What is Thermodynamics: Definition and 1000 Discussions
Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, radiation, and physical properties of matter. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities, but may be explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a wide variety of topics in science and engineering, especially physical chemistry, biochemistry, chemical engineering and mechanical engineering, but also in other complex fields such as meteorology.
Historically, thermodynamics developed out of a desire to increase the efficiency of early steam engines, particularly through the work of French physicist Nicolas Léonard Sadi Carnot (1824) who believed that engine efficiency was the key that could help France win the Napoleonic Wars. Scots-Irish physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854 which stated, "Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency."
The initial application of thermodynamics to mechanical heat engines was quickly extended to the study of chemical compounds and chemical reactions. Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged. Statistical thermodynamics, or statistical mechanics, concerns itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented a purely mathematical approach in an axiomatic formulation, a description often referred to as geometrical thermodynamics.
Homework Statement
An insulated piston-cylinder device contains 5 L of saturated liquid water at a constant pressure of 175 kPa. Water is stirred by a paddle wheel while a current of 8 A flows for 45 min through a resistor placed in the water, If one-half of the liquid is evaporated during this...
I am graduate student from structural mechanics of solids and need to learn 1 course from fluids and thermal group which includes fluid mechanics or thermodynamics+heat transfer. I am unsure which one would be better to learn, especially which would be helpful in future for solid mechanics. Can...
Homework Statement
A train engine climbs a hill. The engine is 30% efficient. The train has a mass of 12000kg. The hill is 750m in height, with an incline of 20° form the horizontal. Friction exerts a force opposing motion of 8000N throughout the climb. Find w, Qin and Qout for the engine...
Is there a definition for "reversible process" that applies to mechanical systems (such as a block sliding down a frictionless inclined plane) that is distinct from the definition of "reversible process" in thermodynamics?
If we apply the thermodynamic definition of "reversible process" to...
Hello! I am a bit confused by the formula ##dU = TdS - PdV##. If I want to compute for example ##\frac{\partial U}{\partial V}## I obtain ##-P##, but how should I proceed to obtain, for example ##\frac{\partial U}{\partial P}## or ##\frac{\partial P}{\partial T}## which are not obvious from the...
Homework Statement
Determine electron concentration for both Helium and Nitrogen as a function of pressure at 300K.
This is from preliminary task for Energy loss of alpha particles in gases laboratories. It's too late to submit this, I'd just like to understand. Can post more info from the lab...
I have learned that ΔG is the amount of available energy. So to understand it i used a simmple body system rather than chemical reaction,which is the sliding of a block on a fixed wedge(height h and inclination angleθ).
1)my system is ball -earth and rest surrounding both in thermal eqilibrium...
Homework Statement
The tires on a bicycle require an air pressure of 80 psig. When isothermally pumped up the bicycle tires, the volume of the air (that was originally in the atmosphere) is reduced by a factor of 5.7. Please determine the work that must be done on each lbm of air that is pumped...
Hello chemists, need some help here.
I'm trying to calculate the power output of a certain otto cycle using different fuels, specifically gasoline, ethanol and different combinations of the two like 85% ethanol and 15% gasoline or 50% ethanol and 50% gasoline. However I have found it difficult...
Hi guys,
I'm doing some research in papers and literature to solve this problem but I've not found anything useful. I want to know the air velocity inside a pipe by the only effect of natural convection. I've attached a picture of the system right here:
I hope you can help me to find the...
Homework Statement
Hello, i have the following assignment due for monday and i have truly no idea how to tackle it, i have already tried it many times but all my results have been wrong. the problem is as follows.
inside a sealed container is an amount of water: mass=90.26 kg; pressure 9.1842...
Homework Statement
Find the average energy ##\langle E \rangle## for
(a) an n-state system in which a given state can have energy 0, ε, 2ε, 3ε... nε.
(b) a harmonic oscillator, in which a state can have energy 0, ε, 2ε, 3ε... (i.e. with no upper limit).
Homework Equations
Definition of...
Homework Statement
By applying the first law to a quasi static process, show that the entropy can be expressed as
S = (16σ/3c) VT3
Homework Equations
U = 4(σ/c) VT4
PV = 1/3 U[/B]The Attempt at a Solution
I know I should be using
dS = dQ/T but it's unclear to me how to use this unless I...
Homework Statement
[/B]
This is a very basic question. I have a cylinder filled with air having stops at a particular height .
First part of the process is isobaric as piston is free to move and P is constant.
When piston reaches stops this becomes isochoric process as volume is constant.
So...
Homework Statement
a system uses monoatomic ideal gas describing the following cycle (quasi static)
and basically the p-v graph is a circle,and it starts on the left side of the circle with states A, B, C, D (so that B and D are top an bottom) and so P on A (PA) is equal to PC and VB= VD
given...
Homework Statement
The total pressure of a mixture of oxygen and hydrogen is 1.00 atm. The mixture is ignited and the water produced is removed. The remaining gas is pure hydrogen and exerts a pressure of 0.34 atm when measured in the same volume and at the same temperature as the original...
I have a thermodynamics question I'm having difficulty with...
I have a steam generator heated by a 39MW nuclear reactor that powers two 4.5MW turbine generators. It produces dry saturated steam at 330psig, and enters the turbine at those conditions. It exits the turbine to a condenser...
Hi guys, 42 year old engine hobbyist here, not a student. I've had great luck figuring out my questions in this portion of the forum in the past and look forward to your input. Keep in mind that I'm not formally educated, so if it's possible to dumb something down a bit I'd appreciate it.1...
Homework Statement
A cylinder fitted with a frictionless piston contains 5.0×10-4m3 of an ideal gas at a pressure of 1.0×105 Pa and temperature of 300K.
The gas is then
(i) heated at constant pressure to 450K, and then
(ii) cooled at constant volume to the original temperature of 300K. The...
Ecosystems are open systems, they receive solar energy and other materials from outside the ecosystem and migration of animals is also witnessed.
I read Physics uptil class XII and have done a bit of research on google books and have come across these three books:
1.Towards a Thermodynamic...
Homework Statement
Homework Equations
Q1 + Q2 = 0
The Attempt at a Solution
I found the mass of water needed to cool the lava to a solid. I'm not sure how to find the rate of water needed to stop the lava...
Homework Statement
Calculate the vapor pressure of water at 25°C, based on the Gibbs free energy when vaporising from liquid water to vapor (so at 1 atm and 25°C ).
Homework EquationsThe Attempt at a Solution
After integrating d g/d p= RT/p. I get my formula p = p0*exp (-delta gm(p0, T)/RT). I...
Hi guys, I was watching an episode of stargate and I got this idea, I've been trying to explain to myself. It has to do with time dilation and the first law of thermodynamics. So here it is. Imagine a small time dilation field, a small sphere or something, with an accelerated time. A simple...
I have been trying to determine the efficiency of an ideal Otto cycle based on the compression ratio of my car and the heat of combustion of gasoline and I think I'm not entierly wrong but there is something quite off. When trying to calculate the temperature of the combustion stage my result...
I'm trying to build a heat treating oven/kiln and I'm having a difficult time identifying equations to assist in sizing and insulation.
I have info on sizing a heating element based on available power and I have and equation to quantify heat transfer through the walls and insulation but I'm...
Homework Statement
Initially you have mW = 4.6 kg of water at TW = 74°C in an insulated container. You add ice at TI = -19°C to the container and the mix reaches a final, equilibrium temperature of Tf = 33°C. The specific heats of ice and water are cI = 2.10×103 J/(kg⋅°C) and cW = 4.19×103...
I was wondering all the assumptions I need to make regarding a design for a heat exchanger and cooling tower design from a IC engine testbed. Each engines average output is 55kW and the water jacket temperature is 80 degrees (C) and has to be cooled to 65 degrees (C). The ambient atmospheric...
Hi, I need help
I got a project for school about jet engines. They say bysubstitution of equations 5.1, 5.2, 5.5 and 5.6
butI don't know the steps how i get t0 the last formule.
Thank you
Maximilian Popelier
Homework Statement
You have 1.0kg of ice at 0.0 deg C in a pot on a stove that produces 900 W of power. Assuming that the pot and the stove are 'perfect' (i.e., no heat lost) and ignoring the heat capacity of the pot, compute the time it will take for this ice to boil away completely...
Hi,
I am trying to understand which thermodynamics process or processes could model a vacuum engine (mostly known by the name "flamelickers") and similar engines..
In a vacuum engine you have a cylinder and piston system that draws hot air from a heat source, cools it and mechanical work is...
Hello,
Few years back I was reading about calculating multiplicity using hypercube (n-cube). Multiplicity was normalized using this method. I wanted to read it again but I just cannot find it now. I tried every combination of keywords. I remember it was a Wikipedia link. Any help would be...
A diabatic process is defined as follows:
Rapidly changing conditions prevent the system from adapting its configuration during the process, hence the spatial probability density remains unchanged. Typically there is no eigenstate of the final Hamiltonian with the same functional form as the...
Hello Pf's members
Suppose we isolated a methane's molecule at a room with 213 kelvin.
According to second law, methane's molecule tends to break it's bond for reaching whole system (methane's molecule and surroundings) to maximum entropy.
On the other hand for breaking these bonds we need...
I have a brayton refrigeration cycle with a regeneator same as the picture below only with irreversible regenrator, compressor and turbine (And different values).
The given in my problem are:
Ti=0 C, T3= 35 C, T5= -80 C, mass flow rate m= 0.4 kg/s
Turbine efficiency Et=0.85, Compressor...
1. Given the following p-V diagram of an ideal Stirling Cycle, determine the theoretical values of W12, Q12, W34 and Q34 in terms of T1, T2, V1, V2, n (the number of moles) and R (the universal gas constant). Determine the total theoretical p-V work W12341 for the full cycle.2. dU = dQ-Pdv3...
1.Recently, we performed an experiment to measure the efficiency of the Stirling Engine. The experimental method can be seen in the image provided. We have been asked to calculate the power dissipation PR and the energy dissipation per cycle WR as part of our lab report. The other variables...
I am going to learn an introductory to thermodynamics in my chemistry book(Senior year) so I thought I could ask some questions here about it to confirm my understanding:
1) Temperature: I have seen a lot of discussions here about what temperature really is. I came up with a summary (Thanks to...
Homework Statement
The figure below shows a combined cycle formed by a gas turbine and an organic Rankine bottoming cycle. Steady-state operating data are labeled on the figure. Owing to internal irreversibilities, the generator electricity output is 95% of the input shaft power. The...
Homework Statement
An isolated box contains two chambers separated by a thermally insulating but moveable partition. Both chambers contain dilute gas (same kind) at different densities and temperatures. The left chamber contains 1.0 x 10^22 particles at 25 degrees celsius and the right chamber...
Homework Statement
This is question 2.18 from Bowley and Sanchez, "Introductory Statistical Mechanics" .
Show with the help of Maxwell's Relations that
$$T dS = C_v dT + T (\frac{\partial P}{\partial T})_V dV$$
and
$$TdS = C_p dT - T( \frac{\partial V}{\partial T})_P dP.$$
Then, prove that...
Homework Statement
An inventor claims to have invented four engines, each of which operates between constant-temperature reservoirs at 400 and 300 K. Data on each engine, per cycle of operation, can be found in the table below. Of the first and second laws of thermodynamics, which (if either)...
Homework Statement
Two moles of a monatomic ideal gas are at a temperature of 300K. The gas expands reversibly and isothermally to twice its original volume. Calculate the work done by the gas, the heat supplied and the change in internal energy.
So:
T = 300K; ΔT = 0
n = 2; R = 8.314 J K-1...
Homework Statement figure: http://www.chegg.com/homework-help/questions-and-answers/dot-figure-represents-initial-state-gas-isotherm-dot-divides-p-v-diagram-regions-1-2-follo-q5905441
The dot in Figure (b) represents the initial state of a gas, and the isotherm through the dot divides the p-V...
Hi,
In a standard converging-diverging rocket nozzle, we have (ex.) the relation:(1-M^2)\frac{dV}{V}=-\frac{dA}{A}By substituting in definitions, we can obtain\left(1-\frac{V^2}{\gamma R T}\right)\frac{dV}{V} = -\frac{dA}{A}This shows the dependence on temperature.
The relation assumes that...
It was only the psychrometry came; I read about vapour pressure is equal to the saturation pressure at 100% relative humidity. While before even in the textbooks both terms are used frequently as same. I fully understood what saturation pressure is; learned during phase change phenomenon of...
Homework Statement
A certain humidifier operates by raising water to the boiling point and then evaporating it.
Every minute 30 g of water at 20◦ C are added to replace the 30 g that are evaporated. The
heat of fusion of water is 333 kJ/kg, the heat of vaporization is 2256 kJ/kg, and the...
Homework Statement
The formation of ice from water is accompanied by:
A. absorption of energy as heat
B. temperature increase
C. decrease in volume
D. an evolution of heat
E. temperature decrease
For the first one I think it's correct but I don't know the explanation
For second one it...
Homework Statement
55. Solid A, with mass M, is at its melting point TA. It is placed in thermal contact with solid B, with heat capacity CB and initially at temperature TB (TB > TA). The combination is thermally isolated. A has latent heat of fusion L and when it has melted has heat capacity...
Homework Statement
The 4 processes involve one mole of either mono- or di-atomic gas with the same amount of heat (absorbed or discharged)
•Which belong to the mono and which to the diatomic gas?
Homework Equations
i don't know which equations I should use and how start solving it..
I...