Vertical Cooling Device Using Heat-Pipe Based on
Natural Convection "PowerKicker"

Furukawa Electric has recently developed and released"PowerKicker", a vertical cooling device using heat-pipe
based on natural convection to be used for thyristors inrailways' substations. The device features high efficiency,
non-powered operation based on natural convection andsmall footprint along with the use of water that is a working fluid of global-environment friendliness.
Concurrently with the development of power electronics
in late years, semiconductor power devices such as gate
turn-off (GTO) thyristors, thyristors and diodes are used inrailways' substations for power conversion of high output.
These devices require some cooling means to remove theheat generated at the conversion.
Conventionally, boiling cooling device using CFCs or
CFC substitutes as cooling medium were generally usedin this industrial field together with heat-pipe coolingdevices of horizontal type. However, there has been agrowing requirement for a new cooling method in view of
equipment's footprint reduction as well as global environment preservation to cope with the global warming problem caused by ozone depletion. To make a heat-pipe
cooling system maintenance-free, it was normal practice
to employ a horizontal-cooling scheme based on naturalconvection. Such a horizontal-cooling scheme, however,often caused problems of installation space because theheat-radiating fins had to be very long because of theirpoor heat radiating efficiency.
In an effort to solve this problem, Furukawa Electric hasdeveloped the PowerKicker that enables footprint reduction regardless of being a natural convection type, and put
it into practical application. See Photo 1.

Photo 1

Vertical cooling device using heat-pipe based on natural convection "PowerKicker".

Common fin

CFC
Reservoir

1.

STRUCTURE AND FEATURES OF POWERKICKER

Conventional boiling cooling system as shown in Figure 1
creates problems about global environment preservationsuch as ozone depletion and global warming because its
structure is such that heat-generating components are
directly immersed in an electrical-insulating cooling medium such as CFCs or CFC substitutes consuming a large
amount of such a cooling medium.
On the other hand, horizontal cooling device using heatpipe based on natural convection as shown in Photo 2
can, since it uses heat-pipes as a heat-radiating compo-Thyristor stack

Figure 1

Conceptual image of conventional cooling device ofevaporation boiling type using CFC reservoir. (Crosssectional front view)nent toward the fins, not only provide high thermal conductivity due to the use of heat-pipes but also take global
environments into consideration due to the use of deionized water as a working fluid. The heat-pipe is known for
its high thermal conductivity, where the heat is received as1

Table 1
Applicable heat dissipation

Photo 2

Specifications of PowerKicker products.
Dimensions (mm)Thermal resistance

Receiving block ✕ Fin width ✕ Total length

K/W (for a pair)

300 W(140 ✕ 110 ✕ 68) ✕ (120 ✕ 242) ✕ 850

0.12500 W(140 ✕ 110 ✕ 68) ✕ (120 ✕ 242) ✕ 1155

0.072

800 W

(140 ✕ 110 ✕ 68) ✕ (120 ✕ 242) ✕ 1580

0.044

Typical horizontal cooling device using heat-pipe
based on natural convection.

latent heat of vaporization and is instantaneously transferred to the radiating end to be released as latent heat ofcondensation.
In such horizontal installation and in case of greater
amount of heat generation, however, the length of heatradiating fins sometimes reached 1 to 1.5 m, causing
problems of extraordinary footprint and space for installation.
Furukawa Electric has been successful, solving theproblems mentioned above, in the development and practical application of PowerKicker, a new vertical coolingdevice using heat-pipes based on natural convection.
The PowerKicker developed at this time has a simplified
structure such that a heat receiving block made of copperand a set of heat radiating fins with special fin configuration are installed on the respective ends of multiple heatpipes straight in shape. The new product efficientlyreceives the heat generated by the electronic components
at the heat-receiving block using copper. At the heat-radiating end, a special fin configuration was developed andemployed, in which the airflow in the heat-radiating fin set
is not stagnated but enhanced, even under conditions ofvertical installation, based on natural convection. Thus avertical heat-pipe cooling device the performance of whichis as good as that of horizontal cooling devices has beenrealized.

2The features of this vertical heat-pipe cooling device areas follows:
1) Space saving
Owing to vertical installation, the installation spacecan be minimized in terms of projected ground area.
Compared with our horizontal cooling devices, thespace can be saved by as much as 50 %.
2) Contributive to global environment preservation
The use of deionized water as working fluid of heatpipes contributes to preserving the global environment.
3) Ease of maintenanceIndividual heat-generating component is mechanically sandwiched between the heat-receiving block of
the heat-pipe cooling device. Thus, unlike in the caseof cooling device of boiling type, check-up, repair andmaintenance can be easily carried out in a short time.

2.

SPECIFICATIONS AND APPLICATIONSOF POWERKICKERS

Table 1 shows the product specifications of three types ofPowerKicker having a heat-radiation capacity of 300 W,
500 W and 800W respectively.
The PowerKicker of 800 W capacity has been introduced for cooling the electronic power devices of rectifiersin the railways' power substations and the delivery has
just begun. In the future, it is expected that the productrapidly gain in popularity among many railways' power
substations as well as other uses.
For more information, please contact:
Thermal Products Department,Components Division
TEL: +81-463-24-9721
FAX: +81-463-24-9786

Electronics

Furukawa Review, No. 222002