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

Hoang, Triem T.; O’Connell, Tamara; Ku, Jentung

doi:10.2514/6.2004-5577

Cited by 9 publications

(8 citation statements)

References 4 publications

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“…Thus, any error in predicting the heat leak can have a larger effect on the results. In fact, this has been a consistent problem for predicting the LHP performance at low powers as it was previously reported in several works (e.g., [7,15]. It can also be speculated that at low powers, the active evaporation area on the wick exterior surface is somehow limited.…”

Section: Resultsmentioning

confidence: 79%

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Transient Thermo-Fluid Modeling of Loop Heat Pipes and Experimental Validation

Nishikawara

Nagano

Kaya

2013

Journal of Thermophysics and Heat Transfer

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A transient mathematical model is developed to study the transient response and analyze the distribution of heat load in a loop heat pipe. The model is based on the one-dimensional and time-dependent conservation equations for heat and fluid flow. The momentum and energy conservation equations for each of the loop heat pipe components are solved. The model results are compared against the data obtained from two miniature loop heat pipes using polytetrafluoroethylene wicks, ethanol, and acetone as working fluids. The mathematical model satisfactorily predicts the dynamic behavior of the loop heat pipe unit. It is shown that the percentage of heat leak across the wick decreases and the ratio of latent heat increases with increasing heat load. Some temperature overshoots observed in the calculation results are not observed in the experimental data. When a new power is applied, no time lag is observed in the loop heat pipe response between the simulation and experimental results. Nomenclature A = cross section area, m 2 A s = surface area, m 2 C = heat capacity, J∕kg c = constant in Chisholm correlation c p = specific heat at constant pressure, J∕kg K D = diameter, m f = Darcy's friction coefficient G A B = thermal conductance between A and B, W∕K Gr = Grashof number g = gravity, m∕s 2 h = heat transfer coefficient, W∕m 2 K h lat = latent heat, J∕kg k = thermal conductivity, W∕m K L = length, m _ m = mass flow rate, kg∕s Nu = Nusselt number Pr = Prandtl number p = pressure, Pa _ Q A B = rate of heat transfer from A to B, W _ Q apply = heat load, W q = amount of heat transfer per volume, W∕m 3 Re = Reynolds number T = temperature,°C u = velocity, m∕s V = volume, m 3 X = ratio between vapor and liquid frictional pressure loss Greek β = coefficient of volume expansion, 1∕K ε = porosity ν = kinematic viscosity coefficient, m 2 ∕s ρ = density, kg∕m 3 τ w = wall shear stress, Pa Φ i = square root of ratio between the frictional pressure loss in single phase i and two-phase flow Subscript amb = ambient bay = bayonet tube cc = compensation chamber e = evaporator eff = effective fc = forced convection gr = groove hb = heater block int = interface l = liquid nc = natural convection sat = saturation sub = subcooled v = vapor 2f = two phase

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Section: Resultsmentioning

confidence: 79%

“…In the past, several steady-state mathematical models to predict the operational characteristics of LHPs have been published [5][6][7][8][9][10]. Maidanik et al [5] developed an analytical model with a closed form solution using the energy and pressure balances.…”

mentioning

confidence: 99%

Transient Thermo-Fluid Modeling of Loop Heat Pipes and Experimental Validation

Nishikawara

Nagano

Kaya

2013

Journal of Thermophysics and Heat Transfer

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“…Ref. [19] first established a steady-state mathematical model of a LHP with multiple capillary pumps and multiple condensers, and the predictions agreed well with available test data, which could provide a better simulation tool for space applications. Further improvement of the model of LHPs was attempted in Ref.…”

Section: Introductionmentioning

confidence: 60%

Parametric analysis of steady-state operation of a CLHP

Bai

Lin

Wen

2010

Applied Thermal Engineering

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“…Multiple loop heat pipe (MLHP) is a kind of LHP which has multiple evaporators and multiple condensers, it has been demonstrated in the year 1997 [3]. The mathematical models has been established in the year 2004, 2005 [4] [5].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Loop Heat Pipe with Two Evaporators/Two Condensers under Thermal Vacuum Condition

Chang¹,

Nagano²

2016

JAMP

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Multiple loop heat pipe is a high-functional thermal transport device. This work was conducted to confirm the working performance of Multiple loop heat pipe under thermal vacuum ambience with the working fluid ammonia. Asmall multiple loop heat pipe with two evaporators and two radiators was designed and fabricated. Then thermal vacuum test was conducted. The heaters were fasten on both evaporators, both radiators, both compensation chambers. In the case that both evaporators were heated, the multiple loop heat pipe can transport 120/120 W for 1.5 m, in the case that only one evaporator was heated, evaporator 1 can transport 80 W for 1.5 m, while evaporator 2 can transport 120 W for 1.5 m. Two flow regulators were installed near the confluence of liquid line to prevent uncondensed vapor penetrating into returning liquid when the temperature difference exists between two radiators. In the case that the heat load at both evaporators were 40/40 W and one radiator was heated, the flow regulator1 can tolerate the 160 W of heat load which was supplied to radiator1 while the flow regulator2 can tolerate the 100 W of heat load which was supplied to radiator2. To demonstrate the multiple loop heat pipe's startup behavior at lowheat load, each of the compensation chamber was preheated to change the initial distribution of liquid and vapor in the evaporator and compensation chamber, in the result, each evaporator can start up at 5W through preheating.

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

Cited by 9 publications

References 4 publications

Transient Thermo-Fluid Modeling of Loop Heat Pipes and Experimental Validation

Transient Thermo-Fluid Modeling of Loop Heat Pipes and Experimental Validation

Parametric analysis of steady-state operation of a CLHP

Experimental Investigation of Loop Heat Pipe with Two Evaporators/Two Condensers under Thermal Vacuum Condition

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