Mathematical Modeling of Loop Heat Pipes with Mutiple Capillary Pumps and Multiple Condensers, Part I Steady State Simulations

2004 ◽  
Author(s):  
Triem Hoang ◽  
Jentung Ku
Keyword(s):  
Mathematical Modeling ◽  
Steady State ◽  
Heat Pipes ◽  
Loop Heat Pipes

scholarly journals Literature review: Steady-state modelling of loop heat pipes

2015 ◽  
Vol 75 ◽  
pp. 709-723 ◽  
Author(s):  
Benjamin Siedel ◽  
Valérie Sartre ◽  
Frédéric Lefèvre
Keyword(s):  
Steady State ◽  
Literature Review ◽  
Heat Pipes ◽  
Loop Heat Pipes

Steady State Parametric Modeling of Non-Conventional Loop Heat Pipes

2013 ◽  
Author(s):  
Karthik S. Remella ◽  
Frank M. Gerner ◽  
Ahmed Shuja
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Transfer Coefficient ◽  
Thermal Energy ◽  
Heat Pipes ◽  
Parametric Model ◽  
Parametric Modeling ◽  
Working Fluid ◽  
Loop Heat Pipes

Loop Heat Pipes (LHPs) are used in many thermal management applications, especially for micro-electronics cooling, because of their ability to passively transport thermal energy from a source to a sink. This paper describes the development of a parametric model for a non-conventional LHP operating in steady state, employed to cool Light Emitting Diodes (LEDs). This device is comprised of a flat evaporator, and a finned circular loop wherein condensation and sub-cooling of the working fluid takes place. Unlike a conventional LHP, this device has no compensation chamber. In the mesh screen of the evaporator, the vapor flow entrains liquid and hence the quality of the two-phase mixture leaving the evaporator (xevap) is less than unity (unlike in a conventional LHP where saturated vapor leaves the evaporator). Since this lower quality (approximately 0.2) results in a smaller ratio of latent energy to sensible energy being removed by the condenser and sub-cooler respectively; the ratio of the length of the sub-cooler to condenser length is significantly larger. This results in more stable and controlled operation of the device. Mathematical models of the evaporator, the condenser and the sub-cooler sections are developed, and two closure conditions are employed in this model. For consistency and accuracy, some parameters in the model, such as the natural convection heat transfer coefficient (h o) and a few thermal resistances in the evaporator, are estimated empirically from test data on the device. The empirically obtained value of the heat transfer coefficient is in very good agreement with correlations from the literature. The parametric model accurately predicts the LED board temperature and other temperatures for a specific amount of thermal energy dissipated by the LEDs.

Steady State Numerical Modeling of Non-Conventional Loop Heat Pipes (LHPs)

2012 ◽  
Author(s):  
Karthik S. Remella ◽  
Frank M. Gerner ◽  
Ahmed Shuja ◽  
Praveen Medis
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Single Phase ◽  
Heat Pipes ◽  
Working Fluid ◽  
Vapor Interface ◽  
Loop Heat Pipes ◽  
Led Array ◽  
Fill Volume ◽  
Liquid Vapor

Loop heat pipes (LHPs) transport energy from an evaporator to a condenser in the form of latent heat. In conventional LHPs, the vapor pressure is significantly higher than the liquid pressure across the liquid-vapor interface due to the small pores and the corresponding capillary forces in the wick. This large pressure difference transports the single phase vapor after evaporation from the evaporator to the condenser and once the vapor is condensed, a single phase liquid from the condenser back to the evaporator. This current work involves the development of a steady state design model of the LHP system consisting of a planar evaporator package and a finned copper tube loop, which serves as an air-cooled condenser. Although evaporation due to the heat transfer creates the pressure in the vapor which drives the flow, contrasting to the conventional loop heat pipes, the pressure drop across the liquid-vapor interface is much smaller. A positive hydrostatic head is applied to the liquid above the wick and there is entrainment of liquid from the wick in the evaporator. Therefore, the fluid flow leaving the evaporator package is a two-phase flow, assumed to be saturated liquid and saturated vapor in equilibrium. The primary objective of this non-conventional LHP device is to remove the thermal energy dissipated from a Light Emitting Diode (LED) array. A major portion of this energy causes evaporation of the working fluid within the wick. The remaining energy reheats the liquid in both the liquid return line and within the evaporator package. The evaporator package is modeled as a one-dimensional thermal resistance network and these resistances are empirically determined from experiments. It is found that the convective heat transfer co-efficient of air plays a pivotal role in the heat dissipation and hence, is empirically determined in this work. This value is fairly agreeable with the Nusselt number correlation on the air side developed by Hahne et al. [1]. A mass balance relates the fill volume with the length of the condenser. The temperatures within the LHP are predicted by applying the principle of conservation of energy over the evaporator, the condenser and the sub-cooler sections of the heat exchanger loop. Finally, this LHP model predicts an approximate fill volume necessary for the LHP to operate properly.

scholarly journals Mathematical modeling of loop heat pipes

1999 ◽  
Author(s):  
Tarik Kaya ◽  
Triem Hoang ◽  
Jentung Ku ◽  
Mark Cheung
Keyword(s):  
Mathematical Modeling ◽  
Heat Pipes ◽  
Loop Heat Pipes
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