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Heat Engines

A heat engine is a system that converts heat to mechanical work. It does this by bringing a fluid from a higher temperature to a lower temperature. A heat source will create thermal energy that brings the fluid to the high temperature. The fluid creates work in the engine while transferring heat to the colder sink until it reaches a low temperature state. During this process some of the thermal energy is converted into work by exploiting the properties of the working substance. The fluid can be any system with a non-zero heat capacity.

Heat engines are different from other engine types by the fact that the efficiency is defined by the Carnot’s theorem. Although the efficiency restriction is a negative, an advantage of heat engines is that most energy forms can be converted easily to heat. Since the heat source supplies energy to the engine, it can be powered by virtually any kind of energy. Heat engines have a wide range of applications. Some examples of heat engines include steam engines, diesel engines and gasoline engines in a car. These are powered by the expansion of heated gases.

Categories within Heat Engines

Second Law of Thermodynamics

Postings: 38

The second law of thermodynamics states that the entropy of the universe always increases in the course of every spontaneous change.


Postings: 23

Maintaining a process at constant temperature.

PV Diagrams

Postings: 7

A pressure volume temperature is used to describe corresponding changes in volume and pressure in a system.

Pressure difference between atmosphere and an evacuated tank.

It is proposed that a device be constructed to operate as follows: an evacuated tank of volume 1m3 is attached to the exhaust of an air-turbine-driven grinding wheel. Air at atmospheric pressure and 300K will be allowed to enter the turban inlet, while the pressure drop between the atmosphere and the tank serves to operate the t

Carnot Heat engines operating in series

Consider two Carnot heat engines operating in series. The first engine receives heat from the reservoir at 1800 K, and rejects the waste heat to another reservoir at temperature T. The second engine receives the energy rejected by the first one, converts some of it into work, and rejects the rest to a reservoir at 300 K. If the

Carnot Cycle - Efficiency of heat engines

A Carnot engine operating at 30% efficiency exhausts heat into a heat sink at 283 K. By how much would the temperature of the heat reservoir need to be raised to increase the efficiency of the engine to 45% I believe the answer is 111 K. I need to see each step and formula to solve this question. Please assume I know nothing



Tension, Work and Energy Consumption

1. A 200 lb metal object is suspended in a liquid with a specific gravity of 1.6. The metal object has a weight density of 150 lb/ft^3. If the object is only 3/4 submerged, what is the tension in the support cable? 2. A vertical cylinder is closed by a freely moving piston at its top. The piston has a mass of 5 kg and an area

Thermodynamics: Heat Engine

A heat engine (thermodynamic cycle) with a fixed amount of working gas is shown in diagram. If the gas temperature at point 3 is 400 K, then how many moles of gas are in the engine? What is the temperature at point 2? Is process stroke 2,3 a heat intake or cooling stroke? How much work is done by process stroke 2,3? How much net

Carnot Heat Engine

Question: The exhaust temperature of a carnot heat engine is 350 degrees Celsius.What is the intake temperature if the efficiency is 25%? a) 400 b) 543 c) 558 d) 830

The rate of revolution of a multicylinder gasoline engine, as well its intake energy and exhaust energy, are given. Compute the fuel consumption per hour and the torque exerted by the crankshaft on the load.

The rate of revolution of a multicylinder gasoline engine in an airplane, operating at 2500 rev/min, takes in energy 7.89*10^3 J and exhausts 4.58*10^3 J for each revolution of the crankshaft. How many liters of fuel does it consume in 1.00 h of operation if the heat of combustion is 4.03 * 10^7 J/L, and what is the torque exert

Carnot Engine

A 20% efficient real engine is used to speed up a train from rest to 5.00 m/s. It is known that an ideal (Carnot) engine using the same cold and hot reservoirs would accelerate the same train from rest to a speed of 6.50 m/s using the same amount of fuel. The engines use air at 300 K as a cold reservoir. Find the Temperature

Carnot heat engine

A Carnot heat engine receives heat from a reservoir at 1700 degrees Farenheit at a rate of 700 Btu/min and rejects the waste heat to the ambient air at 80 degrees Farenheit. The entire work output of the heat engine is used to drive a refrigerator that removes heat from the refrigerated space at 20 degrees Farenheit and transfer

Problem 19.62

Please do not place your response in a .pdf or .cdx format, but Word documents are okay. Thanks! Here's the actual problem: A heat engine using 3.30 grams of helium gas is initially at STP. The gas goes through the following closed cycle: -Isothermal compression until the volume is halved. -Isobaric expansion until the v

Determine the temperature of the gas at different points

A heat engine using 130 mg of helium as the working substance follows the cycle show in the figures (attached). Please do not place your response in a .pdf or .cdx format, but Word documents are okay. Thanks! Please see attached for actual problem.

Reversible heat engine with multiple reservoirs

The heat engine in the atachment operates reversibly and draws 1200 KJ of heat from the 200 K reservoir. The work produced is 200 KJ. Determine the amount and direction of heat interactions with the other reservoirs.

Steam plant: Estimate the amount of cooling water circulated in the condenser

In a steam plant the steam leaves the boiler at 2000kpa+250C deg. It is then expanded in an engine + finally exhausted into a condenser. The press+ condition of the steam at entry to the condenser are 15kpa+0.82 dry respectively. Assume the whole of this heat drop is converted into useful work in the engine. Show engine powe