Finned surfaces length

A = (fti external finned surface per ft length from Table 10-39 or other specific tube data) (U, net effective tube length) (N number of tubes) (10-5)... 

Tubes are copper 1-in. nominal O.D. X 14 BWG (0.083-in. thick at finned section) X 19 fins/in. Wolverine Trufin (standard tube (unfinned) wall thickness = 0.095 in.). Finned surface area/ft length = 0.678 fti/ft. Plain tubes are 0.5463 ftVft. 

L that is attached to the surface with a perfect contact (Fig. 3-40). Hiis time heat is transfered from the surface to the fin by conduction and from the fin to the surrounding medium by convection with the same heat transfer coefficient h. The temperature of the fin is at the fin base and gradually decreases toward the fin tip. Convection from the fin. surface causes the temperature at any cross section to drop somewhat from the midsection toward the outer surfaces. However, the cross-sectional area of the fins is usually very small, and thus the temperature at any cross section can be considered to be uniform. Also, the fin lip can be assumed for convenience and. simplicity to be adiabatic by using the corrected length for the fin instead of the actual length. 

CXitside surface area (without finsVunit length of pipe, i4, = r(0.028) = 0.0879mVm Outside surface area not covered with fins/unit length of pipe,... 

The upper and lower surfaces of a triangular fin of length 90 min transfer heat with a coef-... 

In order to improve the heat transfer characteristics of air cooled exchangers, the tubes are provided with external fins. These fins can result in a substantial increase in heat transfer surface. Parameters such as bundle length, width and number of tube rows vary with the particular application as well as the particular finned tube design. 

A longitudinal tin on the outside of a circular pipe is 75 mm deep and 3 mm thick. If tire pipe surface is at 400 K. calculate the heat dissipated per metre length from the fin to the atmosphere at 290 K if the coefficient of heat transfer from its surface may be assumed constant at 5 W/m2 K, The thermal conductivity of the material of the fin is 50 W/m K and the heat loss from the extreme edge of the fin may be neglected. It should be assumed that the temperature is uniformly 400 K at the base of the fin. 

Tubes are 0.75-1.00 in. OD, with 7-11 fins/in. and 0.5-0.625 in. high, with a total surface 15-20 times bare surface of the tube. Fans are 4-12ft/dia, develop pressures of 0.5-1.5in. water, and require power inputs of 2-5HP/MBtu/hr or about 7.5HP/ 100 sqft of exchanger cross section. Spacings of fans along the length of the equipment do not exceed 1.8 times the width of the cooler. Face velocities are about 10 ft/sec at a depth of three rows and 8 ft/sec at a depth of six rows. 

Wt at launch, 26.5kg length, 1130mm diameter, 130mm rocket motor, solid control, control surfaces on fins warhead, HEAT with DA fuze range, 600—2500m and penetration, 400mm+... 

Fins are frequently installed on tubes by a press-fit process. Consider a circumferential aluminum fin having a thickness of l.O mm to be installed on a 2.5-cm-diameter aluminum tube. The fin length is 1.25 cm, and the contact conductance may be taken from Table 2-2 for a l00-/xin ground surface. The convection environment is at 20°C, and h = 125 W/m2 °C. Calculate the heat transfer for each fin for a tube wall temperature of 200°C. What percentage reduction in heat transfer is caused by the contact conductance ... 

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