Question

In: Mechanical Engineering

Atmospheric air enters the heated section of a circular tube at a flow rate of .005...

Atmospheric air enters the heated section of a circular tube at a flow rate of .005 kg/s and a temperature of 20 degrees Celsius. The tube is of diameter D = 50 mm, and fully developed conditions with h = 25 W/m^2K exist over the entire length of L = 3m.

a) For the case of the uniform surface heat flux at q''s = 1000 W/m2 , determine the total heat transfer rate q and the mean temperature of the air leaving the tube Tm,o. What is the value of the surface temperature at the tube inlet Ts,i and the outlet Ts,o? Sketch the axial variation of Ts and Tm. On the same figure, also sketch (qualitatively) the axial variation of Ts and Tm for the more realistic case in which the local convection coefficient varies with x.

b) If the surface heat flux varies linearly with x, such that q''s(W/m2) = 500x(m), what are the values of q, Tm,o, Ts,i, and Ts,o? Sketch the axial variation of Ts and Tm. On the same figure, also sketch (qualitatively) the axial variation of Ts and Tm for the more realistic case in which the local convection coefficient varies with x.

c) For the two heating conditions of parts (a) and (b), plot the mean fluid and surface temperatures, Tm(x) and Ts(x), respectively, as functions of distance along the tuble. What effect will a fourfold increase in the convection coefficient have on the temperature distributions?

d) For each type of heating process, what heat fluxes are required to achieve an air outlet temperature of 125 degrees Celsius? Plot the temperature distributions.

Solutions

Expert Solution


Related Solutions

Water enters a circular tube whose walls are maintained at constant temperature at a specified flow rate and temperature.
Water enters a circular tube whose walls are maintained at constant temperature at a specified flow rate and temperature. To compute the rate of heat transfer between the walls and the fluid, using the flow Nusselt number the following temperature difference is used;                                                                 a.   The difference between the inlet and outlet water bulk temperature   b.   The difference between the inlet water bulk temperature and the tube wall temperature c.   The log mean temperature...
Air is heated from 25c to 150c . The flow rate of air at the exit...
Air is heated from 25c to 150c . The flow rate of air at the exit of the heater is 1.25m^3/min and the air pressure is 122 Kpa absolut . calculate the heat requirement in KW , assuming ideal gas behavior and that the kinetic & potential energy are negligible.
Fluid enters a tube with a flow rate of 0.021 kg/s and an inlet temperature of...
Fluid enters a tube with a flow rate of 0.021 kg/s and an inlet temperature of 20°C. The tube, which has a length of 6.280 m and diameter of 15 mm, has a surface temperature of 30°C. Determine the heat transfer rate to the fluid if it is water. The heat transfer rate to the fluid, in W is?
Air enters the compressor of a regenerative air-standard Brayton cycle with a volumetric flow rate of...
Air enters the compressor of a regenerative air-standard Brayton cycle with a volumetric flow rate of 100 m3/s at 0.8 bar, 280 K. The compressor pressure ratio is 20, and the maximum cycle temperature is 1800 K. For the compressor, the isentropic efficiency is 92% and for the turbine the isentropic efficiency is 95%. For a regenerator effectiveness of 86%, determine: (a) the net power developed, in MW. (b) the rate of heat addition in the combustor, in MW. (c)...
Air enters the compressor of an air-standard Brayton cycle with a volumetric flow rate of 60...
Air enters the compressor of an air-standard Brayton cycle with a volumetric flow rate of 60 m3/s at 0.8 bar, 280 K. The compressor pressure ratio is 17.5, and the maximum cycle temperature is 1950 K. For the compressor, the isentropic efficiency is 92% and for the turbine the isentropic efficiency is 95%. Determine: (a) the net power developed, in kW. (b) the rate of heat addition in the combustor, in kW. (c) the percent thermal efficiency of the cycle....
Air enters the compressor of a regenerative air-standard Brayton cycle with a volumetric flow rate of...
Air enters the compressor of a regenerative air-standard Brayton cycle with a volumetric flow rate of 60 m3/s at 0.8 bar, 280 K. The compressor pressure ratio is 20, and the maximum cycle temperature is 1950 K. For the compressor, the isentropic efficiency is 92% and for the turbine the isentropic efficiency is 95%. For a regenerator effectiveness of 86%, determine: (a) the net power developed, in MW. (b) the rate of heat addition in the combustor, in MW. (c)...
Air enters the compressor of a regenerative air-standard Brayton cycle with a volumetric flow rate of...
Air enters the compressor of a regenerative air-standard Brayton cycle with a volumetric flow rate of 20 m3/s at 0.8 bar, 280 K. The compressor pressure ratio is 20, and the maximum cycle temperature is 1950 K. For the compressor, the isentropic efficiency is 92% and for the turbine the isentropic efficiency is 95%. For a regenerator effectiveness of 86%, determine: (a) the net power developed, in MW. (b) the rate of heat addition in the combustor, in MW. (c)...
Convection Heat transfer internal flow Consider water flowing in a heated tube. The tube is 14...
Convection Heat transfer internal flow Consider water flowing in a heated tube. The tube is 14 m long with an inner diameter of 1 cm. The heat is added at 1500 W/m2 uniformly along the tube. Water flows at 0.3 m/s. Use the following water property ? = 1000 kg/m3, ? = 1.4 × 10?3 kg/m·s, cp = 4.2 kJ/kg·K, k = 0.58 W/m·K, and determine 1. Heat transfer coefficient at the tube exit. 2. Tube surface temperature at the...
Consider the following combined cycle. The mass flow rate of air is 73 kg/s. Air enters...
Consider the following combined cycle. The mass flow rate of air is 73 kg/s. Air enters the compressor at state 1 with Patm =1 atm and Tamb = 20°C. The compressor has a pressure ratio of 7.5 and an efficiency ?c = 0.85. Air enters the combustor and is heated to a temperature TH = 1250°C. The turbine has an efficiency of ?t,1 = 0.87. The air leaving the turbine enters the steam boiler where it transfers heat to the...
reveals a longitudinal section of a circular tube with a length of l = 300 m....
reveals a longitudinal section of a circular tube with a length of l = 300 m. Additionally, the absolute roughness of the boundary, the diameter of the circular tube, the continuous loss over the whole length and the kinematic viscosity of the real fluid are given. Longitudinal section of a steel tube Given l = 300 m k = 1 mm d = 1.00 m hLoss, continuous = 0.50 m ν = 1.3 * 10-6 m2 /s For a similar...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT