1. Engine oil (cp = 2100 J/kg-°C) is to be heated from 20 °C to 60 °C at a rate of 0.3 kg/s in a 2-cmdiameter thin-walled copper tube by condensing steam outside at a temperature of 130 °C (hfg = 2174 kJ/kg).
a. For an overall heat transfer coefficient of 650 W/m2 -°C, determine the rate of heat transfer and the length of tube required to achieve it. Determine also the rate of steam condensation, in kgsteam/sec. (Ans: 25.2 kW; 7.0 m)
b. What would the tube length have to be if we wanted to heat the oil to 100 °C in the same 2-cm diameter tube and at the same flow rate? How about heating to 120 °C?
In: Mechanical Engineering
list the material selection criteria for a newly developed part?
In: Mechanical Engineering
In a controlled experiment, it takes 3700 J to melt the amount of metal that is in a weld bead with a cross-sectional area of 6.0 mm2 that is 150.0 mm long. (a) Using Table 28.2, what is the most likely metal? (b) If the heat transfer factor is 0.85 and the melting factor is 0.55 for a welding process, how much heat must be generated at the welding source to accomplish the weld?
In: Mechanical Engineering
Q2. Two kilograms of air within a piston-cylinder configuration execute a Carnot power cycle between temperatures 750 K and 300 K. The isothermal expansion is associated with a release of 60 kJ of heat into the surroundings. The volume after expansion has occurred isothermally is 0.4 m3 . Assuming air behaves as an ideal gas, calculate: (i) thermal efficiency for the cycle (ii) pressure and volume at the beginning of the isothermal expansion, in kPa and m3 , respectively. (iii) the work and heat transfer for each of the four processes, in kJ.
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write a conclusion and recommendations about
Vibrational and Acoustical analysis of a vacuum brush? how to
improve it ?
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Engine oil (raffinate) with a flow rate of 5 kg/s will be cooled from 60°C to 40°C by sea water at 20°C in a double-pipe heat exchanger. The water flows through the inner tube, whose outlet is heated to 30°C. The inner tube outside and inside diameters are do = 1.315 in. (= 0.0334 m) and di = 1.049 in. (= 0.02664 m), respectively. For the annulus, Do = 4.5 in. (= 0.1143 m) and Di = 4.206 in. (= 0.10226 m). The length of the hairpin is fixed at 3 m. The wall temperature is 35°C. The number of the tubes in the annulus is 3. The thermal conductivity of the tube wall is 43 W/m ? K. Calculate: a. The heat transfer coefficient in the annulus b. The overall heat transfer coefficient c. The pressure drop in the annulus and inner tube (only straight sections will be considered) d. What is your decision as an engineer? How can you improve the design?
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Describe the difference between spectral and total blackbody emissive power.
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The clausius statement of the second law denies the possiblity of transferring energy by heat from a cooler to a hotter body. I think it true because the statement says that " no process is possible in which the sole result of it would be the transfer of heat from a cooler to a hotter body" However, the textboox solution says otherwise. can somebody explain
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Thermodynamics
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1. Correct Answer: 8.0087 ± 0.1% Steam at 1 MPa, 593.2oC, expands in a turbine to 0.01 MPa. If the process is isentropic, find the specific entropy (kJ/kg-K) at the exit of the turbine. Note: Give your answer to four decimal places. |
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2. Correct Answer: 301.43 ± 0.08% |
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Initially, an insulated rigid tank contains 19.37 kg of water at 27.04oC and 101 kPa. The tank also contains a 4.42 kg copper block at 87.13oC. Assume constant specific heats where Cwater = 4.179 kJ/kg-K and CCu = 0.385 kJ/kg-K. Determine the final equilibrium temperature (K). Note: Give your answer to two decimal places. |
In: Mechanical Engineering
Air at 40 degrees C is humidified by flowing over a 1-m-long container filled with water. The surface area of container is 0.5m^2.The interfacial temperature is 20 degrees C. If the initial humidity of the air is 0% and its velocity is 0.5 m/s, calculate the mass flow rate of vapor evaporated.
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Compute the maximum thrust density, power density and specific impulse for a 3-grided ion engine, having an acceleration voltage of 2000 V, and a voltage difference of 2500 V and a gap of 1.5 mm between the plasma and the first acceleration screens. Compute the propulsive parameters for the following propellants: xenon, argon, and molecular hydrogen.
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Discuss the bene?ts and drawbacks of bond-then-form versus form-then-bond approaches. In your discussion, include discussion of processes which can use secondary support material and those which do not.
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Thermodynamics
Air at 3.5 MPa and 500°C is expanded in an adiabatic gas turbine to 0.2 MPa. Assume that the process is reversible. Changes in KE and PE may be neglected and the average temperature of the gases is 550 K.
(a) Create a schematic representation of the equipment. (b) Represent the process on a T-s diagram. (c) Determine the polytropic exponent. (d) Determine the change in entropy for this expansion process
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A rocket motor burns LH2 and LOX. The combustion chamber pressure and temperature are 25 atmospheres and 3517 K, respectively. The area of the nozzle throat is 0.1 m^2. The nozzle exit area is designed so that the exit pressure equals the ambient pressure at 30 km altitude. For the combustion gases, assume gamma is 1.22 and the molecular weight is 16. At an altitude of 30 km, where the local atmospheric pressure is 1186 Pa, calculate (a) the specific impulse, (b) the thrust, (c) the area of the exit, and (d) the exit Mach number
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The measurement of heat loss through egg shell and the thermal energy contained in a boiled egg.
Deriving the convection heat transfer coefficient between the egg shell and ambient air might be the key in solving this question.
How can I determine this through experimentation?
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