Heat Definition and 1000 Threads

The kinetic theory says that temperature is the measure of the average kinetic energy. That would mean then : The temperature rises with the rise in kinetic energy. We know that when matter changes state 'latent heat' helps in 'breaking the bonds' at the transition phase and that this 'extra...

NO TEMPLATE---MISPLACED HOMEWORK So it seems like a pretty simple question, and in all likelihood it is, but my lecturer somehow managed to miss this bit in his lecture notes. A heat engine operates between 500K and 300K with 20% of the efficiency of Carnot engine operating between the same...

Homework Statement A 10.0 g sample of solid platinum is placed in a large, sealed vessel at a sufficiently low pressure that the platinum is able to sublimate directly to a gas. Some thermodynamic properties of platinum at low pressure are given in the following table. Molar mass, M - 195...

1. Homework Statement Homework Equations First law of thermodynamics, ΔU=q+W The Attempt at a Solution Ok so, I know that when liquid evaporates, the change in volume is much greater than that when solid melts. And for both cases, distance of separation of atoms increases too, so PE...

I'm looking to model the heat transfer by conduction from the aperture to the base of a compound parabolic dish (CPE). Here's what I have so far, thanks to CFDFEAGURU's solution for a cone at https://www.physicsforums.com/threads/heat-transfer-by-conduction-in-a-truncated-cone.368972/ let θ =...

I have a simulation with a bunch of particles with volume bouncing around in a box with no interaction between them, a hard-sphere gas. Initially, they all have the same momentum |p|=√(2⋅m⋅2/3⋅k⋅T) to have the average kinetic energy 3/2⋅k⋅T. I'm asked to add a constant energy flux to the system...

Homework Statement A spacecraft is protected from the Sun’s radiation by a planar baffle whose size is much greater than that of the spacecraft itself. The baffle is aligned perpendicular to the direction of the Sun. Show that the equilibrium temperature of the baffle is...

After a cookout on Saturday, I left two cans of Coca-Cola in my bag. Around Monday morning which is almost two days later, when I left for school, the cans were still cold with moisture on it. The next day, I put another can of Coca-Cola in the car and only left it overnight to see what the...

So i am making a simple demonstration of ideal gas law using a cylinder piston system, heating the system so the piston is pushed up, i wanted to calculate the heat transferred into the system, will it be Cp(Tf-Ti) or Cp(Tf-Ti)+ work done by the system ?

I don't understand how compression of a gas causes heat to flow out of the container of that gas... Could someone please help? Thank you in advance!

I've been trying to wrap my head around the relationship between temperature increase of an object at a distance and temperature of a heat source. From what I've found, the temperature increase of an object from thermal radiation is affected by the inverse square law...

Homework Statement I know that for constant volume ∂q=du and so du=Cv.dT However i don't understand how did we get to ∂q=du by neglecting the vdP term of enthalpy What I am trying to say is, is enthalpy this ∆U+P∂V+V∂P or this ∆U+P∂V? I don't understand since the definition of enthalpy is...

Hi all. I'm currently working on a problem where I have to determine individual and overall heat transfer coefficients for a vertical cylinder with water flowing on the inside and steam on the outside (parallel flow), studying the cases of free and forced convection. I only have four...

If I wanted to calculate, say, the heat released during space shuttle re-entry, how should I do it? I know they provide the heat on their website, but if I wanted to arrive at the result just through calculation, would that be easy?

Homework Statement In each of the following, state and explain which container will have the hotter liquid after thirty seconds: a) You pour equal amounts of of hot coffee into two cup s from a percolator. The cups are the same general size and shape. One is made from heavy china one is made...

Homework Statement We previously solved the heat conduction problem in a ring of radius a, and the solution is c into the sum, perform the sum first (which is just a geometric series), and obtain the general solution, which should only involve one integral in ϑHomework Equations...

From what I know, temperature is defined to be the average kinetic energy of molecules within a system while heat is said to be the total kinetic energy of molecules. I know this might be something we can never achieve in real life but here's how my thought process went. Imagine you have a box...

I've read some articles online saying that the temperature is a measure of average kinetic energy of molecules so as the temperature increases, more molecules will bump into each other. However, I still don't quite understand why we feel hot when more molecules bump into each other. Is high...

Hi everyone! I have a silver plated copper heat exchanger (with an internal embedded circuit where liquid nitrogen flows) attached to a bigger aluminium block in order to cool it down. First, I want to estimate it's instantaneous cooling power during cool-down to a stable temperature. I have...

Homework Statement A metal sphere is subjected to a heat flux, 5000 W/m2. It is originally at 20 C. How long does it take to heat to 90 C? D = 5 cm density = 8522 kg/m3 cp = 0.385 kJ/kg-K k = 104 W/m-k Homework Equations rate of heat input = rate of heat accumulation -k*A*dT/dr = m*cp*dT/dt...

Can you derive the heat conduction equation from the navier stokes equations (particularly the energy eqn)?

I had an exam last week and I just got it back today. On the exam was a question that I got wrong even though his wording was terrible (he's from India) and I feel that it was not clearly expressed what he was saying. The question is: "A heat engine is 20% efficient. If it absorbs 500 J of heat...

Hello, all! I am involved in a discussion where the topic is the heat of fusion for hydrogen. From what I've found, the heat of fusion for H2 is around 22.5 million °F and the average house fire is no more than 1,800 °F or so. So, what I'm trying to find is, how far from 0.10 grams of a...

Have been slightly racking my brains trying to remember the basics of this, but have a quick and probably pretty simple heat transfer problem. Was in a discussion Two standard 1000 liters square enclosed plastic HDPE containers (1m x 1m x 1m). One is filled up 800 liters (some air present at...

I am wondering if equation $$C_v=(\frac{∂U}{∂V})_T$$ applies only to ideal gases or applies generally for any other system? The second question I have is can we use the following relation: $$dU=nC_vdT$$ in processes that are non isochoric (that is for processes where volume is not constant)? I...

One is always told that a heat pump (heating water) should receive return water with a temperature as low as possible. I've never really understood why. My initial thought is that if the return is higher, then it's "easier" for the heat pump to heat the water up to whatever supply temperature...

Hi everybody! To begin I'd like to say a big thanks to everyone who helped me on the forum lately: I passed my exams recently and without your help I'm not sure I could have done it! 1. Homework Statement Now I'm on thermodynamics :) A mass m1 = 150g of water ice of temperature T1 = -10C is...

By physical form I mean stored chemical or actual be a physical thing you can touch. Yes I understand it already is a physical form in atoms but I mean is it possible to have a jar of heat.

I am currently working on my college project about the design and optimization of plate heat exchanger. However, i have no idea where to start the project. Here is my first thought: - I set the hot and cold fluid to be water, 90 degC for the hot inlet and 30 degC for the cold inlet. - 50mm inlet...

Hi, I'd like to know how I'd put together, either elegantly or at least in physical terms, that surely water evaporation in a large pool of V volume and S surface is influenced by wind (increased by it as opposed to having side barriers), temperature (increased by direct sunlight as opposed to...

Homework Statement A system of N distinguishable particles, each with two energy levels. The lower energy level has energy equal to zero, and the higher energy level has energy ##\epsilon##. The higher energy level is four fold degenerate. Calculate the heat capacity. Homework EquationsThe...

I don't understand why heat transfer from hot reservoir to the system is considered reversible in case when Treservoir = Tsystem + dT but it's considered irreversible in this case: Treservoir = Tsystem + ΔT Where dT is infinitesimal difference while ΔT is finite difference in temperature...

Homework Statement Suppose you walk into a sauna that has an ambient temperature of 57.0°C. Calculate the rate of heat transfer to you by radiation given your skin temperature is 37.0°C, the emissivity of skin is 0.95, and the surface area of your body is 1.60 m2. I solved this first part and...

Homework Statement A 112 hp car engine operates at 11% efficiency. Assume the engine's water temperature of 85°C is its cold-temperature (exhaust) reservoir and 445°C is its thermal "intake" temperature (the temperature of the exploding gas-air mixture). (a) What is the ratio of its efficiency...

Hi PF! For the longest time I thought an energy balance and the heat equation were identical procedures. However, recently I saw an example of a steady state, constant property, laminar flow of fluid between two flat surfaces where the top surface moves in the ##x## direction at ##V_1## and we...

[Mentor's note: this was originally posted in a non-homework forum and therefore does not use the homework template.] Hi everyone, I'm a bit stuck on this question and hoping someone could give me the solution. "A lump of lead, moving with a velocity of 22.0 m/s, is brought to rest. If 55.0%...

What is the heat capacity values of diesel in liquid and vapour state?

Hi all, I am new here, and want to thank you for help in advance! I am working on a project and need some help - I need to figure out surface temp on an object at some distance from the heat source: I need some help getting started. Is it going to be: Heat transfer (radiation) + Heat...

Let's consider two spherical blackbodies at two foci inside an ellipsoidal heat-reflecting shell. Consider the situation that they both have different radii and that their temperatures are such that they emit the same power. Thus, the surface power flux density of each is inversely proportional...

Homework Statement Two identical tanks of water are at absolute temperatures ##T_A## and ##T_B## respectively, where ##T_{A} > T_{B}##. The tanks each have a heat capacity ##C##, and they are thermally isolated from their environment. Suppose that a heat engine is installed in contact with the...

Homework Statement My answer is question 3 part c the graph. SHC = c http://www.ocr.org.uk/Images/61757-question-paper-unit-g484-the-Newtonian-world.pdf [See page 7]Homework Equations E=mcdelta theta Power=Energy/Time Therfroe Power*Time = Mass*c*delta theta. The Attempt at a Solution See in...

Homework Statement An insulated beaker with neglible mass contains .3kg of water at a temp of 78.6 C. How many kg of ice at -19.6 C must be dropped into the water to make Tf= 22.7C? Specific heat for water= 4190 J/kgK specific heat for ice= 2100 J/kgK heat of fusion for water= 334kJ/kg...

Hello Im looking to build a very small electrical resistance heater. It should produce no more than 1 to 3 degrees of heat. This is for a personal project of mine. I need to know what types of materials I need to use. Id like the device to be both battery powered and plug in. Can anyone...

Every thermodynamics cycle needs to do negative work to the environment, which lower its total positive work. For example, in Carnot cycle, the most efficiency possible: 1/ Engine receives heat from hot reservoir, expands and do positive work to surround 2/ Surround does work to engine...

I read that if the temperature of 1 Kg of gold rises by 10°C its mass increases by 1.4 * 10^-14 kg. Can you please explain how you get such value from E= mc^2? I think the increase corresponds to E = h f =1.53*10*10^36 and since 1 kg has 1.1*10^30 electrons, each one gets 1.4*10*6 h but 10...

I'm in charge of designing a battery bank (using 18650 batteries) that will produce large amounts of heat for a short period of time. The battery bank will be in a near vacuum (~800 Pa), so convective heat transfer will not be effective. Since the operation time is only ~80 seconds, my thought...

Homework Statement [/B] I have two spherical metallic shells with radius ##3a## and ##a##, the little one is placed inside the larger so that the center of the little one is at a distance of ##a## from the center of the larger. The outer one has a charge ##3Q## and the one inside has a charge...

Homework Statement The combustion of hydrazine, N2H4, produces nitrogen gas and water vapor. The heat of combustion for this reaction is -618 kJ/mol. If 1.6 g of hydrazine are combusted in a bomb calorimeter at 298 K and with a heat capacity of 6.2 kJ/C, what will be the temperature of the...

Homework Statement A wire is moved with constant velocity such that the motion is perpendicular to the length of the wire in a region containing magnetic field perpendicular to the plane of motion. The wire has a resistance R. Will thermel energy be generated in the wire? Homework Equations...

Homework Statement Calculate the thermal resistance of the heat sink required for the regulator of the question above given the information below [from the datasheet] and the data in the table. Max Load Current (Ilm)= 1A Max Ambient Temp (Ta)= 75°C Thermal Resistance Case to Heat (θchs)=...