Questions tagged [thermal-conduction]

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Isn't the Newton's cooling law for heat convection too macroscopic for CFD simulations?

In CFD (Computational Fluid Dynamics) simulations, the space is discretised into a huge number of tiny cells and, therefore, one has the opportunity to use a model of heat transfer that takes into ...
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49 views

Critical Radius of Insulation

Consider a long pipe inside which a hot fluid flows. The pipe is exposed to ambient air which is at at some temperature $T_\infty$. Let the inner radius of the pipe is $r_1$ and the outer radius is $...
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280 views

Why does the author assume the temperature to remain constant, in this case, along the axial direction?

This is in regards to steady heat conduction taking place in a pipe. Within the pipe a hot fluid flows and heat transfer first takes place via convection to the pipe and then via conduction within ...
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1answer
51 views

What causes the temperature to drop at the interface when two slabs are brought in contact?

Consider two slabs made up of different materials which are brought in contact with each other as shown. Thermal energy is supplied from the left, and it flows through the two slabs towards right. ...
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121 views

Time required for balls to cool down

Two balls A and B, made of different materials, having the same radius, are initially heated to the same temperature $T_i$ and then are kept in the same environment which is at a temperature $T_\infty$...
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1answer
38 views

Thermal Conductivity and Energy gain

I have a two part question: Part 1: I understand thermal conductivity as The measure of a material's ability to allow thermal energy transfer to it, from it and within it via conduction My very first ...
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2answers
60 views

What and why thermal diffusivity?

I understand the following properties: Thermal Conductivity: It tells how well thermal energy can get transferred to a material, from a material and within the material. A material with higher thermal ...
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1answer
27 views

Best metal for solar energy collection in an evacuated tube solar water heater

I am building an evacuated tube array for a solar water heater and I am selecting the materials to use for the tubing and the collectors (the places connected to the tubing that help absorb the solar ...
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2answers
75 views

Examples of two dimensional heat conduction problems

Can anyone give me some examples from real life, where the heat transfer can be modelled as two dimensional. Also if one could explain why we can model it as 2 dimensional.
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27 views

Question regarding evaluating 1D heat transfer PDE

My question regards cooling of an object using 1D-heat transfer with fixed surface temperatures. First I need to find the solution to this PDE: Based on the conditions, I worked out that the ...
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1answer
62 views

Equivalent Resistance Between Two Points in a Wye Network

I am interested in learning how to calculate the equivalent resistance between two points in a wye circuit for application to thermal networks (i.e. I'd like to calculate the equivalent thermal ...
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42 views

Cold Plate Thermal Resistance

I am designing a cold plate that will have 4 Power Modules Mounted on it. The total power loss from the modules is 5000W(1250W per Power Module). I have simulated the results on ANSYS Fluent and ...
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1answer
98 views

Filling gaps in heatsink design to improve thermal conductance?

I am currently pondering modifying my laptop's heatsink and am curious whether I stand to gain any benefit at all. The CPU and GPU (similar heatsink design) reach high temperatures (90°C +) under load ...
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1answer
74 views

surface temperature due to constant heat flux

Imagine a hollow cylinder with the outside surface exposed to air (convection). If there is a constant heat flux on the inside surface how would I calculate both the inside and outside surface ...
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2answers
109 views

Boundary conditions at interface for1D transient heat conduction problem in cylindrical coordinates

The problem I am currently working on involves rapidly cooling liquid aluminum in a cylindrical graphite crucible and getting the radial temperature distribution over time, possibly using finite ...
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56 views

Heat Transfer FEA with matlab

I have to write a matlab code using finite element method to solve this problem. I have solved it as follows but I dont know how to apply it in matlab. I have to write a matlab code using finite ...
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28 views

Air Conditioner for an Acrobat Plane

What kind of Freon air conditioner would work upside down? Or somehow make it cut off and start working again when upright? I have a small cabin so it can be electrically driven. I know they have an ...
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1answer
42 views

Thermal conductivity listed in the rather complicated Btu/s-in.²-°F/in - am I converting this right?

I'm currently working through some rather old documentation which gives the thermal conductivity of a material as 9.8 x 10⁻⁶ Btu/s-in.²-°F/in. There are many typical ways to give a thermal ...
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2answers
116 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
167 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
65 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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16 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
60 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
34 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
412 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
72 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
104 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
35 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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47 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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1answer
35 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
56 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
67 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
151 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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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
101 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
70 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
83 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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36 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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3answers
128 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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27 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
179 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
105 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
260 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
69 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
45 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
181 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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42 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
63 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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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
75 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,...