Thermal Definition and 1000 Threads

I'm not sure I fully understand the difference between thermal conductivity and thermal diffusivity as thermal properties of a material and would appreciate if anyone could clarify. I understand thermal diffusivity is for a transient case and conductivity is for steady state. This is what...

I want to circulate cold water through copper tubing curled in a spiral about a fan. I'll cool the water with a large block of ice that I can remove and replace like a battery. To avoid making a mess I can freeze the ice inside of a copper housing, and pump the water in copper tubes around that...

Homework Statement A rectangular plate extends to infinity along the y-axis and has a width of 20 cm. At all faces except y=0, T= 0°C. Solve the semi-infinite plate problem if the bottom edge is held at T = {0°C when, 0 < x < 10, T = {100°C when, 10 < x < 20. Homework Equations ∇2T=0...

My University just build this amazing library exclusively for the engineering departments and similar fields of study. This is my first time taking advantage of the new complex and I am sitting on the 3nd floor over an all glass-wall window. As the sun was setting I notice tiny popping noises on...

Law of cooling states that the rate of loss of heat by a body is directly proportional to the excess temperature of the body above that of its surroundings. The equation of determining temperature in time T(t)=Ta+(T0-Ta)*e^kt (Ta-ambient temperature, T0-initial temperature, k-heat transfer...

Homework Statement Starting from rest, a railroad car rolls down a hill 20 m high and hits another identical car at rest. The cars lock together after the collision. What fraction of the first car's change in potential energy is converted into thermal energy in the collision?Homework Equations...

The thermal energy comes from the translational kinetic energy right? The relationship between the two being E(kin)=1.5kT how would i go about finding the total thermal energy of a system of a given volume and pressure?

question:Calculate the total thermal energy in a liter of helium at room temperature and atmospheric pressure. Then repeat the calculation for a liter of air. I'm just confused because i thought thermal energy only depended on the translational kinetic energy of the particles. So why do i...

Which mechanism in semiconductors is responsible for electron excitation from valence to conduction band in thermal equilibrium at temperature T? Do valence electrons take their excitation energy from the lattice by absorbing phonon? If so, they can be excited at each arbitrary temperature no...

All bodies with a temperature emit electromagnetic radiation also known as thermal radiation or blackbody radiation. If I understand it correctly, the origin of this is the thermal motion (acceleration) of the atoms and their included positive and negative charges leads to EM radiation...

Hi, I am new to this Forum... So please let me know this is not the correct sub heading under which i am suppose to post the question... I would like to the basic relation between the Air density, Air Mass Flow Rate and heat Transferred to air by Convection... Changing the Air Flow Rate...

I have an aluminum disc that is 15in in diameter and about 1in thick. I am going to put it in a 400°F oven and I need to know how much the diameter will expand. One of the engineers I work with(i'm an intern) is using what I found to be the linear expansion equation (ΔL/Li=αΔT)...so Length...

1.The center rod CD of the assembly shown in the figure is heated from T1 = 30oC to T2 = 180oC using electrical resistance heating. The two end rods AB and EF are heated from T1 = 30oC to T2 = 50oC. At the lower temperature T1, the gap between C and the rigid bar is 0.7 mm. Rods AB and EF are...

1.A brass ring of diameter 10.00 cm at 20.0°C is heated and slipped over an aluminum rod of diameter 10.01 cm at 20.0°C. Assuming the average coefficients of linear expansion are constant, (a) to what temperature must this combination be cooled to separate them? Is this attainable? (b) What if...

Homework Statement Problem is described as follows, I have a pressure vessel which basically consists of a hollow cylindrical body with two hemispherical shells attached to both ends. Within the vessel, there is a gas flowing from top to bottom. Over a period of one week, the vessel was...

Homework Statement A silver block, initially at 58.5* C is submerged into 100.0 g of water at 24.8* C, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 26.2* C. What is the mass of the silver block? Homework Equations q = M x Cs x Δ T 1/M...

Dear visionary inventors, megalomaniac engineers and audacious explorers, Chemical rocket engines aren't up to our desire to hop in the Solar system: go quickly to Mars, deviate Earth-threatening objects, and so many more missions. We need a higher ejection speed to save propellant mass, but...

1. a steel plug has a diameter of 10.0 cm at 30 degrees celsius. at what temperature will the diameter be 9.986 cm? 2. a steel measuring tape is exactly 50,000 m long at 20 degrees celsius . (a) what is the length on hot summer when the temperature is 35 degrees celsius? (b) if such steel tape...

I have a question. From this government reference: http://www.ncnr.nist.gov/resources/n-lengths/ the thermal neutron cross section for stable isotope Be-9 = 0.0076 barns. This means Be-9 is not expected to absorb a thermal neutron, the probability of this is very, very low. The Be-9...

Homework Statement A physicist pours 100g of water at 100'C into a 20g aluminium cup which already contains 50g of water at 20'C. The final equilibrium temperature of the water is 71.847. C(water)=4186J/kgC C(aluminium)=900J/kgC 1. the amount of heat lost by the hot water 2. the amount...

Hi, I was hoping someone could enlighten me on the thermal conductivity of air. I'm aware the λ for air is 0.024. Meaning its a very good insulating material. Much better than the conventional insulating material we use for conventional buildings such as EPS and XPS which are at λ 0.030...

Homework Statement I am working on a project where I have to design and size an aquifer. There are two which either store hot or cold water for 6 months which is then pumped up to be used in either the summer or winter. The aquifer is going to be 80 meters under the ground. The rest is...

Hello, Greetings! How do I get the convective surface matrix from ANSYS for 3D thermal problem. Consider a volume, where some of its surfaces are subjected to convective boundary conditions. What is the way to get those (only convective surface) matrices generated by ANSYS. Any help in...

Hi Guys I'm analysing a heat exchanger based on an existing commercial model in SolidWorks Simulation. The same materials etc have been applied to it in the Static analysis. Deflection on the heat exchanger is very small. The one thing that baffles me though is how, regardless of even...

Can you please help me? I am trying to calculate this equation but can't get correct answer: Thermal Efficiency, Brake = 1/(bSPC x QHV) bSPC (brake Specific fuel consumption) = 0.396 kg/KWh QHV (Heating Value for fuel) = 44 MJ/Kg The correct answer is meant to be: Thermal Efficiency, Brake...

I want to know the reason why the thermal neutrons with energy of 0.0253eV is so important. As far as I know, a neutron with an energy of 0.0253 eV is used as reference to measure nuclear cross sections such as absorption, fission, scattering, etc. And I want to know the details and more...

Homework Statement At a temperature of 18°C a beam of diffracted monochromatic x-rays is observed at an angle of 150.8° to the incident beam after being diffracted by a crystal with cubic structure. At a temperature of 318°C the corresponding beam makes an angle of 141.6° with the incident...

I have some questions regarding thermal radiation spectra of different objects. Is thermal radiation of objects due to electromagnetic radiation alone? Does my desk which is at room temperature emit as a blackbody with the proper factor for emissivity? Where is the "cavity" that the radiation is...

Homework Statement 1. a 100m long copper wire of diameter 4mm is heater from 20C to 80C. What is the change in the length of the wire? 2. a 0.2m diameter aluminium sphere is cooled from 250C to 0C. What is the change in the volume of the sphere? The coefficients of linear and cubic expansion...

Homework Statement A rod, with sides insulated to prevent heat loss, has one end immersed in boiling water at 100C and the other end immersed in a water/ice mixture at 0C. The rod has uniform cross-sectional area of 4.04 cm^2 and length 91cm. Under steady state conditions, heat conducted by...

I am doing a research on activation radionuclides resulting from thermal neutron(2200 m*s-1 or 0.0253eV) capture. The activation cross section of some nuclides(H-3,C-14,54Mn,58Co), still can't be found even many efforts were taken. The related reactions...

Hey guys. From my understanding, Temperature is a measure of the average kinetic energy of the molecules within a substance. Heat is the transfer of thermal energy between a system and its surroundings Internal Energy is the total energy (kinetic + potential) of the molecules of a...

Homework Statement A mathematical model for temperature T as a function of depth y (in m) and time t (in days) is: (T(y,t)-T0)/(Tsurf(t)-T0)=e^(-y2/4αt) (2)where Tsurf(t) is the water temperature of the lake surface at time t, α is a property called the “eddy thermal diffusivity” and T0...

A potential difference of 50 mV is maintained between the ends of a 9.70 m length of wire whose cross section area is 25.0mm^2. The conductivity of the wire is 6.80 x 10^6 (ohm.m)^-1. Determine the rate at which the energy in the wire is transformed into kinetic to thermal energy. 2. Homework...

How can I determine the thermal conductivity of two different aerial coolers' tubes, taking into account the ambient temperature of the air? The overall goal is to determine which cooler is able to cool water the best, but the data was taken during different outside air temperatures. Below...

Homework Statement Two ideal gases are separated by a partition which does not allow molecules to pass from one volume to the other. Gas 1 has: N1, V1, T1, Cv1 for the number of molecules, volume it occupies, temperature in kelvin, and specific heat per molecule at constant volume...

Homework Statement Three identical wires Lo, diameter d, are arranged like a Y letter (please see attachment) Each end of the wires is secured to a wall. Initial tension is approximately zero. If the wires are cooled ΔT, find the distance the knot moves to the right and the final tension in...

chem12 Thermodynamics -- thermal energy question Homework Statement Which would have a higher amount of thermal energy: cup of tea @ 75°C OR bathtub of water @ 50°C Homework Equations q=mcΔT The Attempt at a Solution I know both are made of water with a specific heat...

This is a question about the proper form for thermal noise from a resistor. This is purely academic for me - I always work in the regime where \hbar \omega << k T so the noise spectrum is simply P \approx kT. When this no longer holds, quantum effects matter of course. Then I have seen...

Homework Statement Hi! I need some help by my phisycs homework at universty. Here is the problem: We have a steel ball, with density of 7800kg/m^3, with speficic heat capacity 460J/kgK. Temperature of the ball is 1700K. How much time does the ball need to cool down to half of it's temperature...

Homework Statement Prove a rule for adding of Thermal resistances for: A)R1 and R2 in Series B)R1 and R2 in Parallel Homework Equations The Attempt at a Solution According to the book the result should be : A) R = R1 + R2 B) 1/R = 1/R1 + 1/R2 So i thought we can get some ideas from the...

I use RTV silicone rubber to make moulds for hard candy. Hard candy is basically boiled sugar that is poured into moulds at just under 300 degrees F. The castings of hard candy develop bubbles on the surface because the silicone does not dissipate the heat, unlike traditional metal moulds...

I was just wondering what would be sources of error in calculating thermal expansion

The ocean’s average temperature has risen by approx 0.375°C over the century. Use this value to estimate by how much the ocean water might have expanded in items of percentage increase. This is what i started doing but I do not think this is right. Coefficient of Cubical Thermal Expansion...

Task: A steady flow boiler takes in feed water at 1.5kg/s, at a temperature of 30 °C. The water is heated and turned into wet steam. This leaves at 1.5kg/s, with a pressure of 10 bar and a dryness fraction of 0.97 to the superheater, where it receives heat at a constant pressure and emerges...

If an iron rod, inside two coils, incurs current going through the coils in the same direction, then the rod will increase in length and then it will begin to reduce in length. This is due to the magnetostrictive properties of the iron. When the currents oppose each other, so as to cancel...

why is thermal analysis done in implicit scheme

A cylinder is constructed from a super insulator. The dimensions of the cylinder are Length L: 1 M; inside diameter i.d.: 12 mm. The entire Length of the cylinder contains copper (cases described below). Heat (T > 100C) is continuously applied to the copper on one end of the cylinder...

Homework Statement One mole of copper at a uniform temp. of 0 Celsius is placed in thermal contact with a second mole of copper which, initially, is at a uniform temperature of 100 Celsius. The pressure in the system is maintained at 1 atm. The two moles of copper are thermally insulated from...

Identify the incorrect statemet from the following: A) The thermal energy of an object is the sum total of the kinetic energy of random motions of all its atoms/molecules. B) Heat is the flow of thermal energy. C) Temperature is a measure of the average kinetic energy of random...