Chapter 8, Problem 8.45P

A large heat pump should upgrade 4 MW of heat at 65 C to be delivered as heat at 145 C. What is the minimum amount of work input that will drive this?

According to the Carnot cycle, the thermal efficiency of a working heat machine is 28%, and water vapor is used as the working fluid. Heat transfer to the working fluid occurs at 350°C, and at this time the fluid passes from a saturated liquid state to a saturated vapor state. Since 5 kg of fluid circulates per hour in the cycle, find the power of this heat machine using the entropy of evaporation.

Consider three reservoirs that are TH = 473.2 K, TL = 293.2 K and TI = 277.2 K.  A Carnot heat engine can be reversed and used as either a heat pump or a refrigerator.  In the case of a heat pump the heat flow to the higher temperature reservoir is the desired output and it is used to heat a room or building.  In the case of the refrigerator the desired energy flow is the heat in from a region to be cooled.  For the heat pump or refrigerator, the work input is provided by electricity. A region is to be cooled to a temperature of 277 K using a Carnot refrigerator.  The heat that must be removed is 15,000 W. The heat rejected from the refrigerator is to a heat reservoir at TH. Consider the cooling for a period of 3 hours. Answer the following: a)Determine the electrical energy input to the Carnot refrigerator. b)Determine the Coefficient of Performance (COP, the efficiency) of this cooling system. c)Determine the entropy production for this this cooling system.  In this case you should…

Consider three reservoirs that are TH = 473.2 K, TL = 293.2 K and TI = 277.2 K.  A Carnot heat engine can be reversed and used as either a heat pump or a refrigerator.  In the case of a heat pump the heat flow to the higher temperature reservoir is the desired output and it is used to heat a room or building.  In the case of the refrigerator the desired energy flow is the heat in from a region to be cooled.  For the heat pump or refrigerator, the work input is provided by electricity. A region is to be cooled to a temperature of 277 K using a heat powered Carnot refrigerator.  The heat that must be removed is 15,000 W.  The heat rejected from the refrigerator is to a heat reservoir at TL. The heat input to this device is from a reservoir  at TH.  This is a Carnot model of an absorber refrigeration system.  In it a Carnot heat engine operates between reservoirs at TH and TL.  The work output from this Carnot heat engine is the input to a Carnot refrigerator that operates between TI and…

Consider three reservoirs that are TH = 473.2 K, TL = 293.2 K and TI = 277.2 K.  A Carnot heat engine can be reversed and used as either a heat pump or a refrigerator.  In the case of a heat pump the heat flow to the higher temperature reservoir is the desired output and it is used to heat a room or building.  In the case of the refrigerator the desired energy flow is the heat in from a region to be cooled.  For the heat pump or refrigerator, the work input is provided by electricity. Efficiency of the Carnot engine is 38%. For this information answer the following questions: A room is maintained at a constant temperature of 20 C and has a heat loss of 20,000 W.  Consider this room for a period of 3 hours.  The surroundings are at a temperature of TI.  In one option the room is heated using resistive heaters that are operated with electricity.  a)Determine the electrical energy input to these heaters. b)Determine the efficiency of this heating system. c)Determine the entropy production…

Consider three reservoirs that are TH = 473.2 K, TL = 293.2 K and TI = 277.2 K.  A Carnot heat engine can be reversed and used as either a heat pump or a refrigerator.  In the case of a heat pump the heat flow to the higher temperature reservoir is the desired output and it is used to heat a room or building.  In the case of the refrigerator the desired energy flow is the heat in from a region to be cooled.  For the heat pump or refrigerator, the work input is provided by electricity. A region is to be cooled to a temperature of 277 K using a heat powered Carnot refrigerator.  The heat that must be removed is 15,000 W.  The heat rejected from the refrigerator is to a heat reservoir at TL. The heat input to this device is from a reservoir  at TH.  This is a Carnot model of an absorber refrigeration system.  In it a Carnot heat engine operates between reservoirs at TH and TL.  The work output from this Carnot heat engine is the input to a Carnot refrigerator that operates between TI and…

Consider three reservoirs that are TH = 473.2 K, TL = 293.2 K and TI = 277.2 K.  A Carnot heat engine can be reversed and used as either a heat pump or a refrigerator.  In the case of a heat pump the heat flow to the higher temperature reservoir is the desired output and it is used to heat a room or building.  In the case of the refrigerator the desired energy flow is the heat in from a region to be cooled.  For the heat pump or refrigerator, the work input is provided by electricity.  For this information answer the following question: a) Calculate the Carnot Efficiency of a heat engine that operates between TH and TL.

Consider three reservoirs that are TH = 473.2 K, TL = 293.2 K and TI = 277.2 K.  A Carnot heat engine can be reversed and used as either a heat pump or a refrigerator.  In the case of a heat pump the heat flow to the higher temperature reservoir is the desired output and it is used to heat a room or building.  In the case of the refrigerator the desired energy flow is the heat in from a region to be cooled.  For the heat pump or refrigerator, the work input is provided by electricity. Efficiency of the Carnot engine is 38%. For this information answer the following questions: 1) A room is maintained at a constant temperature of 20 C and has a heat loss of 20,000 W. Consider this room for a period of 3 hours. The surroundings are at a temperature of TI.  In one option the room is heated using resistive heaters that are operated with electricity.  For the same conditions described in part 1 above, consider using a Carnot heat pump to supply the heat to the room.  The low temperature…

A cold storage is to be maintained at -5°C while the surroundings are at 35°C. The heat leakage from the surrounding into the cold storage is estimated to be 29 kW. The actual COP of the refrigeration plant is one-third of an ideal plant working between the same temperatures. Find the power required to drive the plant.