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experimental investigation on grooved heat pipes using copper oxide nan fluid.

by:Mingfa Tech     2020-02-18
The heat pipe is a closed tube or chamber of different shapes, and the inner surface is covered with porous capillary core.
The Wick is saturated by the liquid phase of the working fluid, and the remaining volume of the tube contains the vapor phase.
The heat applied by the external source on the evaporator evaporates the working fluid of this part.
The resulting pressure difference drives the steam from the evaporator to the condenser, in which the steam condensation releases the potential steam heat into the radiator of this part of the pipe.
Evaporation and exhaustion of liquid can lead to liquid-
The Steam interface in the evaporator enters the surface of the wick and creates a capillary pressure.
The capillary pressure pump returns the condensate pump to the evaporator for re-evaporation.
The heat pipe can continuously transfer the evaporated waste heat from the evaporator part to a higher density without drying the wick.
As long as the flow channel of the working fluid is not blocked and sufficient capillary pressure is maintained, the process will continue.
Heat that can be transmitted as latent heat of evaporation is usually several orders of magnitude larger than heat that is transmitted as heat sensation in conventional convection systems.
Therefore, the heat pipe can transport a large amount of heat in a small unit size [1].
Typically, a wick structure consisting of a transparent structure consisting of interconnected holes.
The covered channel consists of a liquid flow area enclosed by a finer mesh capillary structure.
This category includes a groove heat pipe with gauze covering grooves and arterial Wick.
Groove is a kind of Wick widely used in spacecraft applications, but it cannot support important capillary head in Earth gravity. it is a widely used system.
The easiest way to produce a longitudinal groove in a heat pipe wall is to squeeze or pull alternating arrangement, including the use of a faucet or a single-
Point cutting tool.
In the evaporator and condenser parts, the radial thermal resistance of the groove will be completely different.
This is because of the different heat transfer mechanisms.
In the evaporator, land or fin tip does not work during heat transfer.
The possible heat flow path is through the fin conduction, conduction, through the liquid film at the curved moon surface, evaporation at the liquidvaporinterface.
In the condenser part, the grooves are submerged and the fintip plays an active role in the heat transfer process.
The accumulation of liquid film on the tip of the fin will provide the main resistance to the heat flow.
The thickness of the liquid film is a function of the condensation rate and moisture properties of the working fluid [2]. Zhen-Hue Liu et al. [3]
Experimental study on thermal properties of inclined micro-groove heat pipes with water
Based on Coo nanofluids.
They report that the inclination has a great impact on the heat transfer performance of heat pipes using water and nana fluids.
The best results achieved at the tilt angle of 75 [degrees].
In heat pipes using nano-fluid, the maximum heat flow of the inclined heat pipe can be doubled, while the tilt angle itself has little effect on the maximum heat flow. Horng-
Jou Wang and others-Se Such et al. [4]
The thermal properties of micro flat heat pipes with axial ladder grooves are analyzed and studied.
They studied the flow of ladder liquid and steam and the effects of variable shear stress along the liquid and Steam interface.
Betthold junior high school, etc. [5]
A dynamic test method for determining the capillary limit of the axial trough heat pipe was studied.
The drying limit in the heat pipe was tested by dynamic method.
Zed Lataoui, etc. [6]
The thermal behavior and performance of the axial groov-shaped heat pipe were investigated.
In this work, the maximum heat transfer capacity can be determined and a significant increase in the average evaporator temperature can be checked.
Peter Stephen and Kristoff Brandt7]
An advanced capillary structure with high efficiency, low axial pressure drop, high capillary pressure and high boiling limit was developed.
It combines the openmini channel with an open WeChat made vertically at the top of the mini channel.
They reported the heat transfer coefficient in the evaporator area, which is a characteristic value of thermal effectiveness, up to 3.
Compared with similar structures without microchannels, it is 3 times higher.
A combination of Micro
And developed a macro phenomenon.
Kym Hung Dao et. al [8]
A mathematical model was established to predict the thermal performance of flat micro-heat pipes with rectangular trough core structure.
The results obtained from the proposed model are very consistent with several existing experimental data in terms of wall temperature and maximum heat transfer rate.
Using the proposed model, the maximum heat transfer rate of the amicro heat pipe with slot core structure is optimized according to the width and height of the slot core structure.
In this work, the performance of the groove heat pipe was analyzed using copper oxide nanofluid as working fluid.
The effects of thermal input, tilt angle and filling ratio of the working mass were analyzed and reported.
Table 1 gives the specification of the heat pipe.
The microstructure of the hole-like structure of the heat pipe is shown in figure 2. II.
Experimental settings and procedures: the experimental setting of the heat pipe is shown in figure 3, and the position of the thermocouple is shown in figure 4.
Adiabatic part of the heat pipe is covered with insulation material (glasswool).
Power input (heat)
The evaporator area of the heat pipe is applied by using an electric heater and measured using an electric sensor (wattmeter).
Place three thermocouple along the length of the pipe to measure the temperature of the evaporator and condensation section, and place four thermocouple to measure the temperature of the insulation section.
In addition, two other thermometers are placed along the path of the coolant to measure the temperature of the coolant (water)
Entrance and exit.
The uncertainty of temperature measurement is [+ or -]0. 1[degrees]C.
The nanoparticles used in the experiment are copper oxide particles with a size of 50 nm.
The basic working solution is DI water.
The mixture is made using an ultrasonic homogenizer.
In this study, nanofluids with a concentration of 100 mg/kWh were used.
In this experiment, the input heat flow is assigned to the evaporation area by using variables, and can be measured with wattmeter.
In the test, the power is on, the power is added at this point, it takes about 50 to 90 minutes to achieve stability-state. Once stable-
State conditions have been reached, and the temperature distribution along the heat pipe and other experimental parameters have been measured and recorded.
The power is increased from 30 W to 70 W, and the increment value is 10 W.
This process is repeated for different tilt angles (0[degrees], 15[degrees], 30[degrees], 45[degrees],60[degrees], 75[degrees]& 90[degrees])
And with different fillingratios (
25%, 50%, 75%, 100% and 125%). 3.
Experimental results and discussion: 3.
1 Effect of thermal input, tilt angle and filling ratio thermal efficiency: the thermal efficiency of the heat pipe is defined as the ratio of the thermal rejection rate in the condenser to the heat provided in the evaporator part [12].
Accept heat in October 12, 2016;
October 20, 2016 address: SenthamaraiKannan Gajalakshmi, associate professor, Mechanical Engineering Department, Faculty of Engineering and Technology, kudarol-607003, India. E-
Mail: gajakannan @ rediflmail
Title: figure
Description: Figure 1: microstructure of the fluid in the trough heat pipe
2: SEM image of copper subtitles: Figure
Figure 3: Description of experimental setup
5: For the filling ratio of 25%, the effect of thermal input and tilt angle on thermal efficiency
6: For the filling ratio of 50%, the effect of thermal input and tilt angle on thermal efficiency
7: For the filling ratio of 75%, the effect of thermal input and tilt angle on thermal efficiency
8: For the filling ratio of 100%, the effect of thermal input and tilt angle on thermal efficiency Title: Fig.
9: effect of heat input and filling ratio on thermal efficiency Title: figure
10: For the filling ratio of 25%, the effect of thermal input, tilt angle on the thermal resistance
11: For the filling ratio of 50%, the effect of thermal input, tilt angle on thermal resistance Title: Fig.
11: For the filling ratio of 75%, the effect of thermal input, tilt angle on thermal resistance Title: Fig.
13: effect of thermal input, tilt angle on the thermal resistance of 100% fill ratio Title: Fig.
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