HEAT+MASS TRANSFER:FUND.+APPL.
6th Edition
ISBN: 9780073398198
Author: CENGEL
Publisher: RENT MCG
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Chapter 8, Problem 73P
Air at
(1atm) enters into a 5-mm-diameter and 10-cm-long circular tube at an average velocity of 5 m/s. The tube wall is maintained at a constant surface temperature of
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Recall that the CWH equation involves two important assumptions. Let us investigate how these
assumptions affect the accuracy of state trajectories under the control inputs optimized in (a) and (b).
(c.1): Discuss the assumptions about the chief and deputy orbits that are necessary for deriving CWH.
PROBLEM 2.50
1.8 m
The concrete post (E-25 GPa and a
=
9.9 x 10°/°C) is reinforced with six
steel bars, each of 22-mm diameter (E, = 200 GPa and a, = 11.7 x 10°/°C).
Determine the normal stresses induced in the steel and in the concrete by a
temperature rise of 35°C.
6c
"
0.391 MPa
240 mm
240 mm
6₁ =
-9.47 MPa
For some viscoelastic polymers that are subjected to stress relaxation tests, the stress decays with
time according to
a(t) = a(0) exp(-4)
(15.10)
where σ(t) and o(0) represent the time-dependent and initial (i.e., time = 0) stresses, respectively, and t and T denote
elapsed time and the relaxation time, respectively; T is a time-independent constant characteristic of the material. A
specimen of a viscoelastic polymer whose stress relaxation obeys Equation 15.10 was suddenly pulled in tension to
a measured strain of 0.5; the stress necessary to maintain this constant strain was measured as a function of time.
Determine E (10) for this material if the initial stress level was 3.5 MPa (500 psi), which dropped to 0.5 MPa (70
psi) after 30 s.
Chapter 8 Solutions
HEAT+MASS TRANSFER:FUND.+APPL.
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- This is an old practice exam question.arrow_forwardSteam enters the high-pressure turbine of a steam power plant that operates on the ideal reheat Rankine cycle at 700 psia and 900°F and leaves as saturated vapor. Steam is then reheated to 800°F before it expands to a pressure of 1 psia. Heat is transferred to the steam in the boiler at a rate of 6 × 104 Btu/s. Steam is cooled in the condenser by the cooling water from a nearby river, which enters the condenser at 45°F. Use steam tables. NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part. Determine the pressure at which reheating takes place. Use steam tables. Find: The reheat pressure is psia. (P4)Find thermal efficiencyFind m dotarrow_forwardAir at T1 = 24°C, p1 = 1 bar, 50% relative humidity enters an insulated chamber operating at steady state with a mass flow rate of 3 kg/min and mixes with a saturated moist air stream entering at T2 = 7°C, p2 = 1 bar. A single mixed stream exits at T3 = 17°C, p3 = 1 bar. Neglect kinetic and potential energy effects Determine mass flow rate of the moist air entering at state 2, in kg/min Determine the relative humidity of the exiting stream. Determine the rate of entropy production, in kJ/min.Karrow_forward
- Air at T1 = 24°C, p1 = 1 bar, 50% relative humidity enters an insulated chamber operating at steady state with a mass flow rate of 3 kg/min and mixes with a saturated moist air stream entering at T2 = 7°C, p2 = 1 bar. A single mixed stream exits at T3 = 17°C, p3 = 1 bar. Neglect kinetic and potential energy effects Determine mass flow rate of the moist air entering at state 2, in kg/min Determine the relative humidity of the exiting stream. Determine the rate of entropy production, in kJ/min.Karrow_forwardAir at T1 = 24°C, p1 = 1 bar, 50% relative humidity enters an insulated chamber operating at steady state with a mass flow rate of 3 kg/min and mixes with a saturated moist air stream entering at T2 = 7°C, p2 = 1 bar. A single mixed stream exits at T3 = 17°C, p3 = 1 bar. Neglect kinetic and potential energy effects (a) Determine mass flow rate of the moist air entering at state 2, in kg/min (b) Determine the relative humidity of the exiting stream. (c) Determine the rate of entropy production, in kJ/min.Karrow_forwardA simple ideal Brayton cycle operates with air with minimum and maximum temperatures of 27°C and 727°C. It is designed so that the maximum cycle pressure is 2000 kPa and the minimum cycle pressure is 100 kPa. The isentropic efficiencies of the turbine and compressor are 91% and 80%, respectively, and there is a 50 kPa pressure drop across the combustion chamber. Determine the net work produced per unit mass of air each time this cycle is executed and the cycle’s thermal efficiency. Use constant specific heats at room temperature. The properties of air at room temperature are cp = 1.005 kJ/kg·K and k = 1.4. The fluid flow through the cycle is in a clockwise direction from point 1 to 4. Heat Q sub in is given to a component between points 2 and 3 of the cycle. Heat Q sub out is given out by a component between points 1 and 4. An arrow from the turbine labeled as W sub net points to the right. The net work produced per unit mass of air is kJ/kg. The thermal efficiency is %.arrow_forward
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