This is an experiment I have wanted to do for a few years now but don't have the necessary equipment. GR tells us if you have identical objects with the same weight exactly when they are at the same temperature, then when one object is heated, it will weigh more. This is because the...
Does anyone here have experience with COMSOL?
I want to model a system where i have a fluidic channel containing warm fluid running through a block and I want to analyze the heat transfer from the channel into the block .
To establish the warm fluid I put an initial temperature condition at...
A HUGE topic of conversation on many car forums, I thought I would bring it here.
Many cars have chrome tin in the engine compartments to make them look flashy. However, for decades now, people say the chrome reflects the heat back onto the engine block and to paint the engine compartment black...
Hello, I have a final tomorrow and I am having a difficulty to understand the heat treatment subject. I would be happy if someone can explain this question or suggest a good document shorter than Askeland (i know it is very good but there is no time unfortunately). Thank you.
Two different high...
Homework Statement
I would really appreciate if you could give me some hints regarding what exactly to do at iv)[/B]
iv)
Given formulas:
Homework Equations
f(y)=(ro*R^5/E*t^2)
The Attempt at a Solution
we know that f(y)=0.75
1ton TNT=4.184*10^9 J
ro=1.003kg/m^3
We have the above...
Homework Statement
so, i had this question where i had a sphere and a cylinder with given dimensions and propreties ( roh, C and k) he also gave me initial temperatures, then both of them dipped in a bath of water of given temperature but unknown h ( convective coefficient) then he gave me the...
Homework Statement
Homework Equations
The Attempt at a Solution
I do not know exactly how to start this problem.
I would really appreciate it if you could give me some hints.
I know that e^ - t/tau=T(t)-Twall/Ti-Twall
where tau=m*cp/hA
where h=convective heat tr.coeff
and T(t) is desired temp...
Hi Guys
While studying physics for my masters (doing it in material science engineering), huge amount of questions appeared.
First, let's imagine two experiments
1) One enclosure with perfect reflective walls (R=1 over the entire thermal radiation spectra) at a temperature T1 and a body inside...
Homework Statement
State and use simple assumptions to show that ' Power is proportional to V^5' is the expected relationship for a pure tungsten filament bulb.
Homework Equations
V=IR
I=dq/dt
Q=mcT
The Attempt at a Solution
I tried to use a simple model where the rate of heat loss is...
Hey all, first time posting!
So I'm having trouble with understanding the differences between the constant heat flux and constant temperature condition when not in a textbook. Some research I have begun working on involves a strip of heat tape sandwiched between two aluminum plates which are...
Hello, i am new at the forum and i hope i can help and get helped so we can move forward in our projects/jobs/studies. I also ask please to correct any gramatical or vocabulary mistake, since i am still learning english.
Now to the actual problem.
I am already building some kind of epoxy resin...
Homework Statement
Using equipartition law, find specific heat of gas containing triatomic linear molecules. Will the result be different if the molecule was non- linear? In what way?
Homework Equations
According to equipartion theorem, each degree of freedom gets (1/2)kT kinetic energy and...
I have uploaded a page from my prof's lecture on specific heat.
Its given that average energy for each vibrational mode is $$\frac{h\nu}{e^{\frac{h\nu}{T}}-1}$$
Hence $$U=(\text{number of vibrational modes)}\times\frac{h\nu}{e^{\frac{h\nu}{T}}-1}$$
In the lecture slide, the number of...
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...
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...