Refrigerant 134a at p1 = 30
lbf/in2, T1 =
40oF enters a compressor operating at steady state with
a mass flow rate of 400 lb/h and exits as saturated vapor at
p2 = 160 lbf/in2. Heat
transfer occurs from the compressor to its surroundings, which are
at T0 = 40oF. Changes in kinetic and
potential energy can be ignored. The power input to the compressor
is 4 hp.
Determine the heat transfer rate for the compressor, in Btu/hr, and
the entropy production rate for the compressor, in
Btu/hr·oR.
In: Mechanical Engineering
Answer the following
a)State any advantages or disadvantages you see in measuring vibrations with a strain gauge as opposed to the other methods we have used. What effect would changes in temperature have on strain gauge readings and is it possible to eliminate this effect? It was briefly mentioned that different bridge configurations can eliminate temperature effects, but what are those effects and how does that work?
b)In order to get the most accurate readings, should a strain gauge have a high stiffness or a low stiffness? Explain.
In: Mechanical Engineering
Potential GDP is 24.3 mln and actual GDP is 24.1 mln. Price level is 98. 1. What phase of business cycle takes place in the short run (Expansion or Recession)? 2. Draw the graph for this short run economic situation and 3. Describe the problems (changes in macroeconomic variables: GDP, Unemployment and Price level) 4. Explain the appropriate monetary policy to bring the economy back to its long run Macroeconomic equilibrium. What tools would CB will use? 5. How will macroeconomic variables change?
In: Economics
Consider the following reaction:
PCl5 (g)⇄ PCl3 (g) + Cl2 (g) ΔH = 87.9 kJ/reaction
For each of the following changes, indicate whether the reaction will proceed towards products, towards reactants, or have no net reaction to reestablish equilibrium.
a. ___________ Temperature is increased
b. ___________ The pressure is increased by decreasing the volume.
c. ___________ The pressure is decreased by removing some PCl 5 (g)
d. ___________ The pressure is increased by adding N2(g)
e. ___________ Cl2(g) is removed
f. ____________ The temperature is increased and the volume of the vessel is increased simultaneously.
In: Chemistry
Humid air is enclosed in a 5.00-liter flask at 40.0°C. The flask is slowly cooled. When the temperature reaches 20.0°C, drops of moisture become visible on the flask wall. Although the pressure in the flask changes when the temperature drops, it remains close enough to 1 atm for the psychrometric chart to provide a close representation of the behavior of the system throughout the process. Use a psychometric chart to determine the relative humidity, absolute humidity, and wet-bulb temperature of the air at 40.0°C. And please explain how you found it!
In: Chemistry
Air is compressed from an initial state of 1 bar and 298.15K to a final state of 5 bar and 295.15K by three different mechanically reversible processes in a closed system: • Heating at constant volume followed by cooling at constant pressure • Isothermal compression • Adiabatic compression followed by cooling at constant volume Show these processes in a PV diagram and calculate the work required, heat transferred, and the changes in internal energy and enthalpy of the air for each process. For air, Cv ig = 20.785 and Cp ig = 29.100 J/mol/K
In: Mechanical Engineering
Consider a galvanic cell based on the following line notation at 295 K:
Fe|Fe3+||Cu2+|Cu
where the standard cell potential is 0.38 V. What will the following changes do to the potential of the cell?
a) Add water to the anode portion of the cell
increase potential
decrease potential
no change in potential
b) Add equal amounts of water to both the anode and cathode portions of the cell
increase potential
decrease potential
no change in potential
c) Increase the mass of the Cu
increase potential
decrease potential
no change in potential
In: Chemistry
When an iron bar of mass m is dropped through a
height difference Δh, its potential energy changes by the amount
mgΔh, where g is the acceleration of gravity, equal to 9.81 m
s-2. Suppose that when the bar hits the ground, all that
energy is converted to heat, increasing the temperature of the bar.
If the specific heat capacity of the material in the bar is
0.444 J K-1 g-1, calculate
the height from which the bar must be dropped to increase the
temperature of the bar by 2.24 °C.
In: Chemistry
A sample of 4.63 mol of xenon is confined at low pressure in a volume at a temperature of 51 °C. Describe quantitatively the effects of each of the following changes on the pressure, the average kinetic energy per molecule in the gas, and the root-mean-square speed.
(a) The temperature is decreased to -66
°C.
(b) The volume is halved.
(c) The amount of xenon is increased to
6.02 mol.
Give each answer as a decimal factor of the form: new value = factor old value. A factor of 1 means no change.
| Change | P | KEavg | urms |
|---|---|---|---|
| (a) | |||
| (b) | |||
| (c) |
In: Chemistry
Transferred-in costs, FIFO method (continuation of 17-33). Refer to the information in Problem 17-33. Suppose that Larsen Company uses the FIFO method instead of the weighted-average method in all of its departments. The only changes to Problem 17-33 under the FIFO method are that total transferred-in costs of beginning work in process on October 1 are $2,881,875 (instead of $2,932,500) and that total transferred-in costs added during October are $7,735,250 (instead of $7,717,500). Using the FIFO process-costing method, do Problem 17-33.
In: Statistics and Probability