Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Maybe combine with [tag:statistical-mechanics].

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Several questions about spring chiller and LMTD

I'm designing a simple copper coil wort chiller. Digging formulas I'm having hard time to figure some things out, perhaps some simple guides may help me to go the right direction: LMTD need inlet ...
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50 views

Heat contained in compressed gas [closed]

I am trying to compute the amount of energy released in the form of heat if I compress 1 cubic meter of Hydrogen to 0.1 cubic meter while submerged in a large body of water of a given temperature - ...
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30 views

Does a flame produce free electrons? [duplicate]

Possible Duplicate: Does Fire Conduct Electricity? Why? Is fire plasma? Does a flame produce free electrons ? Or is the answer sometimes depending on the chemicals ? Does the answer depend ...
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3answers
289 views

Is enthalpy defined under non-isobaric conditions?

My question is this, Does Enthalpy have a meaning under non-isobaric conditions? Is its existence as a property of a system independent of whether the system is under isobaric condition or not? ...
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45 views

Any new texts directly on second law of thermodynamics? [duplicate]

Possible Duplicate: Recommendations for Statistical Mechanics book Is anyone aware of any recent text that summarises the research and arguments on second law of thermodynamics and also on ...
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1answer
279 views

Does a Peltier Thermoelectric layer make a good regulator for LN2 heat-sink interfacing

I understand that when cooling water with LN2 directly (through pipes for example), that it can be too effective, freezing the water (and blocking the pipe). From what I read, regulation of the heat ...
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286 views

Simple heat transfer question [closed]

You add an unknown volume of milk of $5.2 ^\circ C$ to a cup of coffee ($40 mL$ of water, temperature: $80.3 ^\circ C$). After a while of stirring the temperature reaches $73.2 ^\circ C$. The ...
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46 views

Free Energy and quantum measurement

Free Energy must be expended to reset the state of an measurement apparatus. Is this statement valid in all situations? Is there a Definitive mathematical exposition?
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125 views

“This is not a perpetual motion machine, because reservoir temperatures are changing.” Is it a valid argument?

I've already faced this situation several times: given a statement (in area of thermodynamics) I used it to provide an example of some perpetual motion machine (of first or second kind). Therefore, I ...
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1answer
124 views

Physics of homebrewing heat exchangers

In homebrewing on of the key steps when brewing with extract is to rapidly chill the wort from boiling temperatures to about 80F in 30 min. This is needed to reduce risk of environmental ...
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59 views

Temperature measurement, precision

I am having problems with one of the problems I have done (a) which is basically $\theta = 273.16K (19/15) = 346.00K$ For (b) I am given that the length is 15.00cm when the thermometer is incontact ...
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56 views

upper bound for the Kelvin scale [duplicate]

Possible Duplicate: Why is there no absolute maximum temperature? On the Kelvin scale, absolute zero represents the temperature at which there is no thermal motion. Consequently, speaking ...
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45 views

What is the fluid approximation for BCS action?

For a system with free fermion gas at finite density (i.e. free Dirac action), we have an ideal fluid description with rho, p, n. What is the fluid description for BCS action? Suppose we have a box ...
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1answer
177 views

What kind of phases nanoparticles have (gas-solid-liquid)?

If a phase transition requires a number of particles that is in the TD-limit, can nanoparticles (~10 atoms) have phase transitions? What kind of phases and transitions nanoparticles have?
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208 views

Centrifugal Compressor Flow Rate

For a centrifugal compressor, as found in most turbochargers on internal combustion engines, is there a noticeable change in flow rate versus a naturally aspirated flow rate? In other words, does the ...
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332 views

Is the $mL_c$ value for triangular and rectangular fins the same value?

I am looking at the solutions that my professor put up and I feel that he did something wrong. Here is the question and I will give my stab at the solution so you can see why I think that it is wrong. ...
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393 views

How equivalent are heat energy and work energy in connection with a spinning flywheel?

Let's say we have two identical spinning flywheels, that have arbitrary geometry, and are made of copper. Now we apply some heat energy at the center point of flywheel A, causing it to slow down a ...
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305 views

Exam review question on thermodynamics [closed]

A cube has a side length of $20\text{ cm}$. An atom in the gas moves around the cube as shown. It continually bounces off the four lateral walls of the cube. The atom has a mass of $6.6\times ...
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63 views

How many times brighter could the stars shine without raising the temperature of space?

If my understanding is correct, the temperature of space (as defined by the temperature that a black-body will reach) has been decreasing since the big bang. It has never increased. Additionally, ...
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577 views

Do the properties of two streams flowing into an engine add together when they mix?

Let's say I have two stream supplys that have separate mass flow rates, enthalpies, and velocities that flow into an engine. Upstream of the engine's inlet, the two streams mix to form one stream that ...
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2answers
159 views

Relationship of the abundance of an isotope and the vapor pressure

Say I have a sample of some alkali metal - Rubidium for example. A sample of Rubidium consists of approximately 27% $^{87}$Rb and 73% $^{85}$Rb. Does the vapor pressure of each isotope individual ...
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93 views

How to compute the heat flow for a specific material for some given boundary temperature?

Assume I have a bounded material with heat sources inside. The material is known (i.e. I know heat capacity and all relevant data) and the temperature of the boundary is fixed. I solved the (steady ...
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732 views

Why is it when you microwave cold coffee and then add milk it creates a foam head? [closed]

As compared to when the coffee is just hot from brewing. I suspect it has something to do with the way the microwaves are affecting the molecules of the coffee.
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4answers
2k views

Physics of a burning log of firewood

According to my knowledge, heat is nothing but the result of the vibrations of atoms and molecules. I guess this mean that in heating up a gas or liquid, we are increasing the rate at which the ...
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1answer
218 views

Maxwell's Demon bug, trapdoor space and time

What about the size of the door (space) and how long has it to be opened (time)? I think Maxwell's demon would have a problem with space, if the door is too wide (more than one particle size), then ...
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2answers
409 views

Why doesnt this violate 2nd law of thermodynamics?

Consider an ideal gas in a cylindrical container in a gravitational field, with a piston on top pushing down by gravity. The piston has some locking mechanism that locks it in place if it is displaced ...
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226 views

Second law of thermodynamics implies a linear cosmology?

If one applies the second law of thermodynamics to the Universe[1] as a whole then one might expect that the entropy of the Universe always increases as time goes forward (or more accurately that the ...
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3answers
627 views

Why isn't the Bekenstein-Hawking Entropy considered the quantum gravitational unification?

Based on the Bekenstein-Hawking Equation for Entropy, hasn't the relationship between quantum mechanics and gravity already been established.
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1answer
319 views

Does heat always rise?

Does heat always rise in a gravitational field? I recently read that heat could be traveling down to the deep part of the ocean. Is there some new or old physics that makes heat sink?
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2answers
243 views

Why are some of the biggest stars known blue?

My question refers to an overview of the biggest stars we know: http://farm5.static.flickr.com/4138/4820647230_faba1c9f3b_o.jpg Why are some of those blue?
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4answers
143 views

How to measure the energy consumption class of a home appliance? [closed]

Some of you may be familiar with the EU energy consumption classes for domestic appliances (or equivalents in other areas). Let's say we have a domestic appliance which was made before the energy ...
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2answers
54 views

Measurement of heat in electrons

Is there any method to measure the heat of an electron and if there is; then is it a constant or a variable.
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2answers
66 views

Why cannot wood be fully burnt?

Burning wood emits smoke and black. Provided more oxygen or whatever required, can wood be practically burnt fully like petroleum gasses that emits a blue flame and little smoke and little black.
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1answer
269 views

Ideal gas temperature and pressure gradients?

Consider an ideal gas in a $d\times d\times L$ box with the $L$ dimension in the $x$-direction. Suppose that the opposite $d\times d$ sides of the box are held at temperatures $T_1$ and $T_2$ with ...
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3answers
1k views

How can there be heat in a vacuum?

I keep reading in the Physics World focus issue on vacuum technology about scientists creating high temperatures in the vacuums etc. If heat is caused by thermal energy being radiated from particles ...
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219 views

Why can the entropy of an isolated system increase?

From the second law of thermodynamics: The second law of thermodynamics states that the entropy of an isolated system never decreases, because isolated systems always evolve toward ...
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2answers
893 views

Is carbon dioxide a greenhouse gas? [duplicate]

Possible Duplicate: What experiments prove the greenhouse effect? I am seeking for a proof that CO2 is a greenhouse gas. I posted this on Skeptic.SE recently but found no help in seeking ...
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2answers
131 views

What to do when you are sitting in a closed room without any fan or AC

I suffered this today, when the solar panels of our college stopped to work. Imagine a situation in which you are sitting in a botany lecture conducted by a 73 year old man, who cannot speak loud and ...
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3answers
86 views

Is it possible to have $\Delta T\neq 0$ with no heat exchange $Q=0$, no work $W=0$ done, and no change in internal energy $\Delta E=0$?

Is it possible to have $Q=0$, $\Delta E=0$ and $W=0$, but $\Delta T\neq 0$? In particular, if there is no change in internal energy, doesn't that imply it is an isothermal process, and therefore that ...
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2answers
50 views

Heating a black body

By definition, Black body has absotivity=emmisstivity=1. This means the black body radiates all energy it accepts. Does this mean the black body cant be heated?
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922 views

How temperature gradient is a vector?

Everyone knows Temperature gradient is a vector quantity having direction from cold to hot.My confusion: why is temperature gradient vector if its direction is always fixed (as in the case of ...
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2answers
3k views

Plotting the maxwell-Boltzmann velocity distribution in matlab

I'm trying to plot a maxwell-boltzman velocity distribution in matlab. I have also asked this question at cross validated without much luck The PDF is f(v)=sqrt(m/2*pi*k*T) * exp(-m*v^2/2*k*T) ...
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2answers
441 views

Why laundry dry up also in cold/frost?

Why laundry dry up also in cold/frost? When you have frost, water in the clothes should freeze, but if clothes are dry, then it should be possible that steam in the clothes does not have time to ...
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1answer
825 views

Salt and boiling speed

When we add a compound (salt) to a solvent, the boiling points rises. But, what could we say about the speed the solvent reaches the boiling point? It's better to add salt before or after boiling ...
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1answer
219 views

Is this a simple system in which no heat transfer is possible?

Let's say that a hot gas is trapped in a metal box. This metal box is magnetically suspended in another structure with a low temperature. The inner box does not touch anything. And there is a void in ...
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5answers
2k views

What is the most energy efficient way to boil an egg?

Starting with a pot of cold tap water, I want to cook a hard-boiled egg using the minimum amount of energy. Is it more energy efficient to bring a pot to boil first and then put the egg in it, or to ...
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3answers
35 views

Why radiant heat only travels as infra-red waves and not as other types of em waves like UV rays

Heat is a form of energy and em waves carry energy as momentum of photons. So, I think, radiant heat can travel at any frequency. Please correct me.
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2answers
82 views

requirements for hydrogen fusion

What are the requirements for hydrogen atoms to go through fusion? Is it a ratio of heat to pressure or are there specific heat and pressure values that must be met (per atom or per mole?) Are there ...
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4answers
208 views

Is vapour pressure based on partial pressures or just total pressure on the liquid?

The explanation for the boiling point of water is that at 100C, the vapour pressure becomes greater than atmospheric pressure. But say you had a a jar of water sealed in argon at 1atm, which is larger ...
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2answers
442 views

Difference between pressure and stress tensor

What is the difference between hydrostatic pressure and stress tensor?