![]() ![]() ![]() To repeat this process, the piston needs to be returned to its starting point. (c) Heat transfer of energy to the environment further reduces pressure in the gas, so that the piston can more easily return to its starting position. Gas pressure and temperature decrease during expansion, indicating that the gas’s internal energy has decreased as it does work. ![]() (b) The force exerted on the movable cylinder does work as the gas expands. Thus, heat transfer of energy to the gas in the cylinder results in work being done.įigure 12.13 (a) Heat transfer to the gas in a cylinder increases the internal energy of the gas, creating higher pressure and temperature. The gas does work on the outside world, as this force moves the piston through some distance. This increases the gas temperature, which in turn increases the pressure of the gas and, therefore, the force it exerts on a movable piston. Fuel combustion releases chemical energy that heat transfers throughout the gas in a cylinder. Gasoline and diesel engines, jet engines, and steam turbines that generate electricity are all examples of heat engines.įigure 12.13 illustrates one of the ways in which heat transfers energy to do work. A heat engine does exactly this-it makes use of the properties of thermodynamics to transform heat into work. One of the most important things we can do with heat is to use it to do work for us. In this section, we’ll explore how heat engines, heat pumps, and refrigerators operate in terms of the laws of thermodynamics. Heat Engines, Heat Pumps, and Refrigerators Ask students whether they can explain the limits on efficiency in terms of what they have now learned. Review the ideal gas law, laws of thermodynamics, and entropy. Return again to the discussion of efficiency that was begun at the start of the module. ![]()
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