Steady-State and Transient Performance of a Miniature Loop Heat Pipe

Abstract

A series of tests have been carried out with a miniature loop heat pipe (mLHP), which has been developed for consumer electronics cooling, for horizontal and four vertical orientations under different sink temperatures. The mLHP has a cylindrical evaporator of 5 mm outer diameter and 29 mm length. The steady-state operating characteristics are similar for different orientations except for the orientation where the evaporator is above the compensation chamber. At an evaporator temperature of 75 °C, an evaporator heat load up to 70 W can be reached with thermal resistance of about 0.2 °C/W. The transient behavior of the mLHP is studied in detail. In general, the mLHP can be started up with very low power input (5 W). Big temperature oscillations in the liquid line were found in many cases, however, the temperature oscillations in the evaporator are minimum. The orientations greatly influence the operating characteristics of the mLHP. At least for the horizontal orientation, the overall performance of the tested mLHP is satisfying.

Characterization of cooling systems based on heat pipe principle to control operation temperature of high-tech electronic components

“…Water, ammonia, acetone, propane and toluene are usually used as working fluids. The temperature difference between evaporator and heat sink increases with heat flow rate, Q, whereas the total thermal resistance decreases with Q [2,[8][9][10]. Thermal performance of a heat pipe, expressed by high values of Q, is improved at large values of diameter and inclination angle as well as at low values of length and wall thickness [8,11].…”

“…It is defined as the temperature difference between the evaporator and the heat sink divided by the dissipated heat flow rate, Q. The total thermal resistance is a function of a large number of variables, such as heat pipe geometry and material, wick structure, working fluid properties, evaporator and condenser length [2,4,[8][9][10][11]. There are several types of wick structures, e.g.…”

“…Generally speaking of a PC (a desktop or a notebook), it is important to maintain the operation temperature of the central processing unit (CPU) below a certain level, otherwise the PC reliability is compromised [1]. Miniature heat pipe coolers fitted with a heat sink are an optimum choice, taking into account both cost and performance, due to their simple structure, lack of active elements needed for working fluid transport and high efficiency of heat transfer [2][3][4][5][6][7][8][9][10][11].…”

Characteristics of Heat Transfer for Heat Pipe and Its Correlation

“…The model was able to predict the decreasing length of the condenser two-phase zone under the constant conductance mode caused by the volume expansion of the liquid in the compensation chamber, and was in good agreement with the experimental data. A series of tests have been carried out by Chen et al [7] with a miniature loop heat pipe (mLHP), which was developed for consumer electronics cooling with four horizontal and four vertical orientations under different sink temperatures. The mLHP was a cylindrical evaporator of 5 mm outer diameter and 29 mm length.…”

Effect of evaporator tilt on the operating temperature of a loop heat pipe without a secondary wick

“…So far, there have been quite a few literatures that reported the operation characteristics of LHPs on the ground, which showed their capability of transporting heat over a long distance under antigravity conditions and revealed their transient startup and power cycling characteristics [21][22][23][24]. It has been found that the relative orientation of the components has significant effect on the startup and steady-state performance of LHPs under terrestrial surroundings, which is briefly reviewed here.…”