Published at : 17 Dec 2020
Volume : IJtech
Vol 11, No 7 (2020)
DOI : https://doi.org/10.14716/ijtech.v11i7.4499
Wayan Nata Septiadi | 1. Department of Mechanical Engineering, Udayana University, Kampus UNUD Bukit Jimbaran, Badung, Bali 80361, Indonesia 2. Heat Transfer Laboratory, Department of Mechanical Engineering, Udayana Unive |
Komang Wahyu Tri Prasetia | Undergraduate Student of Mechanical Engineering Study Program, Udayana University, Kampus UNUD Bukit Jimbaran, Badung, Bali 80361, Indonesia |
Made Ricki Murti | 1. Department of Mechanical Engineering, Udayana University, Kampus UNUD Bukit Jimbaran, Badung, Bali 80361, Indonesia 2. Heat Transfer Laboratory, Department of Mechanical Engineering, Udayana Unive |
I Gusti Ketut Sukadana | 1. Department of Mechanical Engineering, Udayana University, Kampus UNUD Bukit Jimbaran, Badung, Bali 80361, Indonesia 2. Heat Transfer Laboratory, Department of Mechanical Engineering, Udayana Unive |
Fazlur Rahman | Undergraduate Student of Mechanical Engineering Study Program, Udayana University, Kampus UNUD Bukit Jimbaran, Badung, Bali 80361, Indonesia |
Gerardo Janitra Puriadi Putra | Undergraduate Student of Mechanical Engineering Study Program, Udayana University, Kampus UNUD Bukit Jimbaran, Badung, Bali 80361, Indonesia |
Komang Manik Marianti | Undergraduate Student of Mechanical Engineering Study Program, Udayana University, Kampus UNUD Bukit Jimbaran, Badung, Bali 80361, Indonesia |
Developments
in recent electronics result in electronic components that produce heat, namely,
Central Processing Units (CPUs). One solution to this problem is using a heat
pipe. In this study, a cascade straight heat pipe (CSHP) is analyzed as a CPU
cooling system with three effective lengths: 20 cm, 23 cm, and 26 cm. The first
workload provided was Idle; the processor only ran the operating system
without a software load, so that the processor utilization was only 1-10%. The
second was full load, where the processor utilization was 95-100%. The
CSHP-based CPU-cooling system with an effective length of 20 cm was able to
reach processor temperatures of up to 43.32oC (idle) and 63.62oC
(full load). For the effective length of 23 cm, processor temperatures of 46.99oC
idle) and 64.81oC full load was attained. Lastly, while using the effective
length of 26 cm, processor temperatures of 50.67oC idle and 65.21oC
full load were reached. CPU cooling systems using CSHP are thermally resistant
when in idle conditions; respectively, the temperatures for the effective
lengths of 20 cm, 23 cm, and 26 cm are 0.168oC/W, 0.197oC/W,
and 0.223oC/W. In contrast, for the same effective lengths, the
thermal resistance at full load was 0.262oC/W, 0.236oC/W,
and 0.224oC/W, respectively. Overall, the cascade heat pipe shows
better cooling performance than a stock cooler.
Cascade heat pipe; Cooling system; Effective length; Thermal resistance
For several decades,
the development of electronics, especially in terms of computers, has been
experiencing very rapid progress (Septiadi
et al., 2019). One such computer component that is
progressing quite rapidly is the CPU (Brenner,
2007). The development of CPUs, i.e., smart
technology with smaller, lighter dimensions with improved performance and
efficiency, is advancing that stated by Cai et al., and Terrado et al., at
research by Chen
and Huang (2017). The development of smart technology has had
an impact on certain computer components, producing heat flux and leading to
overheating, which must be dissipated to ensure the performance and life of the
computer system (Paiva
and Mantelli, 2015).
In its development, various methods have
been attempted to overcome the CPU cooling system problem. One of them involves the use of a
heat pipe (Kusumah
et al., 2019). A heat pipe is considered a very high-thermal
conductance device (Reay
et al., 2013) and is a type of high-efficiency passive heat-transfer
technology. Heat pipes have a structure allowing high thermal conductivity and
transfer while maintaining uniform temperatures between the evaporator and
condenser (Jouhara
et al., 2017). Research and development on heat pipe shapes
have been conducted by several researchers; for example, loop heat pipes (Maydanik
et al., 2018), U-shaped heat pipes (Kusuma
et al., 2019), L-shaped heat pipes (Putra
and Ariantara, 2017), flat heat pipes (Arya
et al., 2018), oscillating heat pipes (Zhou
et al., 2018), etc. The high heat dissipated from the
condenser is proof that heat pipe technology has not reached its maximum
potential (Putra
et al., 2013).
Modification and enhancement
of heat pipes have been performed in recent decades. Fins are some of the common
things applied to heat pipes to enhance heat transfer by adding more surface
area in the condenser (Ibrahim
et al., 2018). According to Huang
et al. (2019), fin surface area is
affecting the capability of heat pipes to absorb heat; the temperature
distribution is increasing as fin surface areas increase due to higher heat
absorption. Normally, heat collected in the fin dissipates into the air via
natural convection; consequently, the surrounding air temperature rises. This
temperature rise can affect the thermal resistance between the fin and the air (Xie
et al., 2020). In order to ensure
the heat dissipation rate, an electric-powered fan is commonly used to improve
the cooling performance by increasing airflow to the heatsink (Xiao
et al., 2017). The deficiency of using a fan with a CSHP is
that the heat from the CPU absorbed through the evaporator at level I is not
released directly into the environment. The absorbed heat is then transferred
to the heat pipe evaporator level II and finally discharged through the level
II condenser, and theoretically, the temperature of the heat discharged will be
smaller. Therefore, the use of electric-powered fans is no longer beneficial (Septiadi
and Putra, 2014).
Modification on cascade
heat pipe is conducted to enhance the thermal performance. An experiment with a loop heat pipe for high heat
transfer capacity has been conducted by Maydanik et
al. (2018). The result stated that after thermal tests, the loop heat
pipe improves power and heat transfer-distance significantly without additional
energy source (Maydanik et al.,
2018). The effect of the heat pipe
effective length also affects the velocity of the mass flow rate along the pipe,
which also affects the final heat dissipation generated by the CPU (Muhammaddiyah et al., 2018; Winarta et al., 2019).
Tan et al. (2005) conducted an analytical study of flat plate
heat pipe effective length using a point source approach. They stated that heat
source could affect heat pipe effective length through the formulation provided
in the research. The heat pipe maximum capillary heat transport limit and heat
pipe optimum heat source position can be determined through the effective heat
transport length (Tan et al., 2005).
In order to improve the
CSHP performance, an analysis of the CSHP effective length was conducted. This
research aims to find the effective length of CSHP so it could handle the
maximum heat produced by the CPU without fan assistance while still paying
attention to space availability inside the case.
An experiment was conducted to analyze the effective
length of cascade heat pipes as CPU cooling systems. This experiment was
carried out to find the most effective cascade heat pipe length so that fan
assistance for CPU cooling is not required.
The effective length ratio affects the rate of heat
transfer in a CSHP as a CPU cooling system, where a smaller effective length
variable has a higher heat transfer rate, and a higher effective length ratio
has a lower heat transfer rate. This is due to the distance the fluid travels
along with the length of the heat pipe. A cascade heat pipe’s effective length
also influences the thermal resistance of the system. A shorter cascade heat
pipe effective length results in higher thermal resistance and vice versa due
to intense partial evaporation.
Cascade straight heat pipes show better cooling
performance than stock coolers without fan assistance. Cascade straight heat
pipes with 20-cm effective lengths have the best cooling performance among CSHPs.
According to the results, CSHPs are applicable to replace conventional
fan-assisted heat pipes as cooling devices for CPUs. Modification and
improvement of CSHPs can vary the working fluid and heatsink design for better
cooling performance.
Thanks go to the Ministry of Technology and Higher Education and the Udayana Institute for Research and Community Service for their financial support through the 2019 Penelitian Terapan Unggulan Perguruan Tinggi (PTUPT) scheme with contract number 492.29/UN14.4.A/LT/2019.
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