Questions tagged [thermal-conduction]

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2answers
65 views

How do I calculate final equilibrium temperature of a pot of water on a stovetop vs. after I add food to it?

So I'm trying to come up with a simple hack to heat up food in a water bath to hopefully +-1ºC of a target temperature, but I really don't understand the physics of it all so much. I'm pretty sure I ...
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1answer
77 views

How to calculate heat loss across a process pipe with perpendicular air flow

My thermodynamics knowledge is extremely rusty, so I would appreciate some guidance on how to solve this problem. As illustrated here, I have a process pipe (steel) with a gas flowing through it (blue)...
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1answer
49 views

How can I trust a K-type thermocouple purchased from a no-name company?

I am doing some temperature measurements for reliability testing, over an expected range of 16C to 45C. I have an NIST traceable thermocouple thermometer (S220-T8), however it does not come with ...
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0answers
12 views

Thermoelectric cooler parasitics

So I'm looking at performance curves for thermoelectric coolers, and it seems like these curves are so misleading as to be useless unless I'm missing something fundamental. Suppose I have a ...
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2answers
40 views

Through which medium is most of the heat transferred down (downwards) a glass tube filled with water: the glass walls or the water column?

If a much hotter object is attached to the tube from the outside, and the heat in question is transferred to the part of the tube that is below the source of heat, so there is no convection. The ...
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2answers
28 views

What happens in Thermal boundary layer in a flow with cooled plate?

All the notes on Thermal boundary layer(TBL) explains the growth of TBL over a heated flat plate ie cooler fluid is flowing over a hotter plate (heat is flowing from the plate to the fluid). How does ...
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2answers
137 views

Why does the thermal boundary layer(TBL) thickness increase with decreasing Prandtl number?

Consider a liquid flow in which, keeping all else constant, we can vary the thermal conductance(K). Now, if we increase the thermal conductance of the fluid the Prandlt number will decrease. I read ...
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1answer
59 views

How to heat up a swimming pool with the sun

I'm trying to figure out how to heat my pool most efficiently using the sun. Currently, I've got 2 black panels (made up of a bunch of black pipes) on the roof that the pool pump cycles the water ...
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1answer
67 views

Trapping sun heat the most - greenhouse

Greenhouse have recently caught my attention lately, which yesterday I posted in Why greenhouse's inside temperature never been infinitely hot? From what I understand recently, greenhouse gases traps ...
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1answer
34 views

What material might by used to 'staple' coils down in this stovetop element?

I have the stovetop element shown in the image below. If you look at the coils, they're fixed down by what look like little staples. I'm wondering what material those staples might be. The surface ...
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0answers
30 views

Internal Tent Temperature

Here is the problem I am working on: "Consider a perfectly sealed polygonal tent with the sun directly overhead. The solar irradiance of a surface 90° to the sun’s rays is 1,000 W/m2. However, ...
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25 views

how to obtain solution of this bessel equation using Frobenius method

Given this equation: $$ \frac{1}{r}\frac{d}{dr}\bigg(r \frac{dT}{dr} \bigg) - \bigg(\frac{2h}{bk} \bigg)(T-T_a) = 0 $$ I can let $x=r\sqrt{(2h/bk)}$ and $z=T-T_a$ to obtain the bessel equation using ...
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1answer
34 views

Is it just surface area alone that causes bridges to freeze?

Scenario: Object 1, a bridge freezes over do to the surface area exposed to the below freezing air. Object 2 has the same surface area exposed to the same air, but its base sits on the ground that is ...
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3answers
40 views

Material selection of heating element

I am interested in heating coils which are heated using Ohmic/Joule/resistive heating - specifically, how the material for the heating coil is selected. When I read about heating coil materials - ...
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2answers
60 views

Heat conduction in a hollow cylinder with low conductvity coefficient - Why do I get negative temperatures?

I have a hollow cylinder with a heat source inside. The generated heat flow is $\dot{Q}_g = 14\ 962 \ \text{W}$ , the cylinder has the radius $r = 20 \ \text{mm}$, the length $l = 50 \ \text{mm}$ and ...
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3answers
79 views

Are there differences between Ice Packs?

My girlfriend will get a refrigerator from the landlord, but right now she hasn't one. But she has a freezer. So we will get ice packs (images: 1, 2, 3) and use a cooling box for the time. Now I was ...
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9 views

Heat Conduction/Convection Along discontinuous tube

I have a question regarding heat conduction/convection. I have a metallic tube over which a rope heater is wound, supplying power. A glass tube and a 2nd metallic tube lies at the exit of the first ...
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1answer
53 views

Analytical solution of thermal stress in a bi-metallic cylinder

As a side project I have looked to solve using Python an analytical solution for one-dimensional transient heat transfer in a thick cylinder with cladding on the inside surface, wherein the fluid in ...
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1answer
38 views

Heat transfer for a copper rod

For a copper rod heated by a heat gun, why might the temperature of the rod continue to increase for a short time after the heat gun has been removed as the heat source? With reference to transient ...
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1answer
67 views

Heat Transfer Problem , 1 Dimensional Conduction Extended Surfaces

enter image description here So I am having issue solving this problem, I solved one part by the fact that in the given distance of 2L , 2 tubes are involved so I can find the heat conducted per unit ...
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33 views

How to calculate heat transfer between two solids in a medium?

If I have a cuboid block of metal and there is a cylindrical source of heat input (A) and I want to determine the heat energy at B (also cylindrical) how would I do this? I understand considerations ...
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2answers
87 views

How to calculate the volume of air required to keep electrical box cool?

I have a steel electrical box that is 15 cm x 15 cm x 10 cm. The weight of the box is 1kg. Inside the box is a relay that loses 30 Watts of heat while in operation (it's attached to a heat sink that ...
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22 views

What material characteristics are most important for heating element material selection?

I want construct a heating element by screen printing a flat coil pattern of conductive paste onto an insulated substrate. This conductive paste consists of a powder of conductive metal contained in a ...
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2answers
123 views

Time to change temperature inside the box

I have an interesting problem here. I have a box of certain dimensions. Inside of the box is some insulation and another box, from the same material as the outer box. I know everything possible about ...
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1answer
84 views

Wire heating and heat transfer in a cylindrical pattern

I have a series of copper coils with ¼” cooling plates between each coil. The cooling plates will be manufactured from aluminum and cooled using copper tubing. There are seven in series, and a plate ...
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2answers
183 views

Simple Thermal Analysis for sealed Aluminum box with 3.7 Watts of heat generation internally

I am looking for a starting back of the envelope calculation to determine if an aluminum box with just free convection can dissipate 3.7W of internal heat generation or if I need to think about adding ...
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1answer
39 views

In a warmer/sunnier climate, window (or roller shutters) superior to curtains?

When -on a hot day- the sun is incident on a window covered from the outside by a closed window shutter, the resulting heat is absorbed by the layers of air surrounding the shutter, subsequently ...
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1answer
41 views

Wall temperature of pressure cylinder - Boundary condition

I have a thick-walled pressure cylinder, that transports fluid and experiences only internal pressure. During the process, the outer wall temperature is measured. And I have no clue about the inner ...
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1answer
150 views

Heat Transfer in Different Wire Configurations

I am trying to create a program which estimates the final temperature of a magnet made of copper wire. I have different configurations in mind, but I will start off with a straight square wire with a ...
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39 views

Can radiant induction heat thermally decompose wood

Is it possible to thermally decompose an indicator like wood in a induction heating container made of stainless steel if the induction frequency is low enough to heat the container about 1000°c. ...
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2answers
57 views

Powder form of material with high thermal transfer

The Engineering Toolbox presents a chart of "common" materials and their thermal conductivity coefficients. I'd read or learned some time ago that diamond was superior in this respect. The chart shows ...
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0answers
21 views

DIY Thermal Solution [closed]

What would be the best way to design a sealed computer containing a gas or liquid circulated by a fan/pump to cool the components? ( With a metal case ) Then the computer would not be susceptible to ...
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1answer
56 views

Conductive Heat Transfer calculation over time

I am trying to heat the oil in a 1/2 inch thick rectangular steel box by using an Insulated heated blanket covered on all 6 faces of the box, the working conditions of the operation are at -50 Celsius,...
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0answers
42 views

Flow of hot gasses around the pipe

I have the following problem: there is a copper pipe getting through a wooden wall. On one side of the wall (hot side), I have elevated temperature which is defined by radiation and convection. On the ...
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1answer
69 views

Easily compute a good approximation of heat conductivity of cooled semi-vacuum (water vapor + air)

I am preparing a classroom demonstration about heat, including a demo of how a satellite loses heat only radiatively, since it's flying through a vacuum. I'd like to make the vacuum-production ...
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2answers
1k views

Calculation for heat transfer rate / cooling capacity for air cooled solid

I have a pipe which is channeling air flow from a compressor with a known mass flow rate and temperature. I can adjust the mass flow rate (power setting) and measure the delta T for the temp of air ...
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1answer
71 views

How cold for lack of heat?

I know that on the moon, while the daytime surface temperature can be above 270° F, in the shade but a few feet above the surface temperature can get quite low. Wondering whether a similar phenomenon ...
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2answers
159 views

Thermal oil in Boiler not reaching desired temperature

The thermal oil Feroline U in Boiler is not gaining the desired temp of 240 Degrees. We have physically measured the temp using digital thermometer at a distance of 20 cm where the boiler temp sensor ...
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2answers
1k views

Use two passive CPU coolers on one single CPU?

I aim on building a silent, completely passively cooled PC, with no moving parts at all (I am aware that it is cheaper to go for an inaudible computer instead, using low speed fans. This is not the ...
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2answers
47 views

Thermal Conductivity? Units On a Data Sheet

I've been trying to find the value of thermal resistivity for some linear disc resistors. I know that Thermal Resistivity is the reciprocal of Thermal Conductivity but the thermal conductivity on the ...
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4answers
177 views

Rapidly cool a flue gas without water circulation

I am a newbie at this!! For an experiment, I have a diesel generator that releases hot flue gases at 150-160 Degree Celcius. I want the output gas to be at less than 75 degrees for a duration of ~ ...
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0answers
3k views

What is the gray-body emissivity value of air

Wonder if anyone would know what is the average thermal emissivity value of air relative to blackbody at near room temperatures? I am looking for that magical number between 0 and 1. Looked everywhere ...
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1answer
83 views

Insulator thermal resistance

I have a machine that has power output of 2750 watt, which is blasted to a insulator foam with thermal resistance of 2.1 m2 kelvin/watt where the insulator is 5 cm thick and it drives the heat into ...
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2answers
4k views

Calculating R-value from temperature differential

A home windows installation rep gave me a quote today and conducted the following temperature differential demonstration. Alice pointed a heat gun (with a surface temperature of 165F) at the interior ...
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2answers
183 views

Winding a wire heating element after a few uses

I bought recently 10 meters of Kanthal A1 AWG18 wire, which is a type of heating element (FeCrAl alloy). I intend to make a coil out of it, but it's no use doing that right now, I need more of it for ...
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1answer
692 views

How thick do I need to make the insulation in my homemade furnace?

(This is probably a simple question, but I've been staring at it so long I'm not sure I know how to do it any more. I have an Excel spreadsheet with like 3 different ways to calculate this, and they ...
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3answers
84 views

Temperature of a material in a furnace

I am conducting few trials for checking the placement of a thermocouple on a valve for measuring the temperature of the valve and the material is an X45 alloy. You can see the slot taken on the valve ...
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2answers
713 views

Heat Loss in Typical House

I recently looked up the recommended insulation value for my area (7) and was surprised how much lower the wall insulation value was shown to be. As you can see it is almost a third of the recommended ...
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1answer
238 views

Most effective heat transfer in a vertical pipe with small top/bottom temperature difference?

What would be most effective way to transfer heat in the following situation? Specific conditions: A vertical cylinder or pipe, 30-100cm long, 5-10 cm in diameter, heavily thermally insulated except ...
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0answers
64 views

Heat switch material

Sort of a general question, but does there exist or might there exist a sort of thermal switching material? A material that could be switched from a thermal insulator (maybe more of a thermal ...