Heat transfer intensification by increasing vapor flow rate in flat heat pipes

2015 ◽  
Author(s):  
Silviu Sprinceana ◽  
Ioan Mihai ◽  
Marius Beniuga ◽  
Cornel Suciu
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Heat Pipes ◽  
Vapor Flow ◽  
Heat Transfer Intensification

Suppression of the Sonic Heat Transfer Limit in High-Temperature Heat Pipes

1989 ◽  
Vol 111 (3) ◽  
pp. 605-610 ◽  
Author(s):  
Flavio Dobran
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Pipes ◽  
Vapor Flow ◽  
Transport Capacity ◽  
Flow Area ◽  
Temperature Heat ◽  
Liquid Evaporation ◽  
Heat Transfer Limit ◽  
Axial Heat

The design of high-performance heat pipes requires optimization of heat transfer surfaces and liquid and vapor flow channels to suppress the heat transfer operating limits. In the paper an analytical model of the vapor flow in high-temperature heat pipes is presented, showing that the axial heat transport capacity limited by the sonic heat transfer limit depends on the working fluid, vapor flow area, manner of liquid evaporation into the vapor core of the evaporator, and lengths of the evaporator and adiabatic regions. Limited comparisons of the model predictions with data of the sonic heat transfer limits are shown to be very reasonable, giving credibility to the proposed analytical approach to determine the effect of various parameters on the axial heat transport capacity. Large axial heat transfer rates can be achieved with large vapor flow cross-sectional areas, small lengths of evaporator and adiabatic regions or a vapor flow area increase in these regions, and liquid evaporation in the evaporator normal to the main flow.

Modeling of the Flow and Heat Transfer in Micro Heat Pipes

2004 ◽  
Author(s):  
C. B. Sobhan ◽  
G. P. (Bud) Peterson
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Radius Of Curvature ◽  
Vapor Flow ◽  
Axial Distribution ◽  
Cross Sectional ◽  
Flow And Heat Transfer ◽  
Physical Phenomena ◽  
Micro Heat Pipes

The fluid flow and heat transfer characteristics of micro heat pipes are analyzed theoretically, in order to understand the physical phenomena and quantify the influence of various parameters on overall thermal performance of these devices. A one-dimensional model is utilized to solve the governing equations for the liquid/vapor flow and the heat transfer in the heat pipe channel. Variations in the liquid and vapor cross-sectional areas along the axial length of the heat pipe are included and the equations are solved using an implicit finite difference scheme. Appropriate models for fluid friction in small passages with varying cross-sectional areas have been incorporated to yield the axial distribution of the meniscus radius of curvature and the velocity, temperature and pressure in both the liquid and the vapor phases. Using this information, the effective thermal conductivity of the micro heat pipe is modeled, and parametric studies are performed by changing the heat load and cooling rate. The results of the analysis are discussed and compared with other theoretical models and experimental results found in the literature. By so doing, this analysis provides greater insight into the physical phenomena of flow and heat transfer in micro heat pipes and identifies a methodology for optimizing the design of these devices.

An Investigation of the Liquid Distribution in Annular-Mist Flow

1970 ◽  
Vol 92 (4) ◽  
pp. 651-658 ◽  
Author(s):  
J. T. Pogson ◽  
J. H. Roberts ◽  
P. J. Waibler
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Liquid Film ◽  
Flow Rate ◽  
Droplet Size Distribution ◽  
Correlation Equation ◽  
Vapor Flow ◽  
Two Phase ◽  
Liquid Distribution ◽  
Liquid Film Flow

The results of an experimental investigation of the average liquid film thickness are presented for vertical upward annular-mist two-phase flow, with and without heat transfer. The effects on the film thickness for variations in vapor flow rate, liquid flow rate, vapor density, and heat transfer are described. A correlation equation is presented for the local time-averaged thickness and for the droplet size distribution. In addition, an equation is given for the liquid film flow rate as a function of the average film thickness.

Consecutive-Photo Method to Measure Vapor Volume Flow Rate During Boiling From a Wire Immersed in Saturated Liquid

1998 ◽  
Vol 120 (3) ◽  
pp. 561-567 ◽  
Author(s):  
C. N. Ammerman ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Measurement Technique ◽  
High Speed ◽  
Laser Doppler Anemometry ◽  
Volume Flow Rate ◽  
Nucleate Boiling ◽  
Volume Flow ◽  
Bubble Velocity ◽  
Vapor Flow

A photographic measurement technique is developed to quantify the vapor volume flow rate departing from a wire during boiling. The vapor flow rate is determined by measuring the volume of bubbles after departure from the boiling surface in consecutive frames of high-speed video. The measurement technique is more accurate and easier to implement than a previously developed photographic/laser Doppler anemometry (LDA) method. Use of the high-speed camera in place of a standard video camera eliminates the requirement for LDA-acquired bubble velocity measurements. The consecutive-photo method requires relatively few video images to be analyzed to obtain steady-state vapor volume flow rates. The volumetric flow rate data are used to calculate the latent heat transfer and, indirectly, sensible heat transfer which comprise the nucleate boiling heat flux. The measurement technique is applied to a 75-μm diameter platinum wire immersed in saturated FC-72.

Steady Liquid Flow and Liquid-Vapor Interface Shapes in Different Groove Structures in Micro Heat Pipes

2006 ◽  
Author(s):  
Mulugeta Markos ◽  
Vladimir Ajaev ◽  
G. M. Homsy
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Liquid Flow ◽  
Heat Pipes ◽  
Type Model ◽  
Practical Applications ◽  
Design And Optimization ◽  
Flow And Heat Transfer ◽  
Micro Heat Pipes

The paper presents a lubrication-type model of liquid flow and heat transfer in different groove structures in micro heat pipes under negligible gravity and small capillary number. In the adiabatic region the flow rate can be controlled by changing the shape of the cross-section. We have computed the flow rate as a function of geometric parameters. Determination of the vapor-liquid interface shape in the grooves requires coupling of fluid flow and heat transfer. We examined the shape of the interface when thermocapillary effect is insignificant and then consider the effect of thermocapilarity. Practical applications of our results are discussed in relation to the design and optimization of micro heat pipes.

scholarly journals Thermodynamic performance evaluation of an air-air heat pipe heat exchanger

2014 ◽  
Vol 18 (4) ◽  
pp. 1343-1353 ◽  
Author(s):  
Mohan Kumar ◽  
S.C. Kaushik ◽  
S.N. Garg
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pipe ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Pipes ◽  
Heat Transfer Analysis ◽  
Thermodynamic Performance ◽  
Pipe Heat

In this paper, heat transfer analysis for an air-air heat exchanger was experimentally carried out to find its thermal performance and effectiveness. Air-air heat exchanger equipped with finned heat pipes was considered for the experimentation. Mass flow rate of air was considered in between 0.24 to 0.53 [kg/sec]. The temperature at the condenser side of the heat pipe heat exchanger was kept constant at around 23 [?C] and at the evaporator part it was varied from 88 to 147 [?C]. The performance of heat pipe heat exchanger was evaluated at different mass flow rate of air, in terms of effectiveness and compared with its corresponding value found by theoretical analysis.

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