1. 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
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2. 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.

3. 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

4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME
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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

5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME
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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

6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME
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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

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
272
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