Questions relating to the various laws of thermodynamics, transformation or movement of a form of energy to another form, primarily but not limited to heating or cooling of a fluid.
Questions tagged [thermodynamics]
625 questions
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Is it possible to build an air compressor with no moving parts?
Is it physically possible to build an air compressor with no moving parts? I'm envisioning a thermodynamic cycle capable of compressing air with no moving parts and operated in a stationary way. There is no limitation on the compression factor,…
user3368561
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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 don't refrigerators have parts outdoors?
I've always wondered why refrigerators don't have some of their parts located outdoors like an air conditioner.
In warm weather, it seems like it would make sense to have the condenser outside like an AC unit to avoid heating the room. In cold…
Justin Trzeciak
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18
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Pound-force (lbf) vs Pound-mass (lbm)
Given:
My thermodynamics text reads as follows:
In SI units, the force unit is the newton ($N$), and it is defined as the force required to accelerate a mass of $1\cdot kg$ at a rate of $1\cdot\frac{m}{s^2}$. In the English system, the force unit is…
Jules Manson
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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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14
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What limits a power plant's load gradient?
Each power plant has a load gradient characteristic, describing to what extent it can change the output of its generators in a given timeframe. Reading the literature, I know that, for example, a gas turbine power plant has a vastly higher load…
Technaton
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13
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Why does moving air feel cold?
I'm taking a thermodynamics class and had the following question. I was going to ask my professor directly, but it seems like a stupid question with a simple answer, so I thought I'd try my luck here in fear of embarrassment.
When air flows through…
user01101001
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Thermoelectric Technology to Harvest Energy from Internal Combustions Engines
Background:
In an automobile, only 1/3 of the potential energy in the fuel is converted into mechanical energy and significant portion of the energy is lost as heat.
There have been previous attempts to recuperate this lost energy. In the early…
Mahendra Gunawardena
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Why was Freon used in spray cans before it was declared a threat to ozone?
I've heard that in the past, spray cans (aerosol cans) contained Freon. I found that the Montreal Protocol made the usage of Freon illegal due to its effect on the ozone layer, but I can't find the reason for why Freon was used in the first place. I…
Physther
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11
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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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11
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What fundamentally distinguishes cavitation and boiling as different phenomena?
Cavitation and boiling are names for phenomenon that both involve sudden appearance of bubbles of vapor within a liquid, and in both cases they happen when the local hydrostatic pressure is lower than the vapor pressure of the fluid, but that…
uhoh
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Are all pressure-volume processes polytropic?
I was searching for information about pressure-volume processes when I read, in a heat engineering book, "The process is polytropic with $PV^n = \text{constant}$."
How can I know that a real life process follows this model? Are all processes…
user2703642
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10
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Harvesting thermoelectric energy from computer graphics cards
During CES2015 a well know Graphic Processor Unit (GPU) manufacturer introduced a new GPU. These GPUs need complex thermal management to keep the processor cool. Most GPU accelerator card manufacturers develop new graphics accelerator cards that use…
Mahendra Gunawardena
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5 answers
Difference in energy consumption between empty fridge and fridge filled with bottles of water
I have about 12 bottles of water. If I want to minimize the energy consumption of my refrigerator, should I put these bottles in the fridge or leave them out?
fronthem
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