Method and apparatus for radiative heat transfer augmentation for aviation electronic equipments cooled by convection   

Abstract: A method and apparatus for radiative heat transfer augmentation for aviation electronic equipments cooled by forced and/or natural convection are disclosed. In one embodiment, the apparatus includes a first heat dissipation device to dissipate heat from the aviation electronic equipments housed in an aviation electronic equipment rack using forced convection. Further, the apparatus includes a second heat dissipation device to enhance heat dissipation from the aviation electronic equipments by radiation and natural convection. Furthermore, the second heat dissipation device is strategically disposed with respect to aircraft skin and configured to maximize radiative view factor.

Benefit is claimed under 35 U.S.C. 119(a)-(d) to Indian Provisional Application Serial No. 1757/CHE/2011 entitled “METHOD AND APPARATUS FOR RADIATIVE HEAT TRANSFER AUGMENTATION FOR AVIATION ELECTRONIC EQUIPMENTS COOLED BY CONVECTION” filed on May 24, 2011 by Airbus Engineering Centre India.

Embodiments of the present subject matter relate to dissipating heat from electronic equipments. More particularly, embodiments of the present subject matter relate to dissipating heat by radiation augmentation for electronic equipments on board aircraft cooled by forced and/or natural convection.

Electronic equipments installed inside aircraft, often contain many heat generating components that are housed in racks. Existing techniques for cooling such electronic equipments primarily depend on ventilation systems based on forced and/or natural convection. Typically, ventilation of such electronic equipments is based on forced airflow from the bottom of the racks, which then passes through the electronic equipments. The heated air coming from the electronic equipments is then collected and exhausted from the aircraft. Such method of heat extraction is generally referred to as “forced ventilation”. Further, the ventilation of such electronic equipments is also based on natural convection. Generally, natural convection does not occur due to fluid motion generated by an external source (e.g., a pump, a fan, a suction device and the like), but occurs due to density difference in the fluid occurring as a result of temperature gradients.

However, a failure in the forced ventilation system can lead to complete dependence of cooling of the electronic equipments by natural convection and this may not be sufficient and can lead to failure of the electronic equipments.

SUMMARY

A method and apparatus for radiative heat transfer augmentation for aviation electronic equipments cooled by convection are disclosed. According to one aspect of the present subject matter, heat from the aviation electronic equipments housed in an aviation electronic equipment rack is dissipated by forced convection using a first heat dissipation device. Further, heat dissipation from the aviation electronic equipments by radiation and natural convection is enhanced using a second heat dissipation device. In one embodiment, the second heat dissipation device is strategically disposed with respect to aircraft skin and configured to maximize radiative view factor.

According to another aspect of the present subject matter, the apparatus for radiative heat transfer augmentation for the aviation electronic equipments cooled by forced and/or natural convection includes the first heat dissipation device to dissipate heat from the aviation electronic equipments housed in the aviation electronic equipment rack using forced convection. Further, the apparatus includes the second heat dissipation device to enhance heat dissipation from the aviation electronic equipments by natural convection. Furthermore, the second heat dissipation device is strategically disposed with respect to the aircraft skin and configured to maximize radiative view factor.

The methods and apparatuses disclosed herein may be implemented in any means for achieving various aspects. Other features will be apparent from the accompanying drawings and from the detailed description that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are described herein with reference to the drawings, wherein:

FIG. 1 is a side elevation view of an aircraft showing location of avionics bay, in the context of the invention;

FIG. 2 is an isometric view of the avionics bay in the aircraft, such as those shown in FIG. 1, in the context of the invention;

FIG. 3 is a schematic showing a radiative heat transfer augmentation technique deployed in the aircraft for aviation electronic equipments cooled by forced and/or natural convection, according to one embodiment; and

FIG. 4 illustrates a flow diagram of an exemplary method for radiative heat transfer augmentation for the aviation electronic equipments cooled by forced and/or natural convection, such as those shown in FIG. 3, according to one embodiment.

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

A method and apparatus for radiative heat transfer augmentation for aviation electronic equipments cooled by convection are disclosed. In the following detailed description of the embodiments of the present subject matter, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the present subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present subject matter, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present subject matter. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present subject matter is defined by the appended claims.

FIG. 1 is a side elevation view of an aircraft 100 showing location of avionics bay 102, in the context of the invention. Particularly, FIG. 1 illustrates a portion of the aircraft 100 including the avionics bay 102, a cockpit 104, a cabin 106 and a cargo bay 108. As shown in FIG. 1, the avionics bay 102 is, typically, located below the cockpit 104. However, one can envision, the avionics bay 102 being located anywhere else in the aircraft based on the design and configuration of an aircraft. Further as shown in FIG. 1, the avionics bay 102 includes aviation electronic equipments housed in racks 110. For example, the aviation electronic equipments housed in racks 110 can include one or more aviation electronic equipment racks 110A-N.

Referring now to FIG. 2, an isometric view of the avionics bay 102 in the aircraft 100, such as those shown in FIG. 1, is illustrated, in the context of the invention. Particularly, FIG. 2 illustrates the aviation electronic equipments housed in racks 110, in the avionics bay 102, including one or more aviation electronic equipment racks 110A-N. As shown in FIG. 2, each of the aviation electronic equipment racks 110A-N includes one or more heat generating aviation electronic equipments. Exemplary aviation electronic equipments include equipments used for navigation of the aircraft 100, control of other equipments in the aircraft 100 and the like. For example, the aviation electronic equipments can also be arranged in the form of stacks or the aviation electronic equipments can be placed independently. Further, the aviation electronic equipments in the aviation electronic equipment racks 110A-N are cooled by forced and/or natural convection.

In operation, the aviation electronic equipment racks 110A-N are cooled using sources of cold air 202A-N in each of the aviation electronic equipment racks 110A-N, respectively, as shown in FIG. 2. Further, the cold air is passed through the aviation electronic equipments in the aviation electronic equipment racks 110A-N to extract the heat from the aviation electronic equipments and is output as hot air. Furthermore as shown in FIG. 2, the hot air is collected, from the aviation electronic equipment racks 110A-N, in collectors for disposing hot air 204A-N in each of the aviation electronic equipment racks 110A-N, respectively. This is explained in more detail with reference to FIG. 3.

Referring now to FIG. 3, a schematic 300 shows a radiative heat transfer augmentation technique deployed in the aircraft 100 for an aviation electronic equipment rack 322 cooled by forced and/or natural convection, according to one embodiment. Particularly, FIG. 3 illustrates a first heat dissipation device 320 and a second heat dissipation device for cooling the aviation electronic equipment rack 322. In one embodiment, the second heat dissipation device includes an external thermal radiator 308 and one or more heat pipes 310A-C.

As shown in FIG. 3, the first heat dissipation device 320 includes the aviation electronic equipment rack 322, a collector for disposing hot air 304 and a source of cold air 306. For example, the aviation electronic equipment rack 322 can include any one of the aviation electronic equipment racks 110A-N, shown in FIG. 2. Further, the collector for disposing hot air 304 and the source of cold air 306 can include any of the corresponding sources of cold air 202A-N and the collectors for disposing hot air 204A-N associated with the aviation electronic equipment racks 110A-N, as shown in FIG. 2.

Further as shown in FIG. 3, the aviation electronic equipment rack 322 includes a plurality of hot units 312A-F. Exemplary hot units 312A-F include the heat generating aviation electronic equipments, as shown in the aviation electronic equipment racks 110A-N in FIG. 2. However, one can envision a hot unit in aviation electronic equipments arranged in the form of stacks or an aviation electronic equipment placed independently. Furthermore as shown in FIG. 3, each of the hot units 312A-F include one or more hot spots H314A1-AN, H314B1-BN, H314C1-CN, H314D1-DN, H314E1-EN and H314F1-FN, respectively. The hot spots in the hot units 312A-F are heat generating areas in the hot units 312A-F.

In operation, the first heat dissipation device 320 dissipates heat from the hot units 312A-F housed in the aviation electronic equipment rack 322 using forced convection. In dissipating heat from the hot units 312A-F, the first heat dissipation device 320 uses cold air streams 316 capable of causing forced ventilation. As shown in FIG. 3, the source of cold air 306 injects cold air streams 316 into the hot units 312A-F. Further as shown in FIG. 3, the arrows coming from the source of cold air 306 and into the hot units 312A-F indicate the direction of the cold air streams 316.

Further in operation, the cold air streams 316 pass through the hot spots in the hot units 312A-F and is output as hot air streams 318. As shown in FIG. 3, the dotted line arrows coming from the hot units 312A-F indicate the direction of the hot air streams 318. Furthermore in operation, the hot air streams 318 are collected by the collector for disposing hot air 304. Moreover, the collector for disposing hot air 304 is connected to ventilation ducts for extracting the hot air streams 318 from the avionics bay 102, shown in FIG. 2, and disposing the hot air streams 318 outside the aircraft 100. In addition to heat dissipation by forced convection, the first heat dissipation device 320 also dissipates heat from the aviation electronic equipment rack 322 by natural convection, in thermal contact with the hot spots in the hot units 312A-F, shown in FIG. 3.

In one embodiment, the second heat dissipation device, which includes the external thermal radiator 308 and the heat pipes 310A-C, enhances heat dissipation from the hot units 312A-F by natural convection and radiation. In this embodiment, the external thermal radiator 308 is strategically disposed with respect to aircraft skin 302 to maximize radiative heat dissipation from the hot units 312A-F. As shown in FIG. 3, the external thermal radiator 308 includes heat collectors that are coupled to the hot spots in the hot units 312A-F using thermal conductors. In this embodiment, the thermal conductors are the heat pipes 310A-C, shown in FIG. 3. The heat pipes 310A-C have high thermal conductivity in the longitudinal direction. Further in this embodiment, the heat pipes 310A-C are connected to the hot spots of the hot units 312A-F to facilitate the heat transfer from the hot units 312A-F to the external thermal radiator 308.

Furthermore in this embodiment, the external thermal radiator 308 is sized to complement the cooling provided by the first heat dissipation device 320 when the ventilation provided by the forced convection is lost. Also, the external thermal radiator 308 is configured to maximize heat dissipation by radiation and to obtain high radiative view factor. The radiative view factor is the fraction of radiation heat leaving the external thermal radiator 308 which is incident on the aircraft skin 302. In this embodiment, the external thermal radiator 308 is located and oriented in such a way that the radiative view factor is maximized. Also in this embodiment, the hot units 312A-F are strategically disposed in the avionics bay 102 to maximize the radiative view factor with the aircraft skin 302.

Generally, when the aircraft 100 is cruising, the aircraft skin 302 is at a very low temperature. Therefore, the temperature difference between the aircraft skin 302 and the surface of the external thermal radiator 308 is very high. As a result, the heat dissipated by radiation from the external thermal radiator 308 to the aircraft skin 302 is maximized. Further, the heat is transferred from the external thermal radiator 308 in two modes, which include radiation and convection. The heat transferred from the external thermal radiator 308 by radiation is transferred to the aircraft skin 302 and the heat transferred from the external thermal radiator 308 by convection is transferred to the surrounding air. Further, the heat transferred from the external thermal radiator 308 by radiation can be computed using equation:

qradiation=εAσF(T4surface−T4skin)  (1)

wherein,

qradiation is radiative heat transfer rate;

ε is an emissivity of the surface;

A is area of emitting surface;

σ is the Stefan-Boltzmann Constant;

Tsurface is an absolute temperature of emitting surface of the external thermal radiator 308 (K);

Tskin is an absolute temperature of the aircraft skin 302 (K); and

F is a radiative view factor from the surface of the external thermal radiator 308 to the aircraft skin 302.

Furthermore, the heat transferred from the external thermal radiator 308 by convection can be computed using equation:

qconvection=hA(Tsurface−Treference)  (2)

wherein,

qconvection is convective heat transfer rate;

h is the heat transfer coefficient; and

Treference is an absolute temperature of surrounding air (K).

It can be seen from the equation (2) that convective heat transfer is proportional to the difference between the temperature of the emitting surface of the external thermal radiator 308 and the surrounding air. Further, it can be seen from the equation (1) that radiative heat transfer is proportional to difference in fourth power of temperature values of the aircraft skin 302 and the external thermal radiator 308. Therefore, it can be seen that, higher the difference in temperature between the aircraft skin 302 and the external thermal radiator 308, the higher is the radiative heat flux. The large temperature difference between the aircraft skin 302 and the external thermal radiator 308 while the aircraft 100 is cruising results in the radiative heat transfer dominating the convective heat transfer. Since the heat transferred from the external thermal radiator 308 by radiation is transferred to the aircraft skin 302, the temperature of the surrounding air is not increased. This effectively increases the temperature difference between the emitting surface of the external thermal radiator 308 and the surrounding air resulting in higher convective heat transfer rates.

Typically, radiative heat transfer increases the temperature of the surrounding air when the surrounding air has high humidity content. However, in this embodiment, the participation of humidity in the radiative heat transfer is negligible as humidity level in the avionics bay 102, shown in FIG. 2, while the aircraft is cruising, is typically very low. Hence, the heat transfer between the external thermal radiator 308 and the aircraft skin 302 does not result in an increase in the surrounding air temperature in the avionics bay 102, shown in FIG. 1.

Referring now to FIG. 4, which illustrates a flow diagram 400 of an exemplary method for radiative heat transfer augmentation for the aviation electronic equipment rack 322 cooled by forced and/or natural convection, such as those shown in FIG. 3, according to an embodiment. At block 402, heat is dissipated from the aviation electronic equipments housed in the aviation electronic equipment rack by forced convection using a first heat dissipation device. In dissipating heat from the aviation electronic equipments, the first heat dissipation device uses air stream capable of causing forced ventilation. Further in dissipating heat from the aviation electronic equipments, the first heat dissipation device cools the aviation electronic equipments by natural and forced convection in thermal contact with one or more hot spots of the aviation electronic equipments. This is explained in more detail with reference to FIG. 3.

At block 404, heat dissipation from the aviation electronic equipments by radiation and natural convection is enhanced using a second heat dissipation device. In this embodiment, the second heat dissipation device is strategically disposed with respect to the aircraft skin and configured to maximize radiative view factor. Further in this embodiment, the second heat dissipation device is an external thermal radiator. Furthermore, the external thermal radiator includes a heat collector that is coupled to the one or more heat spots of the aviation electronic equipments using thermal conductors. The thermal conductors are heat pipes having high thermal conductivity in the longitudinal direction. This is explained in more detail with reference to FIG. 3.

In addition in this embodiment, the second heat dissipation device is sized to complement the cooling provided by the first heat dissipation device should the forced convection be lost. Also in this embodiment, the second heat dissipation device is disposed with respect to the aircraft skin to maximize heat dissipation by radiation.

In various embodiments, the methods and systems described in FIGS. 1 through 4 enable extracting heat from the aviation electronic equipment racks in the avionics bay using the external thermal radiator which increases the radiation heat transfer to the aircraft skin. Further, the method described in FIGS. 1 through 4 enable substantially eliminating heat transferred to the surrounding air in the avionics bay.

Although the present embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments. Furthermore, the various devices, modules, analyzers, generators, and the like described herein may be enabled and operated using hardware circuitry, for example, complementary metal oxide semiconductor based logic circuitry, firmware, software and/or any combination of hardware, firmware, and/or software embodied in a machine readable medium. For example, the various electrical structure and methods may be embodied using transistors, logic gates, and electrical circuits, such as application specific integrated circuit.