Efficiency Definition and 950 Threads

Homework Statement Find the isentropic efficiency of the pump: effpump=(h4s-h3)/(h4-h3) state 3: p3=1.5 bar, h3=467.11, x3=0, v3=1.0528/1000 m3/kg ,s3=1.4336 kJ/kg*K, T3=111.4 deg C state 4: p4=60 bar, h4=474.14, compressed liquid state 4s: p4=60 bar, s3=s4s The values in red are the ones I...

Homework Statement The temperature inside the room ##T_I= 25 C ## and the temperature outside the house is ##T_O = 32C##. The temperature difference causes energy to flow into the room (by conduction through the walls and window glass) at the rate 3,000 J/s. To return this energy to the...

Hi can anyone help me about the following ? if I have the experimental data of inlet and outlet of expander (temperature and pressure) working in ORC. Now if I want to find the Isentropic efficiencie : the Isentropic expansion can be found by (entropy in = entropy out) but how to find the...

Homework Statement Energy conversion efficiency of the elevator is 80%, it is working from 220 volts. How much current does the electro motor consume while it is constantly lifting the 500 kg cabin at 2 m/s. The attempt at a solution I=P/U, so I figured I need to know the power. P=F*v. I...

Hi, I am trying to do a comparison of electrical efficiencies between 2 HVAC compressors but struggling to find formulas or calculations to figure it out. Can anyone help me?

Homework Statement The armature resistance per phase is given as 24.7ohms. Delta configured machine. Open circuit voltage is 220v, short circuit current is 1.1A at 3000rpm. Rpm is dropped to 1500rpm and no load line voltage is 100. Find power and efficiency if an inductive load of 1.4H is...

I would like ask comments about assumed photon detection efficiency model used in these experiments that test Bell inequalities and consequences if it does not hold. http://arxiv.org/abs/1511.03189 http://arxiv.org/abs/1511.03190 Detection efficiency is calculated as two-fold coincidence events...

Wind turbines apparently now produce electricity only at some minimum wind speed.In my conception,the wind pressure of a lower wind speed is used to exert a force on a diaphragm or vane which stores torque in a spring or other mechanism,This torque could be used to help overcome the initial...

I read in a couple of papers about asteroid hunting that they used artificially implemented asteroids in real images to see if their detection algorithms could find them. This way, the scientists determined their asteroid survey efficiency in real data. As I don't have the resources to work so...

I've heard that alternate current is more efficient than direct current. I've heard is easier to transport than dc current. Is that true? Why is that? Also, why are three phase systems better than monophasic ones? Thank you very much!

Homework Statement Nitrogen enters an insulated compressor operating at steady state at 1 bar, 310 K with a mass flow rate of 1000 kg/h and exits at 10 bar. Change in KE and PE is zero. Heat transfer is zero. Assume ideal gas with k=1.391. Find minimum theoretical power input required and the...

Homework Statement A ball that weights 1kg is thrown in the air, the hand being 1m above the ground. The velocity the ball was thrown at was 14m/s and it's maximum height was 6.5m above the ground. What is the efficiency for this energy transformation? Homework Equations Do I just get the...

Hi, I'm trying to figure which is more fuel efficient, turbine vs stroke generators. This honda stroke engine generator does 1000w for 3.8 hrs with 0.6 gallons of fuel or 2.3 liters, so the power per liter of fuel is 1,300 kW. http://powerequipment.honda.com/generators/models/eu1000i Then I...

Homework Statement Is it possible to calculate the work done heat transfer, and efficiency of an object in a thermodynamic system, given the Temperature vs Entropy graph? Example: Homework Equations ∆U=Q-W ∆S=dQ/T e=1-(Qc/Qh) e=W/QhThe Attempt at a Solution Since this is a T vs S diagram,i...

I'm struggling to understand the Carnot efficiency. I can follow proofs that prove efficiency= 1- (Th/Tc), and I understand the nature of the processes that make up a carnot cycle - however I still can't make sense of it in my head. I've looked online and most people try and explain it...

Hi, When the modern 80 plus power supplies are quoted as being "87% efficient" on 100% load, does this mean that an 80 plus Gold PSU rated at for example 1000 Watts will provide 1000 Watts to the internal PC components, and therefore draw 1000/(0.87) = 1149.43 W from the wall? OR does it mean...

I regret to say that I know little of engineering, but, to make a long story short, I'm nagged by two questions about energy conversion efficiency. There is a thread i made titled "giant railguns recycling their own energy in space" in the science fiction & fantasy forum here that explains my...

The efficiency of a Carnot Engine is described by the relationship: Tc/Th = Qc/Qh, so that e(Carnot) = 1 - Tc/Th For heat engines, can their efficiency also be related to temperature as well? Or is the description of their efficiency just: e(heat engine) = W / Qh = 1 - Qc/Qh I am inclined to...

Q1. I know a DMM will anticipate a sineusoidal supply, thus there can be problems with spiky supplies. Even if you have a true RMS meter, it it's a spikey supply, non-sineusoidal, you still can't calculate the peak of a spiky supply? Does a DMM measure the peak, then calculate from THAT the...

Energy efficiency related question: please help with an anwer to the following: Given a flat electrical coil of known dimentions, this coil is used as an induction coil, laid flat, on top of the cooking surface of an induction cooker. Basically, the induction cooker has a copper braided coil...

What information can one obtain from the plots of the background vs signal efficiency? \epsilon_{bkg}(\epsilon_{sig})? In particular I attach some plots I made by hand and I want to understand how to obtain what each tells us.

Hello, I've been trying to wrap my head around this topic and came across such a thread here: https://www.physicsforums.com/threads/propulsive-efficiency.643646/ but still don't get it. Why is it that that accelerating one unit of mass by two units less efficient than accelerating two units of...

I was told that "piezoelectric materials can become more efficient if they were made to reduce their elasticity (the ones such as PVDF films that are flexiable).This is because the external energy is used to force the film back to its original shape just like when a spring is squashed; so most...

In the proof of Clausius inequality ##\oint\frac{\delta Q}{T}<0## for an irreversible cycle, I always find the fact that the thermal efficiency of an irreversible machine is **stricly less** than the thermal efficiency of a reversible machine, both operating between temperatures ##T_H## and...

The efficiency of a scientific camera like http://www.princetoninstruments.com/products/imcam/proem/ is specified by the quantum efficiency vs wavelength. The meaning is simple enough. Assuming a fill factor of 1, it's the fraction of incident photons that generate a charge. But photographer...

[Moderator's note: Recategorized thread to "Basic".] While driving alone through the beautiful scenery of Banff and Yoho national parks, a question formed in my mind. Which of these modes of slowing down a vehicle by an equal amount is likely to minimize the resulting overall increase in...

Recently I've been in a discussion with someone online who claimed that the efficiency of a computer with regards to energy is not a linear relationship. I assumed that if you were to halve the power going into a computer chip (assuming it was designed to deal with that and wouldn't just turn...

Homework Statement An "energy bar" contains 22 g of carbohydrates. If the energy bar was his only fuel, how far could a 68 kg person walk at 5 km/h? Mass(person) = 68 kg; v = 5km/h; 22g carb = 4 Cal/1 carb = 88 Cal; P(power of man walking) = 380W (this is derived from my textbook). Homework...

"A Faraday cage or Faraday shield is an enclosure formed by conductive material or by a mesh of such material. Such an enclosure blocks external static and non-static electric fields by channeling electricity along and around, but not through, the mesh, providing constant voltage on all sides of...

I tried to calculate the efficiency of a engine using the formula : Efficiency = (Net Work Done) / (Heat absorbed) And then I tried to calculate the efficiency of respective Carnot engine by two ways : 1) Efficiency = (Net Work Done) / (Heat absorbed) 2) Efficiency = 1 - (Temperature Lowest /...

Hi, so I was wondering about how the car's LED, MP3/IPOD, AC systems consumes up electrical power and then to fuel? Let's say that the loads are running for 5-7 hours. Thanks for the replies/ideas!

How to calculate the efficiency of a generator? Any formulas?

Which one do you think that is more efficient? I think that lecturers, from the fact of being humans, commit more mistakes than books when they give information because they can forget to transmit important details. Books are written carefully in order to be easy to understand, what's said was...

" A intelligence signal is amplified by a 80% efficient amplifier before being combined with a 12kW carrier to generate the AM signal. if it is desired to operate at 100% modulation, what is the DC input power at the modulator" The choices are a: 12kW b. 7.14kW c.7.5kW d. 15kW my solution...

I reference this forum all the time and you guys are always good at breaking down confusing questions so I decided I needed to make an account and get some help with a mental struggle I have been having for quite some time! Two commonly discussed ways of improving a compressor's efficiency in a...

Homework Statement Can the power efficiency of the domestic hair dryer be improved by reducing the heat energy and increasing airflow? Homework EquationsThe Attempt at a Solution

Homework Statement Hi! I have a problem with the following problem: Calculate the efficiency of the solar cells with the characteristics given in the table below Power (28 degrees, BOL): 300 W/m2 Absorptance: <91 , emittance: >82. Reliability: 0.999 . Mass: 2 kg Homework Equations I know...

(b) An energy audit was conducted on a building to demonstrate energy savings opportunities by replacing the air handling unit or AHU fans motors, condensing and chilled water pump motors of the water cooled chilled water air-conditioning installation with newer, more efficient motors of the...

I'm constructing a quantum circuit that implements a gray code that connects the binary strings |0001> and |1110> using CNOT gates. Since the two strings are negations of each other, two equivalent circuits can be designed where the control qubit conditions are negated. My question is what is...

Homework Statement In a 30% efficient, -16°C fridge, how much electrical energy will be used up to lower the temperature of 250 mL of 75°C water? If the fridge is rated at 150 W, how long will this process take? Specific Heat Capacity of Water = 4200 J/Kg×K Specific Heat Capacity of Ice = 2000...

Is the efficiency of a cell in a closed circuit always 50%?

I can't realize the proving why Carnot engine has the highest efficiency. "Let εc be the efficiency of a Carnot engine operating between two given temperatures.If an engine X, which has an efficiency εx that is greater than εc.We can couple engine X to a Carnot refrigerator , and they make a...

Homework Statement The oxygen contained in a thermally insulated container will be cooled down to its boiling point (-183 C), and then condensed. Thereby one uses a reverse Carnot process operating between the oxygen gas (instantaneous) temperature and the room temperature (17 C). What is the...

Changing the potential energy of water is frequently used as a means of storing excess renewable energy when it is not needed and using it when it is needed. An electrically-powered pump with efficiency 62 % raises a 10 kg mass of water a height of 10 m. The water is subsequently allowed to...

Hey guys I was wondering what would happen if: took a ball neo magnet, balanced it on a few other magnets to basically make it a frictionless bearing. Then spin the ball magnet to 10k rpm. But do all this in a box that's a vacuum. Would the neo ball magnet spin basically for a VERY long...

Homework Statement A possible ideal-gas cycle operates as follows: (i) from an initial state (p1,V1), the gas is cooled at constant pressure to (p1,V2) (ii) the gas is heated at constant volume to (p2,V2) (iii) the gas expands adiabatically back to (p1,V1). Assuming constant heat capacities...

I am doing an experiment to determine the performance of a steam plant cycle and analyse it in comparison with the ideal rankine cycle. I have a sketch of the actual and real T-S diagram for the steam plant (See attached) I am unsure what factors cause the change in the shape of the T-S...

Hello all, this is my first time posting here so please excuse if this maybe isn't the appropriate thread to post this in but I figured it may be the most relevant. I am working on writing a proposal (small, just 450 words), that aims to address the energy efficiency of a university, ie...

Homework Statement Figure 2 represents a model for the thermodynamic cycle of the Stirling engine, patented by Scottish clergyman Robert Stirling in 1816. The engine operates by burning fuel externally to warm one of its two cylinders. A xed quantity of inert gas moves cyclically between the...

1-Is the efficiency of heat engines working in cycles other than Carnot independent of the nature of substance used? Can we still claim that maximum efficiency in converting heat to work is attained during reversible processes for such cycles? For which engines/cycles can we do this? 2- Why is...