 was observed. In general, while some variation in performance was observed, all three micro heat pipe radiators were found to be capable of meeting the thermal requirements of long-term missions.

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.

Heat Transport Limitation of a Triangular Micro Heat Pipe

2003 ◽  
Author(s):  
D. Sugumar ◽  
Kek Kiong Tio
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Operating Temperature ◽  
Working Fluid ◽  
Transport Capacity ◽  
Condenser Section ◽  
Micro Heat Pipe ◽  
Evaporator Section ◽  
Higher Temperature ◽  
Specific Temperature

A micro heat pipe will operate effectively by achieving its maximum possible heat transport capacity only if it is to operate at a specific temperature, i.e., design temperature. In reality, micro heat pipe’s may be required to operate at temperatures different from the design temperature. In this study, the heat transport capacity of an equilateral triangle micro heat pipe is investigated. The micro heat pipe is filled optimally with working fluid for a specific design temperature and operated at different operating temperatures. For this purpose, water, pentane and acetone was selected as the working fluids. From the numerical results obtained, it shows that the optimal charge level of the micro heat pipe is dependent on the operating temperature. Furthermore, the results also shows that if the micro heat pipe is to be operated at temperatures other than its design temperature, its heat transport capacity is limited by the occurrence of flooding at the condenser section or dryout at the evaporator section, depending on the operating temperature and type of working fluid. It is observed that when the micro heat pipe is operated at a higher temperature than its design temperature, the heat transport capacity increases but limited by the onset of dryout at the evaporator section. However, the heat transport capacity decreases if it is to be operated at lower temperatures than its design temperature due to the occurrence of flooding at condenser end. From the results obtained, we can conclude that the performance of a micro heat pipe is decreased if it is to be operated at temperatures other than its design temperature.

Investigation of a Novel Flat Heat Pipe

2005 ◽  
Vol 127 (2) ◽  
pp. 165-170 ◽  
Author(s):  
Yaxiong Wang ◽  
G. P. Peterson
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Thermal Design ◽  
Experimental Results ◽  
Design Parameters ◽  
Working Fluid ◽  
Transport Capacity ◽  
Maximum Heat ◽  
Mesh Screen ◽  
Flat Heat Pipe

A novel flat heat pipe has been developed to assist in meeting the high thermal design requirements in high power microelectronics, power converting systems, laptop computers and spacecraft thermal control systems. Two different prototypes, each measuring 152.4 mm by 25.4 mm were constructed and evaluated experimentally. Sintered copper screen mesh was used as the primary wicking structure, in conjunction with a series of parallel wires, which formed liquid arteries. Water was selected as the working fluid. Both experimental and analytical investigations were conducted to examine the maximum heat transport capacity and optimize the design parameters of this particular design. The experimental results indicated that the maximum heat transport capacity and heat flux for Prototype 1, which utilized four layers of 100 mesh screen were 112 W and 17.4W/cm2, respectively, in the horizontal position. For Prototype 2, which utilized six layers of 150 mesh screen, these values were 123 W and 19.1W/cm2, respectively. The experimental results were in good agreement with the theoretical predictions for a mesh compact coefficient of C=1.15.

Investigation of Polymer Based Micro Heat Pipes for a Flexible Spacecraft Radiator

2001 ◽  
Author(s):  
D. McDaniels ◽  
G. P. “Bud” Peterson
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Power Density ◽  
Polymeric Material ◽  
Heat Dissipation ◽  
Effective Conductivity ◽  
Chemical Reactivity ◽  
Working Fluid ◽  
Maximum Heat ◽  
Micro Heat Pipe

Abstract In response to the space industry’s pursuit of interplanetary travel and a continuous human presence in space, there is increasing focus on spacecraft that change configuration while in space. Flexible thermal radiators are being developed to accommodate various collapse and deployment mechanisms. An analytical model suggests that a lightweight polymeric material with imbedded micro heat pipe arrays can meet heat dissipation requirements while contributing less mass than competing flexible materials. The capillary pumping limit is evaluated as a function of operating temperature using two candidate working fluids. Using water, the maximum heat transport is 18 mW per channel at 140/160 °C. The maximum heat transport using methanol is 2.2 mW at 120 °C, an order-of magnitude difference. A thermal circuit model translates heat transport per channel into total radiator capacity as a function of source temperature and environmental sink temperature. Using water as the working fluid, the radiator capacity was shown to vary from 6.0 kW to 12.2 kW for source temperatures of 20 °C to 50 °C. For source temperatures of 40 °C and higher, the capacity meets or exceeds the dissipation requirements of a reference spacecraft design. While evaluated, methanol is not recommended as a working fluid because its radiator capacity is two to three times lower than water. Although thermal system constraints place limits on the micro heat pipe operating range, design changes directed at alleviating capillary limitations should increase radiator capacity. Technical issues for further study include effects of film billowing, performance limitations related to vapor viscosity, working fluid diffusion, and chemical reactivity between case and working fluid. Compared to a competing graphite fiber weave, the polymeric material has an effective conductivity over ten times higher. Its area power density (in kW/m2) is 18% to 60% lower than the graphite weave, but its mass power density (in kW/kg) is several times higher. Greater flexibility and lower weight also make it more amenable to structural integration. Recently developed space-stable polymers offer resistance to harsh temperature and radiation environments, helping to clear the path toward a more extensive use of polymers within the space industry.

The Effect of Type of Working Fluid on the Heat Transport Capacity of a Micro Heat Pipe

2005 ◽  
Author(s):  
Sugumar Dharmalingam ◽  
Kek Kiong Tio
Keyword(s):  
Surface Tension ◽  
Heat Pipe ◽  
Heat Transport ◽  
Operating Temperature ◽  
Working Fluid ◽  
Liquid Viscosity ◽  
Transport Capacity ◽  
Temperature Range ◽  
Controlling Effect ◽  
Micro Heat Pipe

In order to elucidate the effects of working fluid’s properties on the heat transport capacity of a micro heat pipe, 3 commonly used fluids are selected for this study: water, ammonia and methanol. From the results obtained, it shows that for operating temperatures lower than 50°C, ammonia is preferred, but if the operating temperature exceeds 50°C, water is more suitable in transferring heat. Over the temperature range of 20°C∼100°C, the behavior of the heat transport capacity is found to be dominated by a property which is the ratio of the working fluid’s surface tension and liquid viscosity. This property which has the dimension of velocity has a controlling effect on the working fluid’s rate of circulation and therefore, the heat transport capacity.

Theoretical Analysis of the Maximum Heat Transport in Triangular Grooves: A Study of Idealized Micro Heat Pipes

1996 ◽  
Vol 118 (3) ◽  
pp. 731-739 ◽  
Author(s):  
G. P. Peterson ◽  
H. B. Ma
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Control Volume ◽  
Flow Characteristics ◽  
Heat Pipes ◽  
Vapor Flow ◽  
Transport Capacity ◽  
Maximum Heat ◽  
Micro Heat Pipes ◽  
Theoretical Minimum

A mathematical model for predicting the minimum meniscus radius and the maximum heat transport in triangular grooves is presented. In this model, a method for determining the theoretical minimum meniscus radius was developed and used to calculate the capillary heat transport limit based on the physical characteristics and geometry of the capillary grooves. A control volume technique was employed to determine the flow characteristics of the micro heat pipe, in an effort to incorporate the size and shape of the grooves and the effects of the frictional liquid–vapor interaction. In order to compare the heat transport and flow characteristics, a hydraulic diameter, which incorporated these effects, was defined and the resulting model was solved numerically. The results indicate that the heat transport capacity of micro heat pipes is strongly dependent on the apex channel angle of the liquid arteries, the contact angle of the liquid flow, the length of the heat pipe, the vapor flow velocity and characteristics, and the tilt angle. The analysis presented here provides a mechanism whereby the groove geometry can be optimized with respect to these parameters in order to obtain the maximum heat transport capacity for micro heat pipes utilizing axial grooves as the capillary structure.

Modeling and Thermal Optimization of a Micro Heat Pipe With Curved Triangular Grooves

2003 ◽  
Author(s):  
Kyu Hyung Do ◽  
Sung Jin Kim ◽  
Gunn Hwang
Keyword(s):  
Numerical Model ◽  
Heat Pipe ◽  
Heat Transport ◽  
Interfacial Shear Stress ◽  
Axial Direction ◽  
Transport Rate ◽  
Maximum Heat ◽  
Steady State Condition ◽  
Thermal Optimization ◽  
Micro Heat Pipe

Heat transfer and fluid flow characteristics in a micro heat pipe with curved triangular grooves are investigated using numerical and experimental methods. In the numerical part, a one-dimensional mathematical model for micro heat pipe with curved triangular grooves is developed and solved to obtain the maximum heat transport rate, the capillary radius distribution, the liquid and the vapor pressure distributions along the axial direction of the micro heat pipe under the steady-state condition. In particular, the modified Shah method is applied to calculate the pressure drop induced by the liquid-vapor interfacial shear stress. Experiments are conducted to validate the numerical model. In the experiments, the micro heat pipe with 0.56 mm in hydraulic diameter and 50 mm in length is tested. The experimental results for the maximum heat transport rate agree well with those of the numerical investigations. Finally, thermal optimization of the micro heat pipe with curved triangular grooves is performed using the numerical model.

Theoretical Analysis and Experimental Investigation on Designing Method of Micro-Groove Heat Pipe

2011 ◽  
Vol 483 ◽  
pp. 350-353
Author(s):  
Tian Han ◽  
Xiao Wei Liu ◽  
Ning Cui
Keyword(s):  
Experimental Investigation ◽  
Steady State ◽  
Heat Pipe ◽  
Transport Capacity ◽  
Maximum Heat ◽  
Interface Friction ◽  
One Dimensional ◽  
Steady State Model ◽  
Simulation Results ◽  
Designing Method

In this paper, a kind of one-dimensional steady-state model is used to analyze and simulate the capillary motion of the working material in micro heat pipe. The character of this model is that it includes the influence of the interface friction, and the influence of the friction to the micro heat pipe’s performance is also simulated and analyzed. The maximum heat transport capacity and the optimizing size of the grooves are calculated by this model. Some experiments have been carried out to evaluate the simulation results.

NUMERICAL AND EXPERIMENTAL INVESTIGATION ON A NEW TYPE ELECTRICAL HEAT STORAGE BASED ON FLAT MICRO HEAT PIPE

2018 ◽  
Author(s):  
Zeyu Wang ◽  
Yanhua Diao ◽  
Yaohua Zhao ◽  
Chuanqi Chen ◽  
Lin Liang ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Heat Pipe ◽  
Heat Storage ◽  
Micro Heat Pipe ◽  
New Type
Sign in / Sign up

Export Citation Format

Share Document