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.
thermal expansion of wire??
hi I've got this 3mm iron-chromium-aluminium wire fixed at both ends, heated to approx 1000k (max 1200K) and suspended horizontally approx 1metre long.
the wire it would appear has been extended by about 8mm, similar to what would be expected when its hot, only it...
For example, I place a simple steel cube weighting 1 kg in a room [filled with air] at 20C [room temperature]. - how fast would the cube heat up to 20C (yes, actually equilibrium would be a bit lower than 20C, but lets.. imagine that is is a infinitely large room and .. yes, you get it ) ?
Yes...
Stainless steel has emissivity of 0.12. It means it only absorbs 12% of radiation and reflect the rest of the 88% as well as tranmitting the 12%. Now if you heat the stainless steel to say 300 Celsius. It won't transmit the 300 Celsius but only a little of it. This is why thermal imagers can see...
I want to calculate the time it takes for a spherical sample (radius, r) to reach thermal equilibrium in an oven where the temperature is held constant.
I don’t need a super accurate answer, within 5-10 seconds is sufficient. Is it reasonable to simply say that when the Fourier Number (Fo) is...
Homework Statement
To a very good approximation, ammonia obeys the Bertholet equation of state,
which readsPV=nRT+\frac{9}{128}(\frac{nRTc}{Pc})(1-6\frac{Tc^2}{T^2})Pa)Suppose we have 500 grams of ammonia under a pressure of P=3.04 atm
and at T=323K. Calculate the volume of ammonia according...
Homework Statement
i need to find the thickness of the insulating material that is needed to block out the heat that is coming into the room.
the area of the affected wall is 3.3m2 the temp in first room is 18 degree celsius while the 2nd room is 45 degree celsius.
the thermal...
In my thermo class I'm currently taking, the professor constantly says thermal energy cannot be completely converted into energy of motion. Just to be clear, I'm not arguing this point. I'm just wondering why we say that, when earlier in the course it said that thermal energy at the...
Homework Statement
Two infinite plates are kept at different temperatures T_{cold}<T_{hot}, with vacuum between them. A very thin plate, isolated from the environment, is inserted between the two plates. How will the net rate of heat emission from the hot plate to the cold plate change...
Dear all,
I am not an expert of Chemistry and I would like to know if there is a reversible reaction that can be activated only by thermal energy. The result of the reaction should be something which can be brough again to the initial state, releasing again the thermal energy stored. I was...
Hi,
Can anyone tell me at what temperature a 25micron sulphuric acid anodic coating will start to breakdown. I have noticed that after exposure to 135°C the electrical properties of the coating have dropped drastically.
Regards
Dan
So I have been reading about the cross section of neutron capture and have been reading about how the cross section for neutrons in a given material depends on neutron energy, the most important factor obviously. But I have not seen as much information on how, for a neutron of a given thermal...
Hi.
I am trying to calculate the thermal stresses in a steel cube which is placed inside another steel cube of bigger dimensions, supported by steel bars at the base and sides.
Both the cubes are in contact with fluids at different temperatures.
Can someone please suggest the methodology as i...
Not homework, just need some help with explaining the effect of the following 2 things on the melting point/freezing point and boiling point of water;
1. Pressure is increased
2. Impurities are added
If possible, can the explanations be as explicit as possible?? I have really no idea how to...
A layman with an interest in quantum mechanics here.
Just want to check I understand something...
Is the phenomenon of electromagnetic waves being emitted by an atom due to it being hot (black body radiation) different to that of such waves being emitted as a result of absorbing light...
Hi,
I have to model a transient thermal problem in Ansys. I just need an outline of how I should proceed.
The Problem:
I am trying to model the cooling of a solar collector reciever tube from 150 degree celsius to ambient.
My attempts have involved the following:
1. Initial condition...
Homework Statement
You use a steel measuring tape and measure the length of an aluminum bar. You measure a length of 20.700 m when the temperature is 21.2 degrees C. What is the measured length when the temperature is 29.4 degrees C?
Homework Equations
L = L0(1+\alpha\DeltaT...
Hey all,
I'm using a peltier device for a cooling system I'm working on. The metal leads connecting the peltier to a power source keep falling off. I am looking to coat them with epoxy that must be a thermal insulator. It also MUST be an electrical insulator.
The problem I've had is that...
Note : My syllabus only go until thermal equilibrium in 2 objects , i am wondering what will happen and how to calculate if there are 3 substances in contact. So i formed a question on my own hoping it can be solved.
*my teach refused to show me calculations saying it is unrelevant to exam...
Hi All,
I'm looking at the fundamental aspects of heat transfer - as I'm not a mechanical/thermal engineer but soon to undergo a project wherein I need to deal with some aspects of thermal engioneering.
In the text, which I've been reading (for finite element analysis), it talks of mass...
Homework Statement
HELP with physics homework, thermal energy?
I cannot figure out how to solve this problem, can someone show me how?
A small engine pumps 100 liters of water from a well 300m deep. What would the change in temperature be for the engine 20 liter cooling system (filled...
Homework Statement
obtain an expression for the thermal conductivity of a gas at ordinary pressures. The thermal conductivity of Argon (atomic weight 40) at STP (standard temp and pressure) is 1.6e-2 W/mK. Use this to calculate the mean free path in Argon at STP. Express the mean free path...
Hello all,
Sorry if this is under the wrong section. I need to attach some thermocouples to a light to test how it heats up over time, and I was wondering what type of tape I should use to attach them. I was thinking some kind of conductive tape. Has anyone done this before/have a suggestion...
Homework Statement
In an experiment to measure the temperature of the flame of a Bunsen burner, a lump of copper of mass 0.12 kg is heated in the flame for several minutes. The copper is then transferred quickly to a beaker, of negligible heat capacity, containing 0.45 kg of water, and the...
Hello,
An electrical power station situated in Northern Canada uses water to cool the steam as it leaves the turbine. Suggest why the efficiency of the turbine would be greater in winter than in summer:
I first started to think in terms of the efficiency equation I have for heat engines...
Hi, :smile:
While running, a person generates thermal energy but maintain approximately constant temperature:
Distinguish between the terms: Temperature and Thermal Energy
I know temperature is a measure of the average Kinetic Energy of molecules but I always get confused when it comes...
Homework Statement
Determine the actual shape of a copper bar in contact with a furnace at a constant 200 C at one end and a constant ice bank at 0 C at the other end.
Diameter of the rod is 2.54 cm. Length is .5 meters. Thermal conductivity of copper is 380 J /
(smC)
Homework...
Hi,
I have read the defination of a time constant on the internet and yet still don't quite understand it. How do I relate it to the following sentece and what does it mean:
" The transient energy will have a duration much shorter than the thermal time constant of a bridge wire."
ANY...
Homework Statement
\"Explain why the joule expansion experiment implies that (dT/dV) const U = 0\"
Homework Equations
The Attempt at a Solution
So I\'m not sure how to do this!
Using 1st law we can say that at const U Tds = pdV, but not sure how to get what they want..
Hi :smile:
1. A car tyre has a volume of 18 x 10-3 m3 and contains air at an excess pressure of 2.5 x 105 N/m2 above atmospheric pressure (1.0 x 105 N/m2) Calculate the volume which the air inside would occupy at atmospheric pressure assuming that its temperature remains unchanged:
My...
Hi Experts
I'm joining aluminium fins to an aluminium body as part of a heat exchanger project. There are a number of variables here and I would like to evaluate them to achieve the best results.
The best (simplest ?) method I can come up with is to attach several groups of fins to a common...
The thermal conductivity of wood is 1 BTU per hour, per square foot, for a temperature gradient of 1 F° per inch. Convert this to units of W/mK, knowing
1 F° = 5/9 C°
1 inch = 0.0254 m
1 foot = 0.3048 m
1 lb = 0.453593 kg
1 kcal = 4184 JI know there are conversions between BTU and...
Hi
The mass of liquid nitrogen in an open beaker is found to have decreased by 46.3 g in 10 minutes. If the S.L.H of vaporization of nitrogen at is boiling point is 1.99 x 105 J/Kg, at what rate were the surroundings heating the beaker?
This is what I did:
Q / 600 = 0.0463 / 600 x 1.99...
Hi :smile:
The mass of liquid nitrogen in an open beaker is found to have decreased by 46.3 g in 10 minutes. If the s.l.h of vaporisation of nitrogen at its boiling point is 1.99 x 105, at what rate were the surroundings heating the beaker? Why is the heat capacity of the beaker irrelevant...
I understand that thermal conductivity is W/(m.K) and u-factor is W/m² K. Obviously U factor is energy transfer over an area but how does this compare to thermal conductivity?
Homework Statement
An ipod is left running inside a thin insulating case 2.5mm thick with thermal conductivity of 0.02W/K/m. The case is black and at 25 degrees C and exchanges energy with its surroundings, all of which are at 20 degrees C by radiation alone. What is the temperature inside...
Homework Statement
A student measures the length of a brass rod with a steel tape at 20.0°C. The reading is 80.00 cm. What will the tape indicate for the length of the rod when the rod and the tape are at each of the following temperatures?
a) -18.0°C
Homework Equations...
Guys,
Maybe someone can help, as I am having a brain fart here trying to think of how this all works. Say for instance I have an electrical part that dissipates 10 W of power and I am removing this power through the use of a thermal strap to a heatsink.
I think the...
Hi, :smile:
I am learning about thermal physics and I have a doubt:
Say that water and a box of wood, both with the same mass, are at 50 degrees Celsius.
This does not mean that they have the same amount of energy (internal energy in this case?) right?
That is because in water for...
Hi everyone.
I am working to find out temperature distribution and thermal stresses in a structure. Can anyone please advice on which could be the best computational tool (ANSYS or ABAQUS or any other) for such kind of calculations.
Thanks in advance.
Hello,
I would like to compare rods made of different materials based on the amount of force or stress they would generate when fixed at both ends. normally, I would just compare the product of the coefficient of thermal expansion ( \Alpha ), change in temperature ( \Delta T ) and modulus (E)...
We know that youngs modulus(E) is stress/strain. In case of free body thermal expansion, if the material is allowed to expand and contract freely, than there are no stresses in the body. The body has only strains.
That means the stresses are zero in case of free expansion. So in this case...
i have a question:
In an Insulated Vesse, 250 g of ice at 0 degree Celsius is added to 600 g of water at 18 degree Celsius. Find: a) Final temperature of the system. B) How much ice remains.
PLEASE POST THE WAY HOW TO DO THIS QUESTION :D
Hi to all
Can some one help me for below question:
What is different between "isotropic thermal conductivity" with " anisotropic thermal conductivity" ?
where and when we must use isotropic or anisotropic ?
which one is more accurate?
I solve an example in a FEM software and it is...
Homework Statement A cylinder contains a mixture of helium and
argon gas in equilibrium at a temperature of
121 C.
Boltzmann’s constant is 1.38066 ×
10−23 J/K, and Avogadro’s number is 6.02 ×
1023 mol−1. What is the average kinetic energy of each
type of molecule?
Answer in units of J...
Homework Statement
Homework Equations
\alpha(T)dT = \frac{\partial L}{L} <--- Differential Equation given on formula sheet
The Attempt at a Solution
\alpha(T)dT = \frac{\partial L}{L}
\int_{l_0}^{l_1} \frac{\partial L}{L} = \int_{T_0}^{T_1} \alpha(T)dT...
Homework Statement
Homework Equations
\alpha(T)dT = \frac{\partial L}{L} <--- Differential Equation given on formula sheet
The Attempt at a Solution
\alpha(T)dT = \frac{\partial L}{L}
\int_{l_0}^{l_1} \frac{\partial L}{L} = \int_{T_0}^{T_1} \alpha(T)dT...
Hey, i just have a couple questions that need answers. Below I have a list of notes I have taken whilst researching how to analyze thermal and pressure stresses in a y bar exhaust. Things I need to design include the valve and the exhaust pipe itself. Am I missing anything to analyze? About...
For those of us trapped in a corner with difficult choices of whether to believe many worlds are splitted off billions of times every second or whether there is Godlike power to collapse the wave function in the universe or whether waves can travel forward or backward in time (Transactional) or...
Homework Statement
The mass of the water m_w in a beaker is 0.03988kg
the mass m_g of the glass the beaker is made of is 0.031kg
the specific heat c_p_g of the glass is 800 J/(kg*degrees C)
the specific heat c_p_w of the water is 4178 J/(kg*degrees C)
m_w*c_p_w = C_w where C_w is the...