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- Question No. 3: During a cold winter day, wind at 55 km/h is blowing parallel to a 4-m-high and 10-m-long wall of a house. If the air outside is at 5°C and the surface temperature of the wall is12°C, determine the rate of heat loss from that wall by convection. What would your answer be if the wind velocity was doubledarrow_forwardA long 10-cm-diameter steam pipe whose external surface temperature is 110°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 10°C and the wind is blowing across the pipe at a velocity of 8 m/s.arrow_forwardHot engine oil at 150°C is flowing in parallel over a flat plate at a velocity of 3.30 m/s. Surface temperature of the 1.800-m long flat plate is constant at 50°C. The properties of engine oil at Tf = (150°C + 50°C)/2 = 100°C are k = 0.1367 W/m∙K, v = 2.046 × 10−5 m2/s, Pr = 279.1. Determine the local convection heat transfer coefficient at 0.200 m from the leading edge and the average convection heat transfer coefficient. The local convection heat transfer coefficient at 0.200 m from the leading edge is ___ W/m2·K. The average convection heat transfer coefficient is ___ W/m2·K.arrow_forward
- Air at 200C and at a pressure of 1 bar is flowing over a flat plate at a velocity of 3 m/s. If the plate is 280 mm wide and at 560C, calculate the following quantities at x = 280 mm given that properties of air at the bulk mean temperature 20 + 56/2= 380C are: (i) Boundary layer thickness,(ii) Local friction coefficient,(iii) Average friction coefficient,(iv) Shearing stress due to friction(v) Thickness of the boundary layer,(vi) Local convective heat transfer coefficient,(vii) Average convective heat transfer coefficient,(viii) Rate of heat transfer by convection(ix) Total drag force on the plate, and(x) Total mass flow rate through the boundaryarrow_forwardA 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_forwardIn the effort to increase the removal of heat from a hot surface at 120°C, a cylindrical pin fin (kf = 237 W/m.K) with diameter of 5 mm is attached to the hot surface. Air at 20°C (1 atm) is flowing across the pin fin with a velocity of 10 m/s. Determine the maximum possible rate of heat transfer from the pin fin. Evaluate the air properties at 70°C.arrow_forward
- Water at 43.3°C flows over a large square plate at a velocity of 28 cm/s. The plate is 1.2 m long (in the flow direction) and its surface is maintained at a uniform temperature of 10.0°C. The width of the plate is 1.2 m. Calculate the steady rate of heat transfer for the entire width of the plate in watts (W). The properties of water at the film temperature of (Ts + T∞)/2 = (10 + 43.3)/2 = 27°C are ρ = 996.6 kg/m3, k = 0.610 W/m·°C, μ = 0.854 × 10–3 kg/m·s, and Pr = 5.85. The steady rate of heat transfer per unit width of the plate is ___ W.arrow_forwardDuring a cold winter day, wind at 55 km/h is blowing parallel to a 4m high and 10m long wall of a house. If the air outside is at 5 degrees Celsius and the surface temperature of the wall is 12 degrees Celsius , determine the rate of heat loss from the wall by convection. What would your answer be if the wind velocity has doubled? From Table A-1:thermal conductivity, k = 0.0246 W/m degrees Celsiusviscosity, v = 1.4 x 10^-5 m^2/sPrandtl no. Pr = 0.717arrow_forwardMetal plates (k = 150 W/m·K, ρ= 2800 kg/m3, and cp = 900 J/kg·K) with a thickness of 2 cm exiting an oven are conveyed through a 10-m long cooling chamber at a speed of 4 cm/s, as shown in the figure. The plates enter the cooling chamber at an initial temperature of 500°C. The air temperature in the cooling chamber is 15°C, and the plates are cooled with blowing air and the convection heat transfer coefficient is given as a function of the air velocity h(V) = 33V0.8, where h is in W/m2·K and V is in m/s. To prevent any hazard to workers handling the plates, it is necessary to design the cooling process such that the plates exit the cooling chamber at a relatively safe temperature of 50°C or less. Determine the air velocity V and the heat transfer coefficient h such that the temperature of the plates exiting the cooling chamber is at 50C.arrow_forward
- A long 8-cm diameter vertical steam pipe whose external surface temperature is 90 degrees C passes through some open area that is not protected against the wind blows. Determine the rate of heat loss from the pipe per unit length when the air is at 1 atm, 7 degrees Celsius and the wind is blowing across the pipe at a velocity of 50 km/h. From Table A-1:Thermal conductivity, k = 0.0275 W/m degrees Celsius ,viscosity, v = 1.77 x 10^-5 m^2/sPrandtl no. Pr = 0.71arrow_forwardThe average temperature of the soil to a considerable depth is approximately 277.6 K (40°F) during a winter day. If the outside air temperature suddenly drops to 255.4 K (0°F) and stays there, how long will it take for a pipe 3.05 m (10 ft) below the surface to reach 273.2 K (32°F)? The convective coefficient is h = 8.52 W/m2 -K (1.5 BTU/h-ft2 -°F). The soil physical properties can be taken as 5.16 x 10–7 m/s (0.02 ft2 /h) for the thermal diffusivity and 1.384 W/m-K (0.8 BTU/h-ft-°F) for the thermal conductivityarrow_forwardOver the outside part of the room window, the wind is blowing with a speed of 10 m/sec. Due to this wind motion, the temperature on the outer surface of the window is 5 degrees lower than the room temperature. Determine the convective heat flux if the wind temperature is 10 C with a heat transfer coefficient of 10 W/(mK). Accept the temperature inside the room as 25 C. A) 200 W B) 100 W C) 200 W/(m^2) D) 100 W/(m^2) E) Not sufficient informationarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning