Chapter 20.4, Problem 1CE

The energy output of a heat pump is greater than the energy used to operate the pump. Why doesn't this statement violate the first law of thermodynamics?

A heat pump has a coefficient of performance of 3.80 and operates with a power consumption of 7.03 103 W. (a) How much energy does it deliver into a home during 8.00 h of continuous operation? (b) How much energy does it extract from the outside air?

Give an example of a spontaneous process in which a system becomes less ordered and energy becomes less available to do work. What happens to the system's entropy in this process?

Consider these scenarios and state whether work is done by the system on the environment (SE) or by the environment on the system (ES): (a) opening a carbonated beverage; (b) filling a flat tire; (c) a sealed empty gas can expands on a hot day, bowing out the walls.

The bulldozer for the DPWH road widening project at Koronadal City has a gasoline engine that takes 10,000 J of heat and delivers 2,200 J of mechanical work per cycle. (a) What is the thermal efficiency of this engine? (b) How much heat is discarded in each cycle?

With 2.56×106J of heat transfer into this engine, a given cyclical heat engine can do only 1.50×105 J of work.  (a) What is the engine's efficiency? (b) How much heat transfer to the environment takes place?

A heat engine running backward is called a refrigerator if its purpose is to extract heat from a cold reservoir. The same engine running backward is called a heat pump if its purpose is to exhaust warm air into the hot reservoir. Heat pumps are widely used for home heating. You can think of a heat pump as a refrigerator that is cooling the already cold outdoors and, with its exhaust heat QH, warming the indoors. Perhaps this seems a little silly, but consider the following. Electricity can be directly used to heat a home by passing an electric current through a heating coil. This is a direct, 100% conversion of work to heat. That is, 19.0 kW of electric power (generated by doing work at the rate 19.0 kJ/s at the power plant) produces heat energy inside the home at a rate of 19.0 kJ/s. Suppose that the neighbor's home has a heat pump with a coefficient of performance of 3.00, a realistic value. NOTE: With a refrigerator, "what you get" is heat removed. But with a heat pump, "what you…

An enclosure is initially at the same temperature as the outside, which is 20°C. In it there are two 50 W lamps each, a 100 W TV, a 200 W refrigerator, which works 2/3 of the time, and a 500 W iron. Assuming that no heat is transferred through the walls, calculate the rate of increase of the energy content in the room, when all these appliances are turned on?

(a) How much heat transfer occurs to the environment by an electrical power station that uses 1.25×1014 J of heat transfer into the engine with an efficiency of 42.0%?                                                                                              (b) What is the ratio of heat transfer to the environment to work output?(c) How much work is done?