flotherm_论文
APPLICATION OF COMPUTATIONAL FLUID DYNAMIC (CFD) TECHNIQUE IN THERMAL AND AIRFLOW IMPROVEMENT OF TM’S TYPE
A OUTDOOR CABINETS, BATTERY
COMPARTMENT
This research was supported by TM Bhd. Project No. R04-0576-0
R. Wan1, K.N.A.Wahib 2, K.Yusoff 1, B.M Shariff 1
1Lightning Protection & EMC Unit, 2 Prototyping Unit,
TM Research & Development Sdn Bhd,
UPM-MTDC Lebuh Silikon, 43400 Serdang, Selangor
Email: wanrazli@https://www.sodocs.net/doc/0f7062040.html,.my; khairulnazri@https://www.sodocs.net/doc/0f7062040.html,.my
Abstract ? In this paper we are presenting the thermal and airflow improvement of battery compartment in a TYPE A TM’s outdoor cabinet’s (one of the cabinets) by using the CFD technique. It solves the convection and temperature problems within the battery compartment by giving the best fan and its best location for better ventilation inside. The simulation and measurement results show the improvement of airflow and the temperature uniformity, thus also improve the charging scheme of the batteries.
Keywords - Outdoor Cabinet, Battery Compartment, Temperature Uniformity.
1.0INTRODUCTION
The thermal condition of the battery is also dependent on its environment. If its temperature is above the ambient temperature it will loose heat through conduction, convection and radiation. If the ambient temperature is higher, the battery will gain heat from its surroundings. When the ambient temperature is very high the thermal management system has to work very hard to keep the temperature under control. The battery must be kept within a limited operating temperature range so that both charge capacity and the life cycle can be optimised. A practical system especially in the tropical region may therefore need a cooling element to keep it not just within the battery manufacturer's specified working limits, but within a more stringent range to achieve optimal performance [1]. Besides the charging system and the batteries ambient temperature factors, it was reported in [2], that the temperature uniformity within the battery compartment with the series charging and standby mode condition is also important to prolong the batteries life span. Previous study [3], shows that there is the need for the improvement of airflow and thermal inside a TM’s outdoor cabinet’s battery compartment. The improvement of the thermal and airflow will also improve the temperature uniformity inside the battery compartment.
Here, in this paper we will present the thermal and airflow improvement of a TYPE A TM’s outdoor cabinet battery compartment (one of the cabinet in TM Malaysia operation) by using the CFD technique. It solves the convection and temperature problems within the battery compartment by giving the most effective off-the-shelf fan and determining its best location for better ventilation inside.
The objectives of this study is to find the optimum solution for the existing design of the TM’s TYPE A battery compartment by ensuring temperature within the compartment is fairly distributed (temperature uniformity) and to improve the air flow.
2.0DESCRIPTION OF THE BATTERY
COMPARTMENT OF TM’S TYPE A
OUTDOOR CABINETS
Battery compartment of TM’s TYPE A outdoor cabinets is attached to the equipment chamber cabinets. The batteries operate in a standby
mode condition, meaning that they are only utilized as a backup power supply during the event of power failure. Figure 1 below, shows the TM’s TYPE A Cabinet’s Battery Compartment that underwent the study.
Figure 1: Subject of study
3.0MODELLING AND SIMULATION FLOTHERM TM version
4.1 [4] was used for CFD modelling and solving. The analysis approach for “before” and “after” modification is by relative comparison. The temperature distribution, air flow behaviour and pressure profile are the best prediction by the software. The assumptions for original design made are:
1-Each battery generates 5 Watts.
2-Heat transfer from electrical
compartment atop at 55oC.
3-1000 W/m2 solar radiation on the
right.
4-0.5 emissivity due to paint effect. Figure 2: Simplified model of TYPE A battery
compartment
Figure 2 shows the simplified model of TYPE A battery compartment and the placement of the batteries. Note that the front and top wall are removed for viewing purpose.
Figure 3: Isometric view of monitor pints Figure 3 shows an isometric view of monitor points that are populated across the volume.
3.1Results of the CFD modelling (original
design): radiation and naturally convected heat transfer.
Figure 4: Simulated temperature distribution
(original design)
Figure 5: 45oC (and higher) simulated
temperature distribution (original design). Note that it is worthy to emphasize that the temperature profile is the best prediction. Also please note that only the temperature surrounding the units is accountable for comparison. In other words, since it is a simplified model, the temperature inside the batteries is not considered for analysis.
TM’s TYPE A Cabinet’s Battery
Compartment
Figure 6: Simulated airflow pattern (original
design)
Figure 7: 45oC (and higher) simulated airflow
pattern (original design)
The figures above illustrate the flow path at a vertically sliced section of the model. The flow information is helpful to locate any recirculation or undesired flow path. From the section airflow animation, it can be seen that
i)Inlet air coming in from bottom
left and right.
ii)Air is circulating clockwise
within the compartment.
iii)Air exiting at top left and right.
iv)Some air coming from bottom
right exit right away through
top right
3.2Results of the CFD modelling (original
design): Radiation and naturally convected heat transfer.
To improve airflow within the cabinet, introduction of axial fan is identified as the best solution since it is practical, cheap and manageable. Improving the airflow will meet our objectives; which are to reduce temperature gradient within the compartment and to reduce overall temperature within the compartment. Optimizing the design is just a click away with the Command Center feature. There are two key parameters needed for Command Center to determine the optimum fan size and its location while dictating the temperature within the compartment at its lowest. The optimum fan size and its parameters will later be matched to the similar off-the-shelf fan available which will later be used for field trial experiment.
Figure 8: 45oC (and higher) simulated airflow
pattern (optimized).
Figure 9: 45oC (and higher) simulated airflow
pattern (optimized design).
Figure 10: Simulated airflow pattern (optimized design). Note that air is moving
from left to right with the fan blowing against
the side wall.
Figure 11: Temperature table of monitor points. The figures clearly show the temperature reduction across the compartment with the implementation of an optimized fan at the determined location. Standard deviation of the temperature difference with ambient temperature of the original and the optimized design is much lower on the optimized design thus conforming better temperature uniformity. Later, field trial will be experimented to ensure the simulation results are in agreement with actual data. Catalogued fans were compared and one of a Sanyo Denki of model was
selected for the experimentation.
4.0 MODIFICATION
IMPLEMENTATION AND IMPROVEMENT
Based on the result of the CFD simulation, we have translated the solution into a practical solution in the field. Figure 12 shows the implementation in the field. The selected Sanyo Denki fan was power up with DC 48 volt from the cabinet’s rectifier and was trigger at 35oC. The fan will not be functional at the ambient temperature of 35oC and below.
Figure 12(a): Adding a fan at the specified location as simulated to the battery Compartment in TM’s TYPE A Outdoor Cabinet.
Figure 12(b): Thermostat trigger at 35oC
4.1 Improvement of Temperature
uniformity
Figure 13: The measurement setup
Figure 13 shows the measurement setup for the improvement measurement of the temperature uniformity and voltage charging scheme versus
temperature. The measurement will give us the data of temperature and the voltage of every battery versus time. The temperature data was acquired automatically by the use of Testo T4 temperature data logger that is placed inside the cabinet battery compartment. While the measurements for the voltage charging of every battery was collected manually at the interval time of 15 minutes. All the measurement was conducted in the normal system working environment with the cabinet door closed. To achieve this condition, we have to lay an adequate length of cable from outside of the cabinet to the + and – terminals of every battery. The batteries voltage was measured at the other end of the outside cables.
There were 2 types of measurement conducted:
1) “Before” measurement: To measure
the voltage charging scheme versus temperature for every battery and the temperature uniformity within the
battery compartment. 2) “After” measurement: To measure the
temperature uniformity and voltage
charging scheme versus temperature for every battery within the battery compartment after modification was introduced.
The temperature measurement points and the time were maintained for the both
measurement.
4.2 Results and Discussion
Figure 14 below shows the temperature uniformity improvement before and after modification.
Cabinet A: Chan1/2 Diff. Before Modification
94507A M 100007A M 101507A M 103007A M 104507A M 110007A M 111507A M 113007A M 114507A M 120007P M 121507P M 123007P M 124507P M 130007P M 131507P M 133007P M 134507P M 140007P M 141507P M 143007P M 144507P M 150007P M 151507P M 153007P M 154507P M 160007P M 161507P M
Time
T e m p . D i f f . D e g . C
Figure 14(a): Before modification: Temperature uniformity within the battery
compartment
Cabinet A: After Modification, Channel 1/2 Difference
94507A M 100007A M 101507A M 103007A M 104507A M 110007A M 111507A M 113007A
M 114507A M 120007P M 121507P M 12
3007P M 124507P M 130007P M 131507P M 133007P M 134507P M 140007P M 141507P M 143007P M 14
4507P M 150007P M 151507P M 15300
7P M 154507P M 160007P M 161507P M
Time
T e m p D i f f D e g C
Figure 14(b): Before modification: Temperature uniformity within the battery
compartment
From Figure 14(a), the average
temperature difference (before modification) recorded was 3.74oC with highest temperature difference recorded of 9.1oC while figure 14(b) shows an obvious improvement of temperature uniformity (channel 1/2 difference) after modification was introduced. The average temperature uniformity after the modification is 1.42oC with the highest temperature difference recorded of 3.8oC. It was observed that with the improvement of the temperature uniformity within the battery compartment, we managed to get a better batteries charging scheme versus temperature. The entire figures below, explain the finding.
Cabinet A before modification, Battery 1: Float Voltage Vs Temperature
Temperature Deg C
V o l t a g e V
(a) Before
Cabinet A: after modification, battery 1: Float Voltage Vs Temperature
Temp. Deg C
V o l t a g e V
(b) After
(b) After
Figure 15: Battery 1, Float Voltage versus temperature
Cabinet A: before modification, Battery 2: Float Voltage Vs Temperature
Temperature Deg C
V o l t a g e V
(a) Before
Cabinet A: after modification, battery 2: Float Voltage vs Temperature
Temp Deg C
V o l t a g e V
(b) After
(b) After
Figure 16: Battery 2, Float Voltage versus temperature
Cabinet A: before modification, battery 3: Float Volatge Vs Temperature
Temp. Deg C
V o l t a g e V
Cabinet A: after modification, battery 3: Float voltage vs temperature
Temp Deg C
V o l t a g e V
Cabinet A: before modification, battery 4: Float volatge vs Temperature
Temp Deg C
V o l t a g e V
(a) Before
(b) After
Figure 17: Battery 3, Float Voltage versus temperature
(a)
(a) Before
(b) After
Figure 18: Battery 4, Float Voltage versus temperature
From the results of ‘before’ measurement, it shows that the real voltage charging scheme versus temperature for every battery is simply like yo-yo pattern. There is no linear relation between voltage charging and temperature compared to the linear pattern of the ideal condition (the battery manufacturer recommendation).
Whereas the results of ‘after’ measurement, show the improvement of battery’s voltage charging versus temperature pattern in term of linearity and the reduced gradient between ideal voltage charging and real voltage charging (recorded). The average of the battery’s voltage charging gradient between the ideal and the real (recorded) after modification is only 0.1 Volt compared to 0.2 Volt before modification.
5.0 CONCLUSION
It is proved that the CFD technique can be used to assist finding the practical and cost effective solution in thermal management problems. By adding the suitable fan we can manage to get better temperature reading and uniformity within the battery compartment. This shows that the result from FLOTHERM is extremely helpful in determining the right fan and its location for this case. The results also clarify that the fan is not only implemented to reduce the temperature within battery compartment but it is also necessary to help making the temperature within battery compartment uniform in order to get a better charging scheme for the batteries that will help to prolong the batteries life span. The goal of this study to maximize the thermal performance and keep the design such that it is easily manufacturability and low in cost was achieved.
R EFERENCES
[1]https://www.sodocs.net/doc/0f7062040.html,/thermal.htm
[2]R.Wan, K.N.A. Wahib, B.M. Shariff, K.Yusoff, “A
method to prolong the batteries life span in series
charging and standby mode condition: Temperature
uniformity within Battery Compartment of TM
outdoor cabinets”, published in TM Research and
Development Sdn. Bhd. Research Journal.
[3]R.Wan, K.N.A. Wahib, B.M. Shariff, K.Yusoff,
“Application of Computanional fluid dynamics (CFD)
technique in thermal evaluation of a battery
compartment in TM’s outdoor cabinets”, published in
TM Research and Development Sdn. Bhd. Research
Journal.
[4]FLOTHERM, v4.1, Flomerics Limited, Surrey,
England
[5]Dan Nguyen, Matti Kokko, “Application of CFD
Technique in Thermal Design of a
Telecommunication Base Station”, 9th International
Flotherm User Conference, Orlando, FI. October 18-
19, 2000.
Wan, Razli
graduated from
University Science
of Malaysia with a
B.Eng(E&E). &
M.Sc. degree in
1996 and 2000
respectively, he
joined Telekom
Malaysia Berhad as Research Officer at Research & Development Division in Mid 1996. He was registered under Board of Engineer Malaysia (BEM) and a member of IEM. He was involved in the ESM and hardware interfacing for C&C system project.
He then joined TM R&D Sdn. Bhd. in mid 2001. Under TM R&D he involved in the “Design And Optimization of ADSL CPE Modem” project 2002-2003. In late 2003, he joined Lightning Protection & EMC unit with
the intention of to be more active in EMC research activities. His mains areas of interest
are related to the high speed circuits’ radiation
and the application of electromagnetic theory.
K.N.A.Wahib
graduated from
University of Hartford,
CT USA with Bsc in
Mechanical
Engineering in 1997.
He attached to few
MNC such as Applied
Magnetics, ACER Technologies and Motorola Technology where
the experience has afforded him to numerous facets of engineering namely process,
production, design and product development.
Most of his professional years in Motorola, he
got involved in design and development of the mechanical aspects of energy system. In late 2003, he then joined TM Research & Development to explore more in product design and development. Apart from his expertise, his other main interest are Aided Engineering where he troubleshoots and optimizes given design using FEA or CFD
tools for mechanical loading issue and thermal management respectively.
Khadijah graduated
from Multimedia
University,
Cyberjaya with a
BEng Electronics
Majoring in
Microwave and
Communications in
2003. In early 2004,
she joined TM R&D Sdn. Bhd. as a researcher
in Lightning Protection & EMC Unit. Her main
areas of interest are related to electromagnetic theory, particularly in Electromagnetic Compatibility (EMC).
Baharin joined Jabatan
Telekom Malaysia
(JTM) on 15/9/1981 and
was assigned to Radio
Unit, JTM Penang on
Sept 1981 - Feb 1983,
for maintenance of
Radio Communication
for Police, Civil Services Communication
and Leased channel. Then, from Mar 1983 -
Jul 1984 he was assigned for maintenance
of Radio Communication and Avionics at
the Bayan Lepas International Airport,
Penang. In mid July 1984, he was transfered
to JTM Selangor and was assigned to
Subang International Airport from Jul 1984
- Oct 1993 for maintenance of Approach
Radar.
Then, he was promoted to Senior
Technician and assigned to Radio Research
Unit, Telekom Research & Development
Division on Nov 1993. He was selected for
an international project entitled “Joint
Development of Advanced 450 Wireless
Systems” with Radio Design AB, Sweden
in 1996. Joined LP & EMC on Nov 1998
and then actively involved in Lightning
Protection and EMC related issues.