| Materials with pores have strong heat-transfer and heat-storage capabilities.In this study,a new flat plate solar collector（FPSC）model with porous metal foam block assistance is created,and its improved thermal performance is numerically calculated.By analyzing the mean Nusselt number（Nug）,friction coefficient（fm）and performance evaluation index（PEC）of the channel,The shape（rectangle,trid,triangle）,number（N=2,4,6）,Darcy number(Da=10-5～10-2),thickness（thickness value,arrangement mode）,material（pure copper,pure aluminum,alumina,stainless steel）,Reynolds number（Re=234,351,468）and nanofluid（volume fraction,mixing ratio）of the porous block were studied The influence of FPSC heat transfer performance.The results show that the maximum Nug of the rectangular porous block is 4.87,6.01,8.11,6.64,5.49and 5.84,respectively,when N=6,Da=10-2,s=0.9H,Cu,Re=468 and 3%Cu-H2O nanofluid.Moreover,there is increasing resistance and pump power loss as heat transfer performance improves.We can determine that the collector channel’s Nug and fmindicate that the PEC channel is a rectangular porous block with the following properties:N=6,Da=10-2,s=0.6H,Re=234 and 3%Cu-H2O nanofluid.The maximum values of 1.24,1.66,1.21,1.6,and 1.58 are reached,respectively.The performance is enhanced by approximately 24%,66%,21%,60%,and 58%compared to the empty channel,respectively.Moreover,the step-decreasing arrangement of porous block thickness will result in a greater Nug when the total thickness of porous blocks is constant and when the number of rectangular porous blocks is low（N=2）.Yet,the sequentially rising arrangement results in a larger Nug of triangular porous pieces.Significant resistance loss will be seen with this kind of step arrangement.As a result,when the channel PEC is organized with equal thickness,it takes on its maximum value.It is important to note that the channel’s thermal performance improves with increasing Cu particle content in the mixed nanofluid.Based on FPSC research,the best design for a porous block is chosen and applied to a Solar photovpolatic/photothermal（PV/T）system,and a PV plate is employed in place of the FPSC system’s heat-absorbing plate.Using a discrete ordinates radiation model,the impact of type,volume fraction（φ）,and mass flow rate（Qi）on PV/T performance was examined.The results show that the mass flow rate is large,the Nugof the channel is large,and the cooling efficiency（η）of the PV module is high.With a constant mass flow rate and the addition of nanoparticles,the fluid viscosity increases,resulting in a Nugsmaller than the base fluid.The greatestηincrease of Al2O3-H2O and Cu-H2O nanofluids at Qi=0.041kg/s andφ=1%is 2.89%and 2.25%,respectively,relative to the base fluid under the influence of drag and pump power loss.It is important to note that compared to Cu-H2O with high effective thermal conductivity,Al2O3-H2O can deliver higher Nug andη,the study’s findings can offer technical assistance for next technological advancement and the achievement of dual-carbon targets.Fig.41 table 9 Ref.80... |
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