Liquid Flow Analysis in Concentric Annular Heat Pipes Wicks

2005 ◽  
Vol 8 (5) ◽  
pp. 471-480 ◽  
Author(s):  
Ali Nouri-Borujerdi ◽  
Mohammad Layeghi
Keyword(s):  
Liquid Flow ◽  
Flow Analysis ◽  
Heat Pipes

Dimensionless Governing Equations for Vapor and Liquid Flow Analysis of Heat Pipes

2006 ◽  
Vol 20 (1) ◽  
pp. 140-144 ◽  
Author(s):  
Gerardo Carbajal ◽  
C. B. Sobhan ◽  
G. P. Peterson
Keyword(s):  
Liquid Flow ◽  
Flow Analysis ◽  
Heat Pipes ◽  
Governing Equations

scholarly journals Numerical Model for Cavitational Flow in Hydraulic Poppet Valves

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Sandor I. Bernad ◽  
Romeo Susan-Resiga
Keyword(s):  
Liquid Flow ◽  
Bubble Dynamics ◽  
Flow Analysis ◽  
Cavitating Flow ◽  
Absolute Pressure ◽  
Two Phase ◽  
Current Effort ◽  
Flow Models ◽  
Density Distributions ◽  
Phase Liquid

The paper presents a numerical simulation and analysis of the flow inside a poppet valve. First, the single-phase (liquid) flow is investigated, and an original model is introduced for quantitatively describing the vortex flow. Since an atmospheric outlet pressure produces large negative absolute pressure regions, a two-phase (cavitating) flow analysis is also performed. Both pressure and density distributions inside the cavity are presented, and a comparison with the liquid flow results is performed. It is found that if one defines the cavity radius such that up to this radius the pressure is no larger than the vaporization pressure, then both liquid and cavitating flow models predict the cavity extent. The current effort is based on the application of the recently developed full cavitation model that utilizes the modified Rayleigh-Plesset equations for bubble dynamics.

Flow analysis in pulsating heat pipes with microchannels

2016 ◽  
Vol 2016 (0) ◽  
pp. J0540201
Author(s):  
Yutaro ABE ◽  
Koichi ISOMURA ◽  
Yuta YOSHIMOTO ◽  
Ikuya KINEFUCHI ◽  
Shu TAKAGI
Keyword(s):  
Flow Analysis ◽  
Heat Pipes

scholarly journals Staying Cool

1999 ◽  
Vol 121 (07) ◽  
pp. 64-65
Author(s):  
Calvin C. Silverstein
Keyword(s):  
Heat Pipe ◽  
Thermal Management ◽  
Liquid Flow ◽  
High Performance ◽  
Heat Pipes ◽  
Flow Channel ◽  
Aircraft Engines ◽  
Chemical Milling ◽  
Combination Of Methods ◽  
Half Thickness

This article reviews heat pipes that address thermal management problems inside high-performance aircraft engines. Higher performance engines demand that compressors develop higher pressure ratios which, in turn, result in higher temperatures at the entrance to the combustor. CCS Associates of Bethel Park, PA, proposes tackling the problem by using pipes to distribute heat more effectively throughout the combustor. The heat pipe liner must handle both acceleration and vibration. The heat pipe arrays, including half-thickness webs, can be fabricated into gas-side and air-side halves by extrusion, forging, stamping, chemical milling, or some combination of methods. The liquid flow channel would be formed as an integral part of the gas-side valves.

Instability of Heat Pipe Performance at Large Axial Accelerations

2006 ◽  
Vol 129 (2) ◽  
pp. 137-140 ◽  
Author(s):  
A. Asias ◽  
M. Shusser ◽  
A. Leitner ◽  
A. Nabi ◽  
G. Grossman
Keyword(s):  
Heat Pipe ◽  
Liquid Flow ◽  
Heat Input ◽  
Large Amplitude ◽  
Heat Pipes ◽  
Strong Increase ◽  
Evaporator Temperature ◽  
Optimal Heat ◽  
Capillary Limit

To investigate the feasibility of using heat pipes in airborne systems, heat pipe performance at large axial accelerations in the range of 3–12g was studied experimentally. The heat input chosen corresponded to the optimal heat pipe performance without acceleration. When applied against the direction of the liquid flow (unfavorable orientation) the accelerations were large enough to exceed the capillary limit, as was seen from the strong increase in the evaporator temperature. The influence of accelerations in the direction of the liquid flow (favorable orientation) was found to be more complicated. While at the acceleration of 3g the heat pipe performance improved, at higher accelerations instability developed with resulting large-amplitude oscillations of the evaporator temperature. The instability found in these experiments is thought to be related to the geyser effect observed in thermosyphons.

Liquid flow analysis in the evaporator grooves of the cold plate

10.2514/3.82 ◽  
1988 ◽  
Vol 2 (2) ◽  
pp. 172-179
Author(s):  
Han Hwangbo ◽  
W. S. McEver
Keyword(s):  
Liquid Flow ◽  
Flow Analysis ◽  
Cold Plate

Investigation of Annular Liquid Flow With Cocurrent Air Flow in Horizontal Tubes

1952 ◽  
Vol 19 (3) ◽  
pp. 267-274
Author(s):  
A. E. Abramson
Keyword(s):  
Liquid Flow ◽  
Flow System ◽  
Air Flow ◽  
Flow Analysis ◽  
Flow Conditions ◽  
Horizontal Tubes ◽  
Air Stream ◽  
Visual Observations

Abstract Visual observations and flow analysis were made of annular liquid flow with cocurrent air flow in horizontal tubes. The effect of liquid properties and air-stream conditions on the characteristics of the liquid flow were observed. The results are presented in form of shadowgraph pictures of the liquid flow. Analysis of the flow system related the characteristics of the liquid flow to the flow conditions.

Nanoscale Wicking Structures

2009 ◽  
Author(s):  
Conan Zhang ◽  
Carlos H. Hidrovo
Keyword(s):  
Theoretical Model ◽  
Mass Flow ◽  
Capillary Flow ◽  
Flow Analysis ◽  
Heat Removal ◽  
Maximum Flow ◽  
Heat Pipes ◽  
Heat Fluxes ◽  
Flow Rates ◽  
Capillary Limit

Heat pipes are ubiquitous in various heat transfer applications due to their low maintenance and lack of moving parts. Their simplicity makes them compact and ideally suited for microelectronics use. Recirculation of the coolant in a heat pipe is done passively by means of a wicking structure that induces capillary-driven flow from the condenser to the evaporator. This fluidic scheme is highly desirable but requires precise optimization of the wicking structure geometry to provide the required coolant flow rates under different heat loads. In this paper we present an ab initio model that simulates the capillary flow within a wicking structure of regular and periodic geometry. An energy formulation incorporating capillary equations for pressure gradient and the Stokes flow equation for frictional dissipation were used in the analysis. The feasibility of using nanostructures for capillary-driven flow was assessed using this theoretical analysis. This model is specifically designed to simulate a nanopillar array wick (or nanowick) but was also extended to incorporate commercially available homogenous wicks through the use of a general Darcy’s flow approach. A Darcy’s flow analysis requires knowledge of the porous structure permeability (κ), which must be empirically determined. However, our first principles approach can be used to estimate the effective permeability of various commercial wicks. Only the characteristic structural dimensions of a wick are needed in our model for an accurate estimate of the permeability and the maximum flow rate the wick can sustain without the necessity for an empirical correlation. The results of the theoretical model were corroborated through experimental measurements of baseline mesh wicks and nanowicks. Since the thermal performance of most heat pipes is usually capped by the capillary limit, this threshold was examined for each wick by measuring the mass flow over time at different heat fluxes. At high heat fluxes, the wick cannot sustain the fluid flow necessary for heat removal and burnout occurs. This phenomenon occurs at the thermal capillary limit. The mass flow ceases to increase in the case of burnout and may actually decrease if a disruptive vapor film is created. Experiments show that the baseline wicks were found to have higher mass flow rates when compared to a nanowick due to the difference in thickness of the wicks. However, when the data were normalized to produce velocity values, the nanowick was found to have a higher velocity than most of the baseline wicks. These experimental results were weighed against the theoretical model results showing very good agreement of the two.

Performance Characteristics of a Concentric Annular Heat Pipe: Part II—Vapor Flow Analysis

1989 ◽  
Vol 111 (4) ◽  
pp. 851-857 ◽  
Author(s):  
A. Faghri
Keyword(s):  
Theoretical Analysis ◽  
Heat Pipe ◽  
Incompressible Flow ◽  
Similarity Solution ◽  
Flow Analysis ◽  
Fluid Motion ◽  
Heat Pipes ◽  
Performance Characteristics ◽  
Vapor Flow ◽  
Pressure Losses

The solutions of the equations of fluid motion for compressible and incompressible flow in a concentric annular heat pipe have been analyzed. In addition, a similarity solution is presented that can predict the pressure losses in all the segments of the concentric annular heat pipe as well as conventional heat pipes. A theoretical analysis to predict the sonic limit for this new heat pipe is also presented.

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