Feasibility of Metallic Structural Heat Pipes as Sharp Leading Edges for Hypersonic Vehicles

2009 ◽  
Vol 76 (3) ◽  
Author(s):  
Craig A. Steeves ◽  
Ming Y. He ◽  
Scott D. Kasen ◽  
Lorenzo Valdevit ◽  
Haydn N. G. Wadley ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Heat Pipe ◽  
Leading Edge ◽  
Niobium Alloy ◽  
Working Fluid ◽  
Flat Surfaces ◽  
Analytical Approximations ◽  
Fluid Systems ◽  
Edge Surface ◽  
Leading Edges

Hypersonic flight with hydrocarbon-fueled airbreathing propulsion requires sharp leading edges. This generates high temperatures at the leading edge surface, which cannot be sustained by most materials. By integrating a planar heat pipe into the structure of the leading edge, the heat can be conducted to large flat surfaces from which it can be radiated out to the environment, significantly reducing the temperatures at the leading edge and making metals feasible materials. This paper describes a method by which the leading edge thermal boundary conditions can be ascertained from standard hypersonic correlations, and then uses these boundary conditions along with a set of analytical approximations to predict the behavior of a planar leading edge heat pipe. The analytical predictions of the thermostructural performance are verified by finite element calculations. Given the results of the analysis, possible heat pipe fluid systems are assessed, and their applicability to the relevant conditions determined. The results indicate that the niobium alloy Cb-752, with lithium as the working fluid, is a feasible combination for Mach 6–8 flight with a 3 mm leading edge radius.

A Heat Plate Leading Edge for Hypersonic Vehicles

2008 ◽  
Author(s):  
Scott D. Kasen ◽  
Doug T. Queheillalt ◽  
Craig A. Steeves ◽  
Anthony G. Evans ◽  
Haydn N. G. Wadley
Keyword(s):  
Heat Flux ◽  
Low Temperature ◽  
Heat Pipe ◽  
Thermal Management ◽  
Leading Edge ◽  
Maximum Temperature ◽  
Working Fluid ◽  
Hypersonic Vehicles ◽  
Vapor Flow ◽  
Leading Edges

The intense thermal flux at the leading edges of hypersonic vehicles (traveling at Mach 5 and greater) requires creative thermal management strategies to prevent damage to leading edge components. Carbon fiber composites and/or ablative coatings have been widely utilized to mitigate the effects of the impinging heat flux. This paper focuses on an alternative, metallic leading edge heat pipe concept which combines efficient structural load support and thermal management. The passive concept is based on high thermal conductance heat pipes which redistribute the high heat flux at the leading edge stagnation point through the evaporation, vapor flow, and condensation of a working fluid to a location far from the heat source. Structural efficiency is provided by a sandwich construction using an open-cell core that also allows for vapor flow. A low temperature proof-of-concept copper–water system has been investigated by experimentation. Measuring of the axial temperature profile indicates effective spreading of thermal energy, a lowering of the maximum temperature and reduced overall thermal gradient compared to a non-heat pipe leading edge. A simple transient analytical model based on lumped thermal capacitance theory is compared with the experimental results. The low-temperature prototype shows potential for higher temperature metallic leading edges that can withstand the hypersonic thermo-mechanical environment.

Heat Pipe Thermal Management at Hypersonic Vehicle Leading Edges: A Low-Temperature Model Study

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Scott D. Kasen ◽  
Haydn N. G. Wadley
Keyword(s):  
Low Temperature ◽  
Heat Pipe ◽  
Thermal Management ◽  
Thermal Flux ◽  
Management Strategies ◽  
Water System ◽  
Leading Edge ◽  
Working Fluid ◽  
Two Phase ◽  
Leading Edges

The intense thermal fluxes and aero-thermomechanical loads generated at sharp leading edges of atmospheric hypersonic vehicles traveling above Mach 5 have motivated an interest in novel thermal management strategies. Here, we use a low-temperature stainless steel-water system to experimentally investigate the feasibility of metallic leading edge heat pipe concepts for thermal management in an efficient load supporting structure. The concept is based upon a two-phase, high thermal conductance “heat pipe” which redistributes the localized thermal flux created at the leading edge stagnation point over a larger surface for effective removal. Structural efficiency is achieved by configuring the system as a wedge-shaped sandwich panel with an I-cell core that simultaneously permits axial vapor and returns liquid flow. The measured axial temperature profiles resulting from a localized thermal flux applied to the tip are consistent with effective thermal spreading that lowered the peak leading edge temperature and reduced the temperature gradients when compared with an equivalent structure containing no working fluid. A simple finite element model that treated the vapor as an equivalent, high thermal conductivity material was in good agreement with these experiments. The model is then used to design a niobium alloy-lithium system that is shown to be suitable for enthalpy conditions representative of Mach 7 scramjet-powered flight. The study indicates that the surface temperature reductions of heat pipe-based leading edges may be sufficient to permit the use of nonablative, refractory metal leading edges with oxidation protection in hypersonic environments.

Experimental Study of an Airfoil Heat Pipe Subjected to an Impingement of Hot Gases

2012 ◽  
Author(s):  
Gerardo Carbajal ◽  
Alberto Vázquez Ramos
Keyword(s):  
Experimental Study ◽  
Heat Pipe ◽  
Heat Input ◽  
Nickel Foam ◽  
Average Pore Size ◽  
Leading Edge ◽  
Jet Impingement ◽  
Experimental Result ◽  
Working Fluid ◽  
Average Pore

An experimental study was performed to an airfoil heat pipe. The airfoil was subjected to a jet impingement of hot gases at the leading edge. The airfoil was also tested first with air and later with water as the working fluid. The experimental result shown that the heat pipe spread better the heat input from the leading edge at very high heat input rate than the air filled airfoil design. The case material was brass, the porous media was nickel foam with 1.70 mm thickness and average pore size of 590 × 10−6 m. Distilled water was used as the working fluid. The experimental data indicate the proposed design can reduce the temperature at the leading edge surface. The temperature reduction in the leading edge airfoil heat pipe was approximately 33 percent compared with the air filled airfoil. The phase change mechanism inside the heat pipe was the key factor to spread better the localized energy input and thus reducing the temperature distribution on the leading edge.

USAGE OF A DIATOMITE-CONTAINING NANOFLUID AS THE WORKING FLUID IN A WICKLESS LOOP HEAT PIPE: EXPERIMENTAL AND NUMERICAL STUDY

2018 ◽  
Vol 49 (17) ◽  
pp. 1721-1744 ◽  
Author(s):  
Adnan Sözen ◽  
Erdem Çiftçi ◽  
Selçuk Keçel ◽  
Metin Gürü ◽  
Halil Ibrahim Variyenli ◽  
...  
Keyword(s):  
Heat Pipe ◽  
Numerical Study ◽  
Working Fluid ◽  
Loop Heat Pipe

Experimental and Numerical Simulation for Thermal Investigation of Oscillating Heat Pipe Using VOF Model

2020 ◽  
Vol 38 (1A) ◽  
pp. 88-104
Author(s):  
Anwar S. Barrak ◽  
Ahmed A. M. Saleh ◽  
Zainab H. Naji
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Input ◽  
Cfd Simulation ◽  
Working Fluid ◽  
Maximum Deviation ◽  
Inlet Temperature ◽  
Maximum Heat ◽  
Oscillating Heat Pipe ◽  
Vof Model

This study is investigated the thermal performance of seven turns of the oscillating heat pipe (OHP) by an experimental investigation and CFD simulation. The OHP is designed and made from a copper tube with an inner diameter 3.5 mm and thickness 0.6 mm and the condenser, evaporator, and adiabatic lengths are 300, 300, and 210 mm respectively.  Water is used as a working fluid with a filling ratio of 50% of the total volume. The evaporator part is heated by hot air (35, 40, 45, and 50) oC with various face velocity (0.5, 1, and 1.5) m/s. The condenser section is cold by air at temperature 15 oC. The CFD simulation is done by using the volume of fluid (VOF) method to model two-phase flow by conjugating a user-defined function code (UDF) to the FLUENT code. Results showed that the maximum heat input is 107.75 W while the minimum heat is 13.75 W at air inlet temperature 35 oC with air velocity 0.5m/s. The thermal resistance decreased with increasing of heat input. The results were recorded minimum thermal resistance 0.2312 oC/W at 107.75 W and maximum thermal resistance 1.036 oC/W at 13.75W. In addition, the effective thermal conductivity increased due to increasing heat input.  The numerical results showed a good agreement with experimental results with a maximum deviation of 15%.

Leading Edge Surface Pressures from Airfoils in a Turbulent Flow

2004 ◽  
Author(s):  
Jonathan L. Gershfeld ◽  
Thomas C. Mathews
Keyword(s):  
Turbulent Flow ◽  
Leading Edge ◽  
Edge Surface

Device Packaging Techniques for Implementing a Novel Thermal Flux Method for Fluid Degassing and Charging of a Planar Microscale Loop Heat Pipe

2011 ◽  
Author(s):  
Navdeep S. Dhillon ◽  
Jim C. Cheng ◽  
Albert P. Pisano
Keyword(s):  
High Temperature ◽  
Heat Pipe ◽  
Thermal Flux ◽  
Anodic Bonding ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Pressure Gradients ◽  
Flux Method ◽  
Double Compression ◽  
Plastic Package

A novel two-port thermal flux method is implemented for degassing a microscale loop heat pipe (mLHP) and charging it with a working fluid. The mLHP is fabricated on a silicon wafer using standard MEMS micro-fabrication techniques, and capped by a Pyrex wafer, using anodic bonding. For these devices, small volumes and large capillary forces render conventional vacuum pump-based methods quite impractical. Instead, we employ thermally generated pressure gradients to purge non-condensible gases from the device, by vapor convection. Three different, high-temperature-compatible, MEMS device packaging techniques have been studied and implemented, in order to evaluate their effectiveness and reliability. The first approach uses O-rings in a mechanically sealed plastic package. The second approach uses an aluminum double compression fitting assembly for alignment, and soldering for establishing the chip-to-tube interconnects. The third approach uses a high temperature epoxy to hermetically embed the device in a machined plastic base package. Using water as the working fluid, degassing and filling experiments are conducted to verify the effectiveness of the thermal flux method.

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.

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