Experimental analysis of liquid cooling system for desktop computers
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Experimental analysis of liquid cooling system for desktop computers

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Experimental analysis of liquid cooling system for desktop computers Experimental analysis of liquid cooling system for desktop computers Document Transcript

  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME 266 EXPERIMENTAL ANALYSIS OF LIQUID COOLING SYSTEM FOR DESKTOP COMPUTERS Dr. R. P. Sharma Dept. of Mechanical Engineering, Birla Institute of Technology, Mesra, Ranchi, 835215 India ABSTRACT A simple liquid cooling system for a desktop computer has been designed. Different types of cooling systems were studied and compared. Liquid cooling system was found to be most effective in terms of performance but not in terms of design, cost and reliability. A simple, economical and reliable liquid cooling system was thus designed. Measurements of the temperature distributions of the system have also been made. Computer CPU usage was varied to determine the maximum, minimum and average cooling requirements and identify critical areas of heat trapping. The liquid cooling system was implemented in the desktop. Experimental and theoretical investigations of different heat sources inside a computer system have been made. An investigation of the optimum cooling condition for the computer the thermal performance of this simple liquid cooling system for a desktop computer have been made. Keywords: Liquid Cooling System, heat trapping, Forced air cooling. 1.0 INTRODUCTION With the rapid development of electronic technology, electronic appliances and devices now are always ever-present in our daily lives. However, as the component size shrinks the heat flux per unit area increases dramatically. The working temperature of the electronic components may exceed the desired temperature level. There are a number of methods in electronics cooling, such as jet impingement cooling [1,2] and heat pipe [3-5]. Conventional electronics cooling normally used forced air cooling with heat sink showing superiority in INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 4, Issue 3, May - June (2013), pp. 266-272 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2013): 5.7731 (Calculated by GISI) www.jifactor.com IJMET © I A E M E
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME 267 terms of unit price, weight and reliability while liquid cooling systems show superiority in terms of performance. At present, heat released by the CPU of a desktop and server computer is 80–130 W and of notebook computer is 25–50 W [6]. In the latter case, the heating area of the chipset has become as small as 1–4 cm2 . This problem is further complicated by both the limited available space and the restriction to maintain the chip surface temperature below 100°C [7]. It is expected that conventional cooling fan system will not be able to meet the thermal needs of the next generation computers. Every component in a computer consumes electric power. In general, the faster a component performs its function, the more electric power it needs. But computer components consume the electric power very inefficiently, and the majority of the power input is wasted as heat with only a small portion being used for data generation [8]. The speed of the central processor (CPU), 3D-graphic card, and hard disk drive (HDD) has continually increased in the last few years. And, HDD has reached a speed of 15,000 RPM, and every component of the computer has to deal with heat dissipation to some extent [9]. The heat generation in all computer chip-sets occurs due to switching between 0 and 1, which requires power consumption. On the other hand, heat is generated by the rotational motion in HDD and CD-ROM devices [10]. Nowadays, as the sizes of chipsets are being reduced, the rate at which the heat has to be transferred per unit area has also increased. Hard disk drive, CD-ROM, Graphics card, Sound card and Processor are the major heat sources inside the CPU. 2.0 COOLING SYSTEM DESIGN The basic design components of the system include a heat exchanger, reservoir, micro-pump, tubing, fan and coolant. A submersible type of the pump, having a head of 2-3m and inlet and outlet diameter of 0.5” is selected to fulfill the required design criteria. A flexible leak proof tubing of diameter 3/16” is selected which should adjust to passages in the motherboard. A fin type radiator of small size having high effectiveness has been selected so that it can allow the heat exchange between air and coolant. A high speed fan of 2000rpm having diameter of 10-12cm has been selected. A leak proof reservoir is selected to house the pump. Fig. 1 Going through the various literatures, this type of heat exchanger design has been selected for the cooling system in desktop.
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME 268 Fig. 2 For fulfilling the requirement of fan in radiator, the CPU fan was used. Water was chosen as the coolant to be used in the present design model. Submersible axial micro pump was chosen because it was easily available in the market and at a reasonable price and it was suitable for our design. Submersible pump was chosen because it would be kept in the reservoir and thus would require less space. Copper tubes (3/16”) to be used in critical heat source areas because of its high thermal conductivity. Separate flexible connecting tubes (1/2”) to be used in connecting the different components. The number of passes around the heat source areas would be maximized to effect greater cooling. Preferred option for the assembly of cooling system was to use a single copper tube to make the part of the system inside the CPU. This method obviates the problem of leakage and elimination of joints, leads to smooth flow with lower frictional head loss. Fig. 3 View slide
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME 269 Mathematical Calculations for thermal parameters: Diameter of copper tubes, d= 3/16" = 0.0047625 m Radius of copper tubes, r = d/2 = 0.00238m Cross-sectional area of tube, A = πr2 = 0.0000178 m2 Calculation of water velocity in tubes: Q = A x v v = Q/A = 0.295 m/s Calculation of Reynolds number for flow inside the tube: Properties of water:- Density, ρ = 1000 kg/m3 Dynamic (absolute) viscosity, µ = 0.001 N-s/m2 Reynolds number , Re = ρvd/µ = (1000 x 0.295 x 0.0047625)/0.001 = 1404.9375 As the value of Re < 2000, thus, the flow is laminar. Calculation of Frictional head loss inside tube: Darcy friction factor for laminar flow is given by, flaminar = 64/ Re = 0.04555 The frictional head loss in the copper tubes is given as, hf = (flaminar x L x v2 )/(2gd) = 0.2325 m Calculation of heat absorbed by the water flowing in the tubes: Q = m x c x ∆T = 65.9604 J/s Calculation of Inner and Outer surface temperatures of the pipe: For Internal flow of water inside the copper tube, we have, Nusselt number, Nu, for fully developed laminar thermal layer = 3.66, thermal conductivity of water, k = 0.667 W/m-K hw = Nu x k/d = 512.592 W/m2 -K For external flow of air over the tubes we have, Air flow rate= 0.0046 m3 /sec (Obtained from fan specifications), Diameter of fan=6cm ; Swept area of fan = 0.00283 m2 ; Re over pipe= ρVL/µ= 1.85 x 104 Nu = c Re m Pr0.333 ; where, c= 0.193 ; m=0.618 Prandtl Number, Pr= µCp/k where, µ= 1.846 x 10 -5 kg/m-sec ; Cp= 1.008 KJ/kg-K ; k= 0.0262 W/m-1 K-1 ; Pr= 0.707 Nu = c Re m Pr0.333 =0.193 x (1.85 x 104 )0.618 x 0.707 0.333 = 74.563 ha = Nu x k/d = 410 W/m2 -K Conduction equation for hollow cylindrical pipe: hw x Ai x (Ti-Tw) = ha x Ao x (Ta-To) = k x 2πL x (To-Ti) where, Tw is average temperature of water (300.5 K),Ta is temperature of air (308 K), Ai = 2πriL, Ao = 2πroL, L is length of heat exchanger tube (2.13m). From the above eq., Ti and To, were found out to be 31.51°C and 31.51 °C respectively. Calculation of heat flow from air into tube: Q= ha x Ao x (Ta-To) = 64.65 W COP of the system: COP = (heat removed by the system / Power used by the pump) = 64.65/12 = 5.387 View slide
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME 270 RESULT AND DISCUSSION The experimentation was conducted on a computer system having specifications as Model: HP-dx2280 MT (RR043Av), Chipset: Intel, Processor: Pentium D 2 CPU 3.4 GHz and 2.37 GHz, Physical Memory: 1.49 GB RAM, Hard disk: 160 GB and Graphics: VGA integrated. The following observations are noted before the inclusion of the cooling system in the CPU and after inclusion of the cooling system in the CPU. The data has been tabulated at high loading condition (CPU usage 75-85 %) and comparison are shown. Table 1: Comparison of Motherboard Heat sink Temperatures Table 2: Comparison of Processor Core Temperatures Table 3: Comparison of Hard disk Temperatures S.No. Temperatures Without Cooling System (° C) Temperatures with Cooling System (° C) 1 39.0 33.4 2 42.3 33.2 3 41.6 34.5 4 40.2 33.6 5 43.5 34.0 6 41.3 32.0 Average 41.32 33.45 S.No. Temperatures without Cooling System (° C) Temperatures with Cooling System (° C) Core 1 Core 2 Core 1 Core 2 1 48.0 52.3 36.7 38.4 2 51.0 50.6 35.8 36.5 3 50.4 51.0 38.2 38.2 Averag e 49.8 51.3 36.9 37.7 S.No. Temperatures without Cooling System (° C) Temperatures with Cooling System (° C) 1 52.0 41.2 2 53.4 41.5 3 49.8 39.9 4 48.5 40.2 Average 50.93 40.7
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME 271 Table 4: Comparison of Processor Heat sink Temperatures Table 5: Comparison of RAM Temperatures It is evident from the above tables that there is great reduction in the temperature achieved in all heat sources of CPU after using the properly designed cooling system. It is a great achievement that after inclusion of the cooling system in the CPU of desktop, huge reduction of Hard disk temperature was found. CONCLUSIONS Different types of cooling systems were studied and compared. Liquid cooling system was found to be most effective in terms of performance but not in terms of design, cost and reliability. A simple, reliable and economical cooling system was designed to meet the cooling requirements of a desktop computer. Measurements of the temperature distributions of the different heat sources inside a computer system have been made. An investigation of the optimum cooling condition for the computer system has also been made. The various Thermal Performance Parameters have been calculated as presented herein. There was a significant improvement in the thermal conditions inside the computer that lead to an ameliorated performance. A noticeable temperature drop in hard disk was attained with the help of the cooling system. S.No. Temperatures Without Cooling System (° C) Temperatures with Cooling System (° C) 1 49.6 41.3 2 50.2 41.5 3 48.9 42.3 4 49.0 43.4 Average 49.43 42.13 S.No. Temperatures Without Cooling System (° C) Temperatures with Cooling System (° C) 1 38.3 36.7 2 40.2 32.0 3 39.4 35.3 4 38.0 36.2 Average 38.98 35.05
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME 272 REFERENCES 1. Y. Chung and K. Luo, Unsteady heat transfer analysis of an impinging jet, J. Heat Transfer, 124 (2002) 1039-48. 2. K. Nishino et al., Turbulence statistics in the stagnation region of an axisymmetric impinging jet flow, Int. J. Heat Fluid Flow, 17 (1996) 193-201. 3. K. Kim et al., Heat pipe cooling technology for desktop PC CPU, Appl. Therm. Eng., 23 (2003) 1137-44. 4. Y. Wang and K. Vafai, An experimental investigation of the thermal performance of an asymmetrical flat plate heat pipe, Int. J. Heat Mass Transfer, 43 (2000) 2657-2668. 5. Z. Zhao and CT. Avedisian, enhancing forced air convection heat transfer from an array of parallel plate fins using a heat pipe, Int. J. Heat Mass Transfer, 40 (13) (1997) 3135-47. 6. Mochizuki M, Saito Y, Wuttijumnong V, Wu X, Nguyen T (2005) Revolution in fan heat sink cooling technology to extend and maximize air cooling for high performance processors in laptop/desktop/server application. In: Proceedings of IPACK’05, San Francisco [CD ROM] 7. Saucius I, Prasher R, Chang J, Erturk H, Chrysler G, Chiu C, Mahajan R (2005) Thermal performance and key challenges for future CPU cooling technologies. In: Proceedings of IPACK’05, San Francisco [CD ROM] 8. E. van Ballegoie, Fast graphics-Cooling, (2000) 104. 9. S. S. Lee, Zero & One, Hello PC, (July, 2000). 10. D. H. Min, HDD and VGA Cooling Solution, Korea Benchmark, (February, 2000). 11. M.M. Shete and Prof.Dr.A.D.Desai, “Design and Development of Test-Rig to Evaluate Performance of Heat Pipes in Different Orientations for Mould Cooling Application”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 360 - 365, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. 12. Kapil Chopra, Dinesh Jain, Tushar Chandana and Anil Sharma, “Evaluation of Existing Cooling Systems for Reducing Cooling Power Consumption”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 210 – 216, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.