THERMAL MODELING AND DESIGN ON SMART PHONES WITH BENDED HEAT PIPE COOLING TECHNIQUE

e-ISSN: 2582-5208 International Research Journal of Modernization in Engineering Technology and Science Volume:02/Issue:10/October -2020

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THERMAL MODELING AND DESIGN ON SMART PHONES WITH BENDED HEAT PIPE COOLING TECHNIQUE Mirza Atiqur Rahman*1, Prof. D.S. Patil*2 *1M.Tech

Final Year, Department of Mechanical Engineering, GHRCEM, Pune, Maharashtra, India.

*2Professor,

Department of Mechanical Engineering, GHRCEM, Pune, Maharashtra, India.

ABSTRACT As we know that smart phones are now an important customer product, so its use is increasing day by day. But at the same time, their app developers (APs) use a lot of power (especially Android phones / mobiles). But as soon as they consume a lot of energy, their performance is limited by thermal barriers. In this paper, we are dealing with the use of bended heat pipe by presenting a compact thermal model and then performing the experiment with bended heat pipe. Heat-cooled technology has been used on smart phones, such as the Redmi not 8 pro, Sony Xperia Z5, Samsung Galaxy S8, and LG G7 and Samsung Galaxy M31s for better cooling performance to reduce APs temperatures. Bendable heat pipes, which can be bent after fabrication as per the need, are the unique devices for thermal management. The effect of bending on the drop in temperature, performance and performance limits has also been investigated. In this exercise, the effects due to bending are studied by working at three different angles of 0 °, 90 ° and 180 °.

In this work, the working of heat pipe was measured in terms of thermal conductance, which is a reciprocal of thermal resistance. Two heat pipes were used for their study. The two heat pipes tested were designated as HP1 and HP2.

Key Words: Heat Pipe, Bended Heat Pipes, Smart Phones, Thermal Conductance, Temperature Drop etc.

I.

INTRODUCTION

The heat pipe cooling system has been used on Smartphones, such as the Redmi not 8 pro, Sony Xperia Z5, Microsoft Lumia 950XL, Samsung Galaxy S8, and LG G7, to achieve optimal cooling efficiency to reduce APs temperatures. However, there are still tools to use the power to move the heat pipe. Recently, depending upon the FDM process, it has been proposed to stabilize the temperature of smartphones to predict the temperature of Application Processors and skin. To simplify the heating model, the active HTCs move from a high-end smartphone to a high-end space. Still, no such circular temperature model of the heat pipe form is available. In this project, we have not only developed a complete heat pipe model of expandable heat pipes to create an effective efficient simulation tool for Smartphones, but also integrated a proposed temperature based simulation tool and a dynamic algorithm to create the flow of Heat pipe design. Heat pipes that are heat transfer devices go well. They use the final heat of the active liquid to transfer the active heat over a very small temperature drop. This document describes the effects of bending on the operation of heat pipes.

Figure-1: Schematic Figure of a MI note 8 pro phones with multiple heat sources.

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Flexible and pre-crushed hot tubs have been studied and have been successfully demonstrated in the past. Heat pipes can be pulled, which can bend after appointment as needed, with novel heat management devices. Also the various effects due to bending upon temperature, its performance and performance limits have been investigated. The heat pipes used for testing were made using oxygen-free copper in the container and water such as water and electricity. The wick is made of sintered copper and provided a design feature for the bending of these heat pipes [1].

Figure-2: Schematic of Construction And Operation of a Typical Heat Pipe The concept of a basic heat pipe can be expressed by a simple cylindrical iron casing with an inner covering cord (Fig. 2). The wick structure has been made up of a variety of materials and has become very popular items for heat pipes. It is usually made of a porous material. The anointed building also can be used. The active fluid is sealed with a pre-determined wire [3]. The active fluid inside can be any computer that has good moisture markings on the wick and is selected on the aspect of the effective temperature of the heating pipe. If kinetic pressure loss and head loss due to housing loss are ignored, the properties of the active fluid can be combined to form a figure of merit M. The heat pipe is broadly divided into three categories, namely: evaporator, adiabatic and condenser. The standard heat exchanger as shown in Figure 2 has one phase of evaporation that removes heat from the source. The heat exerted from the evaporator causes the transition from the active liquid phase from the liquid to the steam. The increased pressure of the vapor in the evaporator causes the vapor to evaporate from the evaporator phase and enter into the adiabatic phase. The vapor then reaches the condenser region where the condensing denies the hidden heat of the flow to the pond. The purified fluid is then reabsorbed in accordance with the negative pressure of the discharge by the combination of capillary pump action and / or high power. This flow cycle is again happened during normal working of the heat pipe and can continue for a long time till there is sufficient amount of vapor pressure and capillary pressure to support its operation.

(1) Where ρ1 = density of working fluid in liquid phase σ1 = Surface Tension of the operating fluid μ1 = dynamic viscosity of working fluid in liquid phase L = length of the given heat pipe

II.

LITERATURE SURVEY

Thang Nguyen et al, Various cooling solutions using heat pipes for cooling a notebook PC. Namely, 1) heat pipe with heat spreader plate, 2) hybrid system—i.e., heat pipe with heat sink and fan, and 3) hinged heat pipe system. For heat input of less than 12W, the thermal resistance measured between the surfaces of the CPU to ambient obtained as follows: greater than 8 C/W for system 1) and 4–6 C/W for systems 2)

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and 3). For the CPU having specification of surface temperature of 95 C and 40 C ambient, then system 1) can be dissipated by about 6W, whereas systems 2) and 3) can handle 13 W. Experimental results of these three systems are included and discussed [1].

Chan Byon et al, The heating pipe is a well-known cooling system for advanced electronic devices. This chapter provides the most important opportunity for all students from the industry and for technologysharing courses and to promote their practical application. [2].

C. M. Arun Kumar et al, The failure rate of electronic equipment’s and Integrated circuit chip increase exponentially and the failure rate is directly linked to their temperature variations. Found that the cooling of electronics compounds is picking up momentum due to Nano fluids such as CNT (Carbon nanotube), Al2O3, TiO2, CuO Nano fluids. Also it was studied that there is scope for the miniaturization of electronic compounds, lowering weight, lowering power consumption, and enhancing their reliability [3].

ZhaoxiaLuo et al, Thermal management is an important problem for mobile phones due to its small space and high energy consumption. Our analysis shows that maximum power consumption is limited to a small area of mobile phone; and the skin temperature should be considered above the temperature of the chips. In addition, this paper introduces some skills on how to calculate the distribution of heat anisotropic resistance and laminated heat sink [4].

L. Vasiliev Jr. et al, Nowadays a small heat pipe with sintered powder inside is widely used for portable PC cooling. A new 5mm exterior design the size of a small heat pipe with advanced biporous cable is proposed as a promising baptism candidate for current and future cooling systems for high-end PC power platforms. [5].

Hong-Wen Chiou et al, While the performance of smartphones is very high, the system processor uses a lot of power. Therefore, it is difficult to meet the heat issues using conventional cooling methods. This work introduces a compatible heating model of curved heat pipes and an effective thermal simulator for smartphones. In addition, with a maze track that is not compatible with the hot-water heat distribution system, a hot-track transmission algorithm is proposed to increase the formation of a curved heat pipe.

The proposed heat exchanger algorithm can reduce at least 10.86% of high temperatures in application processors [6].

Fabian Korn et al, Heat pipes are one of the most effective ways to transfer heat energy from one point to another, especially those used for cooling. This report will highlight the working principal and the most important opportunities for calculating the heat pipe [7].

Arora et al, The paper shows the experimental results of cooling performance of micro heat pipe using infra-red Thermography(IRT) technique for mobile electronic devices and validates those results by using commercial software ANSYS Fluent 16.1 in which 3-D numerical model is developed and solved by Volume of Fluid (VOF) model. It was observed that if we use of Nano-fluid, it reduces 5-10oC of skin temperature of MHP as compared to DW, therefore, Nano-fluid as a coolant in MHP improves the thermal performance as well as reliability of such devices [8].

Amir Faghri et al, An elaborated overview of heat pipes is presented in this paper, including a historical perspective, principles of operations as well as the improvements in computational and experimental methodologies [9].

Ahamed Mohammad Shahed et al, In previous and recent years, heat pipes have been widely used in various hand held mobile electronic devices such as smart phones, tablet PCs and digital cameras.

Characterization and comparison of the module have also been conducted both experimentally and theoretically [10].

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III.

METHODOLOGY

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A. Scope of work The heat pipe cooling technology has been used in various smart phones, like Redmi note 8 pro, Redmi Note 9 Pro, Samsung Galaxy S9, LG G6 and Samsung Galaxy M31s for achieving better cooling efficiency to reduce the working temperatures of application processors.

B. Methodology (Thermal Simulation Flow)

Figure-3: Thermal simulation flow for smartphones with use of bended heat pipe

IV.

MODEL OF PROPOSED HEAT PIPE

Figure-4: Model of Proposed Heat Pipe Above figure shows the actual diagram of heat pipe with drafting. We used this type of heat pipe in Redmi Note 8 pro. Four views are there front view, left view, top view, isometric view.

V.

HEAT PIPE FABRICATION AND ASSEMBLY

Two heat pipes were used for their study. Heat pipes are made with direct cylindrical alignment. Only certain types of fibers can be used in flexible heat pipes, as the wicks tend to separate from the vessel walls under the bend. This division has two adverse effects, assuming that bending occurs in the adiabatic

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phase, as is the case in this study. First, there will be a decrease in the evaporation area which reduces the heat transfer capacity and, secondly, there will be a disruption in the path of the liquid returning to the evaporator. If the bending angle is severe, the cord can stumble and tear in extreme cases. The copper shown by the fibers used in this study provides a flexible fiber that does not break after bending.

Figure-5: Assembly of heat pipe However, a cord made of cut metal powder will break when bent. While some fibers made of steel screens can also work with supporting sources, the screen heaters of the screen have very little heat transfer capability and capillary limit compared to steel that feels the heat pipes of the cable. The screen wiring heat pumps are resistant to gravity and the steel sensor hoses. Heat pipes are bent in one place only to reduce the difficulty of testing. After successful testing of such heat pipes, further studies can be made with more bending. Multiple bending angles (15 °, 30 °, 45 °, 60 ° and 90 °) with a constant bending radius of 18.18mm (radius measured on the axis of the pipe) were tested. A series of photographs at the heat pipe cross-section at the bending center location after bending were taken for various bent configurations and, as expected, wick separation from the container wall was observed.

However, it was noted, as shown in Fig. 6(a)-(f), that the separation from the wall did not increase significantly after 45°.

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Figure-6: Wick Separation near Heat Pipe Wall Due To Bending

VI.

TESTING PROCEDURE

During this work, the performance of the heat pipe is measured in terms of equivalent thermal conductivity, which is a reciprocal of heat resistance. As a data reduction method, this estimated value is similar to the operation of visible thermal material conductivity. The following test procedure had been used. The heat pipe was assigned a heat load in the entire operating range. The evaporator was connected to a heat source, (usually) a temperature block. This heating block is powered by cartridges with electric power that is controlled by a power supply. The heat is extracted from the end of the condenser by a constant water circulation system. The setting is shown in Fig. 7. A record of the temperature of the various electrical temperatures is maintained using two thermocouples mounted on the evaporator and on the edge of the condenser as shown. The chiller was started and the entire heat pipe was allowed to receive a constant temperature of 20 ° C to ensure the first position of all tests. The power is then supplied to the heaters with an increase in the temperature of the heat pipes being monitored until a stable condition is maintained and maintained for at least fifteen minutes. The ambient temperature was maintained between 20-23°C to keep the parasitic losses at the same levels for all tests.

The two heat pipes tested were designated as HP1 and HP2. The first set of tests was performed on HP1 and included tests in horizontal and vertical positions assisted and bent in a horizontal angle of 15 °, 30 °, 45 °, 60 ° and 90 ° continuously Bending radius 18.18mm The HP2 test incorporates a curved heat pipe in both horizontal and gravitational force, in addition to what is done on HP1 and the same series of angles.

Figure-7: Setup of heat pipe for conductance measurement

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VII.

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RESULTS

Values of the maximum copper equivalent conductivity for both heat pipes have been shown in Table 1 for each angle of bend. A graph of temperature drop against power input is shown in Figure 8, Figure 9 and Figure 10. The trend in Figure 8 shows that the temperature drop in axial direction has increased, as the bend angle is increased. A similar trend is also noted for HP2 in horizontal direction, but the increase in value of temperature drop over iterative bending angles was comparatively low, as shown in Figure 9.

Table-1: Maximum Copper Equivalence For HP1 and HP2 HP1 Vertical

HP2 Horizontal

HP2 Vertical

Bend angle

Qinput(W)

Gmax

Qinput(W)

Gmax

Qinput(W)

Gmax

0

34.80

193.86

7.90

139.39

23.43

106.48

15

30.57

248.04

3.93

122.07

7.91

95.65

30

26.74

163.55

3.96

120.69

3.99

102.43

45

38.30

351.51

3.93

109.26

3.97

74.31

60

34.45

108.83

3.89

107.19

3.93

90.85

90

30.58

491.89

3.87

129.47

3.93

110.76

Delta Temperature(C) 6 5 4

8W 16W

3

32W 2

64W

1 0 0

15

30

45

60

90

Bend angles (Degrees) Figure-8: Delta T across HP1 For Various Bend Angles In Vertical Orientation Figure 11 shows the effect on temperature drop across HP2 in vertical orientation and it shows the same trend as Figure 9 for HP1. The possible causes for the increase in temperature drop are due to wick deformation.

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Delta Temperature(C) 14 12 10 8

28W 16W

6

4W

4 2 0 0

15

30

45

60

90

Bend angles (Degrees) Figure-9: Delta T Across HP2 For Various Angles In Horizontal Orientation Delta Temperature(C) 18 16 14 12

4W

10

16W

8

28W 40W

6

52W

4 2 0 0

15

30

45

60

90

Bend angles (Degrees) Figure-10: Delta T Across HP2 For Various Bend Angles In Vertical Orientation

VIII.

CONCLUSION

While calculating the power loss in the limited range of the heat pipe, it was found to be very low i.e. fails to touch capillary border. This can be determined by looking at the Reynolds vapor flow numbers. The flow of vapor was obeyed in all tests and the number of Reynolds numbers ranged from 10 to 900. Low density and high viscosity reduced the expected losses due to the force in the center of the bend which is why the decrease in the stress of the friction was undesirable. The loss of bending rises to higher strength as the value of Reynolds increases due to an increase in the number of vapor. The results of the expanded heat pipes are good, as the heat pipes were working in both positions (horizontal and vertical) up to a 90°

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angle. Also that the effect of high pressure due to bending was inconceivable and the increase in temperature drop due to bending is mainly due to the disruption of the flow of fluid coming to the evaporator from the condenser.

ACKNOWLEDGEMENT The authors would like to thanks Prof. D.S. Patil for whom we have greatest amount of respect admiration. He has not only afforded us the opportunity to work on this topic but also provided valuable guidance and support throughout our time as student in mechanical engineering department of G. H. Raisoni College Of Engineering And Management (Pune). We are sincerely thankful to Dr. R.R. Arakerimath. HOD of mechanical engineering department, for their kind guidance and support throughout this work.

IX.

REFERENCES

[1]

Thang Nguyen, Masataka Mochizuki, Koichi Mashiko, Yuji Saito, Ioan Sauciuc, and Rex Boggs, “Advanced Cooling System Using Miniature Heat Pipes in Mobile PC”,PACKAGING TECHNOLOGY, VOL. 23, NO. 1, MARCH 2000.

[2] Chan Byon, “Heat Pipe and Phase Change Heat Transfer Technologies For Electronics Cooling”,Washington Wiley, 2013.

[3] C. M. Arun kumar and P. C. Mukesh kumar, “Review on Electronics Cooling Systems”,Published BYAENSI Publication, 2013.

[4] ZhaoxiaLuo, Hyejung Cho, XiaobingLuo, Kyung-ilCho , “System thermal analysis for mobile phone”,Huazhong University of Science and Technology, 2017.

[5] L. Vasiliev Jr., M. Rabetsky, A. Kulakov, L. Vasiliev, Z. M. Li, “AN ADVANCED MINIATURE COPPER HEAT PIPES DEVELOPMENT FOR COOLING SYSTEM OF MOBILE PC PLATFORM”,Asian Vital Components Co., Ltd., Beijing, China 2008.

[6] Hong-Wen Chiou1, Yu-Min Lee1, Hsuan-Hsuan Hsiao, Liang-Chia Cheng, “Thermal Modeling and Design on Smartphones withHeat Pipe Cooling Technique” Industrial Technology Research Institute, Taiwan 2019.

[7] Fabian Korn, “Heat pipes and its applications”, Dept. of Energy Sciences, Faculty of Engineering, Lund University, Sweden 2008.

[8] A. Arora , M. S. Lodhi , R. C. Gupta, “COOLING PERFORMANCE OF MICRO HEAT PIPE USED FOR MOBILEELECTRONIC DEVICES”, Department of Mechanical Engineering, Jabalpur Engineering College, Gokalpur, Jabalpur-482011,Madhya Pradesh, India 2018.

[9] Amir Faghri, “Frontiers in Heat Pipes”, Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269, U.S.A. 2014.

[10] Ahamed Mohammad Shahed, Yuji Saito, and Makoto Takahashi, “High Performance Ultra-Thin Heat Pipe Cooling Module for Mobile Hand Held Electronic Devices”, Fujikura Technical Review, 2017.

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