High performance heat exchange assembly
Heat sinks are provided that achieve very high convective heat transfer surface per unit volume. These heat sinks comprise a spreader plate, at least two fins and at least one porous reticulated foam block that fills the space between the fins.
1. A heat sink for electrical or electronic components comprising:
a heat spreader plate to which the components to be cooled are connected;
at least two heat conducting fins that are positioned substantially parallel to one another and which are connected substantially perpendicular to said heat spreader plate;
at least one foam block that is disposed in the space between parallel fins wherein said block is formed of reticulated foam to define a highly porous, heat conducting, open-celled structure that permits a cooling fluid to flow through said block as the cooling fluid passes across said fins; and
said at least one foam block being made from aluminum, copper, graphite, or aluminum-nitride ceramic
wherein the fin height, b, is determined by the relationship,
b
=
0.6498
k
f
δ
f
h
where,
k f is the thermal conductivity of the selected fin material, Btu/ft s ° F.
δ f is the fin thickness, ft
h is the convective heat transfer coefficient for the foam-filled space bounded by said fins and said heat spreader plate, Btu/ft 2 s ° F., and where h is given by the formula,
h
=
1.2704
[
n
0
50
(
1
-
ϕ
)
0.25
]
(
ρ
0
50
k
0.63
c
p
0
37
μ
0.13
)
u
m
0.50
where,
h is the linear density of said at least one foam block, pores per ft
φ is the porosity of said at least one foam block, expressed as a fraction
ρ is the density of the cooling fluid that passes across said fins, lb m /ft 3
k is the thermal conductivity of the cooling fluid, Btu/ft s ° F.
c p is the isobaric specific heat of the cooling fluid, Btu/lb m ° F.
μ is the dynamic viscosity of the cooling fluid, lb m /ft s
u m is the mean velocity of the cooling fluid, ft/s.
2. A heat sink for electrical or electronic components comprising:
a heat spreader plate to which the components to be cooled are connected;
at least two heat conducting fins that are positioned substantially parallel to one another and which are connected substantially perpendicular to said heat spreader plate;
at least one foam block that is disposed in the space between parallel fins wherein said block is formed of reticulated foam to define a highly porous, heat conducting, open-celled structure that permits a cooling fluid to flow through block as the cooling fluid passes across said fins; and
said at least one foam block being made from aluminum, copper, graphite, or aluminum-nitride ceramic
wherein the fin spacing, a, is determined by the relationship,
α=Φδ
where,
Φ is between 1 to 6
δ, ft, is determined by the relation,
δ
=
7.32
kc
ρ
c
p
u
m
where,
c is the selected fin length in the flow direction, ft
k is the thermal conductivity of the cooling fluid that passes across said fins, Btu/ft s ° F.
ρ is the density of the cooling fluid lb m /ft 3
c p is the isobaric specific heat of the cooling fluid, Btu/lb m ° F.
u m is the mean velocity of the cooling fluid, ft/s.
3. A heat sink of claim 1 wherein said heat spreader plate, said fins and said at least one foam block are made from the same or different thermal conducting materials.
4. A heat sink of claim 1 wherein said heat spreader plate and said fins are made from aluminum, copper, graphite or aluminum-nitride ceramic.
5. A heat sink of claim 1 wherein said heat spreader plate and said fins are made from aluminum.
6. A heat sink of claim 1 wherein said fins and said at least one foam block are connected to one surface of said heat spreader plate.
7. A heat sink of claim 1 wherein said at least one foam block is further defined as a plurality of foam blocks.
8. A heat sink of claim 7 wherein said fins are connected to said heat spreader plate through thermal bonding.
9. A heat sink of claim 7 wherein said fins are connected to said foam blocks through thermal bonding.
10. A heat sink of claim 8 wherein said fins are connected to said foam blocks through thermal bonding.
11. A heat sink of claim 1 wherein said fins are connected to said heat spreader plate through thermal bonding.
12. A heat sink of claim 1 wherein said fins are connected to said at least one foam block through thermal bonding.
13. A heat sink of claim 11 wherein said fins are connected to said at least one foam block through thermal bonding.
14. A heat sink for electrical or electronic components comprising:
a heat spreader plate to which the components to be cooled are connected;
at least two heat conducting fins that are positioned substantially parallel to one another and which are connected substantially perpendicular to said heat spreader plate;
at least one foam block that is disposed in the space between parallel fins wherein said block is formed of reticulated foam to define a highly porous, heat conducting, open-celled structure that permits a cooling fluid to flow through said block as the cooling fluid passes across said fins; and
said at least one foam block being made from aluminum, copper, graphite, or aluminum-nitride ceramic,
wherein the fin height, b, is determined by the relationship, and
b
=
0.6498
k
f
δ
f
h
where,
k f is the thermal conductivity of the selected fin material, Btu/ft s ° F.
δ f is the fin thickness, ft
h is the convective heat transfer coefficient for the foam-filled space bounded by said fins and said heat spreader plate, Btu/ft 2 s ° F., and where h is given by the formula,
h
=
1.2704
[
n
0
50
(
1
-
ϕ
)
0.25
]
(
ρ
0
50
k
0.63
c
p
0
37
μ
0.13
)
u
m
0.50
where,
n is the linear density of said at least one foam block, pores per ft
φ is the porosity of said at least one foam block, expressed as a fraction
ρ is the density of the cooling fluid that passes across said fins, lb m /ft 3
k is the thermal conductivity of the cooling fluid, Btu/ft s ° F.
c p is the isobaric specific heat of the cooling fluid, Btu/lb m ° F.
μ is the dynamic viscosity of the cooling fluid, lb m /ft s
u m is the mean velocity of the cooling fluid, ft/s and
a heat spreader plate to which the components to be cooled are connected;
at least two heat conducting fins that are positioned substantially parallel to one another and which are connected substantially perpendicular to said heat spreader plate;
at least one foam block that is disposed in the space between parallel fins wherein said block is formed of reticulated foam to define a highly porous, heat conducting, open-celled structure that permits a cooling fluid to flow through said block as the cooling fluid passes across said fins; and
said at least one foam block being made from aluminum, copper, graphite, or aluminum-nitride ceramic
wherein the fin spacing, a, is determined by the relationship,
α=Φδ
where,
Φ is between 1 to 6
δ, ft, is determined by the relation,
δ
=
7.32
kc
ρ
c
p
u
m
where,
c is the selected fin length in the flow direction, ft
k is the thermal conductivity of the cooling fluid that pas es across said fins, Btu/ft s ° F.
ρ is the density of the cooling fluid lbm/ft3
cp is the isobaric specific heat of the cooling fluid, Btu/lbm° F.
um is the mean velocity of the cooling fluid, ft/s.
15. A heat sink of claim 7 wherein said fins and said foam blocks are connected to one surface of said heat spreader plate.