Questions tagged [heat-transfer]

Questions relating to the transfer of heat via the mechanism of convection, conduction, or radiation, in forms of systems (or your device) attempting to obtain thermodynamic equilibrium with another system (the environment or your other device)

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How to solve transient heat conduction equation at a point in space with volumetric heat source?

My system is a fluid exposed to light and I want to calculate the temperature change with time at a point, hence there are no spatial effects or convection due to the flow of the fluid. The heat ...
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Can pyrolytic graphite sheets effectively be used as a thermal gap-fill interface?

Pyrolytic graphite sheets are used as a high-performance thermal interface in applications with high power density because they can have a very high conductivity of 1000+ W/mK, but only in the ...
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What is the quantity of electric energy necessary to cool the water in a tank heated by P = 30 kW?

A pump draws cold water from the reservoir of industrial chiller and pumps it at a flow q in a 5 m3 tank filled with water. The tank has a 30 kW parasitic heat source inside (see Fig. 1). The ...
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What causes water to always drip from an electric furnace when its turned on?

I made an electric furnace as a university project. It can heat up air inside up to 1000 degrees Celsius. It's not fully sealed so some air can escape from small gaps. Not sure if this would cause a ...
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What is a good way/formula to approximate heat/energy loss of not fully sealed electric oven filled with only air?

I made an electric furnace that consume ~18 kW (3 phase) of power. I want to know how much energy is lost when its used to heat only air. The only sensing tool available as of now are thermocouple ...
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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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Heat Loss from Domestic Oven Door

Our kitchen electric oven has a large glass door approx 530 x 440mm, overall thickness 35mm. There is a front and back glass pane, no insulation and the air cavity is open at the bottom. I'm wondering ...
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What is the solutions of the following 1D diffusion equality using Crank–Nicolson method?

Through my research I faced to the following equality and need to find $c_i^{t+1}$. Moreover, I found that it can be solved by Crank–Nicolson method (see here: https://en.wikipedia.org/wiki/Crank%...
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What happens to insulation?

What exactly happens when an insulating material comes in contact with heat through any mode (conduction, convection, or radiation). Something like aluminized mylar will reflect the heat back. How ...
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What materials to use indoors to absorb sunlight and store it as heat?

This is a very practical question; the underlying principles are, I imagine, extremely well-known. I'm buying a new place in the northern hemisphere (49° N) with lots of southern (or rather SES) ...
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Sun exposure in room as a function of day and time?

Background (may be safely ignored): I am buying (most of) a rowhouse from the 1930s. I am now working with an architect to improve its energy efficiency. Let us focus on the main room, which can be ...
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Changing temperature under adibiatic conditions?

Can a temperature change be adiabatic? For example if no 'heat' leaves or enters the system and we compress a fluid such that it's temperature changes is this still adiabatic? If energy is transferred ...
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How do I find the amount of energy needed to evaporate water below its boiling point?

Let's say I have a container filled with water and its surface is in direct contact with air. How much heat/energy do I have to supply to the water such that it evaporates under its boiling point? is ...
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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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Heat transfer coefficient in forced convection and its dependence of temperature

I'm working on a Ansys Fluent of an Aluminium coil annealing furnace with the goal of estimating the heat transfer coefficients at different temperatures and ventilator/fan speed conditions. The ...
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Mean temperature of a fluid in a pipe

Consider a pipe in which a fluid flows such that the pipe is at a higher temperature than the fluid. At any cross section of the pipe we get a varying temperature profile. We can define a mean ...
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Internal Forced Convection of Water/Air

Should I take the film mean temperature or bulk mean temperature to obtain the water/air properties from the Steam Tables? (In order to calculate Re number - for Petukhov's empirical relation ...
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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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why the fluidity test for casting is made in spiral shape?

Why fluidity test uses a spiral shape of casting? Is it to reduce the heat transfer? make it compact? Or any other reason?
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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 Transfer in a tubular reactor with constant jacket temperature - impossible solution?

I have received from my professor the following problem: A first-order exothermic reaction A -> B takes place in a tubular reactor (typical PFR). The tube is cooled to a constant wall temperature $...
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How to calculate the logarithmic mean temperature difference of a jacketed vessel?

I'm a bit confused on how to calculate the $ \Delta T_{LM}$ of a jacketed isothermal CSTR. Because the formula for the logarithmic mean temperature difference is: $$ \Delta T_{LM} = \frac{\Delta T_{...
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Does a fully mechanical heat pump make sense?

Is it reasonable to operate a fully mechanical heat pump? For example, using a linear back-and-forth motion from a vortex bladeless turbine to operate a mechanical compressor to heat (or cool off) a ...
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Method for computing the pressure drop across a bank of tubes

I would like to determine the pressure drop of fluid in cross flow over a bank of tubes. (see figure 1). Previously, I've used the correlation listed in "Fundamentals of Heat and Mass Transfer&...
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Help Understanding this Animation about the Heat Equation?

https://en.m.wikipedia.org/wiki/Heat_equation#/media/File%3A2D_Nonhomogeneous_heat_equation_.gif In the beginning, is the plate being heated from the center? Or is the plate being heated from the ...
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Intra-facility Heat Pump? (HVAC)

Does anyone know if there exists a type of heat pump for moving heat from one indoor area to another? In this scenario there is a room where excess heat is being generated and could be used in heating ...
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Thermocouple Values Fluctuating

I am trying to measure the surface temperature of a cold plate using K-Type thermocouples. However, the temperature reading on the scope is fluctuating tremendously. IGBTs are attached on the cold ...
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Is a block designed for water cooling effective at dry transmission of heat?

I’m working on a project involving a thermoelectric cooler, and options for small aluminum or copper blocks have been few and far between. However, I found many cheap aluminum and copper blocks on ...
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Temperature of two aluminium plates heated by a heat source

This is my first question here, so, please, let me know if this is not the right place. I have a 3 m long, 4 mm diameter, 45 W heating cable that I need to place inside a fridge. Unfortunately, it ...
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Predicting the behaviour of a boiler system if we modify temperatures

I am currently studying a boiler without many technical data. Below a short description: Fuel is put inside the boiler furnace. Primary (F1) and secondary air (F2) fans allow fresh air to go through ...
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How much a 0.1 mm air gap between 2 materials will affect heat transfer rate?

I have a disc with drilled holes with a 0.1 mm tolerance. The plate is 6061 T6 Aluminum and I want to insert a polyethylene tube with water in it that is frozen. Assuming some tubes are in full ...
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How important is a hot fluid temperature in a heat exchange?

Please consider an air to air heat exchanger. On one side, we have 200°C hot air entering the heat exchanger, and leaving it at 150°C. And on the other side, we have 15°C fresh air to the inlet. ...
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Calculating Indoor temperature of a structure

Background I am designing a simulator for building designs, and need to track the interior temperature of the constructed building. For simplicity, this building will be one room; meaning the only ...
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Solar Thermal Collector to Boil Water (100 deg C)

Is it possible to build a Solar Thermal Collector that boils water to 100 deg C? I've seen a lot of Solar Thermal Collectors that claim to be able to boil water, but every example demonstration that I'...
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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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What could cause nichrome wire to overheat and melt?

Yesterday I wasn't careful enough with my popcorn maker and I managed to break it. The kernels probably restricted the air flow and something blew up. It stopped working and about 2 seconds after that ...
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Electric heating element inside refractory concrete

I'm thinking of making an electric pizza oven in my free time. My thinking at the moment is to have one kilowatt electric heating elements in the bottom as well as the top of pizza oven. I would like ...
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Fire rated EN 13501-1 B-s1/s2, d0 sheets

I'm trying to learn more about the type of sheets I can get for a project, I would of course go for polycarbonate if not for its price, currently the project with PC will cost \$600-\$700 but I'm ...
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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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Can the Whitaker Nusselt number correlation be used for a hot sphere in convection with cool air?

The Whitaker Nusselt number correlation (equation 4 here if you don't know it) seems to not be applicable for when the viscosity of the fluid gets higher away from the surface, but it seems to get ...
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How to model the kinetics of a reaction while its not being stirred in a batch reactor?

lets consider the following reaction: $$ A + B \rightarrow C $$ Where the rate of reaction ($r$) can be expressed as: $$ r = k*c_a*c_b $$ Where $c_i$ is the concentration of species $i$ and $k$ is the ...
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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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What can you coat/seal Gallium with?

If I were to make a sculpture out of Gallium, Ga melts at about 85 °F I think, would I be able to spray it with some sort of solvent based or not solvent based coating to help prevent it from breaking ...
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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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Calculating the difference in heat loss from human body in different environments

I'm interested in personal cooling devices and would like to know if there's a way to make a rough estimate of rate at which you would need to extract heat from the body of an average male walking in ...
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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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Does a higher temperature difference result in a faster rate of heat transfer?

Suppose that I have a thermally insulated tank with hot air at a temperature of 400 C, and the tank is stored in a room with an ambient temperature of 25 C. I also have another identical insulated ...
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Recreate mini fractional distillation column for oil refinery

I am planning to recreate fractional distillation column in my warehouse, size not an issue however want to keep it as compact as possible (ideally should not exceed 8 meters high) Where can I find ...
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