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In a practical heat engine, heat is generated by burning a fuel, work is extracted from this heat resulting in the working fluid cooling, and heat is then rejected at the lower temperature. As you must know, in an internal combustion engine heat is rejected both in the engine cooling system and the exhaust.
In a power plant, using water/steam as the working fluid in a closed cycle, there are four phases in the cycle: 1. Water is pumped at high pressure into a steam raising unit (boiler) 2. Heat from the fuel, be it coal, oil, gas, or nuclear, is added to the water causing it to become steam 3. the steam is expanded through a turbine doing work, that is driving the generator 4. the steam is condensed back to water using external cooling water. This is called the Rankine cycle. At stage 4 heat is being rejected into the external cooling water, and this heat is lost. It is minimised by running the condenser under vacuum so that steam at less than 100 celsius can still do work, and the final turbine discharge temperature is as low as 30C. Theoretically the efficiency of such a cycle is maximised by making the steam to the turbine as hot as material constraints allows, and the condenser vacuum as low as the local cooling water temperature will allow. The maximum practical efficiency of such a plant is about 42 percent, meaning that 58 percent of the heat from the fuel is rejected. For a PWR nuclear plant the steam temperature is much lower and the cycle efficiency is less, more like 30 percent.
I hope this enables you to see why in a practical heat engine there must be heat rejection. There are several entries in Wikipedia for further reading, see 'Heat Engines' first.
Heat rejection occurs in a thermodynamic process to maintain energy balance. When work is done on a system or the temperature of a system is raised, excess heat may need to be removed to maintain the system at a desired temperature or pressure. This helps to ensure that the process runs efficiently and effectively.
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Is heat rejection the same as heat dissipation?
No, heat rejection and heat dissipation are not the same. Heat rejection refers to the process of transferring heat from one place to another, such as releasing heat from a system into the surroundings. Heat dissipation, on the other hand, is the dispersion of heat within a system to lower its temperature.
What is heat rejection?
Heat rejection is the process of transferring heat energy from a system or material to its surroundings. This can occur through various mechanisms such as conduction, convection, and radiation, and is commonly used in cooling systems to dissipate excess heat. Heat rejection is essential in maintaining optimal operating conditions for many systems and devices.
What is the minimum number of stages that a steady state thermodynamic heat engine or heat pump can have?
A steady state thermodynamic heat engine or heat pump must have at least two stages in order to operate effectively. One stage is needed for the heat input process and the other for the heat rejection process.
What is an adiabatic process?
An adiabatic process is one in which there is no heat transfer into or out of the system. This means that any change in internal energy of the system is solely due to work done on or by the system. Adiabatic processes are often rapid and can lead to changes in temperature and pressure without heat exchange.
Explain how you might keep a gas at a constant temperature during a thermodynamic process?
To keep a gas at a constant temperature during a thermodynamic process, you would need to provide or remove heat in such a way that the temperature of the gas remains constant. This can be achieved by using a heat reservoir that can absorb or provide heat to the gas as needed. Additionally, you could use a thermostat to monitor the temperature and adjust the heat input accordingly.
A quantity that gives the direction of a thermodynamic process is?
specific heat
Is heat a thermodynamic function?
what is heat a thermodynamic function
Is heat rejection the same as heat dissipation?
No, heat rejection and heat dissipation are not the same. Heat rejection refers to the process of transferring heat from one place to another, such as releasing heat from a system into the surroundings. Heat dissipation, on the other hand, is the dispersion of heat within a system to lower its temperature.
What is heat rejection?
Heat rejection is the process of transferring heat energy from a system or material to its surroundings. This can occur through various mechanisms such as conduction, convection, and radiation, and is commonly used in cooling systems to dissipate excess heat. Heat rejection is essential in maintaining optimal operating conditions for many systems and devices.
What is the minimum number of stages that a steady state thermodynamic heat engine or heat pump can have?
A steady state thermodynamic heat engine or heat pump must have at least two stages in order to operate effectively. One stage is needed for the heat input process and the other for the heat rejection process.
Can you put the word thermodynamic is a sentence?
yes the word "thermodynamic" can be called a sentence. "THERMO" means heat and "DYNAMICS means motion or movement. -Thermodynamic refers to the study of heat and temperature and their relation to energy and work.
What is an adiabat?
An adiabatic process is a thermodynamic process, there is no gain or loss of heat.
What is an adiabatic process?
An adiabatic process is one in which there is no heat transfer into or out of the system. This means that any change in internal energy of the system is solely due to work done on or by the system. Adiabatic processes are often rapid and can lead to changes in temperature and pressure without heat exchange.
What is meant by adiabatic?
Of, relating to, or being a reversible thermodynamic process that occurs without gain or loss of heat and without a change in entropy. Source: Anwers.com
Explain how you might keep a gas at a constant temperature during a thermodynamic process?
To keep a gas at a constant temperature during a thermodynamic process, you would need to provide or remove heat in such a way that the temperature of the gas remains constant. This can be achieved by using a heat reservoir that can absorb or provide heat to the gas as needed. Additionally, you could use a thermostat to monitor the temperature and adjust the heat input accordingly.
Which thermodynamic process takes place when work is done on the system but no energy is transferred to or from the system as heat?
The thermodynamic process that takes place when work is done on the system but no energy is transferred as heat is an isochoric process, also known as an isovolumetric or constant volume process. In an isochoric process, the volume of the system remains constant, so there is no heat transfer, and all the work done goes into changing the internal energy of the system.
What is isobaric process?
An isobaric process is a thermodynamic process that occurs at a constant pressure. This means that the system is allowed to exchange heat with its surroundings but the pressure remains the same throughout the process. In an isobaric process, the work done is determined by the change in volume of the system.
