Questions tagged [thermal-conduction]
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How to correctly use the thermal conductivity coefficient formula?
I'm trying to help a friend.
We are trying to use the formula below to calculate the thermal conductivity coefficient of a composite material (styro-bamboo).
Q=100 Watts, d (or thickness)= 20mm, A= ...
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How to calculate the thermal conductivity of a composite material
Very new to thermal conductivity calculations, so I'm aware there are already queries on here that may cover this, but I'm struggling to apply them to this instance.
I'm trying to calculate the U-...
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U-value for suspended ground floor
I'm about to finish U-value calculation for a house (an assignment for the Sustainable Technology for Buildings module) but I can't understand the formula. I've got all the data except from "ln&...
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approximate equation for temperature drop near wall in contact with fluid
I am concerned about the following problem and so far I am not able to find a solution. Let us consider an environment at a temperature $T_a$ and the inner surface of a not insulating wall in contact ...
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heat flow in a annular cylinder of insulating material
Maybe this belongs in DIY, because ... I'm trying to analyze the amount of heat required to prevent water supply pipes from freezing. The pipes would be protected by electrical heating tape and ...
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Why Ball-Grid Arrays are More Heat Resistant
I read that for Ball-Grid Arrays, the BGA's act like a thermal dissipator because there are more channels, so it is more heat resistant as opposed to Thin-Quad Flat Pack which uses pins.
Is this ...
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Calculating Glass Wool Insulation Thickness
I intend to calculate required thickness of glass wool insulation for a hot vessel. I know the temperature inside the vessel, the acceptable temperature at the surface of the vessel (after insulation),...
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Modeling 1D Transient Heat Transfer: Wall/Room interface
Consider a 1D adiabatic room (of volume V) with a wall conducting heat on its left side.
The wall is solid and heat conduction in it is driven by the common heat equation.
There is convection at the ...
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High thermal conductivity in soft, fleece-like textiles
Fleeces typically exhibit low thermal conductivity, and are often used in winter clothing for their insulating properties.
I am seeking a material for a radiant heat application that is soft to the ...
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Human lying on a cooled mat - ballpark estimate of heat transfer rate
Hardware builder and youtuber Naomi Wu came up with this idea to help people with acute heat stress due to very hot and possibly moist weather: Instead of cooling all the air in a room, just place the ...
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Heat transfer: does the heat generated in a cable get transferred to the electrical components?
I have a 1000 V, 50 sq mm, double insulated (XLPE) copper conductor cable. This cable is being connected to a power electronic component.
The current flowing through it is 230 Amps DC. The cable ...
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What is the thermal conducivity of Air between two plates?
What is a rough cut figure I could use to determine what the thermal conductivity of 10mil and/or 20mil of air sandwiched between two plates (perfectly conducting)?
I understand that convection dies ...
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Why heat transfer happens only via conduction in this case?
Why heat transfer between a heated flat plate and a fluid happens via conduction only and not convection, when the fluid is present below it?
Consider a plate under which a fluid is present and it ...
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Calculate Thermal Conductivity of Layered Structure
I am having a problem determining the thermal conductivity of a layered sample. The sample is made of two materials, one whose thermal conductivity is known (λ-1) and one whose thermal conductivity is ...
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Does forced convection account for energy transfer in this case?
I have to confess that thermodynamics is not a friend of mine.
My system consists of a volatile droplet sitting on a thermally conductive substrate. The energy balance comprises heat lost due to ...
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Heat Diffusion and Specific heat
Consider two slabs - Slab A and Slab B, insulated on "latereal" faces as shown, initially at the same temperature, and having identical dimensions. The slabs at t= 0 are brought in contact ...
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Why different characteristic dimension for Biot Number and Fourier Number?
In unsteady heat conduction analysis,
Biot Number and Fourier Number are given as follows:
$$Bi=\frac{h L_c}{K}$$
$$Fo=\frac{\alpha t}{L_c^2}$$
where $L_c$ is the characteristic dimension or length
...
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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