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HEAT+MASS TRANSFER:FUND.+APPL.
- A variable-load piston-cylinder device contains air (cp = 1.005 kJ/kgK; cv = 0.718 kJ/kgK) at 500 kPa and T=12 oC. A paddle wheelequipped within the system and turned by an external electric motor until 65 kJ/kg of work has been transferred to the air. During this process the gas volume is quadrupled while maintaining the temperature constant by transferring heat to the gas. Determine (a) the final pressure, (b) the amount of required heattransfer (c) Show this process on a P-v diagram. Do not use Table A-17 while solving this problem. YOUR ANSWER SHEET SHOULD INCLUDE THE SOLUTION AND THE TABLE BELOW (a) Pinal [kPa] = (b) q [kJ/kg]arrow_forwardTHERMOFLUID A 4-in X 5-m X 7-m room is heated by the radiator of a steam-heating system. The steam radiator transfers heat at a rate of 10.000 kJ/h, and a 100-W fan is used to distribute the warm air in the room. The rate of heat loss from the room is estimated to be about 5000 kJ/h. If the initial temperature of the room air is 10°C, determine how long it will take for the air temperature to rise to 20°C, Assume constant specific heats at room temperature.arrow_forward6. The ventilating fan of the bathroom of a building has a volume flow rate of 30 L/s and runs continuously. The building is located in San Francisco, California, where the average winter temperature is 12.2 °C, and is maintained at 22°C at all times. The building is heated by electricity whose unit cost is $0.09/kWh. Determine the amount and cost of the heat "vented out" per month in winter. (The gas constant and specific heat of air are R 0.287 kJ/kg-K and Cp1.0 kl/kg-K. Consider air at P 1 atm. and T-22 °C) 12.2°C 30 L/s 22°C Fan Bathroomarrow_forward
- Steam enters the condenser of a steam power plant at 50 kPa and a quality of 85 percent with a mass flow rate of 400 kg/min. It is to be cooled by water from a nearby river by circulating the water through the tubes within the condenser. To prevent thermal pollution, the river water is not allowed to experience a temperature rise above 20°C. If the steam is to leave the condenser as saturated liquid at 50 kPa, determine the mass flow rate of the cooling water required.arrow_forwardThe evaporator of a refrigeration cycle is basically a heat exchanger in which a refrigerant is evaporated by absorbing heat from a fluid. Refrigerant-22 enters an evaporator at 200 kPa with a quality of 22 percent and a flow rate of 2.65 L/h. R-22 leaves the evaporator at the same pressure superheated by 5°C. The refrigerant is evaporated by absorbing heat from air whose flow rate is 0.75 kg/s. Determine the temperature change of air. The properties of R-22 at the inlet and exit of the condenser are h1 = 220.2 kJ/kg, v1 = 0.0253 m3 /kg, and h2 = 398.0 kJ/kg.arrow_forwardA compressor operating with 7.7 kg/s water vapour with a compression ratio (P2/P1) equal to 3.0 is cooled down by means of a cooling system which extracts 74 kJ/kg of heat (per unit mass of fluid) from the device. The steam enters the compressor as saturated vapor at 1.5 MPa and leaves it at 773 K. Calculate the power required if the compressor operates with an efficiency of 0.94. Give your answer in MW to 1 decimal place.arrow_forward
- The approach and efficiency of cooling tower are 10 oC and 65 %, respectively. If the temperature of water leaving the tower is 27 oC, determine the temperature of water entering the tower.arrow_forwardWater jacketed compressor compresses 5 m³/min of air having an initial specific volume of 0.8m³/kg. During the compression, the enthalpy of air increases by 83.7 kJ/kg and heat is transferred to the cooling water at the rate of 251.1 kJ/min. Determine the work in hp to drive the compressor. 1 hp = 0.746kW = 0.746kJ/s topic: first law of thermodynamicsarrow_forwardA 4-m × 5-m × 6-m room is to be heated by an electric resistance heater placed in a short duct in the room. Initially, the room is at 15°C, and the local atmospheric pressure is 98 kPa. The room is losing heat steadily to the outside at a rate of 150 kJ/min. A 200-W fan circulates the air steadily through the duct and the electric heater at an average mass flow rate of 40 kg/min. The duct can be assumed to be adiabatic, and there is no air leaking in or out of the room. If it takes 25 min for the room air to reach an average temperature of 25°C, find the temperature rise that the air experiences each time it passes through the heater.arrow_forward
- A 4-m × 5-m × 6-m room is to be heated by an electric resistance heater placed in a short duct in the room. Initially, the room is at 15°C, and the local atmospheric pressure is 98 kPa. The room is losing heat steadily to the outside at a rate of 150 kJ/min. A 200-W fan circulates the air steadily through the duct and the electric heater at an average mass flow rate of 40 kg/min. The duct can be assumed to be adiabatic, and there is no air leaking in or out of the room. If it takes 25 min for the room air to reach an average temperature of 25°C, find the power rating of the electric heater.arrow_forwardThe Refrigerating Effect of 94 tons of refrigeration is 127.75 kJ/kg. Determine the mass flow rate of the refrigerant.arrow_forwardA variable-load piston-cylinder device contains air (cp = 1.005 kJ/kgK; cv = 0.718 kJ/kgK) at 500 kPa and T=18 oC. A paddle wheel equipped within the system and turned by an external electric motor until 65 kJ/kg of work has been transferred to the air. During this process the gas volume is quadrupled while maintaining the temperature constant by transferring heat to the gas. Determine (a) the final pressure, (b) the amount of required heat transfer (c) Show this process on a P-v diagram. Do not use Table A-17 while solving this problemarrow_forward
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