Concept explainers
The radiator of a steam heating system has a volume of 20 L and is filled with superheated water vapor at 200 kPa and 200°C. At this moment both the inlet and the exit valves to the radiator are closed. After a while it is observed that the temperature of the steam drops to 80°C as a result of heat transfer to the room air, which is at 21°C. Assuming the surroundings to be at 0°C, determine (a) the amount of heat transfer to the room and (b) the maximum amount of heat that can be supplied to the room if this heat from the radiator is supplied to a heat engine that is driving a heat pump. Assume the heat engine operates between the radiator and the surroundings.
FIGURE P8–31
Trending nowThis is a popular solution!
Chapter 8 Solutions
Thermodynamics: An Engineering Approach
- A piston–cylinder device contains 0.85 kg of refrigerant134a at –10°C. The piston that is free to move has a mass of 12 kg and a diameter of 25 cm. The local atmospheric pressure is 88 kPa. Now, heat is transferred to refrigerant-134a until the temperature is 15°C. Determine (a) the final pressure, (b) the change in the volume of the cylinder, and (c) the change in the enthalpy of the refrigerant-134a.arrow_forward(a) In the thermodynamic laboratory, student Ali prepared a piston-cylinder device which contains refrigerant-134a at 1000 kPa and 50°C. The mass of the refrigerant is 6 kg. The next step of the experiment involves cooling the refrigerant at constant pressure until its state become liquid at 24°C. Show the process on T-v diagram and determine the heat loss from the system. (b) A heat exchanger as shown in Figure 1 is used to cool water flowing in at 1 kg/s water, 10 kPa and quality 0.95 to saturated liquid at 10 kPa. The cooling fluid is water taken from a lake at 20°C and it exit the heat exchanger at 30°C. Calculate the flow rate of cooling water. Assume that the heat exchange is well insulated and there is no heat loss. Lake water Figure 1: Heat exchangerarrow_forwardA room is filled with saturated steam at 100°C with enthalpy of 2675.6 kJ/kg. Now a 5-kg bowling ball at 25°C is brought to the room. Heat is transferred to the ball from the steam, and the temperature of the ball rises to 100°C while some steam condenses on the ball as it loses heat (but it still remains at 100°C). The specific heat of the ball can be taken to be 1.8 kJ/kg · C. The approximate mass of steam that condensed during this process is? what is the answer? a. 80 g b. 252 g c. 351 g d. 128 garrow_forward
- A room is filled with saturated steam at 100°C with enthalpy of 2675.6 kJ/kg. Now a 5-kg bowling ball at 25°C is brought to the room. Heat is transferred to the ball from the steam, and the temperature of the ball rises to 100°C while some steam condenses on the ball as it loses heat (but it still remains at 100°C). The specific heat of the ball can be taken to be 1.8 kJ/kg · C. The approximate mass of steam that condensed during this process isarrow_forwardA frictionless piston-cylinder device initially contains 200L of saturated liquid refrigerant-134a. The piston is free to move and its mass is such that it maintains a pressure of 900 kPa on the refrigerant. The refrigerant is now heated until its temperature rises to 70C. Calculate the work done during this process. ANS. 5571 KJA fixed mass of an ideal gas is heated from 50 to 80°C at a constant pressure of (a) 1 atm and (b) 3 atm. For which case do you think the energy required will be greater?arrow_forwardConsider a vessel which has a resistance heater and a mixer. is filled with 3.6 kg of saturated water vapor at 120°C. Then the heater and mixer are put to work, the water vapor is compressed, and there is 5 kg of heat loss to the air from the surroundings. At the end of the process, the temperature and pressure of the water vapor in the vessel are measure, and they turn out to be 300°C and 500 kPa. Determine: a) The net energy transfer, in kJ, to the water vapor during this process.arrow_forward
- Water vapor at 110 kPa and 150°C is contained in a rigid vessel tank. At what temperature will the vapor start to condense when the container is cooled slowly? How much heat will have to be removed per kilogram in this cooling process?arrow_forwardAn isolated piston-cylinder device contains 5 L of saturated liquid water at a constant pressure of 175 kPa. The water is stirred with a paddle wheel while a current of 8 A flows for 45 minutes through a resistor placed in the water. If theHalf of the liquid evaporates during this process at constant pressure and the work done by the paddlewheel is equal to 400 kJ, determine the voltage of the source. Also, show the process on a P-v diagram with respect to the saturation lines.arrow_forwardA 14-ft3 tank contains oxygen initially at 14.7 psia and 80°F. A paddle wheel within the tank is rotated until the pressure inside rises to 20 psia. During the process 20 Btu of heat is lost to the surroundings. Determine the paddle-wheel work done. Neglect the energy stored in the paddle wheel. The gas constant and molar mass of oxygen are R = 0.3353 psia-ft3/lbm-R and M = 32 lbm/lbmol. The specific heat of oxygen at the average temperature of Tavg = (735+540)/2= 638 R is cv,avg= 0.160 Btu/lbm.R. The paddle-wheel work done is Btu.arrow_forward
- The radiator of a steam heating system has a volume of 150L and is filled with superheated vapor at 200kPa and 200C. At this moment both the inlet and exit valves to the radiator are closed. Determine the amount of heat that will be transferred to the room when the steam pressure drops to 100 kPaarrow_forwardIn a fixed volume container of 0.1 m3, initially there is saturated water vapor at 130 oC. The vessel is connected to a pipe through which steam flows through a valve at 2 MPa pressure and 350 oC temperature. Then the valve opens and steam enters the container. Meanwhile, the temperature of the steam in the container remains constant at 130 oC due to the heat transfer to the environment. When it is observed that 3/4 of the water in the container covers the liquid phase by mass, the valve is closed. wwwww www ww w m ww vww muw m w ww m www wwm w w www ww www wwww www w J n ww ww a) Calculate the final pressure in the container. b) calculate the mass of steam entering the container. www c) Calculate the heat transfer to the environment. Qarrow_forwardA piston-cylinder device contains 0.850 kg of refrigerant-134a at –10.0°C. The piston that is free to move and has a mass of 12.0 kg and a diameter of 25.0 cm. The local atmospheric pressure is 88.0 kPa. Now, heat is transferred to refrigerant-134a until the temperature is 15.0°C. Determine (a) the final pressure, (b) the change in the volume of the cylinder, and (c) the change in the enthalpy of the refrigerant- 134a. Assume the following: va-10°C = 0.2302 m³/kg, va-15°C = 0.2544 m³/kg, ha-10°C = 247.22 kJ/kg, h@15°C = 268.18 kJ/kgarrow_forward
- Elements Of ElectromagneticsMechanical EngineeringISBN:9780190698614Author:Sadiku, Matthew N. O.Publisher:Oxford University PressMechanics of Materials (10th Edition)Mechanical EngineeringISBN:9780134319650Author:Russell C. HibbelerPublisher:PEARSONThermodynamics: An Engineering ApproachMechanical EngineeringISBN:9781259822674Author:Yunus A. Cengel Dr., Michael A. BolesPublisher:McGraw-Hill Education
- Control Systems EngineeringMechanical EngineeringISBN:9781118170519Author:Norman S. NisePublisher:WILEYMechanics of Materials (MindTap Course List)Mechanical EngineeringISBN:9781337093347Author:Barry J. Goodno, James M. GerePublisher:Cengage LearningEngineering Mechanics: StaticsMechanical EngineeringISBN:9781118807330Author:James L. Meriam, L. G. Kraige, J. N. BoltonPublisher:WILEY