Efficiency Definition and 948 Threads

We know that if potential and kinetic energy our negligible, the isentropic efficiency of a compressor is isentropic enthalpy change divided by actual enthalpy change: n=(h2s-h1)/(h2a-h1) So I already answered this question and here is the answer: n1 is the isentropic efficiency of the...

So efficiency is W/Qin. W= 0 for isochoric processes and for the isobaric, P(change in V). So W=Pi(Vi-Vf)+Pf(Vi-Vf) Qin is negative Qs.This would happen at step 2 and 3. For the isobaric, Q=ncv(change in T) and for isochoric, Q=ncp(change in T). Now if I put everything in the equation I get...

I was looking into companies or startups that were doing things with motors to improve efficiency. I stumbled upon Turntide Technologies, which has a partnership with Amazon. Turntide is making a software-driven motor that "enables precise and reliable control to effectively use every watt of...

Summary:: How does the air-gap affect the efficiency ? For a wireless power transmission system, to what extend does the efficiency and coupling parameters get affected by the distance between the coils? What can be done to increase the power transmission or efficiency regardless of the value...

Not sure if this is the right subforum to place this question? I stumbled on this idea, to make the cargo ship industry more efficient. The propellor of a cargo ship (<100m long) is relative inefficient, around 80% ( i know, this is pretty efficient for an boat propellor), and the harder the...

I have a 2-dimensionsal smooth function ##f(x,y,t)##. There may be multiple traveling waves across the domain. None of them are precisely traveling waves (the shape of the wave changes as it travels). Here is how one of these waves would look in 1-dimension: I want to find the speed of these...

Hi. I have a collection of points in 3D space. I'm using MATLAB to find all pairs of points within a certain range from one another. Right now I'm using rangesearch(X,X,r), where X is the collection of points and r is the range. These points are the locations of atoms and I am attempting to...

Hello, I'm looking for data on turboprop aircraft engine propeller efficiencies. I'm hoping for a table of available modern engines with a propeller efficiencies for comparison. I've tried Googling but not much luck. I can't even seem to find propeller efficiencies on the individual engine...

I post the working in the attached file

Hi Guys, Why increasing the pressure ratio in a High-Pressure Turbine ( in a Gas Engine) , will increase the temperature of exhaust gas? Why is the amount of heat added per kg of the gas is higher? Is there any good material where I can read about this? Thank you in advance..

Summary:: I'm going through my homework. I am confident I have everything correct except for my boiler efficiency. It seems too high at 99%. I would like to think my logic is sound but it can't be right. A boiler is designed to generate steam at 5 MPa and 400oC. A fuel is selected with a...

I have a question about building efficient heat engines in outer space. In theory you could have a hot reservoir heated by the sun that was several hundred degrees C, and a cold reservoir that was very cold - maybe 50K - 100K or even colder. Thus, theoretically at least, a heat engine could be...

A Hobson's joint is a kind of gearless angled drive. Most often a fixed 90 degree angle, but there is also versions with free moving joints in each axle so it can move to any angle up to a little over 90 degrees. It is today mostly just a novelty and there is very few applications actually...

Hello! What is the difference between the sensitivity and the efficiency of a detector. In the detector books I found they seem to be treated as 2 different concepts, but based on the descriptions, I can't seem to understand the difference. Efficiency seems to be how many particles you detect...

How to use efficiency in this problem?

If the Summary is not clear, the following is an example translated from: https://telecombloger.ru/7335 '... air conditioning systems. For example, the efficiency of a compressor is about 85%. The remaining 15% is spent on friction, oil movement, overflows, heating, etc. The efficiency of the...

I have found the input power through the efficiency formula, and I deducted that the input energy must derive only from water's kinetic energy... from which have mass/s and then finally the volume/s. After all the calculations and having multiplied the volume/s by 60, I get the result of 6.48 x...

An electric car has, say, a 50 kWhr battery. 1. How much electricity, in kWhr, is needed to add 1 kWhr of stored electricity to the battery? 2. After several years, the battery capacity has, say, fallen to 25 kWhr. How much electricity, in kWhr, is now needed to add 1 kWhr of stored...

Hi, My main question is: should we be subtracting the rotational power losses from the motor output power in our efficiency calculation? My approach: Will skip extra work as I have done the above parts of the question correctly. I used power conservation to state that: $$ P_{input} = P_{motor}...

I have two questions here. In the program, I have two different boolean expressions, one using array A[10], the other just using individual variablesB(0..9). They both do the same thing as in the program. My question which one is faster in real life hardware? My guess is B(0..9) is faster even...

Hi guys, I used to post on here quite a bit back in 2005-2007 when I was studying Physics in school, I remember it always being a great resource so hopefully I can get some similar help with this "real life" problem I'm having now! We are having a mini-heatwave here in the UK the last few...

So we know that every reversible engine working between the same temperatures will have the same efficiency(the same as Carnot engine). So let's consider for example reversible Otto cycle. So as you can see on the picture it is operating between ##T_1## and ##T_3##, so I was thinking that it...

Hello, I have completed the question below. I am just unsure on whether i am correct or not. I am unsure on Mechanical Advantage. As i have seen a few different equations. Question: Answer: a) Velocity Ratio = $$\frac{\text{Distance Moved By Effort}}{\text{Distance Moved By Load}}$$...

Most surface mount types of LED’s have a very nearly cosine distribution of light intensity. If we desire to inject light from an LED to the end of a cylindrical optical guide, what is the coupling efficiency as a function of distance (x) from the end of the guide? Assume that the LED is a...

Here is what I did : work done in going from A to C, W1 = 2nRToln(2) (isothermal process) work done in going from C to B, W1 = pΔV = nRΔT = -nRTo (isobaric process) work done in going from B to A, W3 = 0 (isochoric process) so, total work done = W1 + W2 + W3...

Hello everyone, a friend and I are working on our master project at a university chair. The project is to set up a free space optics communication (FSO) to, eventually, transmit data. For this we want to couple our laser beam into a fiber at the receiving end, which is then plugged into our...

I know how to calculate the power output and input by analyzing the current in put and output with multimeters and using the formula P=VI. But P_out is obviously incomparably smaller than P_in so the efficiency would suck this way. Is there a better way to do this??

Hi Everyone, This is my first post and I hope to work with you on this to gain a fuller understanding. I'm currently designing an LED circuit with 60 3 watt LEDs. Input power is both 120VAC for North American and 230VAC for other countries. I know this is pretty basicbut what is the best way...

For the heat engine: First I converted all the temperatures to Kelvin, ηmax=1-(333)/(1000)=0.667 ηclaim=(1*10^3)/(1.75*10^3)=0.5714 So the heat engine seems to be less efficient than a Carnot heat engine which means it can exist. For the refrigerator: COPmax=(253)/(363-253)=2.3...

I'm looking at two different batteries for home energy storage. Both batteries have a coulombic efficiency in the upper nineties, say 96%. One battery has an energy efficiency of 90%, and the other has an energy efficiency of 60%. I believe both ratings represent loses of usable energy, but I...

The answer in the textbook's

The first picture was provided along the problem statement. The second has my annotations. I initially began by calculating the ratio of efficiencies, since the work done is obviously the same and cancels out, but after failing and having seen the form of the solution I saw that that cannot...

Hi, I was just wondering about the efficiency of a cycle that is not Carnot cycle. In that case one should use \eta = 1-\left|\frac{Q_{\rm out}}{Q_{\rm in}}\right|, where Q_{\rm in} and Q_{\rm out} are the amounts of heat absorbed and released during the cycle. For instance, I guess that in...

I first wrote down that 55% = Eout/Ein I also know that W = (Facos20)(4) and I substitute it into the first equation 55% = Eout/[(Facos20)(4)] But I'm missing two variables here. Did i forget something or is the question missing some information?

I've looked reasonably to see if I could find this answer, I'm not a nuke engineer so perhaps my search terms are not correct. I've seen the fuel cycle charts (eg:https://en.wikipedia.org/wiki/Thorium_fuel_cycle, but not clear how to work from this to a percentage mass consumed) I'm interested...

Q2: An engine has power of 26.5 kW, needs 9 kg coal during an hour for energy. The heat capacity of coal is 7800 cal/g. Define the engine’s efficiency. Qh= mcΔT = 9000x7800xΔT ( stuck) P=26.5kW(is this the power output of the engine in an hour?) If only I could find ΔT, thenI would be able to...

Summary: In a heating by induction experiment performed, the idea was to determine the efficiency of heating up a small steel cylinder, an aluminum cylinder and then compare the two efficiencies. The cylinder was surrounded by a metall coil that alternating current was going through...

Hey everyone, I am taking a circuit 1 course in college and was wondering if an inductor is actually efficient. What I mean is that does it produce more current than the current already supplied. I know it keeps the circuit going even after the voltage source is cut, but does that mean that, if...

Hello, I am having a headache to try understand a possibly simple real-world problem: efficiency (as in number of strokes/cumulative length needed) to saw steel, assuming a constant sawing length per stroke and a known steel sectional area. I began to think about the few assumptions I assume...

Regarding electricity generation from a fusion reactor: I can't seem to find any discussion about the percentage of fusion product neutrons that can be realistically caught in the thermal blanket to utilise the energy they carry from the fusion reaction. The neutrons from fusion have to be...

Hi, I’m an undergraduate student interested in cognitive processes. I’m about to ask a very interdisciplinary question, and so hopefully I can find a physicists that can take on the challenge. What is the fundamental reason behind why modern electronic computers (transistor computers) are...

Hi, of all the main plasma heating techniques employed by multiple fusion reactor designs, namely 1) ohmic heating 2)RF 3)neutral beam 4)some other method? Which of them is the most efficient in terms of how much of the input electricity gets converted to direct heat/kinetic energy of the...

A coal fired steam plant takes in feed water at a temperature of 70°C and produces 15 tonnes of steam per hour at a pressure of 60 bar and temperature 400°C. The fuel consumption rate is 1.5 tonnes per hour and the calorific value of the fuel is 40MJkgˉ¹. Determine the power rating of the boiler...

First some basic figures which are very rounded as I'm interested in the approach to the problem rather than accuracy of the answer at this stage: The field current will be 500/220 = 2.2727 Amps, and so power is a fixed loss at 1136.36 Watts The armature current is 45 - 2.2727 = 42.72 Amps. At...

Hi. I am studying the effect of plasmonic nanoparticles on solar cells. Is there a way to calculate absorption efficiency in different layers of tandem solar cells in COMSOL Multiphysics.

If I am honest with you I don't even know where to start, if someone wouldn't mind helping me find a starting point? Additional information Melting point of aluminium 660°C Specific heat capacity for aluminium (cp): 0.91 kJ/kgK...

[Moderator: Moved from a homework forum. This question is not like most homework.] Problem Statement: I have been lighting and on lumen efficiency and efficacy. I have got bit confused between them Im looking at metal halide and fluorescent. when googling efficiency and efficacy for both. It...

Hi! I found interesting post here: https://electronics.stackexchange.com/questions/325762/how-efficient-are-leds However, it only gives the final results and not the steps he made. I tried to learn the formulas on wikipedia on my own but I couldn't figure out what variables need to have what...

I am working at retrofitting a microwave oven to produce steam for my 3 HP steam engine/generator. I have read estimates of 50-70% efficiency, but I am trying to verify those figures. Can anyone point me in the direction of calculating the efficiency myself?