Questions tagged [thermal-conduction]

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Heat conduction through hollow cylinder with constant internal and external temperature

Consider a hollow cylinder of inner radius $r_1$ and outer radius $r_2$. The entire surface of the cylinder is kept at constant (but distinct) temperatures along the interior and exterior. I found ...
514 views

Are there any thermal insulation equation that uses change over time and temperature?

I'm currently working on a science experiment to find out whether the thickness of a material affects the insulator's ability to insulate, and if so, to what extent. I've set up an experiment where ...
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Which method of heat transfer is faster? Convection or Conduction? [closed]

True or false question! Conduction is the slowest mode of heat transfer - true (given in internet) Now my question is, let's say you want to boil some water, in this case should not be the conduction ...
1k views

Calculating the temperature of flowing gas in copper tube

A copper coil is immersed in a water bath. The water bath provides heat to heat the nitrogen gas when it passes through the copper coil. Nitrogen gas at room temperature is passed through the copper ...
1 vote
938 views

Is rust a good thermal insulator as opposed to bare steel or hardened clay?

I have no idea, if this is the correct site to find an answer on this topic, but considering it's a question of physical interactions I wanna give it a shot. I am in no way a physicist, just a ...
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Using Thermal Conductivity measurements to estimate the thickness of a LI-900 Silica tile required to lower temperatures by 1450K

I'm diving into Fourier's Law at an IB Physics level, where we use the equation ΔQ/Δt = k * A * ΔT/Δx. This equation is directly from the IB Databooklet, and as it's the first time it's been included ...
14 views

Effect of having infrared reflective paint on a room with and without a heat source

I am trying to check if my understanding is correct. This is not really a question but a request for validation. I hope this is allowed. When painting with a heat reflective paint there are two ...
218 views

Heat Transfer - Critical Radius of Insulation

A steel pipe with foam insulation is embedded in a concrete wall. The steel pipe is carrying cold water and therefore gains heat from outside atmosphere. Heat transfers through the concrete wall, foam ...
346 views

Conductive heat transfer water through concrete to water

So I've been asked to do a calculation on heat loss from a floating swimming pool. Strange and not something you're likely to come across on an everyday basis. I have already calculated the ...
957 views

How does hot air rise?

If a balloon is filled with hot air, it is rising due to buoyancy: the mass of the hot air inside the balloon is lower than the mass of the same volume of the cold air outside the balloon cavity. ...
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Is stoßlüften - quick exchange of air through windows actually more efficient than slow exchange through a wall ventilation fan?

In German areas with near air-tight homes, it is recommended that full house ventilation is performed by stoßlüften - opening windows fully to exchange as much air as possible in shortest amount of ...
765 views

Proportion of heat or energy passing through a window by radiation vs conduction

I'm trying to understand how modern window films or coating (so-called "Low-E" coatings) can improve the "R" value of the window just by reflecting internal room radiant energy (presumably long-wave ...
603 views

I have a plastic housing (for a printed circuit board- PCB) in the shape of a box (a *b *c) with L (thickness). Its material properties are: *thermal conductivity: $k_h~[... 12 votes 2 answers 8k views Can a tea light really heat a greenhouse? It is a common suggestion amongst greenhouse enthusiasts that a long-burning tea light inside an upturned terracotta pot can be enough to keep frost away from plants. Is this possible? Instinctively, ... 0 votes 1 answer 309 views Error in thermal time constant from measurement I would like to know how to calculate the error in thermal time constant ($\tau$) based on temperature measurements. For example, lets say I have a plate with a thermocouple and I provide it with a ... 4 votes 2 answers 2k views Calculating new temperature of an object when air temperature changes I'm trying to calculate the new temperature of an object when the air temperature around it changes, given a period of time. Basically I get periodic readings from an air temperature sensor in a ... 8 votes 6 answers 6k views Cup of warm water suspended in a pot of water held at a steady boil The question asked by a website is as such (possibly behind a paywall): A cup of warm water is suspended in a large pot of water held at a steady boil. Will the water in the cup ever boil? Assume ... 0 votes 1 answer 416 views Is it wrong to derive Log mean temperature difference (LMTD) of a Heat Exchanger, this way? I tried deriving the LMTD of a parallel flow double pipe heat exchanger by first finding the temperature profiles of the hot and cold fluid and then averaging them over the entire length of the Heat ... 6 votes 2 answers 1k views Wiedemann-Franz law The Wiedemann-Franz law states that the ratio of thermal conductivity$\kappa$and electrical conductivity$\sigma$for metals fairly accurately obeys$\kappa/\sigma = LT$, where$T$is the ... 1 vote 0 answers 33 views How does white powder coat change aluminum emissivity? I have a telescope with an aluminum tube powder coated white. I took 940 temperature data points from a temp sensor attached to the tube and a weather station for ambient temperature. It seems the ... 1 vote 1 answer 246 views Conductivity of an Ideal Gas I'm currently going through the derivation of heat flow equation of an ideal gas in the An Introduction to Thermal Physics book by Schroeder and had some trouble understanding it. It uses the setup ... 0 votes 1 answer 50 views How does wetting cotton increase its UV transparency? Anecdotally, a dry cotton T-shirt prevents sunburn better than a wet one. This has also been measured (Gambichler et al., "Influence of wetness on the ultraviolet protection factor (UPF) of ... 0 votes 1 answer 321 views Defining convection boundary conditions for 1d transient heat equation in cylindrical coordinates I am currently working on a problem with a hollow cylindrical graphite crucible that will contain liquid aluminum and I am trying to get the transient temperature function using the following heat ... 1 vote 0 answers 19 views Temperature Estimation for Insulated Bottom Surface in Water Cooling In a 2D plane heat flux q'' is incident on an insulation layer (which has a thickness L and a thermal conductivity k). The bottom surface of this insulation layer is exposed to water cooling with a ... 1 vote 2 answers 2k views Rate of conductive heat transfer at a boundary between two different materials I have one block of material 1, and one block of material 2. They are in contact with each other, sharing an interface of area A. Material 1 behaves as a lumped capacitance, with temperature T1(t). ... 2 votes 1 answer 392 views Vapor pressure of sublimating ice in vacuum I am trying to find a vapor pressure of sublimating ice as a function of thermal energy being absorbed by ice. Basically, I am starting with a sample of ice (t=200K) in a vacuum. From there, I am ... 1 vote 1 answer 65 views Thermodynamics: A piston can freely move inside a horizontal cylinder which is closed from both ends Is it safe to say that regardless of where the piston is, the final pressure on each side of it would remain the same. And if yes, then why? 1 vote 2 answers 250 views If the heat transfer in a particular direction is negligible then is it necessary that the temperature variation will also be negligible? Imagine having a rectangular block. If the heat transfer is predominant in only one direction (say x) and the heat transfer in the other two directions (say y and z) is negligible, then can I conclude,... 2 votes 1 answer 543 views Thermal physics of cooking with an electric stove I'm wondering why stoves have a 1-9 scale of the amount of heat and a not temperature scale. My understanding is that for each of the modes corresponding to a number, a certain amount of heat is ... 0 votes 2 answers 449 views Regular vs differential form of Fourier's law? I was watching some of Michel Van Bizen's lectures on youtube, (Heat Transfer, video 16-18) and the guy mentioned that if a pipe or rather a bar was connecting a heat source and a cold source, we ... 1 vote 1 answer 45 views Rate of Thermal Conduction between different materials I'm aiming to use differential equations to simulate thermal transfer between different materials in a 3D space, however, my physics knowledge is lacking. Is there a formula that can give the rate of ... 0 votes 1 answer 35 views How does a counterflow heat exchanger achieve efficiency of 0.5 and greater? Basic thermodynamics says that for thermal energy to flow from one place to another there must be a difference in temperatures. For example typical heat recovery units use hot air (25 °C) to heat cold ... 0 votes 1 answer 297 views Why no heat is absorbed by the conductor in steady state? Why is it that no heat flowing through the conductor is absorbed by any cross section when the conductor is in a steady state , there was a question on PSE about the same concept , but the answers ... 1 vote 0 answers 46 views At temperature$T>0K\$, are all normal vibrational modes present simultaneously in a one-dimensional solid?

I am studying Debye theory of Specific heat. hyperphysics has this picture and there it says "Considering a solid to be a periodic array of mass points, there are constraints on both the minimum ...
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What is the overall rate of heat conduction through two pipes of different dimensions if the thermal conductivity is not constant?

I am trying to work out how I would find the rate of heat transfer through two pipes made of the same material that are joined at their ends but which have different cross-sectional areas and lengths. ...
1k views

Temperature distribution in a current carrying conductor

A rod of uniform cross section and composition is connected across a battery. Let the middle part of the rod(when divided into three equal parts) is heated uniformly. A book says that the temperature ...
1 vote
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Is it possible for an absorption refrigerator to pump heat to a reservoir that is at a higher temperature than the heat source used to run it?

Judging by the wiki page I get the feeling that this type of heat pump would not function if it's radiator were hotter than the heat source, but I can't quite put into words why and I feel like there ...
1 vote
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Why do we move the spoon in a plate to cool it down?

Say we have a plate full of soup, why to cool it down we move the spoon around in the plate? Is it to facilitate the thermal interchange between the air and the soup? Also why is the edge of the plate ...
98 views

Heat being transferred from colder object to hotter object

My son was watching a YouTube video on entropy (The Most Misunderstood Concept in Physics). At about 11:30, it said that in theory it is possible to observe, say, "heat" moving from colder ...
1 vote
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Why is a inviscid flow assumed to involve no thermal conduction and mass diffusion? [closed]

I can understand how the assumption of inviscid flow leads to Reynolds Number (Re) tending to infinity. But how does the assumption of inviscid flow lead to the assumption of no thermal conduction and ...
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Does radiant barrier work if hidden under timber structure

I am insulating my house roof and I wanted to explore the radiant barrier and if these are actually effective in a real life scenario. The desired outcome of installing such barrier, would be to ...
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Heat resistance of sphere

I have been taught that the heat resistance of a hollow cylinder is R(hollow cylinder) is proportional to ln(outer radius/inner radius) It was assumed in the derivation that the inner surface is at ...
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Why haven't we found thermal superconductors?

First of all I want to apologize if this is a stupid question. I'm a layman who's merely very interested in physics, without a degree to my name. I was trying to research electric superconductors ...