Chapter 9.5, Problem 88P

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.

For the flows in Examples 11.1 and 11.2, calculate the magnitudes of the Δ V2 / 2 terms omitted in B.E., and compare these with the magnitude of the ℱ terms.

Calculate ℛP.M. in Example 11.2.

Question 22: The superheated steam powers a steam turbine for the production of electrical power. The steam expands in the turbine and at an intermediate expansion pressure (0.1 MPa) a fraction is extracted for a regeneration process in a surface regenerator. The turbine has an efficiency of 90%. It is requested: Define the Power Plant Schematic Analyze the steam power system considering the steam generator system in the attached figure Determine the electrical power generated and the thermal efficiency of the plant Perform an analysis on the power generated and thermal efficiency considering a variation in the steam fractions removed for regeneration ##Data: The steam generator uses biomass from coconut shells to produce 4.5 tons/h of superheated steam; The feedwater returns to the condenser at a temperature of 45°C (point A); Monitoring of the operating conditions in the steam generator indicates that the products of combustion leave the system (point B) at a temperature of 500°C;…

This is an old practice exam question.

Steam 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 dot

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.K

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.K