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A Compact Lightweight Heat-Dissipating Cabinet

1.

INTRODUCTION

In recent years, with the improvement of communications
infrastructure, many cases arise where communications
equipment are installed outdoors, including remote terminals for the access systems of fixed telephone service
and base stations for mobile phone systems. There isalso an increasing need for implementation of highcapacity, compact and lightweight communications basestations aimed at increasing the capacity and speed ofcommunications (i.e. broadband communications) andsupplementing the dead zones of mobile communications.
To protect the delicate communications equipment fromadverse outdoor environments such as dust and water,
cabinets accommodating these equipment have to besealed in compliance with the JIS grades 4 or 5. But sealing of the cabinet is likely to accumulate the heat generated by the communications equipment, so that having
an efficient technology for heat dissipation has become
important for the downsizing and weight reduction ofbase stations.
A type of cabinet that takes in outdoor air without careful consideration can, although heat dissipation is obviously done efficiently, result in the worst environment forelectronic equipment where the dust, dirt and moisture
may cause disadvantages such as rapid degradation ofelectronic components, short-circuiting and defectivecontacts, because the electronic components are directly
exposed to the outdoor air. Thus such a cabinet frequently causes a failure of equipment soon after installation.
While Furukawa Electric has been offering sealed cabinets incorporated with various heat-dissipating devices
for a range of communications equipment such as
remote terminals and the base stations for mobile communications, the company lately put into practical application a heat-dissipating cabinet for the base stations ofmobile communications that is compact and lightweight
as well as low in noise.

2.

(2) Heat generation rate of communications equipment
contained: 600 W(3) Temperature limit: Ambient (50°C or lower) + 20°Cor lower(4) Noise: 50 dB or lower

3.

STRUCTURE OF DEVELOPED HEATDISSIPATING CABINET

3.1 Cabinet(1) Material: Aluminum except for hinges and the likemade of stainless steel(2) Structure: As shown in Photo 1 and Figure 1

Photo 1Appearance of cabinet.

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DESIGN CONDITIONS(1) Size• Dimensions: (W) 250 × (D) 390 × (H) 590 mm• Mass (including cabinet, heat exchanger andfan): 20 kg or less�������� ��� ������� ������������ �����Figure 1

Schematic of cabinet.

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A Compact Lightweight Heat-Dissipating Cabinet(3) Features:• A heat-shielding plate is provided to suppress
heat input due to sunshine.
• Expanded polypropylene manufactured by Foam
Chemical Products Co. has been adopted as thesubstrate for communications equipment and thesupporting member for the fan, thereby forming
a smooth airflow channel to reduce the pressure
loss as well as to improve noise insulation.
(4) Dimensions: (W) 250 × (D) 390 × (H) 590 mm(5) Mass: 17 kg������� ��������� ���������������� ���Figure 3

Airflow in cabinet.

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3.2 Heat Exchanger(1) Material: Aluminum(2) Structure: As shown in Figure 2������� ���������������� ���������� ��������� ���Figure 4
Table 1

Airflow in heat exchanger.

Thermal performance under full-load condition.
ItemFigure 2

Heat exchanger.

(3) Features:• The outdoor and indoor air countercurrently flowin their own airflow duct, without mixing with eachother due to the water-tight sealing.
• The use of extruded channel bar provides a large
surface area.
• Noise due to the internal fan and the like hardly
leaks because of the tight sealing.
• To reduce the weight, a narrow-pitched fin offolded corrugation was used achieving a weight
reduction of approximately 5 kg.
3.3 Heat Exchanging Method(1) Heat exchanging method• Forced air cooling using the inside and outsidefans. See Figure 3.
(2) Heat exchange• The indoor and outdoor air exchange their heat
via the aluminum plate in the thickness direction.
See Figure 4.

4.

PERFORMANCE OF DEVELOPED HEATDISSIPATING CABINET(1) Thermal performance: As shown in Table 1• Temperature rise: 20°C or lower at a heat generation rate of 600 W: 10°C or lower at a heat generation rate of 300 W

Measured value Calculated value

1 Power consumption (W)227.71

227.7

Input heat from AMP and
AC/DC (W)

84.5

84.5

3 Ambient temperature (°C)

27.7

27.7

4 Airflow velocity at inlet (m/s)——

5 Airflow velocity at outlet (m/s)——Airflow velocity between fins
6(m/s)

—

5.87

27

Temperature at heat exchanger
inlet (average, °C)

42.75

43.7

8

Temperature at heat exchanger
outlet (average, °C)

37.3

38.4

9 Temperature rise (average, °C)

9.6

10.7

10 Thermal resistance (°C/W)

0.031

0.034

11 Cooling capacity (W/°C)

32.52

29.18

• A heater simulating the equipment was accommodated in the cabinet, and the rise in insidetemperature was measured using simulated heating. The simulated heating included the inside
heating of 310 W and the calculated input heat
due to sunshine of 10 W.
(2) Noise: The experimental setup and results of noise
measurement are shown in Photo 2 and Figure 5,respectively.
• 50 dB or lower in all directions in case of folded
corrugation fin.
(3) Other performance• Water-tightness: JIS C 0920, grade 5. See Photo 3• Earthquake resistance: 7 on the Japanese intensity scale

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Photo 2sinks incorporating these heatpipes and thermally conductive sheets together with related technologies, thereby
offering a variety of thermal solutions.
Making best use of the above mentioned technologies,
the heat-dissipating cabinet presented here has beensuccessful in offering an integrated solution to the problems of increasing the capacity and speed of communications including high-heat dissipation, downsizing, weight
reduction as well as noise reduction.
While it is anticipated that the capacity and speed ofcommunications tend to show further increase, we plan torespond, as a total thermal problem solver, to the diversified customers' needs by developing efficient heat dissipation technologies and by offering proposals for downsizing, weight reduction and cost reduction.

Experimental setup for noise measurement.

��������� ���������� ���������� ���������� ���������� ���������� ���������� ������������� ����� ������For more information, please contact:
Thermal and Antenna Solutions Dept., ElectronicComponents Div., Electronics and Automotive Systems
Co.
TEL: +81-463-24-9782
FAX: +81-463-24-9786

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Results of noise measurements.

Photo 3

Water-tightness test.

• EMI: VCCI class A. Shield gaskets were applied
over the openings.

5.

CONCLUSION

Furukawa Electric has developed various heat-dissipateddevices such as large-size to mini-size heatpipes, heat-

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