Thermodynamics heat engine Question

In summary, a 1500kW heat engine with 25% efficiency expels heat energy at a low temperature and is absorbed by a stream of water at 20 degrees C flowing at a rate of 60L per second. Using the equation mCdeltaT = Q, it can be determined that the increase in temperature of the water is 18 degrees C. This is found by converting the flow rate to mass flow rate and taking into account the density of water.
  • #1
blackwing1
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0

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 Equations


mCdeltaT = Q

The Attempt at a Solution


0.75*(1500Kj/s)(1000J/1kJ)(s/60L)(kgdegreesC/4186J) = 4.48
The book says that it is 18 degrees C. The DA that I did cancels out correctly though.

Thanks.
 
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  • #2
You need to convert the 60L/s to mass flow rate in kg/s, you would need to find how many kg is in 1 L.
 
  • #3
It's water, so with a density of 1, the answer should still be what I got.
 

Related to Thermodynamics heat engine Question

What is a heat engine?

A heat engine is a device that converts heat energy into mechanical work. It operates by taking in heat from a high temperature source, converting some of that heat into work, and then releasing the remaining heat to a lower temperature sink.

How does a heat engine work?

A heat engine works by using a working substance, such as a gas or liquid, to absorb heat from a high temperature source. The substance then expands, doing work on a piston or turbine, and releases some of its heat to a lower temperature sink. The substance is then compressed back to its original state, ready to repeat the cycle.

What is the first law of thermodynamics?

The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transferred or converted from one form to another. In the case of a heat engine, the first law dictates that the amount of work done by the engine must be equal to the amount of heat absorbed minus the amount of heat released.

What is the second law of thermodynamics?

The second law of thermodynamics states that the total entropy, or disorder, of a closed system will either remain constant or increase over time. This means that in a heat engine, some of the heat energy will always be lost to the surrounding environment, resulting in a decrease in the engine's efficiency over time.

What factors affect the efficiency of a heat engine?

The efficiency of a heat engine is affected by various factors, including the temperature difference between the high and low temperature sources, the type of working substance used, and the design and operation of the engine. Generally, the larger the temperature difference, the higher the efficiency, but there are also limitations due to the second law of thermodynamics.

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