A thermal column (or thermal) is a column of rising air in the lower altitudes of Earth's atmosphere, a form of atmospheric updraft. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection. The Sun warms the ground, which in turn warms the air directly above it. A thermal is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically.
Hi All,
I'm designing a heater for some cylindrical tubes. In my original design, I simply had a flat plate contacting the bottom of the tube. Since the tubes are only conducting on the bottom, the temperature of the contents in the tube are somewhat off from the actual base temperature. I...
I want to develop a new model for calculating the frequency of thermal radiation.
It is generally accepted that thermal radiation emits white noise with all the frequencies within a certain bandwidth. But when white noise interferes with communication systems, it is carried on what is known as a...
Homework Statement
There is a box of volume V that is divided into two equal parts: Left side = V/2 = right side.
The problem is:
Assume that there are n = (Na/2) + k particles in the left hand partition where k is a small integer ( k << Na). Show that the behavior near the maximum where n...
I am working on some basic calcs for heat transfer from polyethylene pipe. My numbers are not working out right so I need a little refresher.
The PE pipe would have a TC of about .46 W/(m.*C). to get to BTU/(hr.ft.*F), I mult by .5779 to get .266.
Assuming 10sf of PE pipe, and let's...
I am trying to understand stresses that are induced by thermal gradients. Now, I can think of a hundred different questions to ask, but I want to take baby steps to get there. Let's just talk about a simple cantilever beam in the x-y plane where the x-axis is the beam's longitudinal axis and...
I'm trying to measure the thermal white noise generated by chemical batteries.
So far I've measured the current noise, the voltage noise (V noise) and the bandwidth (delta v).
From the equation below, I'm trying to solve the equation for the frequency.
The problem is that there's an...
Homework Statement
A copper sheet of thickness 2.37mm is bonded to a Aluminum sheet of thickness 1.29mm. The outside surface of the copper sheet is held at a temperature of 100.0°C and the Aluminum sheet at 24.5°C.
a) Determine the temperature of the copper-aluminum interface.
b) How much...
Homework Statement
An ice cube at 0.00 °C measures 14.9 cm on a side. It sits on top of a copper block with a square cross section 14.9 cm on a side and a height of 18.1 cm. The bottom of the copper block is in thermal contact with a large pool of water at 92.5 °C. How long does it take the...
Homework Statement
When the temperature of liquid mercury increases by one degree Celsius (or one kelvin), its volume increases by one part in 550,000. The fractional increase in volume per unit change in temperature (when the pressure is held fixed) is called the thermal expansion coefficient...
Hi,
I'm doing a group investigation on external wall insulation for my school building. The walls do not have a cavity and thus it has been proposed to put insulation over the exterior render of the wall.
This is a fairly common building procedure.
However, my task is to investigate the...
Homework Statement
The output of a sensor which produces 10000 electrons is connected to parallel RC circuit with Resistance= 50 ohm, and the capacitance=10pF.
Calculate the signal to noise ratio at temperature 300K.
Homework Equations
SNR= 10 log (power of signal/ power of noise)
Or...
Greetings all,
My first post here on this forum. I'm currently revising for exams and have got stuck on a question where I'm not sure where I'm going wrong...Question:
1g of iron filings at 500 °C are inserted into a sealed 20 litre vessel containing 1 mol of an ideal monatomic gas at a...
Afternoon all.
I've have the following equations:
Cp - Cv = nR = Nkb
Cv = nRf / 2
Cp = nR(2+f) / 2
CvlnT = -nRlnV + const
where f is degrees of freedom
Do the Cp and Cv just stand for pressure and volume (where both are constant), so for example can the first equation only...
Homework Statement
Find an expression for thermal conductivity using kinetic theory.
Given a vacuum flask of these dimensions, find the heat loss per unit time.
Estimate the time taken for the water to cool down to 40 deg.
Homework Equations
The Attempt at a Solution...
Apologies for the break from format, but I'm not sure how to make this fit!
I'm designing an experiment to compare the insulation properties of several materials.
I would like to find the Thermal Conductivity (K) or the U (or R) values of these materials.
However essentially all I am after...
Dear all,
I have a 3D cube with a nonuniform distribution of temperature. In order to calculate the deformation of the cube using the finite element method, we need nodal forces. How we calculate the nodal force from the temperature distribution?
I am aware of a the method based on the...
Is there a relationship between increasing temperature in one test tube and keeping the other temperature constant and the time it takes to reach thermal equilibrium
Homework Statement
Is there are relationship between increasing the temperature of water and keeping the other same and the...
Can anyone explain me why the thermal boundary layer develops faster for viscous fluids?
I would just say it would develop more slowly because due to high viscosities there are low reynoldsnumbers and thus less turbulence or mixing. This causes a slow homogenization of temperature (assume a...
Homework Statement
In a domestic heating system, a room is warmed by a 'radiator' through which water passes at a rate of 0.12kg s-1. The steady-state difference between the inlet and outlet temperatures of the water is 6.0 K.
The radiator is made of iron of thermal conductivity 80 W...
Greetings PFers,
I'm working on a project where micron size metal or plastic particles are carried inside an argon or nitrogen stream at ~1 atm. The particles travel through at 1/4'' ID nylon tube before they enter a chamber where they then travel through a pyrex tube. I have four 4'', 500W...
1. I would like to test myself on how well I know my information about certain metals, some of them get me a bit puzzled.
How would you rate the electrical conductivity of cast iron?
Poor, good, excellent or best?
Also the thermal conductivity of 304 stainless steel?
Poor, good, excellent or...
I would like to test myself on how well I know my information about certain metals, some of them get me a bit puzzled.
How would you rate the electrical conductivity of cast iron?
Poor, good, excellent or best?
Also the thermal conductivity of 304 stainless steel?
Poor, good, excellent...
I was hoping someone could lend a hand with a question about thermodynamics. It's been years since I've done work on thermodynamics.
Let's say I have a plastic 275 gallon liquid container, filled with a mixture of Propylene Glycol and Water (50/50 by volume). The container is placed inside of...
Homework Statement
You build a heat engine that takes 1.00 mol of an ideal diatomic gas through the cycle abc, where segment bc is isobaric and segment ca is isochoric. calculate the thermal efficiency of the engine.
this is a 5 part problem and I already solved for Wo and Wo=Qo I solved...
Homework Statement
The statistical and spectral functions for bosonic operators \phi_a are:
G_{ab}(t,\vec{x})=\frac{1}{2}\langle \{\phi_a(t,\vec{x}),\phi_b(0,\vec{0})\}\rangle ,
\rho_{ab}(t,\vec{x})=\langle [\phi_a(t,\vec{x}),\phi_b(0,\vec{0})]\rangle .
The expectation values are in...
Homework Statement
A deuteron is the nucleus of a hydrogen isotope and consists of one proton and one neutron. The
plasma of deuterons in a nuclear fusion reactor must be heated to about 300 million K.
(a) What is the RMS speed of the deuterons? Is this a significant fraction of the speed of...
Hi,
I have to plan and carry out an experiment on thermal radiation as part of my physics lab module. The description of the experiment is as follows: Investigate the radiation from a bulb filament as a function of input power, using a pyrometer to measure the temperature of the filament...
Homework Statement
Helium in an ideal Diesel cycle is compressed from 4 L to 0.25 L, and then it expands during the constant pressure heat addition process to 0.50 L. Under air standard conditions, the thermal efficiency of this cycle is:
a) 79.5%
b) 20.5%
c) 61.4%
d) 67.4%
e) 84.3%...
1. Units of the Thermal de Broglie wavelength?
2. λ = h / (2*pi*mkT)^(.5)
3. through dimensional analysis i get S (J / kg)^.5
can you even have .5 of a unit?
Ok so I found something online but I need to understand this problem
Prove that the ratio of the adiabatic compressibilty ks to the isothermal compressibility kr is equal to the ratio of the specific heat at constant colume, Cv, to that at constant pressure, Cp
Definitions of the...
Homework Statement
How much work is done on the gas in the process shown in figure P12.24. This is from College Physics: A strategic approach, 2nd addition, by Knight, et al. Ch.12, #24
The graph shown is kPa vs V(cm^3). It's a constant temperature process (isobaric) at 200 kpa. I was able to...
[b]1. Find an expression that relates T and V in a process in which the entropy S is constant, by doing the following:
a) From thermodynamic identity dS=(1/t)dU + (p/v)dV
find the expression for dS as a function of T and V (and dT and dV).
b) Integrate the expression found in (a)...
Homework Statement A scuba diver is 17.4m below the surface of the lake, where the water temperature is 8.25∘C. The density of fresh water is 1000 kg/m3. The diver exhales a 23.6cm3 bubble.What's the bubble's volume as it reaches the surface, where the water temperature is 15.1∘C?
Homework...
Homework Statement
A 61.00m long steel measuring tape is calibrated for use at 20.0∘C. How long is this tape under the following conditions:
a hot day with 38∘C?
Express your answer using four decimal places and include the appropriate units.
i've been losing my mind over this, i swear...
This is not a homework question, but a conceptual question that I am trying to understand.
We all have experienced/heard that if you put a completely full water bottle with the cap on in the freezer, the bottle cracks as the water freezers. The explanation is that the water expand as it...
Hello,
the task is the following:
Consider a two-level system with thermal population.
a) Show that the rate equation for the state N_2 is the following:
\frac{dN_2}{dt}=w(N_1-N_2)-\frac{N_2-N_2^e}{\tau}
w=B_{12}\rho({\nu}) \,\,\, N_2=N_2^p+N_2^e\,\,\, N_1=N-N_2
N_2^p is the portion of...
For a nonmetal what determines thermal conductivity is the propagation of lattice vibrations. As T increases these lattice vibrations collide with each other more often. Does this mean that the thermal conductivity will de- or increase?
I am planing to study thermal physics on my own as I got an incompetent faculty who doesn't know anything about this subject. I want to have a detailed understanding about the topic. So can somebody suggest me which book I should follow from the following list.
1. Schroeder, Thermal...
In the harmonic approximation, why is the volume of a crystal not temperature dependent? Does it have something to do with the fact that the amplitude of a harmonic oscillator is independent of the frequency?
If thermal resistance is additive, then how can the thermal conductivity of two (or more) materials be combined? Can it? Eg. a wall filled with straw and air, a hollow brick, a mixture of polystyrene and fibreglass wool (just some random ideas off the top of my head).
Why is the Fermi level a constant in thermal equilibrium?
just like PN diode (P=material 1 ; N=material 2)
the fermi levels are the same (Ef1=Ef2) in thermal equilibrium
i confused that
why there is no energy transfer
so that can judge each energy E will obey
rate from 1 to 2 ~...
The question:
A perfect gas undergoes the following cyclic processes:
State 1 to 2 cooling at constant pressure.
State 2 to 3 heating at constant volume.
State 3 to 1 adiabatic expansion.
Deduce an expression for the thermal efficiency of the cycle in terms
of r the...
Good day,
I was recently asked to look into the process of thermal annealing of thin metal films in order to induce nanoparticle formation. However, I have been terribly unsuccessful in finding any sources that describe exactly how this works. I understand the basic idea of thermal annealing...
Hi all, could somebody have a look over my answers for this question please? The value I got for the second part seems quite feeble.
Homework Statement
The Attempt at a Solution
Part a)
Key
m = mass
cs = specific heat bronze
cm = specific heat molten bronze
Tfus = melting...
Homework Statement
160 grams of boiling water (temperature 100° C, heat capacity 4.2 J/gram/K) are poured into an aluminum pan whose mass is 950 grams and initial temperature 26° C (the heat capacity of aluminum is 0.9 J/gram/K).
(a) After a short time, what is the temperature of the water...
Hello,
i'm doing my prep for my lab experiment tomorrow and have a few questions about the experiment.
The schematic is attached.
My lab script says the following;
2 questions.
It says the precise rate of flow of water through the heat exchanger is unnecessary to know. Is this...
The question is:
Consider a thermal battery - a device for storing mechanical energy. Use two large containers as heat reservoirs where one contains ice and water in equilibrium and the other contains steam and water in equilibrium. Both are held at pressure=1atm. Energy is stored by using a...