![]() ![]() The cylinder is now placed on the warm reservoir H, from which it extracts a quantity of heat Q 1. Red lines are isotherms, and orange lines are adiabats. Representations of a Carnot cycle on a p–V diagram. A heat engine (or engine for short) is a device that does work through the agency of heat.įig. A working substance is said to undergo a reversible transformation if each state of the system is in equilibrium so that a reversal in the direction of an infinitesimal change returns the working substance and the environment to their original states. Therefore, from ( 3.33), the net heat absorbed by the working substance is equal to the external work that it does in the cycle. Since the initial and final states of the working substance are the same in a cyclic process, and internal energy is a function of state, the internal energy of the working substance is unchanged in a cyclic process. If the volume of the working substance changes, the working substance may do external work, or work may be done on the working substance, during a cyclic process. Hobbs, in Atmospheric Science (Second Edition), 2006 3.7.1 The Carnot CycleĪ cyclic process is a series of operations by which the state of a substance (called the working substance) changes but the substance is finally returned to its original state in all respects. Furthermore, the initial cost of a heat pump is greater than that of many furnaces, so that a heat pump must last longer for its cost to be recovered.John M. Heat transfer occurs from a cold reservoir\boldsymbolis usually supplied by electrical energy that costs more per joule than heat transfer by burning fuels like natural gas. We say backward, rather than reverse, because except for Carnot engines, all heat engines, though they can be run backward, cannot truly be reversed. Heat pumps, air conditioners, and refrigerators utilize heat transfer from cold to hot. Most people don’t realize they are also sharing their homes with a heat pump. Almost every home contains a refrigerator. ![]() ![]() Calculate a heat pump’s coefficient of performance.įigure 1.Explain the differences between heat pumps and refrigerators.Demonstrate how a heat pump works to warm an interior space.Describe the use of heat engines in heat pumps and refrigerators. ![]()
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