The amount of time people spend exercising in a given week follows a normal distribution with a mean of 3.8 hours per week and a standard deviation of 0.8 hours per week.

i) Which of the following shows the shaded probability that a person picked at random exercises less than 2 hours per week?

a.    b.   


ii) What is the probability that a person picked at random exercises less than 2 hours per week? (round to 4 decimal places)    

iii) Which of the following shows the shaded probability that a person picked at random exercises between 2 and 4 hours per week?

a.     b.    


iv) What is the probability that a person picked at random exercises between 2 and 4 hours per week? (round to 4 decimal places)

Reagent A undergoes an essentially irreversible isomerization reaction that obeys first-order kinetics. A --> B Both A and B are liquids at room temperature and both have extremely high boiling points. Pure A at 20^oC is fed into the reactor.

Data:

Reaction rate expression: r = k.C_A

Rate constant at 163 °C = 0.8 hr^-1

Activation energy = 30,000 cal/gmole

Heat of reaction = — 83 cal/g

Molecular weight = 250

C_pA=C_pB=0.5 cal/g.^oC p_A=p_B= 0.9 g/cm3

a) Determine the CSTR volume and heat transfer rate necessary to produce 150 kg/h of B with 60% conversion of A if the reactor is operated at 160^oC.

b) Calculate the CSTR volume and temperature to achieve the same conversion if the reactor is operated adiabatically

In the boiler of a power plant are tubes through which water flows as it is brought from 0.8 MPa, 150°C to 240°C at essentially constant pressure. The total mass flow rate of the water is 100 kg/s. Combustion gases passing over the tubes cool from 1067 to 277 °C at essentially constant pressure. The combustion gases can be modeled as air as an ideal gas. There is no significant heat transfer from the boiler to its surroundings. Assuming steady state and neglecting kinetic and potential energy effects, determine

Let T₀ = 25°C, p₀ = 1 atm.
Round your answers to 3 significant digits.

This is problem 8-7 from El-Wakil’s Powerplant Technology book -- air at 14.696 psia, 40 degF, and with 65 percent relative humidity enters the compressor of a gas turbine cycle. The compressor and turbine have the same pressure ratio of 6 and polytropic efficiencies of 0.8 and 0.9, respectively. Water at 60 degF is injected into the compressor exit air, saturating it. Calculate (a) the air temperature after water injection (b) the percent increase in mass flow rate due to water injection, (c) the compressor work in Btus per pound mass of original air, and (d) the compressor work if water is injected during the compression process to the same temperature as (a), in Btus per pound mass of original air. Use a constant c_p = 0.24 Btu/lb_mdegRankine.

A four-cylinder four-stroke engine is operating at a bmep of 2 bar. The pressure at inlet valve closure is 0.37 bar, and the fmep is 0.8 bar. Assuming that the engine gross indicated efficiency is unchanged, verify that disablement of the valves on two cylinders would reduce the fuel consumption by about 13 per cent compared with about an 8 per cent fuel saving if the fuel was not supplied to two cylinders. Assume that the gross imep is proportional to the pressure at inlet valve closure, and that the gross indicated efficiency is constant. State any additional assumptions that you make. By means of p–V diagram sketches, explain why disabling only the inlet or exhaust valves would have a fuel economy benefit comparable to fuel disablement to two cylinders.