Seyketov Adil.
Doctor of Technical Sciences, Professor.
Al-Farabi Kazakh National university.
Korvyakov Valeriy.
Doctor of Education, Professor.
Academy of Economics and Statistics in Almaty.
CONVECTION OF HEAT FLOWS IN NOTEBOOKS
Summary.
Article is devoted to convection of heat fluxes in environment in notebooks. In
the course of operation processors heat up, influence of temperature is made by a
negative impact on productivity and reliability of the device as a whole. The required
result in the recommended method is achieved by preventing the dissipation of heat
into the interior space of notebooks from the heat-conducting elements between the
heat source and radiators. Thus, the exterior space of the heat-conducting elements,
except the contact area of the bracket with the heat source and radiators, is covered
with the insulating material preventing from transferring the heat from the surface
of the heat-conducting elements before it reaches the radiators. Novelty of the
developed method is supported by the security priority document of the Republic of
Kazakhstan.
Keywords: notebook, micro-electrical circuit’s , the temperature, the processor and
chipsets, heat-conducting elements, convection, heat transfer.
The main advantage of notebooks is known to be their small size. In turn, a
small size is achieved by a compact placement of a computer’s internal components.
Fig. 1 shows how processor and chipset of notebook are equipped.
Figure 1. Device of notebooks.
We should agree with an intelligent and creative approach of placing the
whole complex of the electronic devices within the small interior space existing
there. As a result, notebooks are very convenient devices and are popular not only
with "the people on an assignment", but also with the rest of the progressive
population, including students and average citizens. Nowadays, notebooks provide
any complex work yielding to no desktops in speed and processing any information.
However, not all the problems related to notebooks are solved. According to
statistics, the main problem is the failures caused by the micro-electrical circuit’s
fail due to the temperature effects originating from the processor and chipsets, and
the poor airflow of the interior space. Thus, due to the poor convection in the small
interior space of notebooks, the excess heat affects the electronic devices placed
nearby, and that causes them to work unstably. In general, due to the overheating of
the small area in the processor, the notebook begins to work slowly, "stick", its
performance gets slow, and eventually the notebook just stops and shuts down.
The research proved that the main challenge of creating a safe temperature
field in the processor is a bad intensity of the local heat transfer on the objects’
surfaces within a free or even forced convection. In support of that, for example, the
temperature distribution on the computer enclosure surface in contact with the direct
sunshine on its edge looks in this way.
Figure 2. Shooting by a thermal imager.
Even in a free and unlimited space, the temperature dissipation over the
notebook surface turns out to be distributed over a few square centimeters.
Let us calculate the temperature field boundaries at a given heat flux density
qs (x) within the notebook internal, based on [2]. Thus, let us make the differential
equation for the heat-conducting rods under the following conditions: the heat flux
from the rod surface is dissipated into the environment (air) by convection; the heat
transfer at the ends is neglected; the origin is the lower edge of the rod attached to
the processor, the process is stationary:
𝑑2𝑇
𝑑𝑥 2
−
𝛼𝑘𝑙 (х)𝑃(Т−Тс )
𝜆𝛿𝐿2
+
𝑞𝑠 (𝑥)
𝜆𝛿
= 0,
(1)
where, λ – the thermal conduction of the element; αkl (x) – the coefficient of
the convection radiant heat transfer; P – the perimeter of the rod cutting; T, Tc – the
temperatures of the rod and the environment; L2, δ – the width and thickness of the
rod.
The proposed method of calculation allows setting the temperature of the field
for the heat transfer elements shaped like a flat rod. In this case, equation (1) is
solved, granting
𝑑2𝑇
𝑑𝑥 2
= 0. Then, the expression for the heat flux density is:
𝑞𝑠 (𝑥) =
𝛼кл (х)П(Т−Тс )
𝐿2
.
(2)
The calculation of the convective component of the heat transfer is carried out
as follows:
𝑁𝑢𝑥 = 0.453(𝑃𝑟 + 0.453)−1/4 𝑃𝑟1/2 𝐺𝑟 1/4 .
(3)
The calculations showed that for this case, the uniform temperature field of
the rod is possible to provide, when the distribution of the heat flux density on its
surface is made as shown in Figure 3.
Figure 3. Distribution of heat flux density
Based on the calculations’ results, the important conclusion can be made: the
smaller distance is between the rod and trace elements placed in this area, the more
excess heat they received from the rods. Thus, the received warmth is so high that it
is only 15-20% lower than the one in the processor. Therefore, the micro-electrical
circuit’s fail occurs due to the temperature effects originating from the processor and
chipsets in a notebook.
One of the problem solutions is the continuous monitoring of the temperature
operation of the chipset, CPU, and motherboard, and at detecting the excess of the
thermal burden on any of them, the preventive measures shall be taken. The
supervisory process is facilitated by the fact that at present there are so many
programs, including free ones, enable to record the event in an easy way. For instant,
the well-known company has released the version of the popular utility of
monitoring CPUID HW Monitor, which allows examining the temperature of the
CPU, graphics card and the other components. Not for the advertisement but for the
usage of the utility, the work pattern of the program in the measurement process is
given below.
Figure 4. CPUID HWMonitor.
As it is seen in the figure, the control of the temperature operation can be
performed, including CW, and all the necessary temperature indicators of the
important notebook devices are recorded.
Yet, there is another recommended way, which can solve the problem very
effectively. Here, it shall be noted that the proposed method is currently undergoing
the examination of Kazpatent to obtain an authorial protection.
Referring to Figure 1, let us examine in detail the process of removing the heat
from the heat-generating devices, and transferring it outside.
The removal of the heat from the heat-generating devices is made in three
stages. The first step is the transfer of the heat from the heat source into the heatconducting copper rod (element). The heat source is sure to be tightly connected
with one (hot) end of the heat-conducting element. The second step is the transfer of
the heat through the heat-conducting elements from the hot end of the element (the
heat source) to the radiators. The radiators, in this case, are thermally connected with
the other (cold) end of the heat-conducting element. The third stage is the transfer
of the heat by convection from the radiators to the air. At this stage, both the natural
convection for removing the small amount of heat, and the forced one can be used
through cooling the radiators by fan. The main drawback of this method is that at
transferring the heat from the source to the radiators, the heat-conducting elements
do not transfer all the heat accepted by them. Much of the heat is dissipated in a
natural way along the heat-conducting elements in the air and all the electronic
devices placed nearby, causing their overheating. The situation is exacerbated by the
fact that in the interior space of notebooks, any additional fans for cooling are not
provided, so the bad ventilation also constantly affects the devices.
The required result in the recommended method is achieved by preventing the
dissipation (leakage) of heat into the interior space of notebooks from the heatconducting elements between the heat source and radiators. Thus, the exterior space
of the heat-conducting elements, except the contact area of the bracket with the heat
source and radiators, is covered with the insulating material preventing from
transferring the heat from the surface of the heat-conducting elements
before it reaches the radiators. As a heat-insulating coating, for example, a special
paint containing ceramic inclusions can be used, which can effectively block the heat
diffusion to +200°C and even higher at an average heat blocking function of 5-10
years.
As the preliminary experimental tests showed, the implementation of the
invention allowed reducing the temperature background of the interior space of
notebooks to 40-50%. In tests on time-based continuity of operation, the computer
without any noticeable complications and glitches worked 24 hours, which also
confirms the high efficiency of the invention. The continuity of processors’
operation in the test was provided with a test program on performing an endless loop.
Literature.
1. Tanenbaum E. Arkhitektura of the computer. SPb.: St. Petersburg 2007. – 844
pages.
2. Martynenko O. G., Sokovishin Yu.A., Karyakin Yu.E. The free convection on a
vertical surface and in areas of arbitrary configuration. Minsk: ITMO, 1988. - 49s.:
silt.
3. Patent RK No. 29682 "Cooling system of computer hardware" of 31.10.2013