Heat Definition and 1000 Threads

The heat capacity equation Cp for copper as a function of temperature (Shomate equation) for the solid phase is defined for the range of 298-1358 K in the Nist Webbook and in many books. http://webbook.nist.gov/cgi/inchi?ID=C7440508&Mask=2#Thermo-Condensed And I need to calculate the heat...

Hi. Sorting the exchanges of heat and mechanical work in a thermodynamic cycle by the signs and summarizing, I get ##Q_{in}>0##: heat transferred into the system ##Q_{out}<0##: heat transferred to the cold reservoir ##W_{out}<0##: work done by the system ##W_{in}>0##: work done on the system...

Homework Statement This problem belongs to the Intermediate Physics for Medicine and Biology, Hobbie Chapter 4. The heat flow equation in one dimension $$ j_H=-\kappa \partial_x T $$ where ## \kappa ## is the termal conductivity in ## Wm^{-1}K^{-1}##. One often finds an equation for the...

Homework Statement A pump, operating at 10 W, is used to raise the pressure of a stream of water at 2.5 mol/s from 1 bar to 2 bar. At steady state, if the water temperature should remain constant at 25oC, how much heat exchange between the pump and its surroundings is required? Note that 1 bar...

Heat from the coiled wire is transferred in three possible ways: conduction (through physical contact of the heating element and the material being heated); convection (through the air movement in the kiln); and by radiation (directly from the elements to the material being heated). It seems to...

Homework Statement A spring (k = 500 N/m) supports a 400 g mass which is immersed in 900 g of water. The specific heat of the mass is 450 J/kg and of water is 4184 J/kg. The spring is now stretched 15 cm and, after thermal equilibrium is reached, the mass is released so it vibrates up and...

I've been watching "The Expanse" and considered, if the spaceships are some sort of fusion powered drive, why aren't they covered in radiator panels to reject all the heat from the reactor/drive system? How many square meters of radiator panels would a 20MW (thermal) fission reactor require? An...

Homework Statement A rectangular box measuring a x b x c has all its walls at temperature T1 except for the one at z=c which is held at temperature T2. When the box comes to equilibrium, the temperature function T(x,y,z) satisfies ∂T/∂t =D∇2T with the time derivative on the left equal to zero...

Homework Statement A bolt of mass 0.3 kg falls from the ceiling of an elevator moving down with an uniform speed of 7 m/s. It hits the floor of the elevator (length of the elevator = 3 m) and does not rebound. What is the heat produced by the impact ? Would your answer be different if the...

Morning I am being stupid but cannot work out these problems: 1. Energy supplied to 2.0 moles of an ideal gas is 117J and it changes the temperature by 2.0K (at constant pressure).2. Calculate both molar heat capacities at constant P and V.3. Firstly, I divided 117J by 4 to get the energy...

Homework Statement A furnace is constructed with 0.5 m of fire brick, 0.15 m of insulating brick and 0.25 m of ordinary building brick. The inside surface-temperature is 1530K and the outside surface temperature is 525K. The thermal conductivities of the fire, insulating and building bricks are...

Hello guys, in the question attached, my understanding is that there is a heat transfer that heats the fluid from an initial at the input, to at the output. This heat transfer is via convection from walls of temperature . Firstly, . Because the walls are and the fluid is of a lower...

NO TEMPLATE BECAUSE SUBMITTED TO NON-HOMEWORK FORUM I'm stuck on substituting the following (where gamma is the specific heat ratio): W=(P1v1 - P2v2) / (gamma-1) P1v1^gamma = P2v2^gamma substituting for v2... <= this is where I get stuck... W = [(P1v1) / (gamma-1)] * [(P2 /...

Hi Everyone, I am looking at designing a small impulse steam turbine that runs off of saturated refrigerant vapor delivered from a shell and tube heat exchanger. With the design of the turbine, I am looking to maximize the velocity that the steam can exit from a diverging nozzle in order to be...

I am a retired electronic engineer and no scientist. I am considering the use of a saturated solution of sodium chlorate as a thermal store. My problems are: 1/ I have no idea of the quantities involved in terms of heat/gram of crystals. My intention is to maintain a supply of hot water for a...

Homework Statement An alternating current, with the current value of i = 3*cos314*t, is split into two parts in point A (each part with its own thermal resistance, R1 = 60Ω and R2 = 40Ω), which then connect again in point B. What is the released heat in the part between point A and point B...

Homework Statement Two identical bodies of constant heat capacity ##C_p## at temperatures ##T_1## and ##T_2## respectively are used as reservoirs for a heat engine. If the bodies remain at constant pressure, show that the amount of work obtainable is ##W = C_p (T_1 + T_2 − 2T_f)##, where...

How would one go about determining the amount of heat generated by the decay of a radioactive particle, such as Cesium 137, Polonium 210, or Strontium 90? How would you determine how much of the radioactive material would be needed to heat, say, a cup of water to a certain temperature, taking...

Homework Statement Imagine I have a 3.5 kg brick at 80 °C that I put in 10l of water at 20 °C. What will the final temperature of the water be? SHC brick = 840 J kg-1 °C -1 Homework Equations E = mc∆θ The Attempt at a Solution First I calculated the energy available from the brick to heat...

Hello guys, I was reading some models about the topology and size of the universe (always a controversial topic), then a question came to my mind. It is predicted that our universe will expand until it reaches heat death. Can a closed, finite universe also reach heat death and be described by...

I thought this would be the most logical way to post this, but give me some grace if it is not because this is my first time posting on this site (then relinquish the grace and tell me how to do it properly haha). First: When a physics problem says "sliding past point P" does that mean it stops...

1. Question 2. The attempt at a solution Now I'm not sure where to go next? Do I work out the local heat transfer coefficient at 1.2m or just the heat transfer coefficient? Using h = Nu × k/x or h = Nu × k/d Thanks, Sam.

Homework Statement Homework Equations I could really use a push on how to approach this problem. My primary problem is it asks for the heat flux into the page, which makes no sense to me as that is the z direction and this is in the x/y plane. If anyone could explain this problem and maybe...

Hello all, I am taking a thermodynamics course and unfortunately my professor is not very instructive. I have attended every class and I still feel lost. I was wondering how it is possible to find heat capacity if both the pressure and the volume are changing? I was under the impression that...

Homework Statement A 1.0kg of ice at 0◦C, 3.0kg of water at 0◦C, and 5.0kg of iron at temperature T are placed in a sealed and insulated container. cFe =400J/ kg◦C ,cWater=4200J/ kg◦C , cIce= 2000 J/ kg◦C latent heat for ice is 3.3×105 J . The equilibrium temperature is 20◦C.Homework...

Homework Statement Two glass bulbs of equal volume are connected by a narrow tube and are filled with a gas at ##0^{\circ}C## and a pressure of ##76\text{ cm}## of mercury. One of the bulbs is then placed in melting ice and the other is placed in water at ##62^{\circ}C##. What is the new value...

Homework Statement A sphere of radius r_s is at the center of a spherical shell of inner radius r_i=10\, r_s and thickness s = 10\, {\rm cm}\ll r_i. The sphere has a temperature T_s=1073\, {\rm K} and and an emissivity e=0.90. The inner surface of the shell has a temperature T_i = 873...

Q: Suppose ##u(x,t)## satisfies the heat equation for ##0<x<a## with the usual initial condition ##u(x,0)=f(x)##, and the temperature given to be a non-zero constant C on the surfaces ##x=0## and ##x=a##. We have BCs ##u(0,t) = u(a,t) = C.## Our standard method for finding u doesn't work here...

Homework Statement flue gases = 50,000kg h^-1 surface area = 113.57m^2 Do = 25 + (3*2) = 31mm The tubes within a boiler are 25mm inside diameter with a wall thickness of 3mm. The flue gas velocity through the tubes is to maintain the overall heat transfer coefficient value and minimise...

if a capacitor is connected to a battery and then it is fully charged . then a dielectric slab of k is inserted in the capacitor while the battery is still connected SLOWLY my question is will there be any heat produced?? my approach -- after insertion of dielectric , the charge on the...

How do I relate Fourier's Law of Heat Conduction for 1-D Heat Conduction with the Heat Conduction Equation in a large plane wall and energy balance equation? Fourier Energy Balance energy in - energy out = system energy change rate of energy in - rate of energy out = rate of system energy...

When, as a layman, I read or hear about the Big Bang, it generally comes to the same issues: massive release of energy, very high temperatures, very fast expansion, questions about what came before the Big Bang and so on. Yet, there are some issues that, at least to me, appear to be left aside...

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...

In my labs we use hot plates with a 0-10 temperature knob. The hot plates don't have a temperature monitor, so i have no idea how hot each number can increase it or how hot it is at the time. Sometimes i have labs where i have to heat something to more specific temperatures or else the reaction...

According to Einstein (or Debay) model of solids, heat capacity drops exponentially at low temperatures: question is >> why it changes so dramatically at low temperature that is physical explanation of this?

Homework Statement Calculate surface temp of heat exchanger when it's heating the room with the known power of P. Room temperature T is also known, as is the heater surface area A. ε ≈ 1. Homework Equations P = εσAT^4 is what I've been trying to use. The Attempt at a Solution I've been...

Hello. I was browsing online to answer the question to why RMS voltage is used as opposed to the average voltage (and by average I mean over half a period, roughly 0.64V_peak), and the explanation I found was that the RMS voltage would produce the same heat as equivalent DC through a resistor...

In order to obtain DSC curves the instrument has to measure a HEAT when changing the temperature. During the measuring cycle with increasing temperature, I bet the heat is measured via Joule heating. But how is the sample cooled down together with measuring required heat during a cooling cycle?

Homework Statement What is the final temperature in a squeezed hot pack that contains 23.9 g of LiCl dissolved in 107 mL of water? Assume a specific heat of 4.18 J/(g⋅∘C) for the solution, an initial temperature of 25.0 ∘C, and no heat transfer between the hot pack and the environment...

Homework Statement Determine the heat loss per square meter of skin surface due to convection at -40degreeC in moderate wind (0.5 m/s, Kc=10 Kcal/m2-hr-degreeC), assuming that the skin temperature is 26degreeC. Homework Equations hcov= 10.45 - v + 10√v ΔQ/Δt = A hconv (Tskin - Tair) The...

Hey Guys ! what is the main difference between Heat Exchanger and Cooling Towers?

Homework Statement "In a container of negligible mass, equal amounts (in weight) of ice at 0◦C and steam at 100◦C are mixed at the atmospheric pressure. Assuming no heat exchange with the surroundings, what is the temperature when the system reaches equilibrium? What are the fractions of...

Hey all, I've been thinking of a couple scenarios that involve thin wires (ones that have their diameter in the order of 1 mm). Suppose a gold wire with length L and diameter D is suspended straight in room temperature air and connected to some voltage V. Thus, a current will pass through the...

Hi guis, i need your help... 1. Homework Statement Evaluate the rotational and vibrational contributions to the heat capacity of a gas of DBr (D=deuterium, Br=mixture at 50% of 79Br and 81Br) at 380 K temperature, knowing that the bond distance is 1.41 Å and the vibration frequency of 1H79Br...

I've become nauseated with the recent obsession with colonizing Mars, mining the moon or asteroids, and spending resources on intermittent power production from wind, solar, and batteries. I've looked at numerous sources of energy production and have come to the conclusion that instead of...

How do nuclear submarines (and also newer technologies such as air independent propulsion submarines) get rid of the waste heat generated by their power plants given the high pressure environment they work in and their need for stealth?

When heat is dissipated into a piece of metal(aluminum for example), what happens to the potential energy that was stored in the heat? Does it transform into another form of energy or is it absorbed by the atoms of the metal element?

Hello Physics Gurus, Please critique the following logic... When a runner hikes/runs to the top of a mountain, the chemical potential energy inside the muscles transferred into the potential energy of the runner's body mass at the higher elevation (Pe = mass*gravity*height = mgh). Energy is...

I have been thinking about this. For a wave equation, the acceleration of a point on a drumhead is proportional to the height of its neighbors $$U_{tt}=\alpha^2\nabla^2U$$ The heat equation, change in concentration or temperature is equal to the average of its neighbors...

Homework Statement An infinitely long cylindrical shell has an inner radius a and outer radius b. If the inside is maintained at a temperature Ta and the outside at a temperature Tb, determine the rate of heat flow per unit length between inner and outer surfaces assuming the shell has a...