Heat engine Definition and 157 Threads

Homework Statement A reversible heat engine produces work from the temperature difference that exists between a mass of m = 9 kg of an ideal gas (cv = 716 J/kgK, R = 287 J/kgK) in a rigid container and a heat reservoir at THR = 285 K. The only heat transfer interaction experienced by the...

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...

Homework Statement You have an infinite heat reservoir with temperature Th. But you’ve only got a finite cool reservoir, with initial temperature Tc0 and heat capacity C. Find an expression for the maximum work you can extract if you operate an engine between these two reservoirs. Homework...

What does the P-V diagram for a cycle that violates the Kelvin Planck statement of the second law of thermodynamics look like? Would you say we cannot draw such a diagram BECAUSE of the second law?

Homework Statement Hi, I'm a new user and got this problem. Sorry to bother, but I couldn't find any relevant information from my Physics books.. The problem states: Build a heat engine using these processes: adiabatic, isothermal, isochoric and isothermal. The work-cycle of the engine must...

I'm having a hard time setting up an equation for a heat engine problem with one heat source and two heat sinks given only the temperature of the heat source and temperature of the two heat sinks as: TH = 1000 K TC1 = 200 K TC2 = 300 K It is given that the two heat rejected are of equal value...

Homework Statement A heat engine containing an ideal gas has a reversible cycle which consists of 2 constant volume segments with V = 1ℓ and V = 3ℓ and two constant pressure segments with P = 1 atm and P = 2 atm (see figure below). The temperature at point “c” is Tc = 273 K. A) Is the path...

According to Carnot theorem, the higher temperature of a hot side and the lower temperature of a cold side the higher is the efficiency of a heat engine. Does it mean that in theory it could get anywhere close to 100%? If we take in account that 100% efficiency means it is a perpetuum mobile...

efficiency n=1 -(q1/q2) for a normal heat engine But how efficiency n=1 -(t1/t2) ? for reversible heat engine

Homework Statement [/B] Suppose you build a steam engine that exhausted 1000 J of thermal energy while performing 300 J of work. What is the energy input? What is the efficiency?Homework EquationsThe Attempt at a Solution Would this be correct? Thermal E Input = work + exhaust = 300 J +...

Homework Statement A Carnot heat engine operates between temperatures T1= 400K and T2= 300K. In each cycle the engine receives Qin=1200 J from the high temperature reservoir. a) Calculate the heat Qout delivered to the low temperature reservoir. b) Suppose the engine is operated in reverse as a...

Homework Statement We have a Stirling heat engine. I'm calculating the efficiency \eta. Homework Equations Q_{12} = \frac{m R T_2}{M} \ln(\frac{V_2}{V_1}) > 0 Q_{23} = m c_v (T_1 - T_2) < 0 Q_{34} = \frac{m R T_1}{M} \ln(\frac{V_1}{V_2}) < 0 Q_{41} = m c_v (T_2 - T_1) > 0 \kappa =...

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...

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...

Hi, I am hoping someone may be able to help me as i am quite stuck in this question. Suppose that 156 moles of a monatomic ideal gas is initially contained in a piston with a volume of 0.5 m3 at a temperature of 384 K. The piston is connected to a hot reservoir with a temperature of 1112 K...

what is the need of adibatic process in heat engine? We can work only with isothermal process .Please expalin this.

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?

Homework Statement A haet engine works based on the difference of the temperature at the top and bottom of the ocean. The machine is solar powered and the average solar irradiance is 240W/m^2 and the temperature at the surface of the water is 25ºC. Calculate the temperature at the bottom of...

Homework Statement One end of a metal rod is in contact with a thermal reservoir at 695K, and the other end is in contact with a thermal reservoir at 113K. The rod and reservoirs make up an isolated system. 7190J are conducted from one end of the rod to the other uniformly (no change in...

Homework Statement n = 5 moles, monatomic, ideal gas p1 = 7280 Pa; v1 = 2 m3 p2 = 7280; v2 = 6 p3 = 6500; v3 = 6 What is the change in heat, from 2 to 3, and from 3 to 1? Homework Equations PV = nRT U = (3/2)nRT Q = du + dw The Attempt at a Solution PV = nRT (7280)(2) =...

Hi, I am trying to figure out heat engines. I don't understand why heat from a hot reservoir MUST exhaust heat into a cold reservoir. How does that satisfy the second law of thermodynamics? Why can't all energy from the hot reservoir be used to do work? Thanks

In many textbooks, a proof is provided where the work output of a super-efficient heat engine is provided to a carnot refrigerator, with the net result that a spontaneous heat transfer occurs from the cold reservoir to a hot reservoir. Let's use some numbers, TH = 600 K and TL = 300 K, so...

Homework Statement In winter, you like to keep your house interior at 21.0 degrees C. Your geothermal heating system, which was advertised as being reversible, draws thermal energy from an underground reservoir at 347 K. In a cold winter, with the average outdoor temperature being 0.0...

The figure shows the cycle for a heat engine that uses a gas having gamma =1.25. The initial temperature is T1=300K, and this engine operates at 20 cycles per second. a.) What is the power output of the engine? b.) What is the engine's thermal efficiency? The link to this image is here...

Using Carnot heat engine we connect two objects with the same mass m, specific heat capacities c. At the beginning the body 1 has temperature T_{1} and body 2 T_{2}. Calculate: a) How much mechanical work can this engine give? I tried like this, but i believe this is very wrong :(...

1. Thot reservoir= 600K, Tcold reservoir= 300K, Output= 0.5 J of work for every J of thermal energy extracted from the hot reservoir. What is Qh? 2. efficiency= W/Qh; Carnot efficiency= 1- (Tcold/Thot); 3. I have found the Carnot efficiency to be 0.50. I don't know where to go...

Homework Statement I'm taking a practice test and I need some help with a heat engine problem. There are three parts, the one that's giving me trouble is a-->b. The Volume v. Pressure graph shows a straight line. Pa= 5 atm Va= 5 L Ta=300K and Tb=800K are given. So pressure is decreaseing...

Homework Statement A heat engine uses the closed cycle shown in the diagram below. (Figure 1) The working substance is n moles of monatomic ideal gas. Find the efficiency of such a cycle. Use the values for pressure and volume shown in the diagram, and assume that the process between points...

http://en.wikipedia.org/wiki/Heat_engine This is one of those threads where the OP proposed a device which will not work and hopefully by the end understands why. So here's the device... Air enters through a long intake tube. At the end of the tube it enters a combustion chamber where fuel is...

Homework Statement A nuclear power plant generates 2000 MW of heat energy from nuclear reactions in the reactor's core. This energy is used to boil water and produce high-pressure steam at 300° C. The steam spins a turbine, which produces 700 MW of electric power, then the steam is condensed...

My problem only gives me joules to work with. Is it possible to convert from joules of energy to temperature (Kelvin)?? If so how?

Homework Statement Taken from adkins Introduction to thermal physics A reversible heat engine is operated between two bodies, one of heat capacity C1 initially at temperature T1 and the other of heat capacity C2 initially at temperature T2. As the engine operates, the warmer body gradually...

Homework Statement there is a question solution i am looking at, and it goes from TH(Vb)^(y-1) = TH(Vc)^(y-1) and it appears to be rewritten as Vc=Va(TH/TC)^(1/(y-1)) Can anyone please explain this? thanks

Is it strictly true that an engine will be more efficient if operating in a hotter environment... e.g. your car is more efficient in the summer than the winter? Just going through thermo 1, not a HW question, but it just seems to be true to me because the simple Newton's law of cooling says...

Homework Statement A heat engine operating between freezing and boling points of water takes 20 cycles to raise a mass of 1000kg through a height of 3m. Calculate the minimum energy per cycle that must be extracted from the hot reservoir in order to achieve this. Homework Equations...

Does anyone can help me in this question? Two reversible heat engines operate in series between a source at 600C and a sink at 30C. If the engines have equal efficiencies and the first rejects 400 kJ to the second, calculate: (i) the temperature at which heat is supplied to the second...

Homework Statement A heat engine has a carnot efficiency of 0.11. How much internal energy does this engine use in order to do 5.1 x 10^4 joules of work? How much heat does this engine give off/exhaust?Homework Equations (change in)U=Q-W W=(change in)E

An ideal heat engine operates with an input temperature of 327C and an exhaust temperature of 27C. If the input temperature is lowered to 227C, by how much must be the exhaust temperature be lowered to maintain the same eciency?Im using η= 1-(tc/th) that works out to 1-(300k/600k) = 0.5 then...

Homework Statement Fifty kg of water at 0oC must be frozen into ice in a refrigerator. The room temperature is 20oC. The latent heat of fusion of water is 3.33x105 J kg-1. What is the minimum power required if the freezing is to take place in one hour? m = 50 kg Lf = 3.33x105 J kg-1...

Homework Statement Modern nuclear power plants have an overall efficiency of about 30%. Fossil fuel plants achieve overall efficiencies of 40%. Compare the rate of heat emission from a nuclear plant with that from a fossil fuel plant each of which produces an output power of 1000 MW...

Homework Statement A borehole produces 120kg/s of high pressure water at 165°C. A powerplant is to be designed to extract heat from the water, reducing the temp to 147°C. The plant which will initially be assumed to be reversible, will reject heat at 17°C to a river. Take 147°C as the highest...

I will look at two different engines, which need heater, and no cooler, to operate. First one: A rocket engine, which, instead of burning fuel, simply heats up cold fuel in solid form so the heated and evaporated substance is used as a reaction mass. The nozzle of the rocket engine is in...

Homework Statement An engine operates with n = 1.94 moles of a monatomic ideal gas as its working substance, starting at volume VA = 21.4 L and pressure PA = 2.77 atm. The cycle consists of: - A to B: an isobaric expansion until its volume is VB = 50.1 L - B to C: an isochoric (constant...

Homework Statement A reversible engine contains 0.5 mol of an ideal monatomic gas and operates using a cycle, similar to that shown in Fig. 19.21 on page 324 of the textbook, consisting of constant volume and constant pressure segments. (You will need to draw your own diagram using the data...

I’ve recently become fascinated by high power density energy conversion devices… I was looking at the 100W incandescent light bulb lamp on my desk as 90% of its energy was being wasted as heat and started thinking… I know it is only a rather small amount of energy, but what would be the most...

Homework Statement A 52-kg mountain climber, starting from rest, climbs a vertical distance of 730 m. At the top, she is again at rest. In the process, her body generates 4.1 × 10^10 J of energy via metabolic processes. In fact, her body acts like a heat engine, the efficiency of which is...

Question is attached I have spent a great deal of time on this problem and I am hoping someone can help me out. My attempt at problem. first for the heat engine QL/Qw1 = TL/Twaste so efficiency = 1- Tl/Twaste efficiency = 0.93808 and I know that efficiency = Wout/ Qw1 This is as...

Homework Statement Consider a Carnot engine that operates between a hot reservoir at 63°C and a cold reservoir at -14°C. In running 25 minutes, this engine absorbs 590 J of heat from the hot reservoir. How much heat does it expel to the cold reservoir? Homework Equations Q_H/Q_C =...

Homework Statement A 1500kW heat engine operates at 25% efficiency. The heat energy expelled at the low temperature is absorbed by a stream of water that enters the cooling coils at 20 degrees C. If 60L flows across the coils per second, determine the increase in temperature of the water...

Homework Statement What is the maximum effciency of a heat engine whose operating tempuratures are 550oC and 365oC? Homework EquationsE=1-Thot/Tcold The Attempt at a SolutionPLEASE HELP! My thinking is that the effciency is equal two one minus the temperature in the hot resavour...