Heat Definition and 1000 Threads

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...

Homework Statement I have one dimensional heating system. In the center is heating source which is heating two PVC elements located on both sides of the heating source. Heat distribution in other dimensions is negligible because of insulation. Thickness of one PVC element is 0,051 m and surface...

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 atmospheric pressure. Assuming no heat exchange with the surroundings, what is the temperature when the system reaches equilibrium? What are the fractions of weights of...

Is it possible to heat a specific amount of liquid water, say 1kg, (at 1 atm), let's say from 20°C to 21°C, without changing the universe's entropy? (Sorry but I have a little blackout on simple thermodynamics...) -- lightarrow

Hi PF! I'm wondering if my solution is correct. The PDE is ##h_t = h_{zz}## subject to ##h_z(0,t)=0##, ##h(1,t)=-1##, and let's not worry about the initial condition now. To solve I want homogenous boundary conditions, so let's set ##v = h+1##. Then we have the following: ##v_t = v_{zz}##...

Homework Statement I'm asked to find the specific heat of Metal X in this simulation: http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/thermochem/heat_metal.html Mass of Metal X = 120 g Temp of Metal X = 220 degrees Mass of Water = 30 g Initial Temp of Water = 20...

Hello, I have problem. I'm haveing my soldering iron tips oxidize very fast. I need to know what wattage to use to get melting point of solder. I think I'm overheating my tips. The melting point of the solder I have is 221C (430F). Is there a formula to calculate temperature from wattage input...

Homework Statement I have ##C= NK_B (\frac{\epsilon}{K_B T})^{2}e^{\frac{\epsilon}{K_B T}}\frac{1}{(e^{\frac{\epsilon}{K_BT}}+1)^2} ## and need to sketch ##C## vs. ##T## Homework Equations See above The Attempt at a Solution I have ##C= NK_B (\frac{\epsilon}{K_B...

The heat source for this experiment is a compost pile (1 cubic meter), I know that the inside of the pile will reach approximately 50C for 2 weeks or so. Right now it's winter so the temperature will stay around 0C (average). The thermal conductivity of compost can vary greatly but in this case...

I've found a lot about using water to find the amount of heat released by something but the experiment I want to run would take about two weeks to complete so that's probably not a viable solution for me. I know what the temperature will be and that it will remain mostly constant, is there...

Hello everyone. I've been doing a bit of independent study for this topic without much background and so my thermodynamic knowledge is fairly limited. I came across this problem and I'd like some assistance with it! If anyone can help out, I would be very grateful. A lot of the equations came...

Homework Statement : [/B]At the beginning of the compression stroke of a two-cylinder internal combustion engine the air is at a pressure of 101.325 kPa. Compression redeuces the volume to 1/5 of its original volume, and the law of compression is given by PV^1.2 = const. If the bore and stroke...

I have a dilemma, which has been nagging at me for a week. So first off, can anyone verify my definitions are correct? Heat is the flow of energy, and that flow is caused by the collisions of the atoms in a system. The collisions cause a transfer of KE, hence heat will flow from a substance...

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...

Hello all, this is related to a project that I am working on. It is not directly related to the project but as part of it, I thought it would be a good idea to check the temperature difference that I need to maintain in order to effectively transfer a certain amount of heat between the TH in a...

Hello, Im struggling a bit with this problem. (uploaded)I don't know how to sketch the equivalent thermal circuit for any of them. Does it have to look like anything like that? the thermal circuits are for b) parallel connectd right? and for aswell? And I am getting wrong answers for a)...

What is the physics behind heat transfer between two panes of glass? Commonly windows now are filled with argon (some cost) or krypton (pricey) At a given temperature all gas molecules have the same energy per mode, so heavy ideal gas molecules move more slowly than light ones, so heat...

So I have been studying solving separation of variable, heat equation and came across 2 set of lambda equation. and lambda = 0 have the same equation. Is it different?

ok, we have a really efficient way to make heat (adding energy into a system) all we have to do is pass a current through a high resistance wire, boom, close to %100 heat generation. however, from what I can tell there is no way to create coolness (take energy away from a system) like that. we...

Hi i was thinking about how to calculate the temperature lost by Degree Celsius per minute and was wondering if you had the surface area of the object, its initial temperature, a constant flow rate of air around the object and probably also need some coefficient of heat loss based on the...

Is there a meaningful way to convert the energy of an electromagnetic wave to a temperature? I mean this more along the lines of how the universe has a temperature of 2.7 kelvin due to electromagnetic radiation. I'm honestly just curious to determine the temperature of the universe after nearly...

I got an original side door from 1922. Needless to say it's all warped and dented around the sides. My best attempts to weatherize have failed. It's extremely drafty. Various weather strips have not worked and the storm door helps very marginally. I was about to give up and just plastic wrap it...

I am a little unsure how to get started with a homework question. Essentially, I have to calculate the local heat flux at a distance 1.2m (x) along a pipe. I have the fluid's properties and have calculated the Reynolds number, for which I've determined the flow to be turbulent and therefore do...

Hi. A simple model explains resistance in metals with collisions of the electrons with the stationary atomic cores. So I assume more collisions result in a higher resistance? But for the dissipated power we have ##P=U^2/R## , which is large for small resistance. I have difficulties combining...

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...

Homework Statement Below, two experiments (1 and 2) are described, in which the same quantity of solid carbon dioxide is completely sublimated, at 25ºC: The process is carried out in a hermetically sealed container, non-deformable with rigid walls; The process is carried out in a cilinder...

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...

Hello All, I have a question for heat exchange calculation and hope someone can help. I would like to recover the "cooling energy" from a ice melting pool for air-conditioning for a small office. I plan to install three fan coil units with 800CFM for the office with closed loop water pipe to...

Homework Statement A player bounces a basketball on the floor, compressing it to 80.5% of its original volume. The air (assume it is essentially N2 gas) inside the ball is originally at a temperature of 20.5°C and a pressure of 1.80 atm. The ball's diameter is 23.9 cm. By how much does the...

Is there an easy way to calculate the temperature on one side of a material if we know what material it is, the thickness of it and the temperature on the other side. Basically can we calculated the heat transferred through a material if heated. Thank you

We have a piston with ideal gas in it and a weight. The weight is placed on the piston. The gas is heated externally and the gas expands. Will the expansion be isobaric or isothermal? One argument would be: the expansion will be isobaric because the weight is providing constant pressure. The...

I left my unopened icy cold Coke out on my desk yesterday. When I came in today it had, of course, lost it's icy edge and had achieved room temperature. Then I asked myself...will my drink ever actually achieve room temperature or will it always be slightly colder then room temperature? Can...

Homework Statement Solve the time dependent 1D heat equation using the Crank-Nicolson method. The conditions are a interval of length L=1, initial distribution of temperature is u(x,0) = 2-1.5x+sin(pi*x) and the temperature in the ends of the interval are u(0,t) = 2; u(1,t) = 0.5. Homework...

Homework Statement A 45 kg steel ball is projected vertically with an initial speed of 280 m s . While the ball is rising, 8.5E5 J of heat energy are produced due to air friction. What is the maximum height reached by the ball? Homework Equations Ek = 1/2mv^2 Ep = mgh The Attempt at...

Homework Statement I have a bloc sitting on a horizontal table, and we shoot a ball through it. The speed right before entering the block is v and the speed when it exits the block is v/2. I need to prove that the fraction of the initial energy that is lost due to heat is 3/4 - γ/4, where γ is...

Homework Statement Can you please help me with this thermodynamic question?I am not a student. An aluminum cylinder with an interior area of 4.1875 sq ft (or 603 sq in) contains 7.445 lbs of CO2 gas under pressure.The volume of the cylinder is .582 cu ft.The temperature of this gas is 110 deg...

< Mentor Note -- thread moved to HH from the technical engineering forums, so no HH Template is shown > Hi! We are looking for alternative ways to heat up flat iron without using electricty or fuel or solar panel. So we came up with friction (as it is also a source of heat). But we don't know...

Homework Statement In heat impervious bowl with unknown volume there are unknown amount amount of water(10 degress celcius). Metal ball with unknown mass / volume / specific heat(ball temperature was 100 degress celcius) - was landed in water and managed to raise temperature to 40 degress...

http://lookpic.com/O/i2/73/DYktKEGg.jpeg Hello Dear Friends We produce Lifting Electromagnet for Steel Scrap charging of Induction furnace, bottom plate of electromagnet is made of Stainless steel . my question : Can We use AL OR SILVER Spray for Spraying bottom plate that Radiation heat...

Homework Statement In an industrial fryer is f.e. 400 kW. Heating capacity installed. The fryer may contain as much as 1.450 ltr of oil. I can fry 2.000 kg of chicken nuggets per hour in that. These products loose 7% of moisture/water in this process. That water can only escape from oil in gas...