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Clausius Inequality with three reservoirs

Deriving Clausius inequality in the case of two reservoirs is quite simple. We assume that there is a thermal machine operating between two reservoirs, the first at temperature $T_1$ and the second at ...
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1answer
51 views

Why must the total change in entropy be 0 for a heat cycle to be as efficient as possible?

If $\Delta S_{total}$ were not zero, then heat flow would take place at different temperatures. It is easy to see why this is true by examining the opposite: that when heat flow takes place at the ...
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1answer
41 views

Question about reversible heat engine efficiency

I have a question regarding heat engines that cropped up whilst I was doing a practice question. I will summarise the results I obtained for the previous parts of the question so as to save your time. ...
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1answer
54 views

How long will pressure exist in this case?

I'm currently fabricating my project, which currently exists only on paper, and there's one question to which I have stumbled today. Suppose, that I have a pressure vessel capable of holding upto ...
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0answers
32 views

Exhaust liquefaction in internal combustion engines

Does an internal combustion engine provide enough efficiency to still deliver mechanical power, if it is forced to liquify it's own exhaust gases by compression? If gas containers would be added to ...
3
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0answers
66 views

What is the best material to use in a solar heater box to convert solar energy into heat energy?

Suppose you want to design a solar heater box with the dimensions: 1 sq meter x 30.48 cm H. 5 sides of the box's interior will be insulated and the interior will be totally black. Ideal glass will be ...
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0answers
191 views

How efficient is the Crookes radiometer?

I remember many years ago, I think at 8th grade, seeing the teacher show us a Crookes radiometer. I remember it being very fascinating. Today I read the wiki article on it, after looking up what it ...
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0answers
28 views

Expressing thermal efficiency for a closed Brayton cycle in terms of static enthalpies

I have a Brayton cycle made of a compressor (stage 2 to 3), a heat exchanger (stage 3 to 4) and a turbine (stage 4 to 5). The turbine and compressor are connected through a shaft. The cycle is closed ...
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0answers
11 views

microturbine heat loss

Would the hot combustion gasses in the millimeter-wide turbine in http://thefutureofthings.com/3063-engine-on-a-chip/ lose heat so quickly that the engine efficiency would be low? The velocity of ...
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0answers
44 views

Maximum temperature of an elliptical thermodynamic process

Given a heat engine made from the curve $$V(t)=V_0 +A \cos(\omega t); \qquad P(t)=P_0-B \sin(\omega t).$$ What are the hottest and coldest points of this cycle, and what are the temperatures at those ...
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0answers
24 views

Energy potential of a cold sink inside the sun

An answer in this question discusses using a fusion engine in a theoretical spaceship within a star. ...
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0answers
65 views

Why isn't Hydrogen used as fuel in Internal combustion engine?

I was looking at hydrogen cars and found out that hydrogen is mainly used in hydrogen cells to produce electricity instead of combusting it like gasoline in a cylinder to produce heat energy. Why ...
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0answers
77 views

Carnot cycle's paradox

Carnot cycle is a reversible cycle. By definition a reversible cycle must have an infinitesimal temperature difference. That means ($T_{high}-T_{low}$) is very very small. Any finite temperature ...
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0answers
128 views

Ericsson cycle: what happens if you add more mass?

We recreated the Ericsson cycle using a heat engine apparatus, with air as the working fluid (assumed an ideal gas). During the isothermal compression and isobaric expansion processes, a mass of ...
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0answers
113 views

Efficiency of a compressed air engine

I am doing some personal research on the efficiency of compressed air cars. I am currently trying to come up with an 'ideal' cycle to use as a reference for efficiency (c.f. Otto Cycle for petrol ...
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0answers
73 views

Theoretical efficiency Diesel vs Otto

The efficiency for the otto cycle is defined as: equation 1: $$ n_{otto} = 1 - \frac{T_4-T_1}{T_3-T_2} $$ which can be expressed in terms of the compression ratio: equation 2:$$ n_{otto} = 1 - ...
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0answers
37 views

Water as heat source in a heat pump

Consider we have water flowing in a pipe, which is working as a hot source for a heat pump. We are able to know the temperature of the water in both ends of the pipe, yet we don't have information ...
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0answers
181 views

diesel steam engine

Let's imagine a diesel engine's cylinder head would be heated by external means, to some hundred degree celsius, and the fuel would be replaced by water. We've made modifications so that water ...