Engineering Stack Exchange
Engineering Stack Exchange

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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Windmills in empty fields. Why no trees?

I have noticed that windmills are generally built in empty fields with no trees around, and I've been wondering why... A windmill is generally way taller than trees and I can imagine that trees don't actually affect the flow (see picture). But is…
Physther
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Why does temperature not increase by putting more logs into the fire

Why does temperature not increase by putting more logs into the fire ? It is a very common observation which I have seen but after some research online I found that it is not completely true. One reason which I think is that if I put more and more…
S.M.T
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How do heat pumps output more heat kW than the electrical kW used to run the heat pump?

I understand that a 2 kW electric heater will use 2 kW of electricity and output 2 kW of heat (apart from small losses of energy as infra red, vibration etc.. but let's exclude those for this example as they are negligible). A 2 kW air source heat…
sam
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How does a microbolometer (IR camera) work?

I am currently doing a project which has led me to my first encounter with IR cameras, and I am therefore quite curious as to how they operate. Specifically, I would like to know the following How is heat converted to an electrical signal (current…
Julian
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Should we protect our AC's outdoor unit from sunlight?Does it increases the durability of an AC and its refrigerant if it is well shaded?

My AC outdoor unit gets direct sunlight (no shading whatsoever) from morning to noon. Temperature normally soars up to 40 degree Celsius (I am from India). I have two questions: Is this bad for the AC's refrigerant, does it lose efficiency over…
Paran
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Comparing the performance of glass and granite in a heat storage application

Background I am working with a small team on a university project to build a greenhouse heat sink. This will pass warm air at the top of the greenhouse down through a chamber underground filled with a material to absorb and store the warm air. We…
Ant
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External diffusion: calculation of surface concentration

I am struggling a bit with an external diffusion problem. I am trying to calculate the concentration at the surface (as well as surface reaction rate) and would like some help or guidance. Here is what I have thus far. The reaction taking place,…
Mierzen
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How are the thermodynamics of CPUs and other chips handled?

I hear that designing the thermal efficiency of such systems is very difficult. I'm not sure why, though, and I am interested. On the one hand, I bet the heat is somehow a function of the total power in the system. On the other hand, as individual…
MrSynAckSter
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Is there a way to make an air conditioner without venting heat outdoors?

Is there a way to make an air conditioner for when you can’t vent the heat outdoors? Can you trap the heat in an object or convert it to another form of energy? For example, could you transfer the heat through an electrical outlet? I would be…
1.21 gigawatts
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Can air conditioners/dehumidifiers exhaust their waste heat in their exhaust water?

If I understand correctly, both air conditioners and dehumidifiers conventionally exhaust waste heat through their exhaust air, though both also produce exhaust water. I'd like to know, Are air conditioners or dehumidifiers currently being produced…
TomRoche
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How can one calculate the change in heat energy when the specific heat varies with temperature?

Many materials have a specific heat which varies with temperature, especially as the temperature change grows large. How does one calculate the heat energy that an object receives in this case? Can we simply use the specific heat capacity at the…
Max Ning
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Heat pipes vs fluid cooling

I was wondering about the main difference between using heat pipes and a fluid-based cooling system. In both cases the heat is transported away from the heat-generating area to a place where the heat is dissipated. What is now the advantage of using…
arc_lupus
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Can an isothermal process also be adiabatic?

I came across this question of "can an isothermal process also be adiabatic?", and at first thought that yes, why not? If the temperature is constant and there is no heat loss to the environment, it seems perfectly possible. Now, I don't have too…
TheAlPaca02
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Is there a relation between porosity and PPI density in porous media?

I've seen two methods to describe porosity of porous media (specifically metal foams): Porosity $\epsilon$ which is a ratio between volume of voids and total volume of the medium. PPI (Pores Per Inch) which is the number of pores in one linear…
Algo
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Are smaller heat-pumps more efficient?

I was a doing a placement at a company, and they were designing a new heat pump. I was told the more compact you can make a heat-pump, the better it is for efficiency, and they mentioned something about this was because the power density was…
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