Questions tagged [heat-conduction]

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Equation for simultaneous cooling and conduction

Imagine a long, uniform metal rod placed on the positive $x$-axis being heated with a power $P$ from its end at $x=0$. It is cylindrical in shape and the cross-section is a circle of radius $r$. ...
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4answers
283 views

What is heat and heat transfer?

Physics books write that heat is the transfer of thermal energy. They also write that heat transfer is the transfer of thermal energy from a thermodynamic system of high temperature to a one of lower ...
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1answer
342 views

How to develop a model for cooling rate of steel tube in air?

I am trying to develop an equation to determine the cooling rate of a steel tube in air. I'm using Fourier's Law, Stefan-Boltzman Law, Newton's Law as well as the specific heat capacity equation. The ...
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1answer
474 views

Microscopic level - What happen to the particles in a heat transfer through conduction?

So on a macroscopic level, there is physical contact and the heat energy is being transferred from the higher temp. to lower temp. But what about in a microscopic level, what's going on? As far as I ...
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2answers
61 views

Which heat equation should I choose if I want to toggle between conductive and convective heat transfer?

I have a science project where I have an aluminum cylinder, filled with oil, with a diode chain floating inside of it. The diode chain has a bimetallic temperature switch on it that turns off the ...
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1answer
829 views

Calculating rate of heat loss through conduction and radiation

Calculate the rate at which a hollow cylinder with a heating element inside will lose heat, specifically through both conduction and radiation. My goal is to find the temperature inside this cylinder....
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1answer
22 views

Will a measured “temperature above ambient” remain constant in the face of a changing ambient temperature?

I've got some fully-enclosed, outdoor brass landscape light fixtures. I chose a (12V) bulb that, when measured with a benchtop power supply, dissipates a constant 0.8W. On a cool, windless night, ...
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0answers
26 views

Is heat conduction the dominant form of heat transfer in metals? [closed]

I need to perform a thermal analysis on the metal. A metal placed in the air is brought into contact with a heat source and the temperature change is observed. In this case, which of "heat ...
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0answers
38 views

Thermal contraction for cooling

I've calculated by separation of variables function of temperature $T(x,y,z,t)$ for a cooling cube. I wanted to know how much the cube will contract in one dimension after 10 second of cooling, during ...
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1answer
27 views

What is the temperature profile of hot and cold fluids for a double pipe parallel flow heat exchanger?

In books, they just mention the temperature profile is exponential. Can someone help me come up with the exact temperature profile (the relation) for the hot and cold fluids in a double pipe parallel ...
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1answer
47 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 ...
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0answers
31 views

Could this imaginary cooling solution work?

Imagine a perfectly insulated ideal closed cylinder. Inside, at the two ends there are two bodies, one with the temperature of T the other with temperature -T. Between the almost touching bodies with ...
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15 views

Why doesn't ice in a glacier feel as cold when I touch it as the ice I get from my freezer?

When I was in Iceland, I went to a tour in a glacier and I remember the ice that was there. It looked and felt like a huge amorphous block of glass: hard, smooth, not wet, and not that cold. Not as ...
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0answers
27 views

Why does bologna inflate radially when on stove?

I noticed that when heating up bologna in any way it inflates at the center, while other stuff tends to let the air escape sideways, or inflates in different places, like an egg or sausage. Nothing so ...
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0answers
27 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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1answer
39 views

What is the difference between rate of cooling and rate of heat loss?

I had a perception that rate of cooling and rate of heat loss are synonymous because the rate at which it looses heat indicates the rate at which it is cooling but this question changed my view There ...
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1answer
32 views

Steady State conduction of cylindrical pipeline

I have this problem involving conduction of heat: Suppose that $z = 0$ represents the ground level on a street where an electric cable is buried at $x = 0$ and $z = −D$. The ground is kept at a fixed ...
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29 views

Condensation of saturated vapor on subcooled droplet

Consider the process of condensation of vapor on falling subcooled droplet in the stagnant saturated vapor (neglect the vapor drag on droplet). What can be said about the relation between the droplet ...
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0answers
50 views

How does the change in temperature of water in a tube depend on the angle that the tube makes with the gravitational field/the horizontal?

Let's imagine a tube that is open at one end and is filled with water. A constant source of heat is applied to a specific spot somewhere at the middle of the tube, for a example a preheated soldering ...
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0answers
67 views

How to obtain a solution for the following IBVP?

I am trying to solve the following advection-diffusion equation for transient flow conditions for radial flow. The governing equation is as follows. $$\frac{\partial T}{\partial t} = \frac{\partial^2 ...
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16 views

Coupled solid-fluid heat transfer over a rectangular plate heated from the bottom (Boundary value problem)

I have the two-dimensional temperature Laplacian $(\nabla^2 T(x,y)=0)$ coupled with another fluid equation (which is one-dimensional). The Laplacian is defined over $x\in[0,L], y\in[0,l]$. On ...
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2answers
102 views

After sweating ,why do our body cool down faster under a fan?

The sweat on our body evaporate taking energy from our body in the form of heat.the temperature of our body decreases and we feel cool. Thus sweating cools down our body. Now why does our body cool ...
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1answer
143 views

Calculate rate of heat gain of a steel chain in a campfire [closed]

Up front: I'm trying to be scientifically accurate about heating up a length of steel chain in a campfire to use as a surprise attack tactic in a D&D campaign, but I'm not sure I'm using the ...
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0answers
22 views

Induction cooker

I was using an induction cooker and I kept my steel utensil empty on it and switched it on. After some time the bottom part of it became red hot but the upper part of it was completely cool. Why does ...
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1answer
20 views

Heat Transport in humidity control

PROBLEM 6.11 A humidity box for laboratory use is constructed from panes of window glass of thickness 4 mm. The temperature inside the box is maintained at 90°C and the ambient room temperature is 25℃·...
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39 views

How to calculate the heat energy lost to two steel electrodes in contact with a piece of heated Titanium in a Vacuum

Say within a vacuum chamber I have two steel electrodes in contact with 0.0006 m^2 of Titanium heated to a temperature of 1,800 degrees Kelvin. How would I calculate the heat energy lost via contact ...
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1answer
55 views

I need an explanation of insulation

Clothes reduce the heat loss to keep a person warm. But if the person is always producing more heat than the clothes are losing it, his temperature will rise indefinitely. Is it because as the object ...
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2answers
238 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). ...
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60 views

Thermal resistance calculation

With reference to the given diagram I am asked to find the thermal resistance of the interface(that is the common surface) between 1 and 2.All that I knew was the resistance diagram drawn right below....
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184 views

Thermal diffusion length- heat transfer

what is the difference between thermal diffusivity and thermal diffusion length?since diffusivity itself means the extent of heat penetration into the volume of material?
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0answers
158 views

Neumann boundary condition in spherical coordinates

I'm trying to solve heat equation $$\nabla^2 u = \frac{1}{k}\frac{\partial u}{\partial t}$$ in the region $$ a \leq r \leq b, \ \ \ \ 0 \leq \varphi \leq 2\pi, \ \ \ \ 0 \leq \theta \leq \theta_0 $$ ...
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1answer
139 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 ...
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0answers
28 views

The thickness of the hot air layer above a hot metal

I need a simple way to estimate the thickness of the hot air layer above a metal heated up by about 100K above the room temperature. I'm not sure how to go about estimating this. What happens there, ...
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1answer
109 views

What is the exact usage of internal heat generation term used in a general heat conduction equation?

∂/∂x (λ ∂T/∂x)+ ∂/∂y (λ ∂T/∂y)+ ∂/∂z (λ ∂T/∂z)+ q_v= ρC_p ∂T/∂t------1 T - Temperature (Temperature of the material) ρ - Density of the material C_p - Specific heat capacity of the material t - ...
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66 views

Minimum Wall Thickness Heat Transfer

We are asked to find the minimum wall thickness of a composite wall given an inside wall temperature $T_i$ and outside wall temperature $T_o$. Also we are given three types of bricks $A, B, C$ with ...
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2answers
68 views

A heat flow generalized problem featuring light bulb and oven

If an incandescent light bulb under constant power is taken from room temperature 25 deg C to an oven at 75 deg C, does the filament temperature increase by 50 C? Assume radiated power is negligible ...
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1answer
216 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 ...
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0answers
50 views

How to calculate total heat energy with fluctuating temperatures?

I had a question relating to a math problem that I'm doing. Let's say I have a heater that produces heat until it reaches a specific temperature, after which it turns off until it reaches a minimum ...
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1answer
224 views

thermodynamics problem about thickness of ice

the problem is outside temperature is -10 C and on the lake there is 5 cm of ice. After what time will 15 cm be reached. $Q=\frac{kA(T_2-T_1)}{H}$, where $A$ is area, $H$ thickness of ice, $T$ ...
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1answer
61 views

Clarification on the three omega method for measuring thermal conductivity

I've recently come across the $3\omega$-method for measuring thermal conductivity in materials. Now I'm told that we use a lock-in amplifier to measure the 3rd harmonic in the voltage across the metal ...
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0answers
90 views

A problem in heat conduction at a steady state

Question : Three rods of identical cross-sectional area and made from the same metal form the sides of an isosceles triangle $\triangle ABC$, right angled at $B$. The points $A$ and $B$ are ...
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1answer
127 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 ...
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0answers
16 views

Dependence of heat transfer rate on acoustic boundary layer thickness

I have generated a sine wave acoustic signal of constant amplitude and different frequency (i.e. 50Hz to 250Hz). At low frequency i am getting higher evaporation rate. However, at low frequency ...
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1answer
105 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 ...
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1answer
114 views

Heat equation volume source vs. heat flux boundary condition

I want to solve the heat equation in the 3D unit sphere $B$ with a general heat flux boundary condition, no volume sources and some given constant initial temperature: $$ \rho c_p\partial_t T - \...
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1answer
2k views

How do I convert $W/(mK)$, $W/m^2$ and $W/(m^2K)$ to the same “dimensionality” and unit?

How do I convert $W/(mK)$, $W/m^2$ and $W/(m^2K)$ to the same "dimensionality" and unit? $W/(mK)$ is thermal conductivity. $W/m^2$ is heat flow density related to one unit. $W/(m^2K)$ is the ...
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2answers
40 views

Will “stationary” air sorrounding a hot pipe from a wood stove act as insulation with a given time?

The inner pipe (colored in red) radiates considerable more heat than the current one so I'm planning on extending the more thermally conductive one so that it heats better. Will removing the outer ...
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2answers
172 views

Should I walk or run to my towel when naked and wet? [closed]

This morning when I got out of the shower, I realised I had left my towel in the bedroom. Naked and wet I ran as fast as I could to get the towel. On my way back I didn't run, but rather walked, and ...
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1answer
14 views

Will the temperature reading of a thermostat change as a result of direct skin contact? [closed]

If I was to place my hand on a thermostat for an extended period of time, would this eventually result in the temperature reading rising after a period of time - or would the reading not be impacted ...

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