Optimized heat exchanger and methods for designing the same
A heat storage system, and systems and methods for designing a heat exchanger system included in the heat storage system are disclosed. The heat exchanger system includes a heat exchanger including a plurality of planar fins parallelly arranged between a first header and a second header, and a plurality of tubes configured to be received in axially aligned holes of the plurality of fins, the plurality of tubes being configured to allow flow of a fluid exchanger fluid. The heat storage system also includes a storage tank comprising phase change material (PCM) for at least partially submerging the heat exchanger within the PCM. A spacing between the plurality of fins is optimized using a finite particle model of the heat exchanger to achieve a performance objective of at least 75% thermal heat discharge from the PCM in about 3 hours.
1 . A heat storage system comprising:
a heat exchanger comprising:
a plurality of planar fins parallelly arranged between a first header and a second header and have a plurality of holes through the fins, subsets of the plurality of holes in the fins being axially aligned;
a plurality of tubes configured to be received in the axially aligned subsets of holes through the plurality of fins, the plurality of tubes being configured to allow flow of a fluid exchanger fluid;
a storage tank comprising phase change material (PCM), wherein the heat exchanger is configured to be at least partially submerged within the PCM;
wherein the number of tubes is less than the number of subsets of axially aligned holes, and wherein a spacing between the plurality of fins and a spacing between the plurality of tubes satisfies the following ratios:
fin spacing/tube spacing=0.1 to 0.2;
fin spacing/fin thickness=2.3 to 125;
fin spacing/PCM conductivity=0.5 to 7.5; and
fin spacing (inch)/PCM volumetric latent heat (kJ/m 3 )=0.0000047 to 0.0000006;
and wherein the heat storage system discharges at least 75% thermal heat discharge from the PCM in about 3 hours.
2 . The heat storage system of claim 1 , wherein the spacing is about 0.75 inch to about 0.14 inch.
3 . The heat storage system of claim 1 , wherein a thickness of each of the plurality of fins is about 0.006 inch to about 0.06 inch.
4 . The heat storage system of claim 1 , wherein a spacing between the plurality of tubes is about 2 inches to about 4 inches.
5 . The heat storage system of claim 4 , wherein a diameter of each of the plurality of tubes is about 0.375 inch to 0.16 inch.
6 . The heat storage system of claim 1 , wherein the spacing is optimized to satisfy at least one of the following ratios:
Fins
spacing
tube
diameter
=
0.9
to
2
Fin
spacing
(
inch
)
PCM
specific
latent
heat
(
kJ
kg
)
=
0.0042
to
0.0006
.
7 . The heat storage system of claim 1 , wherein the heat exchanger is a vertical finned horizontal tube exchanger.
8 . The heat storage system of claim 1 , wherein the heat exchanger is a horizonal finned vertical tube exchanger.
9 . The heat storage system of claim 1 , wherein one or more of the plurality of tubes comprise a twisted tape insert.