Heat Definition and 1000 Threads

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...

Homework Statement [Update: just realized that the LMTD is a temperature difference, so my question was not valid] :P Calculate the logarithmic mean temperature difference (LMTD) to heat water flowing through a tube from 21 C (Ti) to 40 C (Te) if the tube has a fixed temperature of 45 C (Ts)...

I am trying to find an expression for the average Nusselt number corresponding to heat transfer from an isothermal disk. Given: ShD≡hm(r)D/DAB=Sho[1 + a (r/ro)n] (1) Sho=hm(r=0)D/DAB=0.814ReD1/2Sc0.36 (2) Relevant equations: Average nusselt number is defined as Nuav=havD/k where k...

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...

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...