Homework Statement
Exhaust gas expands through a nozzle whose isentropic efficiency is 88%. The inlet pressure and temperature are 1.6 bar and 400c respectively. At outlet the pressure has fallen to an ambient level of 1.013 bar. Given that the inlet velocity is negligible, and Cp and...
Hi
Here is the question.
Suppose someone build a thin spherical shield just above the Earth's atmosphere, and it would absorb all the radiation passing through from the sun. What would the average temperature of the Earth's surface be? (Assuming the avg temperature of the Earth is initially 300K)
we know that $\Delta U$ $=$ $\Delta K_{cm}$ $+$ $\Delta I$
where $\Delta K_{cm}$ is the kinetic energy from cm frame of refrence and the other part is the change in change in potential energy due to various conservative forces.
also by first law of thermodynamics $\Delta U$ $=$ $W_{ext} + Q$...
Does the internal energy always depend only on temperature in an ideal gas? Would the equation U=\frac{3}{2}nRT tell us that? are there any other equations?
I'm also confused with the area within a cyclic curve on a PV graph. Does the area within the curve represent the work done ON the...
I have this reaction:
CH4+4(O2+3.76) --> CO2+2H2O+2O2+15.04N2
Through other calculations and given information I have found that the mass flow rate of the air (the O2+3.76N2) is 25kg/s and the mass flow rate of the fuel is .87 kg/s. I am having the hardest time finding, using these mass...
Homework Statement
Consider fuel cell using methane as fuel. Reaction is
CH^4 + 2O_2 -> 2H2O+CO_2
Assume room temperature and atmospheric temperature
Determine values of delta H (Helmholtz) and delta G (Gibbs) for this reaction for one mole of methane.
Question instructed the use of...
Hoping someone can help me here quickly. Trying to get this one question.
a perfect gas is compressed adiabatically from 100 kPa and 17C to a final pressure of 500 kPa and final temp of 77C. The work done during the compression is 45 kJ/kg. Calculate the values of gamma, Cv, R and the...
I think I may have posted this in the wrong forum earlier :\
Homework Statement
An insulated and initially empty 0.7m^3 tank is connected by a valve to a line flowing air at 50degreesC and 200kPa. The valve is opened until the tank is filled, and then the valve is closed. The insulation is...
Homework Statement
An insulated and initially empty 0.7m^3 tank is connected by a valve to a line flowing air at 50degreesC and 200kPa. The valve is opened until the tank is filled, and then the valve is closed. The insulation is then removed from the tank, and a 20degreeC heat sink cools the...
Homework Statement
See Attachment
The Attempt at a Solution
Well to start off I know the gas is monatomic
I can find the work done by finding the area under each curve/line:
W_{AB} = p_0(2v_0-v_0) = p_0v_0
W_{CD} = (p_0/32)(8v_0-16v_0) = \frac{-p_0v_0}{4}
I can't think...
An Ideal monatomic gas at initial temperature T_0 (in Kelvins) expands from initial volume V_0 to volume 2V_0 by each of the 5 processes indicated in the T-V diagram. In which process is the expansion a.)isothermal, b.) isobaric or c.)adiabatic? Explain your answers.
d.) In which process...
Homework Statement
Specify that the finite reservoirs of a Carnot cycle start at initial temperatures T_h and T_c. Acknowledge the consequence of the finiteness of the reservoirs: the hot reservoir will drop in temperature and the cold reservoir will increase in temperature. The two...
Consider a 300 kJ/min refrigeration system that operates on an ideal vapor-compression cycle with refrigerant-134a as the working fluid. The refrigerant enters the compressor as saturated vapor at 140 kPa and is compressed to 800 kPa. Determine the (a) quality of the refrigerant at the end of...
Homework Statement
Rigid tank volume .5m^3 initially evacuated. Tiny hole develops, air seeps in @ 1 bar and 21 degrees C. Pressure in tank reaches 1 bar, slow leak so temp remains 21 deg C inside tank. What's amount of heat transfer?
Homework Equations
Q=T[S(2)-S(1)]
Pv=nRT
The...
Well, it's hard to me at least :frown:
http://img169.imageshack.us/img169/206/questionzg0.png
We are using Schroeders book and this problem was given to us from I assume the book by Reif. We haven't seem to have gotten far enough along in Schroeders book to have gone over this though.
I can...
Hey guys, I have been having a really hard time trying to figure out this question. It seems like everything I do, I can not get resonable answers. If you can help me, that would be great.
Problem: A 500-L tank stores 100kg of nitrogen gas at 150 degrees K. To design the tank, the pressure...
I have question (probably figured that). I have an open system with mass flow rate going into one inlet and going through two outlets. I have all the terms for the two outlets (mass flow, velocity, area, temp, pressure). However for the inlet I'm missing the Velocity and Area.
In solving for...
Hi all.
I've heard from students that Thermodynamics and Fluids are really tough classes. I've taken all the physics and the calculus with no problems. What do you guys think about those classes?
Hi,
I'm stuck. Can someone help me out?
Problem:
The properties of a certain fluid are related as follows:
u=196+0.718t
pv=0.287(t+273)
(a)where 'u' is the specific internal energy(Kj kg), t is in degress Celsius, p is pressure(Kn/m2) and v is specific volume (m3 kg).For this...
Okay, I need some help understanding some of the Thermo principles and I found this forum. I hope someone can help.
I'm working on Energy Analysis of a closed system. Conservation of energy principle and all that. deltaU = Q-W. Every time I think I know what should be considered work and...
I need a kick start for the following question. We're studying open/closed systems at the moment.
"450kg of ice at -18 degrees C is to be removed from a freezer using a jet of steam. How much dry steam at 100 degrees C is required if the final temp of the effluent is 5 degrees C?"
This is...
I am trying to make the connection from statistical mechanics to thermodynamics for the isothermal isobaric ensemble. Partition function = (sum of)exp(-BEj-gamma*Vj).
I have followed T.L. Hill [Statistical Mechanics, p. 67] but can not understand how he justifies dE=(sum of)EdP, rather than...
unit of work and unit of heat
When we study dynamics,the unit of work is in joules which is the energy transferred to a mass which in turn is the product of force and the distance along which the force is applied
When we study thermodynamics, the unit of work is again in joules.
How...
2-48) The 60-W fan of a central heating system is to circulate air through the ducts. The analysis of the flow shows that the fan needs to raise the pressure of air by 50Pa to maintain flow. The fan is located in a horizontal flow section where the diameter is 30cm at both inlet and outlet...
Im having trouble finding the reasoning here. Work done by the system is called positive?
For example, a gas pushing up on a piston and causing the piston to rise.
Well, it seems to me that as the gas pushes up on the piston, the gas does work on the piston, so the gas should LOOSE...
Imagine two infinitely large air tanks connected by a long, straight pipe. Tank A is at a higher pressure than tank B, so air is flowing from one to the other. For the sake of argument, we will say there is no heat flux or work into or out of the pipe.
Now we put a perfectly insulated...
hello the problem is as stated:
a cylinder containing n moles of an ideal gas undergoes an adiabatic process. using W=-\int Pdv and using the condition PV^\gamma=constant, show that the work done is:
W=(\frac{1}{\gamma - 1}(PfVf - PiVi) where Pf is final pressure, Pi is initial pressure...
I...
Hello; I'm having some difficulties with a thermo question of mine.
at low density water vapor conforms well to the ideal gas equation provided the temp is higher than about 320K, but the heat capacity is a function of temperature. The following formula gives the specific heat capacity at...
There are a couple of questions on my practice exam I am stuck on. If you could point me in the right direction I'd appreciate it.
1. A gas is described by the equation PV= RT+aT^2 where a is some gas specific constant. Find (dU/dV)@constant T
And provide an expression for the...
OK, I have a piston-cylinder with water.
V = 50L = 0.05 m^3
T = 25 C
P = 300 kPa
m = 49.85 kg
specific volume @ 25 C = 0.001003 m^3/kg
The water is heated to vaporization with pressure held constant. I need to determine the final temperature and the enthalpy change.
I know what the...
a 2.00 mol sample of helium gas at 300K and 0.400atm pressure is compressed isothermally to 1.20atm
Find the volume of the gas, work done on the gas and the energy transferred by heat
just wondering how to approach this question, and what formulae i hould use where?
hi guys, i have the following question to answer:
a 40g copper calorimeter contains 200g of water at 20 degrees celsius, it asks how much stam must be condensed in order to achieve a final temperature of 50 degrees celsius.
I was just wondering what formula to use?, and do i need to know the...
hi guys, i have a thermodynamics question.
a 2.50 kg iron object is initially at 650 degrees celsius and dropped into a bucket containing 20kg of water at 25 degrees celsius, what is the final temperature?
As always it just a matter of applying the formula, but i don't seem to be applying...
Hello.
I have a thermodynamics exam tomorrow. This is a past exam question and I'm not doing very well with it. If anyone has any ideas please help!
A charge enters a spark ignition engine at 330K and 1 bar, and is isentropically compressed through a ratio of 7:1. Estimate the temp and...
Q. The air in a 6m x 5m x 4m hospital room is to be completed replaced by conditioned air every 20 min. If the average air velocity in the circular air duct leading to the room is not to exceed 5 m/s, determine the minimum diameter of the duct.
We can figure out the volume of the room...
Having problems with a thermo. cycle!
OK, so in the problem A->B is isobaric, B->C is adiabatic, C->D is isothermal, D->A is isochoric.
Pa = 2atm, Va = 2 m^3, n = 1mole, Vb = 1/2Va, Pa = 2Pd (That is all the information that is given.)
I always end up with the temperatures of B and C...
Hello,
If anybody could answer this question for me that would be great. I have been wondering about it all morning. In the Diesel cycle for heat engines, on the second stage of operation, the Volume increases while pressure stays the same. I understand how this can be accomplished by raising...
Hello,
If anybody could answer this question for me that would be great. I have been wondering about it all morning. In the Diesel cycle for heat engines, on the second stage of operation, the Volume increases while pressure stays the same. I understand how this can be accomplished by raising...
Hello all,
I am a little confused on this problem and want to be clear on it.
Given: Water is boiled at 1 atm pressure in a 20-cm i.d. pan. Water level in pan drops by 10cm in 30 min, determine the rate of heat transfer to the pan.
Now correct me if I'm wrong but water boils at 100...
A startled armadillo leaps upwards so that it rises to .56 m in a time .21 s.
Note: I use a web-submitting thing for my answers. So it tells me what is right and wrong.
A: What was the armadillo's initial speed when it left the ground?
3.70 m/s - this part is correct.
B: What is its...
How would you guys explain "qualitatively" the theorem of maximum work based on this diagram. (that is when a process is reversible and no entropy change in the universe)
I don't really know what the graph means. Let's say it's an ideal gas, (S=LnU+...). The diagram divides the plane in two...
For a device operating at steady state, is the change in entropy (S2-S1) equal to 0?
If it is equal to 0, then why doesn't the s2-s1=s(degree)(T2)-s(degree)(T1) - R ln (p2/p1) equation yield 0?
I'm confused on this point...
Any help greatly appreciated!
Need urgent help with thermo problems...
Here are my problems:
1) A rigid tank contains 5 lb of a two-phase liquid vapor mixture of water, initially at 260 F with a quality of .6 Heat transfer to the contents of the tank occurs until the temperature is 320 F. Determine the initial mass of...
Here's my problem:
Measured data for pressure versus volume during the expansion of gases within the cylinder of an internal combustion engine are given in the table below.
Data Point p (bar) V (cubic cm)
1 15...
An ideal gas initially at Pi, Vi, and Ti is taken through a cycle as in Figure P20.38 (n = 2.6).
Figure P20.38 (see attachment)
(a) Find the net work done on the gas per cycle.
PiVi
(b) What is the net energy added by heat to the system per cycle?
PiVi
(c) Obtain a numerical value...
A single 50g ice cube is dropped into a thermally insulated container holding 200g of water. The water is initially at 25oC and the ice is initially at -15oC.
**********
a) What is the final temperature of the system after is has come to thermal equilibrium ?
b) Now let's drop a second...
An aluminum calorimeter of mass 100 g contains 250 g of water. The calorimeter and water are in thermal equilibrium at 12.0°C. Two metallic blocks are placed into the water. One is a 40.0 g piece of copper at 80.0°C; the other block has a mass of 13.0 g and is originally at a temperature of...
A 1.0 g lead bullet at 33°C is fired at a speed of 250 m/s into a large block of ice at 0°C, in which it becomes embedded. What quantity of ice melts?
Heres what I have:
From ΔQ = mcΔT,
mA = dQ/[c(dT)]
And from ΔQA = -ΔQB
...
Further cogitations are in...
An unknown number of Helium atoms are in a 1 liter container at an unknown temperature. The gas is made to expand such that it's final volume is 4 liters and pressure rises 'in direct proportion to its volume'.
1. does 'in direct proportion to it volume' mean Pf = Pi * Vf/Vi or should there...