2
votes
Does fog affect the efficiency of heat pumps?
A more humid environment outside will result in more use of defrost cycles for the outside evaporator, reducing efficiency. I supposed that fog would be the upper limit for humidity.
Heat transfer to/...
- 6,901
2
votes
Accepted
What is the ideal theoretical construction for an insulative box to keep my frosty beverages frosty?
There are two paths to the answer, as follows:
First of all, regarding emissivity and so on, radiative heat transfer scales as the 4th power of absolute temperature so for temperatures near room temp ...
- 14.7k
1
vote
I want to transfer heat from a solar concentrator to be stored in a sand battery , which heat transfer fluid is more viable , cheap and easy to use?
It's hard to beat good old fashioned pressurized water. The attendant technology is fully mature, extremely well-understood, and used all over the world.
- 14.7k
1
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Advice needed on how to cool 50 ml liquid from 60 °C to 30 °C
If you're wondering how long it would take in order to cool that liquid.
$$mc_p\frac{dT}{dt} = \frac{1}{\frac{1}h + \frac{\Delta x}k}A(T_C-T) $$
Where:
$m$ is the mass of liquid
$c_p$ is the heat ...
- 11
1
vote
Accepted
Advice needed on how to cool 50 ml liquid from 60 °C to 30 °C
Place it in an ice bath with a stirrer.
As Q=m Cp (T2 - T1)
and increasing the container surface area in contact with the ice will improve the rate of heat transfer.
- 15.8k
1
vote
How can you determine the heat transfer area of a plate heat exchanger
You should calculate the heat transfer area according to a given formula or procedure within a particular heat transfer calculation method.
In some heat exchangers, each fluid can have slightly ...
- 1,140
1
vote
Why not drive an air source heat pump domestic heating system with an auto engine?
The shaft seals will getcha
The problem with mechanically driving a refrigerant pump is you need very good seals on the compressor input shaft.
Why is that a problem? Well, it's only a problem ...
1
vote
Accepted
Can cascaded heat exchange system transfer more heat?
Question: In a residential setting, how does the heat exchange capability of a cascaded heat exchange system (System 2) compare to a direct heat exchange system (System 1), given the provided ...
1
vote
Can cascaded heat exchange system transfer more heat?
The heat exchange capability of a cascaded system like the one you described in System 2, compared to a direct heat exchange system (System 1), can vary depending on several factors. Here's a ...
1
vote
Accepted
What is the correct way to calculate the efficiency of a heat exchanger?
Effectiveness using $\epsilon = \frac{q_{act}}{q_{max}}$ seems to be most general. It assumes comparing 2 cases and I would choose comparing cases where inlet temperatures and flowrates are fixed for ...
- 1,140
1
vote
Will the COP of 10 stage cascaded refrigeration / AC system be high?
COP for a fridge is limited by the source and sink temperatures, in your case Th=313, Tc=263, COPcooling<Tc/(Th-Tc) so COPcooling<5.26
It doesn't matter how many stages you have that is the ...
- 718
1
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Will the COP of 10 stage cascaded refrigeration / AC system be high?
Coefficient of Performance (COP) = energy moved/energy spent
So if I move 1J through N stages, I've moved 1J, but incurred the spend of N stages.
Supposing I have N stages in series, each with COP=C:
...
- 1,353
1
vote
Any real heat engines based on the Carnot cycle? (or an equally efficient cycle)
In the Carnot cycle, there are no loss mechanisms and no temperature gradients anywhere. Commonly-used thermodynamic heat engine cycles are intended as real-world approximations of the Carnot cycle, ...
- 14.7k
1
vote
Any real heat engines based on the Carnot cycle? (or an equally efficient cycle)
The Carnot cycle is a theoretical cycle and, as such, no practical exngine exists based on this cycle.
This is one of the many reasons that this cycle is used to compare real or practical engines for ...
- 15.8k
1
vote
When was the phrase "lumped thermal capacitance" first coined?
Putting in a self-answer although I'm not entirely satisfied with it:
The use of the word "lumped" to describe thermal systems in this way was introduced by Bickley (1941, Lond. Edinb. ...
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