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Re ≈ 239 |
Re ≈ 4788 |
Channel height |
[ mm ] |
1.15 |
Plate thickness |
[ mm ] |
1 |
Channel length |
[ mm ] |
200 |
Hot inlet temp |
[ C ] |
850 |
Cold inlet temp |
[ C ] |
625 |
Reference pressure |
[ MPa ] |
6.8 |
Hot channel flow rate |
[ kg / s ] |
2.56e-4 |
5.12e-3 |
Cold channel flow rate |
[ kg / s ] |
2.06e-4 |
4.12e-3 |
Table 1 : CHT Validation conditions |
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|
|
Figure 5 : Illustrative diagrams of temperature and velocity streamlines for the counter-flow heat exchanger designs
hD
Nu = h k
Where h is the heat transfer coefficient , D h is the hydraulic diameter of the heat exchanger , and k is the thermal conductivity of the fluid . The losses across the heat exchanger are quantified using the non-dimensional Fanning friction factor
p D f =
2L �u
h 2
where ∆p is the static pressure drop across the heat exchanger , L is the length of the heat exchanger , ρ is the fluid density , and u is the fluid velocity . The Nusselt number represents the ratio of heat transfer by convection to heat transfer by conduction across the heat exchanger . Higher Nusselt numbers indicate more efficient heat exchangers . The Fanning friction factor represents a normalized pressure drop across the heat exchanger . Lower value indicate higher efficiency .
The Nusselt and Fanning numbers for the TOffee counterflow heat exchanger are shown in Table 2 , while those of the aerofoil baseline are shown in Table 3 . The results show that the at low Reynolds numbers the TOffee heat exchanger has a 3 % higher Nusselt number for an equivalent friction factor . At high Reynolds numbers , the TOffee heat exchanger has an 8.5 % higher Nusselt number for an only 4 % higher Fanning number . These are significant gains in heat exchanger performance .
Conclusion Advanced nuclear technologies such as small modular reactors and advanced modular reactors have the potential to support decarbonization beyond just supplying low-carbon electricity . Their higher operating temperatures mean that there is a significant opportunity to exploit downstream cogeneration activities such as hydrogen generation . However ,
Flow Condition Performance parameter
Cold Side
Simulation of design
Hot Side
Laminar ( Re = 239 )
' Turbulent ' ( Re = 4788 )
Nu |
9.36 |
9.6 |
f |
0.59 |
0.52 |
Nu |
21.1 |
22.5 |
f |
0.094 |
0.040 |
Table 2 : Topology optimized counter-flow heat exchanger performance
48 Heat Exchanger World September 2022 www . heat-exchanger-world . com