ME3122-2 FORCED CONVECTION HEAT TRANSFER

BENJAMIN ANG ZI WEI A0072215R GROUP: 3L2 DATE: 7/9/2012

Department of Mechanical Engineering National University of Singapore

OBEJCTIVE The objective of this experiment is to determine forced convection heat transfer coefficients of various elements using different methods of calculations and comparing the results. RESULTS Table 1: Aluminumt sec 0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480 510 540 570 600 Diff Pressure mm water 1.33E+01 1.26E+01 1.30E+01 1.28E+01 1.28E+01 1.30E+01 1.22E+01 1.28E+01 1.33E+01 1.24E+01 1.29E+01 1.25E+01 1.28E+01 1.27E+01 1.28E+01 1.22E+01 1.23E+01 1.24E+01 1.27E+01 1.25E+01 1.15E+01 Sphere Temp C 1.30E+02 1.28E+02 1.14E+02 1.01E+02 8.97E+01 8.01E+01 7.21E+01 6.25E+01 5.64E+01 5.13E+01 4.69E+01 4.32E+01 3.99E+01 3.72E+01 3.50E+01 3.29E+01 3.13E+01 2.97E+01 2.85E+01 2.76E+01 2.67E+01 Air Temp C 2.23E+01 2.22E+01 2.23E+01 2.21E+01 2.21E+01 2.22E+01 2.21E+01 2.22E+01 2.22E+01 2.21E+01 2.22E+01 2.21E+01 2.21E+01 2.21E+01 2.20E+01 2.22E+01 2.22E+01 2.20E+01 2.19E+01 2.23E+01 2.22E+01

Table 2: Brasst sec 0 30 60 90 120 150 180 210 240 270 300 330 Diff Pressure mm water 1.33E+01 1.28E+01 1.28E+01 1.20E+01 1.21E+01 1.28E+01 1.21E+01 1.22E+01 1.32E+01 1.26E+01 1.24E+01 1.26E+01 Sphere Temp C 1.56E+02 1.48E+02 1.33E+02 1.20E+02 1.10E+02 1.02E+02 9.35E+01 8.62E+01 8.00E+01 7.43E+01 6.66E+01 6.20E+01 Air Temp C 2.20E+01 2.21E+01 2.21E+01 2.19E+01 2.17E+01 2.22E+01 2.22E+01 2.21E+01 2.23E+01 2.21E+01 2.23E+01 2.24E+01

360 390 420 450 480 510 540 570 600 630 660 690 720 750 780 810 840 870 900

1.24E+01 1.24E+01 1.27E+01 1.26E+01 1.24E+01 1.19E+01 1.14E+01 1.21E+01 1.22E+01 1.22E+01 1.21E+01 1.20E+01 1.26E+01 1.21E+01 1.27E+01 1.28E+01 1.24E+01 1.23E+01 1.23E+01

5.79E+01 5.42E+01 5.10E+01 4.79E+01 4.53E+01 4.29E+01 4.09E+01 3.91E+01 3.72E+01 3.57E+01 3.41E+01 3.30E+01 3.17E+01 3.07E+01 2.99E+01 2.90E+01 2.85E+01 2.75E+01 2.69E+01

2.24E+01 2.23E+01 2.25E+01 2.24E+01 2.24E+01 2.24E+01 2.26E+01 2.25E+01 2.22E+01 2.24E+01 2.23E+01 2.23E+01 2.22E+01 2.23E+01 2.22E+01 2.21E+01 2.23E+01 2.21E+01 2.22E+01

Table 3: Teflont sec 0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480 510 540 570 600 630 660 690 720 750 780 Diff Pressure mm water 1.30E+01 1.22E+01 1.20E+01 1.24E+01 1.23E+01 1.19E+01 1.25E+01 1.20E+01 1.23E+01 1.19E+01 1.19E+01 1.22E+01 1.24E+01 1.21E+01 1.20E+01 1.21E+01 1.21E+01 1.15E+01 1.19E+01 1.20E+01 1.24E+01 1.24E+01 1.22E+01 1.26E+01 1.24E+01 1.22E+01 1.21E+01 Sphere Temp C 1.19E+02 1.15E+02 1.07E+02 1.03E+02 1.01E+02 9.86E+01 9.67E+01 9.52E+01 9.38E+01 9.22E+01 9.08E+01 8.92E+01 8.75E+01 8.60E+01 8.39E+01 8.22E+01 8.05E+01 7.88E+01 7.72E+01 7.51E+01 7.34E+01 7.06E+01 6.84E+01 6.51E+01 6.38E+01 6.23E+01 6.03E+01 Air Temp C 1.77E+01 2.23E+01 2.22E+01 2.23E+01 2.23E+01 2.21E+01 2.24E+01 2.21E+01 2.21E+01 2.21E+01 2.20E+01 2.22E+01 2.21E+01 2.22E+01 2.22E+01 2.22E+01 2.20E+01 2.21E+01 2.22E+01 2.22E+01 2.21E+01 2.25E+01 2.20E+01 2.24E+01 2.20E+01 2.19E+01 2.19E+01

810 840 870 900 930 960 990 1020 1050 1080 1110 1140 1170 1200 1230 1260 1290 1320 1350 1380 1410 1440 1470 1500 1530 1560 1590 1620 1650 1680

1.20E+01 1.19E+01 1.28E+01 1.19E+01 1.24E+01 1.26E+01 1.24E+01 1.29E+01 1.20E+01 1.26E+01 1.19E+01 1.27E+01 1.22E+01 1.19E+01 1.19E+01 1.18E+01 1.21E+01 1.24E+01 1.22E+01 1.33E+01 1.22E+01 1.23E+01 1.22E+01 1.22E+01 1.23E+01 1.26E+01 1.16E+01 1.21E+01 1.18E+01 1.20E+01

5.88E+01 5.76E+01 5.62E+01 5.45E+01 5.34E+01 5.19E+01 5.08E+01 4.93E+01 4.83E+01 4.72E+01 4.61E+01 4.51E+01 4.41E+01 4.33E+01 4.24E+01 4.13E+01 4.06E+01 3.96E+01 3.88E+01 3.84E+01 3.74E+01 3.67E+01 3.62E+01 3.57E+01 3.48E+01 3.46E+01 3.37E+01 3.35E+01 3.26E+01 3.25E+01

2.16E+01 2.19E+01 2.19E+01 2.17E+01 2.20E+01 2.18E+01 2.23E+01 2.19E+01 2.22E+01 2.23E+01 2.21E+01 2.23E+01 2.22E+01 2.23E+01 2.22E+01 2.23E+01 2.22E+01 2.23E+01 2.22E+01 2.24E+01 2.23E+01 2.21E+01 2.22E+01 2.22E+01 2.21E+01 2.23E+01 2.20E+01 2.24E+01 2.23E+01 2.23E+01

Graph 1

ALUMINIUM - Graph of ln[(T-TA)/(TI-TA)] against (t)/r0.5 0 -0.5 -1 -1.5 -2 -2.5 -3 -3.5 y = -4E-10x + 0.1554 METHOD 1 Linear (METHOD 1) 0 2E+09 4E+09 6E+09 8E+09 1E+10

Graph 2

ALUMINIUM - Graph of Temperature of Sphere(Tsphere)/K against time (t)/s4.10E+02 3.90E+02 3.70E+02 ALUMINIUM - METHOD 2 3.50E+02 3.30E+02 3.10E+02 2.90E+02 0 100 200 300 y = -0.172x + 384.82 400 500 600 Linear (ALUMINIUM - METHOD 2)

Graph 3

BRASS - Graph of ln[(T-TA)/(TI-TA)] against (t)/r0.5 0 -0.5 -1 -1.5 -2 -2.5 -3 -3.5 -4 y = -7E-10x + 0.0247 METHOD 1 Linear (METHOD 1) 0 2E+09 4E+09 6E+09

Graph 4

BRASS - Graph of Temperature of Sphere(Tsphere)/K against time (t)/s4.30E+02 4.10E+02 3.90E+02 3.70E+02 BRASS - METHOD 2 3.50E+02 3.30E+02 3.10E+02 2.90E+02 0 200 400 y = -0.1279x + 393.64 600 800 Linear (BRASS - METHOD 2)

Graph 5

TEFLON - Graph of ln[(T-TA)/(TI-TA)] against (t)/r0.5 0 0 -0.5 -1 -1.5 -2 y = -6E-08x + 0.0674 -2.5 Linear (METHOD 1) 10000000 20000000 30000000 40000000 50000000

Graph 6

TEFLON - Graph of Temperature of Sphere(Tsphere)/K against time (t)/s4.00E+02 3.90E+02 3.80E+02 3.70E+02 3.60E+02 3.50E+02 3.40E+02 3.30E+02 3.20E+02 3.10E+02 3.00E+02 0 200 400 600 800 1000 y = -0.0487x + 377.31 1200 1400 1600 METHOD 2 Linear (METHOD 2)

Table 4: Experimentally determined convective heat transfer coefficients Spheres Reynolds Number Convective Heat Transfer Coefficient, W/m2 K Method 1 Aluminium Brass Teflon Method 2 Method 3 Method 4

SAMPLE CALCULATION: ALUMINIUM METHOD 1 Validity of lumped-heat-capacity method From equations (2) and (6),

Ln

3 (T Ta Ti Ta t r02

hro k

)

Bi

hV / A 1 hro k 3 k

Gradient of Graph 1 = -3( hro/k ) Bi = gradient of graph1 / -3 = -4 x 10-10 / -3 = 1.33 x 10-10 < 0.1 hence lumped heat capacity method is valid