Efficiency Definition and 950 Threads

Hi all, I've been looking for an answer to this for a while now but I can't explain to Google what I want to know. Hope I have better luck here. I'm an aerospace engineer working on a satellite project. In particular I'm currently working on the thermal analysis and I need to model up each of...

Which are more efficient, Rocket Engines or Jet engines, and why? It would make sense that rocket engines are more efficient because they aren't effected by air pressure but I have been told by some people that actually Jet engines are more efficient so I am confused. If you know of any link...

Homework Statement Car (A) C180K WITH A 1.8 litre supercharged spark ignition, Maximum power output 104kw, based upon standard fuel efficiency test a vehicle with this engine would consume 6.1 liters over 100k journey Car (B) C220 CDI with a 2.0 litre turbocharged diesel engine. Maximum...

Homework Statement Here's a link to the pV-diagram I am using - http://session.masteringphysics.com/problemAsset/1396784/2/p16.7.jpg A heat engine takes 2.0 moles of an ideal gas through the reversible cycle abca, on the pV diagram shown in the figure. The path bc is an isothermal process...

Question: An hand crank is used to life a bucket of water from a well. The bucket and water have a combined mass of 12.0 kg and must be raised 8.5 m. The force used to lift this load is 40.0 N and must be applied over a total circular distance of 15.0 m. What is the efficiency of the system...

hi.I would like to know something about the IC engine.I just read an article.It said that 30% efficiency is gone through conduction of heat by the cylinder wall.If it is reason for one of the efficiency loss why can't we build an cylinder coated with a material that is non conduction.So only...

Homework Statement A single phase half wave rectifier produces a DC signal ##V_{DC} = (4.6 \pm 0.78) V## and AC signal ##V_{AC} = (0.22 \pm 0.036) V##. What is the error on the efficiency? Homework Equations Functional dependence, propagation of error: ##\sigma_f = \sqrt{...

Hello Guys, From the torque curves of most of the ic engines it can be seen that torque is maximum at a particular rpm range then it starts dropping. It is said that the torque is maximum when the volumetric efficiency is maximum , i just can't understand the relationship between the both...

Hi there, I have been thinking about attempting to quantify the statement that: "Gasification is more efficient thermodynamically than direct combustion of the fuel source as the gas can be combusted at higher temperatures, resulting in higher thermodynamic efficiencies as defined by...

What do I look for to determine the efficiency factor to know how many watts I can get out of a generator given a specific known HP sized engine? Example: 12.6 HP gives 9395 Watts from the standard HP to Watts conversion... however on a Markon generator, the spec sheet says that a 12.6 HP...

Homework Statement Objects A (2.0 kg), B (1.0 kg), and C (1.0 kg) are pushed up a ramp, which is 4.0 m and 1.2 m high. The applied forces are parallel to the ramp with magnitudes of 9.8 N on A, 4.9 N on B, and 3.1 N on C. Homework Equations Eff = W(output) ÷ E(Input) x 100% W = F...

I read there are transparent solar panels which are also flexible, Then I read carbon base solar panel. Then sun capture that concentrate to panels like other fresnel lens or dish like. Then there is this idea that people can print out their own flexible solar panels with photovoltaic ink...

Homework Statement A snowboarder goes down a ramp when initially at rest. The Total mechanical energy on top of the hill is 980 J and 400J at the bottom of the hill. Calculate efficiency of the ramp. Homework Equations Efficency = (Power out) over (Power in) The Attempt at a...

Discuss two measures that can improve the cooling efficiency.

Please help me with the question below with a proper explanation and also suggest me a reference to read for the same. Thank you! A solar collector receiving solar radiation at the rate of 0.6 kW/m2 transforms it to the internal energy of a fluid at an overall efficiency of 50%. The fluid...

I've be looking at the specs for Heat Recovery Ventilators (HRV). They commonly state that they can recover 85% of the heat. How is that possible? To me you could only every recover 50% in a perfect situation because of the equal volume of airflow's. Won't the air temperatures just stop at...

Thank you in advance for your help!What is the bandwidth efficiency (R/B) of PSK for a bit error rate of 10^-7 on a channel with an S/N of 12 dB?[/b] From the graph, for BER= 10^-7, Eb/N0 = 11.2 dB./b]I have applied the formulae Eb/N0 = S/N * B/R Where, S/N is Signal power over noise power *...

Hi I am trying to calculate the efficiency of my DC motor. I know that efficiency is: Power Out / Power In * 100 I have been told by my teacher that Power In is calculated by the following formula, Power In = Power * Time And Power Out is; Power Out = Mass * Gravity * Height...

Hi, I'm not sure if this is the correct sub-forum to post this question, so I apologize in advance if this post is misplaced. Anyways, a little about my self: I'm a Junior in high school, My passion is in physics and mathematics and I plan to major in physics and preferably get a PHD in it...

Not sure if this should be posted in the general physics forums or in the hw/coursework section. I'm in my second semester of general physics and have to do a class project. For my project I built an alpha type Stirling engine. In the paper I need to write I need to explain how it works using...

A question is being asked about a combustion chamber that has a moving piston; "an engine." "Which expression expresses the efficiency of the engine?" The answer given is: (Pressure(from burning))(Volume)/(moles)(delta H) While this looks some thing like PV = nRT, I don't fully understand...

Not sure if this is the right section for this, I apologize in advance. I have a project to do and my goal is to measure the efficiency of a solar cell INDIRECTLY. I am not sure how to do that. The equation for the efficiency of a solar cell is η = P/E*A. Where P is the cells...

By the conservation of energy, P_in=P_out So,no matter what gear ratio 'i' I choose, P_out=P_in, since the gear ratio 'i' term would get canceled at the numerator and denominator. $$P_{eng}= ω_{eng} M_{eng}= i . ω_{out} \frac{M_{out}}{i}$$ hence P_in=P_out But, what is the drivetrain...

Hi I've been looking in google although I can't find a definitive answer, what are the usual efficiency range for alternators, some talk about brushed ones in the range of 50 to 60 % , brushelss some say go as highas 75%, maybe some of you folks know from your experience what are the typical...

In hilly areas temp is low than plain areas.So the temperature of source as well as sink must be low.But ratio remains same.So efficiency is same as in plain areas? Is my logic correct? Or anything else? Can it be more?

efficiency -- how to get the maximum efficiency in a circuit? Homework Statement I don't quite understand how to get the maximum efficiency in a circuit. Exemple. 4 Volts and 2.0Ω will produce 8 watts with a current of 2.0 amps. 5 Volts and 3.1Ω will produce 8 watts with a current of...

Hi, I am trying to figure out how Li-Ion batteries operate in regards to efficiency. I understand they have rated voltage and current etc. and to operate them at these parameters if possible. However, I'm wondering is it simply the current that has effect on their efficiency. By Efficiency I...

So we've been doing fins in class. I understand that the formulas for fin effectiveness and efficiency are similar, except the area used in the denominator (Ac i.e. area of cross-section for effectiveness and As i.e. surface area for efficiency). However, my question is while designing a...

Homework Statement The Clapeyron cycle efficiency is similar to the Carnot cycle except that two adiabatic paths are replaced with isobaric processes a) based on the above information, draw a Clapeyron cycle. b)Derive the efficiency of the reversible Clapeyron cycle Homework...

Hi, all I'm seeking advice on how to calculate the energy conversion efficiency, in case of heat from light energy. I think that one of the general formulas 'energy output/energy input' can not be applied in this problem. Assuming that light(or laser) has 10W power output and material 1...

My classmates and I are working on a senior design project where we optimize a baseline turbofan for supersonic cruise. We are a little confused about when to use polytropic vs isentropic efficiencies. I have read to begin with isentropic, however is there anyone who could explain a little more...

Homework Statement A Carnot engine operates between a warmer reservoir at a temperature T1 and a cooler reservoir at a temperature T2. It is found that increasing the temperature of the warmer reservoir by a factor of 2.00 while keeping the same temperature for the cooler reservoir increases...

can we convert the linear motion into rotational motion in cars using a fly wheel under the car ?

Dear all, How is the efficiency of piezoelectric transformer higher than electromechanical coupling factor? Thank you, Husain

Is Carnot efficiency the same as thermal efficiency?

Is regenerative brake technology available on vehicles other than ecars and ebikes.if so what is the maximum efficiency reached till now on bikes and cars.

Homework Statement One of your friends is building his own airplane. He has received a quotation for a two-bladed propeller with an efficiency of ##\eta = 80\%## . He asks for your advice on whether it is possible to get a higher efficiency - what is your answer? no, the efficiency based on...

Homework Statement You build a heat engine that takes 1.00 mol of an ideal diatomic gas through the cycle abc, where segment bc is isobaric and segment ca is isochoric. calculate the thermal efficiency of the engine. this is a 5 part problem and I already solved for Wo and Wo=Qo I solved...

Hello, Homework Statement Engine A receives four times more input heat, produces six times more work, and rejects three times more heat than engine B. Find the efficiency of (a) engine A and (b) engine B. Homework Equations e = |W|/|QH| e = 1 - |Qc|/|QH| The Attempt at a...

Homework Statement Determine the amount of time it will take a 1000 W electric kettle to heat up 1.0 L of water to boiling point if the water starts at 10 °C and the kettle is made from 400 g of iron. The transfer of heat energy from the kettle to the water is 63%.Homework Equations P = W/Δt Q...

I am in an introductory physics class and we have been working with Gravitational Potential Energy, Elastic Potential Energy, Kinetic Energy and the Law of Conservation of Energy in relation to bungee cords. Recently, we delved into the topic of efficiency and with it I came upon the following...

Homework Statement Helium in an ideal Diesel cycle is compressed from 4 L to 0.25 L, and then it expands during the constant pressure heat addition process to 0.50 L. Under air standard conditions, the thermal efficiency of this cycle is: a) 79.5% b) 20.5% c) 61.4% d) 67.4% e) 84.3%...

So I was looking through the internet on how one could improve the efficiency of a vacuum system (with a diffusion pump). Lots of websites describe systems with, cold traps to remove condensable vapors such as water. If I am not mistaken, cold traps also help prevent back streaming, similar...

Hello Everybody, Span efficiency factor appears in the lifting-line theory of Prandtl describing Lift and vortex drag of a finite wing. According to this theory, the most efficient wing is an elliptical one and, roughly speaking, the span efficiency factor defines an efficiency of a given wing...

Hello Everybody, Span efficiency factor appears in the lifting-line theory of Prandtl describing Lift and vortex drag of a finite wing. According to this theory, the most efficient wing is an elliptical one and, roughly speaking, the span efficiency factor defines an efficiency of a given...

1. 100kg of methane is compressed from 0.5MPa and 300K to 3.0Mpa and 500K in a closed chamber by a compressor. The compression process is assumed to be adiabatic, calculate the efficiency of this compressor. Specific heat capacity of methane under constant pressure is 35.58 kJ/k.mol.K and ideal...

Question as the title above ! Could we use the wind turbine to compress the air into engine cylinder as the exhaust compression tubine does ? Thanks all for replying !

Homework Statement An incandescent bulb is only 5.0% efficient. How much waste thermal energy is porudced by a 100.0W bulb in 1.0h? (Anwer=95J)Homework Equations P = E/T Efficiency = Eout/Ein x 100%The Attempt at a Solution P = E/T E = PT...

Homework Statement A golf club with 65 J of kinetic energy strikes a stationary golf ball with a mass of 46 g. The energy transfer is only 20% efficient. Calculate the initial speed of the golf ball. Homework Equations efficiency = E out/E in x 100% The Attempt at a Solution I...

Homework Statement If 230 million tonnes of solid waste were burned in waste-to-energy power plants that are 20% efficient a) how many kilowatt- hours of electrical energy could be produced in a year? Compare this quantity with the total US electrical energy production of 3.8 trillion...