Thermo Definition and 267 Threads

Homework Statement A young engineer notices in her plant that 1-kg blocks of brick are routinely removed from a 800 ıC oven and are let to cool in air at 25 ıC. Conscious about cost-cutting and efficiency, she wonders whether some work could be recovered from this process. Calculate the...

Hey, guys. I am currently in a Thermo I class and have ran into a problem that has me completely stumped. I have worked in numerous different ways and anything I come up with doesn't seem to make since or be realistic. Here's the question: Two rigid vessels are connected by a small valve and...

I attached the HW assignment. Its question number 2. I choose a control volume including the cooling stream from the lake and the fluid being condensed. I assumed with this CV that the heat generated was 0 and that the net Work was 0. Using these assumptions I solved for the mass...

Homework Statement Show that in a reversible adiabatic process, for 1 mole of ideal gas P1V1γ=P2V2γ Where, γ=CP/CVHomework Equations Listed above.The Attempt at a Solution Frankly, I don't really understand what I'm being asked to do.

Hi, I have my exam in a couple of weeks. And I get the jist of it. However their is one question that I am completely stuck on. Any help would be appreciated. Looking over a last years practise text for exam and I am having trouble with this. Cu(s) → Cu+(aq) + e ΔH = 602 kJ mol-1 Cu(s)...

Is it strictly true that an engine will be more efficient if operating in a hotter environment... e.g. your car is more efficient in the summer than the winter? Just going through thermo 1, not a HW question, but it just seems to be true to me because the simple Newton's law of cooling says...

Homework Statement A cube of Al (.1m x .1m x .1m with mass=.27kg) is placed on a large thermal mass maintained at constant 40 C (313 K).The cube is separated from the thermal mass by a .01m thick glass plate (.1m x .1m). If the Al block is initially at 10 C, how long does it take to reach a...

Homework Statement Consider a rod that is 1m long whose radius changes from 1cm at one end to 4cm at the other end in a uniform fashion. Assume that the end with r=1cm i kept at 0°C and that the end with r=4cm is kept at 100° C. Determine the temperature profile along the rod. One can assume...

Homework Statement 1 mole of ideal gas initially at 294 K is compressed adiabatically and reversibly from 0.83 atm to 10.0 atm. Calculate the initial and …final volumes, the final temperature, \DeltaU; \DeltaH; Q; and W: Assume that Cv = (5/2)R Given: n = 1 mol T1 = 294 K P1 =...

does this look right? for the quasistatic case you can use thermodynamics to find the temperature at any time, for the other case you have to use dU=dW and so on since its not quasistatic

Homework Statement Air is expanded in a piston-cylinder arrangement at a constant P of 200kPa from a volume of 0.1 m3 to a volume of 0.3m3. Then the temperature is held constant during an expansion to a volume of 0.5m3. Predict the total work done in the air. Homework Equations W = ∫PdV...

Homework Statement My question has to do with heating water to a superheated state inside a constant volume vessel. Given: A pressure vessel with a total volume of 36.77ft^3, is filled with 5 gal of water and heated from room temp. to a final temp. of 1100°F. Obvisouly the initial pressure...

My question has to do with heating water to a superheated state inside a constant volume vessel. Given: A pressure vessel with a total volume of 36.77ft^3, is filled with 5 gal of water and heated from room temp. to a final temp. of 1100°F. Obvisouly the initial pressure is atmospheric and...

If : The total energy of a falling rock = G.P.E. (mass x gravity x height) + K.E. (0.5 x mass velocity^2) But if a rock reaches terminal velocity (i.e velocity remains the same) but height keep decreasing, then surely Kinetic energy is remaining constant and Gravitational potential energy is...

Homework Statement A duct of length 5 m at 38 Degrees inclination to horizon with a cross section dimensions of 0.3 m X 0.4 m is carrying 2 kg/s of a heavy gas at 10C and 1.2 bars and delivers the gas flow at 50C at the end of the duct to a horizontal pipe section. i) Calculate changes to...

Homework Statement Consider a sample containing 2.35 mol of an ideal diatomic gas. (a) Assuming the molecules rotate but do not vibrate, find the total heat capacity of the sample at constant volume. nCv.= (b) Assuming the molecules rotate but do not vibrate, find the total heat...

Hello. I need help with some thermo basics. I can't understand the concept of constant volume compression/expansion. Please help me understand how it occurs. Also, I am not clear on how pressure is an intensive property. To my understanding it IS a quantity dependent on system size (eg...

Hi Can anyone direct me to the correct Thermo formula to solve the following problem. What is the time for water to heat up from 25'c to 75'c when placed in a 1000'c oven? Tnx Ilan

O_o. I know this is a really stupid question, but how the heck did the Q - W get to the other side of the equation? Shouldn't it be W - Q? I'm going to feel really stupid when I hear the answer, I'm sure, and I'm already done with the class so it's ultimately irrelevant, but I'd love to know.

Disclosure: I am studying biochemistry so my thermodynamics education is lacking and I'm likely misinterpreting some of these concepts (that's why I'm here for help). I have always had trouble defining some properties as either intensive or extensive. I understand that extensive are...

Homework Statement 1.A gas increases in temperature from 40 C to 120 C while increasing in volume from 1 m3 to 1:3 m3. Find the nal pressure, if the initial pressure is atmospheric pressure. 2.Estimate the length of time it takes for a 0.1 m x 0.1 m x 0.1 m block of steel to cool from...

Homework Statement Show that processes involving rapid chemical reactions are irreversible by considering the combustion of a natural gas (e.g. methane) and air mixture in a rigid container. Homework Equations Q_{in}+W_{e,in}-W_{b}=\Delta U+\Delta KE+ \Delta PE The Attempt at a Solution I...

Hey, i have a Thermo exam tomorrow, and I've been working through the textbook examples and problems, and i was wondering if anyone here had some helpful problems for me to work out or any general hints or anything. Our textbook is the 7th edition of moran shaprio thermo and the exam is...

Homework Statement A three-step cycle is undergone by 3.8 mol of an ideal diatomic gas: (1) the temperature of the gas is increased from 210 K to 550 K at constant volume; (2) the gas is then isothermally expanded to its original pressure; (3) the gas is then contracted at constant...

Homework Statement A cube of copper of mass 4 kg and initial temperature of 110 oC is set to radiatively cool in an environment of 100 oC. (Note: copper has an emissivity of about 0.05. Also, neglect conduction and convection as cooling agents in this problem.) The surface area of the...

Hey everybody! I'm in my Junior year of undergraduate Mechanical Engineering and am trying to figure out what direction to focus my studies (mainly what industry to focus my pursuit for next job/internship)... Does anyone know of any fields/industries where an engineer can utilize...

Derive the fundamental equations of thermodynamics for an open system containing a onecomponent fluid in terms of the intensive internal energy U = U/N, the intensive Helmholtz free energy A, the intensive Gibbs free energy G, and the intensive enthalpy H. For each of the equations write the one...

I'm trying to calculate the final pressure. I was given initial and final temperatures as well as initial pressure, expansitivy and isothermal bulk modulus. I was also told the volume is constant. Since volume is constant I figured dV=0 so in the formula dV=VβdT - VKdP it reduces to...

Hey I was given this problem: The moles of components of a gas mixture are given. The mole fractions and the apparent molecular weight are to be determined. The given properties are: The molar masses of He, O2, N2, and H2O are 4.0, 32.0, 28.0 and 18.0 lbm/lbmol respectively and there...

"Measured heat capacities of solids and liquids are almost always at constant pressure, not constant volume. To see why, estimate the pressure needed to keep V fixed as T increases, as follows. a)First imagine slightly increasing the temp of a material at constant pressure. Write the change...

Homework Statement In my book it says, "only if the transformation is reversible can we use dS=\frac{\delta Q}{T}", but I don't know why? I think even if it's not reversible we also use \delta Q=TdS to solve the thermo problems, don't we? I'm looking forward to your ideas, thanks.

Thermo Efficiency question! Homework Statement Figure P22.53 represents n mol of an ideal monatomic gas being taken through a cycle that consists of two isothermal processes at temperatures 3Ti and Ti and two constant-volume processes. For each cycle, determine, in terms of n, R, and Ti ...

i heard that fluid dynamics and thermo dynamics are the hardest subjects in mechanical engineering and physics, can somebody elaborate on this issue ?

Hi everybody, I've got a thermodynamics exam coming in a few weeks. I couldn't sit the exam when I took the subject 12 months ago because of work commitments so I'm sitting a deferred exam this semester. Trouble is I have forgotten most of it, and having difficulty getting help from lecturers...

suppose I have a pressurized container filled halfway with water and the rest filled with a noncondensible gas. In one case, I would open a valve at the top and relieve only gas, and in the other case I would open a valve at the bottom and relieve only liquid. If I relieve an equal amount of...

Homework Statement This is really just a question that I can't seem to find a good solution for in my book. Basically I'm trying to understand for the first law of thermodynamics how you can derive the equation in term of P1 and P2. I don't understand how to go from PdV to (something)dP. This...

Link between Thermo and Special Rel? Ok, here's the situation: my friends and I were having a sleepover, and right before we slept, we started to talk about physics (lol... what nerds we are...). I began by saying, what if we achieve absolute zero. My friends said, we already achieved absolute...

I have setup the map of my curriculum until I will be graduating, and due to thermodynamics and dynamics only being taught once a year, if I do not take them this upcoming semester I will be in school an additional year. I am wondering if it is possible to take statics, dynamics, and...

I have a simple question that I cannot find a compelling answer for. If I expend (let's say) 100 kJ bending a steel bar into a right angle, where did the energy go? Some will obviously be expended as noise and heat. Will the rest be expended in the plastic deformation of the bar? No useful...

hi...i'm a mechanical student..this semester I'm taking thesis subject and i must find a topic about these two of my fav scope before this week..thermo fluid and in oil and gas industry...and i just want to know which one of these is better for me to concentrate on my thesis? but first, i search...

Hi all, first post so I hope this is ok to go here. It's not a homework question, just something in my book I don't get... I am looking through my thermodynamics textbook (Smith,Van Ness, and Abbot, Intro to Chemical Eng thermodynamics) and they give the eq (6.19): (\partialH/\partialP)T...

Homework Statement Two containers each contain 0.500 moles of N2 initially at 300. K. One container has a fixed volume, and the other container has a movable frictionless piston. If both containers are heated by 1000. J energy, calculate the final temperature of N2 for each container...

This is a statement in my book 'The heat capacity at constant pressure Cp is generally larger than that at constant volume Cv because at constant pressure, a part of heat added to the substance may be used in work of expanding whereas at constant volume all the added heat produces a rise in...

Question: The heat capacity of a bomb calorimeter was determined by burning 6.79 g of methane (energy of combustion = -802 kJ/mol CH4) in the bomb. The temperature changed by 10.8 degrees C. a. What is the heat capacity of the bomb? b. A 12.6 g sample of acetylene, C2H2, produced a...

Homework Statement The average coefficient of volume expansion for carbon tetrachloride is 5.81*10-4 (°C)-1. If a 49.0 gal steel container is filled completely with carbon tetrachloride when the temperature is 10.0°C, how much will spill over when the temperature rises to 27.0°C...

Hi all. I was perusing the grad course options for mechanical engineering at a local school when I noticed a course in statistical thermodynamics. I know the difference btw classical, chemical, and statistical thermodynamics, and that MEs generally learn classical. What are the ME...

Homework Statement 2 moles of an ideal gas, P1 = 10 atm V1 = 5L, are taken reversibly in a clockwise direction around a circular path given by (V-10)^2 + (P-10)^2 = 25. All I have left to solve for is the minimum temperature. Homework Equations PV = nRT The Attempt at a Solution...

Hello PF. I am an undergraduate in physics doing some work in a research lab at school and I need some help with a time-constant calorimetry experiment I am working on. I am attempting to compute the temperature as a function of time of a small sample of copper that I am heating. I am...

A friend has asked a question of me that has me wishing that my days of thermodynamics were not so long in the past. He and some colleagues have been making electrolytic cells for high production of hydrogen and oxygen from water. In demonstrating one to me he posed an experiment that on the...

Homework Statement A semi-conducting thermistor has a resistance that veries with temperature as follows: R(T)=R_0 exp[\frac{B}{T}] What are the SI units of the calibration constants B and R_0 This is just the intro chapter to my second thermodynamics course. Anyway, I'm not sure how to...