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i have got a staggered tube arrangment, and has and arrangment of 15rows x 15tubes. the tubes are connected to each other with fins. the measurments of the fins and tubes are given in the attachement. i am suppose to find the heat transfer and thus working out the fin effectivness and the efficiency. i am getting confused with the minimmum flow area to which equation to use.
The picture below shows the dimensions of the tubes and the spacing between them. These tubes are to be connected with fins. Each tube will have 6 fins attached to it, which will connect all the tubes together, see figure2(only half the lenghts of the fins are shown here). All the measurements shown in the attachment are in mm. Each of the tube has a length of 76.2mm. The base area which the fines are attached to the tubes is 0.5mm x 0.5mm and the length of the fins depends on the spacing between the tubes. each tube is 76.2mm and for every 5mm of the tube there is 5 fins at a width of 0.5mm( see picture).
Hot water is passing trough the tube, at an entrance temp of 393K and exit of 303K. Outside the tube air is used and at the entrance the temp is 293K and at exit is 318K. the velocity of air just before it reaches the staggered tubes is u∞=37.8m/s and the mass flow rate of water just before it reaches the tubes is 0.23kg/s. the material used for the tubes is stainless steel and thermal conductivity is k = 17W/mºC.
there are a lots of equations to find Nu, but not sure which one to use. please help.
below given is all the values i know for this problem
Air
Tcin – 293K
Tcout – 303K
dynamic viscosity - 1.8975 x 10-5Pa.s
Density – 1.193375 kg/m3
kinematic viscosity - 1.59 x 10-5
Cp – 1005 J/kg.K
k – 0.02964 ( thermal conductivity)
Pr – 0.722
Water
Tcin – 393K
Tcout – 318K
dynamic viscosity- 3.795 x 10-2Pa.s
Density – 974.94 kg/m3
kinematic viscosity - 3.89 x 10-5
Cp – 4194 J/kg.K
k – 0.609 ( thermal conductivity)
Pr – 2.61
Attached Files
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question.doc 127KB
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