The heat transfer coefficient for a gas flowing over a thin float plate 3-m long and 0.3-m wide varies with distance from the leading edge according to
If the plate temperature is 170°C and the gas temperature is 30°C, calculate (a) the average heat transfer coefficient, (b) the rate of heat transfer between the plate and the gas, and (c) the local heat flux 2 m from the leading edge.
Problem 1.18
Want to see the full answer?
Check out a sample textbook solutionChapter 1 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
- An electrical transmission line of 1.2-cm diameter carries a current of 200 amps and has a resistance of 310-4 ohm per meter of length. If the air around this line is at v, determine the surface temperature on a windy day, assuming a wind blows across the line at 33 km/h.arrow_forward5.7 The average Reynolds number for air passing in turbulent flow over a 2-m-long, flat plate is . Under these conditions, the average Nusselt number was found to be equal to 4150. Determine the average heat transfer coefficient for an oil having thermal properties similar to those in Appendix 2, Table 18, at at the same Reynolds number and flowing over the same plate.arrow_forward3.10 A spherical shell satellite (3-m-OD, 1.25-cm-thick stainless steel walls) re-enters the atmosphere from outer space. If its original temperature is 38°C, the effective average temperature of the atmosphere is 1093°C, and the effective heat transfer coefficient is , estimate the temperature of the shell after reentry, assuming the time of reentry is 10 min and the interior of the shell is evacuated.arrow_forward
- . Castor oil at 36 °C flows over a 6 m long and 1 m wide heated plate at 0.06 m/s. For a surfacetemperature of 96 °C, determine (i) the thermal boundary layer thickness at the end of the plate,(ii) the local heat transfer coefficient at the end of the plate, and (iii) the rate of heat transfer fromthe entire platearrow_forwardConsider a 50-cm-diameter and 95-cm-long hot water tank. The tank is placed on the roof of a house. The water inside the tank is heated to 80°C by a flat-plate solar collector during the day. The tank is then exposed to windy air at 18°C with an average velocity of 40 km/h during the night. Estimate the temperature of the tank after a 45-min period. Assume the tank surface to be at the same temperature as the water inside, and the heat transfer coefficient on the top and bottom surfaces to be the same as that on the side surface. Evaluate the air properties at 50°C.arrow_forwardThe nose section of the rocket is made up of a 6 mm thick stainless steel plate (p = 7800 kg/m°, c = 460 J/kg°C, k = 55 W/m°C). It is held initially at a uniform temperature of " T = 47°C. When the rocket enters the denser layers of the atmosphere at a very high velocity the effective temperature of the air surrounding the nose region attains the value 2150 °C; the surface convective heat transfer coefficient is estimated as 3395 W/m?°C. If the maximum metal temperature is not to exceed 1100°C, determine: (i) Maximum permissible time in these surroundings. (i) Inside surface temperature under these conditions.arrow_forward
- A long 8-cm-diameter steam pipe whose external surface temperature is 90°C passes through some open area that is not protected against the winds. Determine the rate of heat loss from the pipe per unit of its length when the air is at 1 atm pressure and 7°C and the wind is blowing across the pipe at a velocity of 50 km/h.arrow_forwardAir at 25 ° C blows over the hot steel plate whose surface temperature is maintained at 150 ° C. The plates are 50 cm x 40 cm in dimensions and 2.5 cm thick. The convection heat transfer coefficient on the upper surface is 40 W / (m² ° C). The thermal conductivity of steel is 45 W / (m ° C). Calculate the hourly heat loss from the plate surface. a. heat loss per hour = Answer kJ. b. If the reverse side surface temperature is maintained, determine the hourly heat loss occurring = Answer kJ. Air at 25 ° C blows over the hot steel plate whose surface temperature is maintained at 150 ° C. The plates are 50 cm x 40 cm in dimensions and 2.5 cm thick. The convection heat transfer coefficient on the upper surface is 40 W / (m² ° C). The thermal conductivity of steel is 45 W / (m ° C). Calculate the hourly heat loss from the plate surface. a. heat loss per hour = Answer kJ. b. If the reverse side surface temperature is maintained, determine the hourly heat loss occurring = Answer kJ.arrow_forwardPartially-frozen ice cream is being placed in a package before completion of the freezing process. The package has dimensions of 8 cm by 10 cm by 20 cm and is placed in air- blast freezing with convective heat coefficient of 50 W/(m2 K) for freezing. The product temperature is -5°C when placed in the package, and the air temperature is -25°C. The product density is 700 kg/m3, the thermal conductivity (frozen) is 1.2 W/(m K), and the specific heat of the frozen product is 1.9 kJ/(kg K). If the latent heat to be removed during blast freezing is 100 kJ/kg, estimate the freezing time.arrow_forward
- Liquid mercury at 250°C is flowing with a velocity of 0.3 m/s in parallel over a 0.1-m-long flat plate where there is an unheated starting length of 5 cm. The heated section of the flat plate is maintained at a constant temperature of 50°C. Determine (a) the local convection heat transfer coefficient at the trailing edge, (b) the average convection heat transfer coefficient for the heated section, and (c) the rate of heat transfer per unit width for the heated section.arrow_forwardFins, or extended surfaces, commonly are used in a variety of engineering applications to enhance cooling. Common examples include a motorcycle engine head, a lawn mower engine head, extended surfaces used in electronic equipment, and finned tube heat exchangers in room heating and cooling applications. Consider aluminum fins of a rectangular profile, which are used to remove heat from a surface whose temperature is100° C . The temperature of the ambient air is 20° C. We are interested in determining how the temperature of the fin varies along its length and plotting this temperature variation. For long fins, the temperaturedistribution along the fin is given byarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning