Lin Guiping

Investigation On Startup Behaviors of a Loop Heat Pipe

The results of ground experiments on startup behaviors of a loop heat pipe are presented. One objective is to investigate the effects of working conditions on the startup of loop heat pipes. Startup behaviors as functions of various parameters, including the vapor/liquid distribution in the evaporator, startup heat load, sink temperature, and adverse elevation are described and explained. The physical process of startup is described, and the explanation that pressure transfer leads to the saturated temperature rise in the compensation chamber during startup is discussed. The other objective is to investigate the effect of startup on the steady-state operation of loop heat pipes. Test results indicate that evaporation inside the wick tends to occur at low startup heat loads when the evaporator, including the vapor grooves and the evaporator core, is flooded with liquid. Some peculiar phenomena, including evaporation inside the wick, temperature oscillation at the condenser inlet, and reverse flow equilibrium, which lead to higher operating temperatures, were observed during startup.

Development and Test Results of a Dual Compensation Chamber Loop Heat Pipe

A dual compensation chamber loop heat pipe is developed to solve the problem of the relative orientation limit between the evaporator and the compensation chambers. The construction of the evaporator and the compensation chambers is presented. The concurrent design method of the working fluid charge mass and the compensation chamber volumes, that can realize the objectives where, within a certain temperature range, the dual compensation chamber loop heat pipe cannot only start up and operate normally at any orientation, but can also avoid the most difficult startup situation, is introduced. The operation and the thermal control characteristics of the dual compensation chamber loop heat pipe are investigated. Test results indicate that in some heat load regions, the operating temperatures vary with the relative orientation between the evaporator and the compensation chambers. This is explained by the thermal equilibrium of the compensation chamber and the usage efficiency of the return liquid subcooling. The test results and discussion of the dual compensation chamber loop heat pipe suggest that part of the return liquid subcooling that cools the liquid to be locally subcooled must be considered in the mathematical modeling of the loop heat pipe.

Investigation of Effects of Auxiliary Measures for Startup of Loop Heat Pipes

Experiments have been conducted to investigate the feasibility of two active measures, namely, local heating on the evaporator and cooling the compensation chamber, with a thermoelectric cooler. A new passive auxiliary measure, which utilizes the latent heat of phase change material to maintain the compensation chamber temperature at the melting point to help estimate the required superheat, has been presented for the first time. The effects of the three auxiliary measures on startups and the steady-state operation have been investigated. Test results indicate that the three auxiliary measures are helpful in establishing the required liquid superheat and reducing the evaporator temperature overshoot, as well as in lessening the startup time. Local heating on the evaporator near the evaporator outlet will not affect the steady-state operation, whereas local heating on the evaporator near the compensation chamber will lead to either sustaining operating temperature rises or higher operating temperatures. The continued operation of the thermoelectric cooler will decrease the operating temperatures at low heat loads and the typical V operating temperature curve will be changed to a nearly linear one. At too low heat loads, the phase change material can only delay the evaporator temperature rise and gain time for the loop heat pipe to wait for the arrival of a higher heat load, which is more favorable for startups.

Electrothermal Airfoil Anti-icing System Simulation

In this paper a simple mathematical model and a numerical simulation method for the analysis of airfoil electrothermal anti-icing systems are presented. With the assumption of that the airfoil surface temperature is equal to the temperature of the runback water film, a mass balance is applied to the runback water flow and an energy balance is applied to the airfoil skin. The flow field and the water impingement are predicted using the Eulerian method, based on FLUENT and its user-defined functions. Reference case is selected for the validation of the presented mathematical model and the numerical method. The results were compared with both the published experimental and numerical results and show satisfactory. Two distributions of heat transfer coefficient for the same case obtained from the literatures are used for studying the influence to the surface temperature and the mass loss of the evaporation. The anti-icing numerical model and simulation method presented in this paper can be applied for the design of the anti-icing system.

Simulation and optimization of a new pulmonary mechanism in electronic oxygen regulator

The bad controllability of pulmonary mechanism was found during the electronic regulator design, and showed up as the sound of snore along with breathing. The experiment for simplified pulmonary mechanism was carried out and defined that the force unbalance point exists in the pulmonary mechanism. The schematic and working principle of the electronic regulator are shown in the paper. Then the FLUENT software was adopted to simulate the force distribution during the valve opening with different given inlet gage pressure. The pressure, velocity distributions and the driving force are shown in results. Based on analysis results, three aspects can be focused on to develop the valve controllability during the valve opening. Meanwhile the results indicate that the positive correlation between motor thrust and valve opening is unavailable. When the cavity pressure relieves after the valve opens, the valve pressure redistributes. Then the force balance point exists during the pulmonary mechanism valve opening. The analysis shows that increasing the spring stiffness and decreasing the valve pedestal area can improve the problem above. Then the reasonable solution can be obtained through the subsequent experiments. Therefore, in the paper, two accessible modified plans are proposed to optimize the system performance in the following system mechanism modification design.

Experimental investigation on the impulse force characteristics in EIDI system

Electro-impulse de-icing (EIDI) system has become one of the important part of aviation de-icing technology, because of its advantages in low power consumption, light weight, convenient maintenance, well reliability, little expense and so on. Electrodynamics analysis is the fundamental basis of the EIDI system design, providing impulse force characteristics for the ensuing stage of structural dynamics analysis and icing region prediction. Since electrodynamics analysis deals with the coupling of electric field, magnetic field and structure deformation, it is incontinent to setup mathematical-physical model close to reality. Therefore, the present work developed a prototype of EIDI system, and investigated the impulse force characteristics experimentally. The feasibility and validity of the EIDI prototype has been verified, and the effect of charging voltage, coil-to-skin gap, skin thickness and conductivity onto the maximum impulse force with has been studied. Moreover, a correlation between the maximum impulse force and the induced peak current intensity is proposed.