1D Mechanistic Model and Simulation Code for Closed-Loop Pulsating Heat Pipes

Lightweight, flexible motion simulation is the demand of airborne laser communication optical transceive when apply to outside test. A new parallel 2_DOF platform that has the function of azimuth and pitching is put forword based on the analysis of airplane position-pose changes affect the performance airborne laster communication APT system, and the kinematics model is established by using closed-loop vector method. Kinematics model is right through the comparison of mathematical model and simulation results of ADAMS, which provides the reference and basis for the design of control system.

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Operational limit of closed loop pulsating heat pipes

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2007.01.033 ◽

2008 ◽

Vol 28 (1) ◽

pp. 49-59 ◽

Cited By ~ 138

Author(s):

Honghai Yang ◽

S. Khandekar ◽

M. Groll

Keyword(s):

Closed Loop ◽

Heat Pipes

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A Comprehensive Experimental Investigation of the Performance of Closed-Loop Pulsating Heat Pipes

Journal of Heat Transfer ◽

10.1115/1.4036460 ◽

2017 ◽

Vol 139 (9) ◽

Cited By ~ 1

Author(s):

M. Halimi ◽

A. Abbas Nejad ◽

M. Norouzi

Keyword(s):

Thermal Resistance ◽

Flow Regime ◽

Thermal Performance ◽

Closed Loop ◽

Heat Pipes ◽

Filling Ratio ◽

Working Fluid ◽

Physical Parameters ◽

Two Phase ◽

Laboratory Conditions

Closed-loop pulsating heat pipes (CLPHPs) are a new type of two-phase heat transfer devices that can transfer considerable heat in a small space via two-phase vapor and liquid pulsating flow and work with various types of two-phase instabilities so the operating mechanism of CLPHP is not well understood. In this work, two CLPHPs, made of Pyrex, were manufactured to observe and investigate the flow regime that occurs during the operation of CLPHP and thermal performance of the device under different laboratory conditions. In general, various working fluids were used in filling ratios of 40%, 50%, and 60% in horizontal and vertical modes to investigate the effect of thermo-physical parameters, filling ratio, nanoparticles, gravity, CLPHP structure, and input heat flux on the thermal performance of CLPHP. The results indicate that three types of flow regime may be observed given laboratory conditions. Each flow regime exerts a different effect on the thermal performance of the device. There is an optimal filling ratio for each working fluid. The increased number of turns in CLPHP generally improves the thermal performance of the system reducing the effect of the type of the working fluid on the aforementioned performance. The adoption of copper nanoparticles, which positively affect fluid motion, decreases the thermal resistance of the system as much as 6.06–42.76% depending on laboratory conditions. Moreover, gravity brings about positive changes in the flow regime decreasing thermal resistance as much as 32.13–52.58%.

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Flat plate solar water heater with closed-loop oscillating heat pipes

Thermal Science ◽

10.2298/tsci200713192c ◽

2021 ◽

pp. 192-192

Author(s):

Piyanun Charoensawan ◽

Patomsok Wilaipon ◽

Nopparat Seehawong

Keyword(s):

Flat Plate ◽

Flow Rate ◽

Thermal Performance ◽

Closed Loop ◽

Water Flow Rate ◽

Heat Pipes ◽

Solar Water Heater ◽

Water Heater ◽

Solar Water ◽

Irradiation Intensity

The flat plate solar water heater, using the closed-loop oscillating heat pipes (CLOHP), was constructed and investigated. The flat plate collector consisted of 10 pipes of CLOHP and the collector area was 1.5?1 m2. Each CLOHP was made of a copper capillary tube with a 1.5 mm inner diameter, a 2.8 mm outer diameter and had 20 turns. The distilled water was used as the working fluid with a filling ratio of 50% the tube?s total internal volume. The evaporator section of the CLOHP was placed on the absorber plate of the collector, and its condenser section was wrapped around the copper tube, in which hot water flowed through. The solar water heater was tested under the solar simulator with halogen lamps generating the uniform artificial solar energy. The irradiation intensity and the water flow rate of the solar water heater were adjusted. It was found that the thermal performance of the solar water heater clearly improved with an increase in the irradiation intensity from 480 to 1086 W/m2. However, the water flow rate in the range of 1.5-3.0 L/min, had a thermal performance that was slightly different. The thermal efficiency of 0.67 was archived at the high irradiation intensity of 947-1086 W/m2. Moreover, the mathematical model to predict the thermal efficiency of the flat plate solar water heater with the CLOHPs was obtained.

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Simultaneous Implosive Accretion and Jet Formation in Quasars: Correlation of Optical Outbursts by VLBI Jets

Symposium - International Astronomical Union ◽

10.1017/s0074180900176661 ◽

1994 ◽

Vol 159 ◽

pp. 490-490

Author(s):

M.M. Romanova ◽

R.V.E. Lovelace

Keyword(s):

Magnetic Field ◽

Angular Momentum ◽

Radial Distance ◽

Compact Object ◽

Simulation Code ◽

Poloidal Magnetic Field ◽

Magnetic Field Fluctuation ◽

Disk Model ◽

Opposite Case ◽

Model And Simulation

A model and simulation code have been developed for time-dependent axisymmetric disk accretion onto a compact object including for the first time the influence of an ordered magnetic field and magnetically driven outflow of energy and angular momentum in (±z) directions (see also Lovelace et al., 1993). It was shown that the system behaviour crucially depends on the amplitude of the poloidal magnetic field fluctuation Bp, compared to the critical value Bcr ∼ (α2T1/2σ/R3/2)1/2, where T(r, t) is the temperature, σ(r, t) the surface density of the disk, R the radial distance, α the alpha coefficient of Shakura-Sunyaev disk model. If the fluctuation is small, Bp < Bcr, then it diffuses outwards with decreasing the amplitude and eventually disappears. In the opposite case Bp > Bcr, a soliton-like structure forms in the disk density, temperature, and magnetic field and propagates implosively inward. In this case the radial accretion speed u(r, t) is shown to be the sum of the usual viscous contribution and magneitic contribution ∼ R3/2B2p/σ. The essential part of angular momentum and energy is going to the jet from the region of fluctuation. Compression of matter in the propagating wave leads to enhancement of magnetic field and more effective angular momentum outflow. This leads in turn to accelerated accretion and subsequent enhancement of magnetic field. It gives the implosive nature of the process, which can be observed as: simultaneous burst in the radiation and outflow. The model is pertinent to the formation of discrete components observed in VLBI jets which appear to originate at times of optical outbursts at some quasars.

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