Heat Definition and 1000 Threads

Homework Statement Problem data:[/B] http://imgur.com/a/hEz16 Homework Equations Rconduction=ln(rout/rin)/2*pi*Length*thermal conduct Rconvection=1/2*pi*Length*routside*convective heat transfer outside =>Qconduct=2*pi*Length*thermal conduct*(Tin-Tout)/ln(rout/rin)...

Homework Statement Hello, I am struggling with this heat transfer and fluid flow problem.I would really appreciate if someone could have a look over what I have done on it. I am not sure if what I have done is correct ,I would really appreciate if you could tell me if it is correct or wrong.And...

I am trying to estimate the amount of electrical power needed to heat up a material from 20C to 1000C in 20 seconds. Assuming it is 18sqin and 3mm thick, I used the specific heat which was given as 0.78 J/gC and weight 11.39g (from the destiny of 3.26). 0.78 J/gC x 11.39g x (1000C - 20C) /...

Homework Statement Silver has a Fermi energy of 5.48 eV. Calculate the electron contribution to the molar heat capacity at constant volume, Cv, of Silver at 300 K. Express your result as a multiple of R. Is the value of Cv due principally to the electrons? If not, to what is it due? ans...

Hello. I am doing a research paper on the relationship of specific heat capacity and refractive index of liquids. I am doing this by finding the relationship between specific heat capacity and concentration and refractive index and concentration. With this I can find a general trend and conclude...

Hello all, I have a question regarding heat transfer. When the Biot number is small (<0.1) a mass can be regarded as lumped. Which means that the temperature is the same everywhere in the mass. Now if the Biot number is larger than 0.1 (say around 0.5-0.8) and I still do a lumped system...

So, i was studying some fin design in a heat transfer course , and then came the part where the efficiency is to be calculated, then i noticed that when he calculated the surface area and the sides of a rectangular fin weren't included, so i searched and i found out that it was neglected...

Homework Statement I'm unsure of what exactly is changing the heat transfer direction in the triangular fin. Homework Equations $$q_{x} = -kA(x)\frac{dT(x)}{dx} (1)$$ $$q_{x+dx} = -kA(x)\frac{dT(x)}{dx} - k\frac{d}{dx}[A(x)\frac{dT(x)}{dx}] (2)$$ $$dq_{conv} = h(x)dS(x)P[T(x) - T_{∞}] (3)$$...

While changing a CD in my vehicle CD player I noticed the CD is quiet a few degrees above ambient after it has been playing for awhile, not measured just felt very warm to touch. the question is what is the source of the heat? I considered the LED but that makes no sense. Is it the motor...

Hi guys, I need help with heat transfer calculations The scenario is : Installing a coil around a hot pipe and extract the heat from the hot pipe to heat the fluid flowing through the coil. The whole assembly is insulated. I need methods/formulas to calculate the amount of heat transferred so...

Homework Statement Explain why a saucepan has a plastic or wooden handle. Homework Equations Maybe Ko = oC + 273o The Attempt at a Solution I tried looking at a book. I also know a saucepan has a plastic or wooden handle because of conducting heat. I think.

It's a well known fact that convergent and/or convergent-divergent nozzles convert internal enthalpy into forward motion i.e. dynamic pressure. But, enthalpy means both internal heat and the pressure-volume. I want to know whether the internal heat of a fluid can also be converted into forward...

Hello, assume I have an air condition unit which is not very strong and thus always runs at full power. If I let water evaporate in the room without adding heat (e.g. by hanging lots of wet towels), will this improve the heat removal by the aircon unit and thus lower the room temperature, or...

Homework Statement Consider a cylindrical tank closed by a movable piston with mass ##m=3 kg##. The radius of the cyclinder is ##r=7.5 cm##. In the tank there is a mass ##m'=2 kg## o water at temperature just below ##100°C##. At the base of the cyclindrical tank there is an electrical heater...

Hi all! I'm analyzing a fermenter and the water cooling system that cools it down. In analyzing this I've found kW and kWh required to cool down the fermenter using Q = dt*cp*m However when I try to find the overall heat transfer coefficient U using the data, I find that it varies with...

In polytropic process if we know p1,v1,v2 and q(heat added in process) then what will be the value of p2 and the coff. Of expansion (n) ?

I came up with a basic doubt on heat exchange. Consider this example situation. A cube of ice of mass ##m## and at temperature ##\theta <0°C## is put in contact with a resevoir exactly at the temperature ##T=0°C##. The question is: does the ice melts, i.e. does the ice pass to liquid state? Or...

Could anyone please help me with the area of heat sink required if I want to dump heat 6 feet below the surface? The heat to be rejected is 20000 kW Temperature of the fluid has to be dropped from 30 deg C to 19 deg C. I need rough estimates of the area required to lay down looped pipelines to...

This may be a matter of me being confused by the definition of heat. However, I view heat as the energy passed between systems of different temperatures. My problem is the following: By the principle of minimum energy/max entropy, in an isolated system (and therefore fixed internal energy)...

The thermal engine efficiency is defined as $$\eta = \frac{W_{\mathrm{produced}}}{Q_{\mathrm{absorbed}}}\tag{1}$$ A more general definition of efficiency (not only for thermal machines is) $$\eta = \frac{\mathrm{Work \, produced}}{\mathrm{Energy \, absorbed}}\tag{2}$$ But suppose that, in one...

I'm a bit confused about the following situation. In a irreversible thermodynamics process the molar heat of an ideal gas changes according to a function of the temperature, say ##c_v=f(T)## (which also leads to ##c_p=R+f(T)##) and I'm asked to determine the heat exchanged during that process...

Here I want to know how to find the heat interactions of non-ideal gases in the following processes. 1. Isobaric process 2. Isochoric process I know that internal energy U depends on temperature and volume. And the enthalpy depends on temperature and pressure. How calculation of heat...

Hi, I'm working on a project and would like some help regarding heat transfer and heat conductivity. Any help would be appreciated, I'm more or less a layman. If I wanted to use heat from the sun to heat water via a metal conductor, does the size of the heat sink have proportional heating...

Hello, I have here a complex question. My background is Chemistry and Optoelectronics. I wasn't the best when we were studying Thermodynamics at uni so I have some knowledge-gaps. Anyways, here is my problem. Can somebody explain me the whole process of the convection in the coffee roaster. So...

I'd like to get a general and clear picture of all the ways heat can be stored in a body. Suppose we have a kiln/furnace in which we put : particles a) electrons,... monoatomic molecules b) atoms of He... diatomic molecules c) atoms of H, O ... pieces of metal d) Fe, Cu... compounf...

I came up with a doubt regarding isochoric irreversible processes. Is it always true that, for any isochoric process, reversible or not, the work exchanged by the system is zero and the heat exchanged is ##Q=\Delta U##? I'm asking this because, in a exercise on thermodynamics trasformations of...

Homework Statement In an adiabatic container are placed , in rapid succession , a mass of ice , ##m_I= 2 kg## , at temperature ##T_I = -10 ◦C## and a mass of water , ##m_W = 1 kg## , at the temperature ##T_W = + 20 ◦C## . Determine : a) the total mass of water present in the container at...

Homework Statement An ideal gass is at constant volume risen to a new pressure level of ##P_f##. Find te expression for the total heat brought to the system. Homework Equations 3. The Attempt at a Solution [/B] So ##PV=nRT## and ##E=Q## ##Q=C_v(T_f-T_i)## so i just have to find...

I'm trying to figure a range of flows of coolant that will pull 200,000 Joules per minute from a heat exchanger cooling oil. The oil is passing through a head that adds 200,000 Joules per minute to 0.5 L / min. The 0.5 L is dumped into a sump with ~7 gallons of oil. The oil then passes...

For an airflow experiencing a large heat transfer, say a delta of ~600 degrees celsius, I assume compressible effects cannot be ignored. I am struggling however with some conceptual elements, such as how the pressure gradient changes along the flow when compared with compressible and inviscid...

Hi, I'm hoping to make small batches of synthetic minerals by compressing & heating small liquid or semi-liquid samples of sodium silicate w/ variable amounts of other salts dissolved within. As I understand it, many of these will require high pressure & temperature to form. So my strategy is to...

Are there any equations out there which can calculate the heat dissipation of a water-cooled radiator with a fan on it? I would assume some of the variables would include: -Volume of the radiator (240 x 199 x 45mm)=2149200mm^3 -Specific heat of water (4.187 kJ/kgK) -Specific heat of the copper...

My question is: according to Carnot cycle, the maximum efficiency of a heat engine is given by 1 - T2/T1, where T2 is the temperature of the cold source and T1 the temperature of the hot source. So, accordingly, as higher T2 is for a same T1, lowest is the efficiency of the engine. But, the...

so for one of my assignments i need to make a calculation which involves the mixture to be made of different types of substance... the heat capacity for each of the different unknown substances that were given: substance 1 = 1250J/kg °C substance 2 = 1130J/kg °C substance 3= 4100J/kg °C i need...

Hello Forum, Thermal energy (heat) is associated to the infrared portion of the electromagnetic spectrum. Why? I know the human body emits radiation in the infrared (10 micron). Heat is associated to warming. Are infrared wavelength the resonant wavelengths at which molecules in most objects...

I'm working on a solar heated pump project and require and suitable metal ..that'll absorb as well as radiate heat well. It should should also be cheap to use .

Homework Statement At low temperatures, the specific heats of metals is described by the expression ## c=kT + AT^3 ## , where k and A are constants. Here the first term describes the contribution of free electrons and the second the lattice contribution. How much heat is required to raise the...

Hi everyone, I have been looking at Carnot heat engines in a bid to better understand entropy, and I can't figure out how it actually does work. Why does the piston move? In some diagrams I have seen weights being removed from the piston, reducing the pressure at constant temperature and...

This is more of a general question about what temps you set your hot air gun. I just got a new rework station and messed around with it for a bit on a old PCB removing large and small components. I find it easy to damage the PCB. In general I tend to solder pretty hot, anywhere from 300C to 400C...

Homework Statement Given that aluminium has a specific heat of 0.9KJ/KgK, a melting point of 660 degrees Celsius and a latent heat of fusion of 390KJ/Kg, calculate the heat energy required to melt a 10Kg ingot, starting from a room temperature of 20 degrees Celsius. Homework Equations dQ= m c...

So let's say a cactus will catch on fire at 500 degrees Celsius. If you use a 500 degree flame it will light on fire. But if you took it into a 500 degree room will it also light on fire?

Hi. I would like to ask a simple question. Here is the link of the file I study on. Immediately before the formula 4.9 for Biot number. Lc=V/As but I cannot understand it and I think it is not clear enough. How it appears, for what the word "characteristic" stands for, for example a pipe? For...

I'm trying to understand the chemistry of stars. At what point do molecules really end? I guess there would be no one temperature where every molecule of hydrogen breaks apart in unison, but there should be an equation that says: if a diatomic gas is held together by 100 kJ/mol, at a...

Dear All, I am facing a problem in Ansys Ansys issue. I am solving a model (Transient Thermal Analysis (Heat Flow from Hydrothermal Vessel)) in Ansys 16.2 Workbench While reaching modeling stage, and upon running the simulation, program gives an below errorAn error occurred while starting...

Homework Statement Homework Equations equation with each part. The Attempt at a Solution I did part a) b) and c) on my own: Part d: I am having trouble at this part. I understand how to draw the heat curve but I am confused on what numbers I should use for the x-axis of the graph. I...

I'm a design draftsman, I have bar of 17-4 stainless steel it weighs 6.9 lbs. The Product Data Sheet shows a specific heat 0.11 (BTU/lb/F (32-212F) (www.aksteel.com) It's at room temperature or 70 degrees F. I want to cool the bar to 50 degrees F. The surface area of the bar is 245 sq. inches...

Homework Statement This is the question as it was given...no other data was given. Obtain Fourier's heat conduction equation in three dimensions in an infinite medium in steady state.What modifications will be required in case of a finite body? 2. The attempt at a solution Well I can derive 3D...

I want to reduce the amount of water present in the digestate coming out of my Anaerobic Digester. The traditional method would be to boil it until I've removed as much off as I want. However, this is expensive from an energy consumption point of view. There's a great video on Youtube showing a...

Is it possible for me to make a flash light into a "laser" hot enough to burn through paper. Here is what I have: a light prism, 2 light splitters,(the can separate light so it goes 2 ways) 2 magnifying glasses, and a microscope.(I don't want to use it though) If there is any thing else you...

If a sheet containing two very thin slits is heated (without damaging it), what happens to the angular location of the first-order interference minimum? a) It moves toward the centerline. b) It moves away from the centerline. c) It doesn't change.Condition for m-order interference minimum...