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engineering
mechanical engineering
Thermodynamics An Interactive Approach 1st edition Subrata Bhattacharjee - Solutions
Water flows steadily through an insulated nozzle. The following data is supplied: Inlet: p = 200 kPa, V = 10 m/s, z = 2 m; Exit: p = 100 kPa, z = 0. (a) Determine the exit velocity. Assume density of water to be 1000 kg/m3. Also assume the internal energy remains constant. What-if Scenario: What
Water flowing steadily through a 2 cm diameter pipe at 30 m/s goes through an expansion joint to flow through a 4 cm diameter pipe. Assuming the internal energy remains constant, determine (a) The change in pressure as the water goes through the transition. (b) Also determine the displacement of a
An adiabatic work producing device works at steady state with the working fluid entering through a single inlet and leaving through a single exit. Derive an expression for the work output in terms of the flow properties at the inlet and exit. What if Scenario: How would the expression for work
A pump is a device that raises the pressure of a liquid at the expense of external work. (a) Determine the pumping power necessary to raise the pressure of liquid water from 10 kPa to 2000 kPa at a flow rate of 1000 L/min. Assume density of water to be 1000 kg/m3 and neglect changes in specific
An adiabatic pump working at steady state raises the pressure of water from 100 kPa to 1 MPa, while the specific internal energy (u) remains constant. If the exit is 10 m above the inlet and the flow rate of water is 100 kg/s,(a) Determine the pumping power. Neglect any change in kinetic energy
Steam flows steadily through a single-flow device with a flow rate of 10 kg/s. It enters with an enthalpy of 3698 kJ/kg and a velocity of 30 m/s. At the exit, the corresponding values are 3368 kJ/kg and 20 m/s respectively. If the rate of heat loss from the device is measured as 100 kW,(a)
Steam enters an adiabatic turbine with a mass flow rate of 5 kg/s at 3 MPa, 600oC and 80 m/s. It exits the turbine at 40oC, 30 m/s and a quality of 0.9. Assuming steady-state operation, determine the shaft power produced by the turbine. Use the PC flow- state daemon to evaluate enthalpies at the
A gas enters an adiabatic work consuming device at 300 K, 20 m/s, and leaves at 500 K, 40 m/s. (a) If the mass flow rate is 5 kg/s, determine the rate of work transfer. Neglect change in potential energy and assume the specific enthalpy of the gas to be related to its temperature in K through h =
An electric bulb consumes 500 W of electricity. After it is turned on, the bulb becomes warmer and starts losing heat to the surroundings at a rate of 5t (t in seconds) watts until the heat loss equals the electric power input. (a) Plot the change in stored energy of the bulb with time. (b) How
A refrigerant is compressed by an adiabatic compressor operating at steady state to raise the pressure from 200 kPa to 750 kPa. The following data are supplied for the inlet and exit ports. Inlet: v = 0.0835 m3/kg, h = 182.1 kJ/kg, V = 30 m/s; Exit: v = 0.0244 m3/kg, h = 205.4 kJ/kg, V = 40 m/s. If
Two flows of equal mass flow rate, one at state-1 and another at state- 2 enter an adiabatic mixing chamber and leave through a single port at state-3. Obtain an expression for the velocity and specific enthalpy at the exit. Assume negligible changes in ke and pe.
Air at 500 kPa, 30oC from a supply line is used to fill an adiabatic tank. At a particular moment during the filling process, the tank contains 0.2 kg of air at 200 kPa and 50oC. If the mass flow rate is 0.1 kg/s, and the specific enthalpy of air at the inlet is 297.2 kJ/kg, determine (a) The rate
An insulated tank is being filled with a gas through a single inlet. At a given instant, the mass flow rate is measured as 0.5 kg/s and the enthalpy h as 400 kJ/kg. Neglecting ke and pe, determine the rate of increase of stored energy in the system at that instant.
Saturated steam at 200 kPa, which has a specific enthalpy (h) of 2707 kJ/kg is expelled from a pressure cooker at a rate of 0.1 kg/s. Determine the rate of heat transfer necessary to maintain a constant stored energy E in the cooker. Assume that there is sufficient liquid water in the cooker at all
Suppose the specific internal energy in kJ/kg of the solid in problem 2-2-1 [NX] is related to its temperature through u = 0.5T, where T is the temperature of the solid in Kelvin, determine the rate of change of temperature of the solid. Assume the density of the solid to be 2700 kg/m3.
A cup of coffee is heated in a microwave oven. If the mass of coffee (modeled as liquid water) is 0.2 kg and the rate of heat transfer is 0.1 kW. (a) Determine the rate of change of internal energy (u). (b) Assuming the density of coffee to be 1000 kg/m3 and the specific internal energy in kJ/kg to
At a given instant a closed system is loosing 0.1 kW of heat to the outside atmosphere. A battery inside the system keeps it warm by powering a 0.1 kW internal heating lamp. A shaft transfers 0.1 kW of work into the system at the same time. Determine: (a) The rate of external work transfer (include
A semi-truck of mass 20,000 lb accelerates from 0 to 75 m/h (1 m/h = 0.447 m/s) in 10 seconds. (a) What is the change in kinetic energy of the truck in 10 seconds? (b) If PE and U of the truck can be assumed constant, what is the average value of dE/dt of the truck in kW during this period? (c) If
An insulated tank contains 50 kg of water, which is stirred by a paddle wheel at 300 rpm while transmitting a torque of 0.1 kN-m. At the same time, an electric resistance heater inside the tank operates at 110 V, drawing a current of 2 A. Determine the rate of heat transfer after the system
Heat is transferred from a TER at 1500 K to a TER at 300 K at a rate of 10 kW. Determine the rates at which entropy (a) Leaves the TER at higher temperature. (b) Enters the TER at lower temperature. (c) How do you explain the discontinuity in the result?
A 10 m3 insulated rigid tank contains 30 kg of wet steam with a quality of 0.9. An internal electric heater is turned on, which consumes electric power at a rate of 10 kW. After the heater is on for one minute, determine (a) The change in temperature. (b) The change in pressure. (c) The change in
One kg of air is trapped in a rigid chamber of volume 0.2 m3 at 300 K. Because of electric work transfer, the temperature of air increases at a rate of 1oC/s. Using the IG system state daemon, calculate: (a) The rate of change of stored energy, dE/dt. (b) The rate of external work transfer (include
A rigid cylindrical tank stores 100 kg of a substance at 500 kPa and 500 K while the outside temperature is 300 K. A paddle wheel stirs the system transferring shaft work at a rate of 0.5 kW. At the same time an internal electrical resistance heater transfers electricity at the rate of 1 kW. (a) Do
A 1 cm diameter insulated pipe carries a steady flow of water at a velocity of 30 m/s. The temperature increases from 300 K at the inlet to 301 K at the exit due to friction. If the specific entropy of water is related to its absolute temperature through s = 4.2lnT, determine the rate of generation
Liquid water (density 997 kg/m3) flows steadily through a pipe with a volume flow rate of 30,000 L/min. Due to viscous friction, the pressure drops from 500 kPa at the inlet to 150 kPa at the exit. If the specific internal energy and specific entropy remain constant along the flow, determine (a)
An electric water heater works by passing electricity through an electrical resistance placed inside the flow of liquid water as shown in the accompanying animation. The specific internal energy and entropy of water are correlated to its absolute temperature through u = 4.2T and s = 4.2lnT (T in K)
An open system with only one inlet and one exit operates at steady state. Mass enters the system at a flow rate of 5 kg/s with the following properties: h = 3484 kJ/kg, s = 8.0871 kJ/kg-K and V = 20 m/s. At the exit the properties are as follows: h = 2611 kJ/kg, s = 8.146 kJ/kg-K and V = 25 m/s.
Steam flows steadily through a work-producing, adiabatic, single-flow device with a flow rate of 7 kg/s. At the inlet h = 3589 kJ/kg, s = 7.945 kJ/kg-K, and at the exit h = 2610 kJ/kg, s = 8.042 kJ/kg-K. If changes in ke and pe are negligible, determine (a) The work produced by the device. (b) The
The following information are supplied at the inlet and exit of an adiabatic nozzle operating at steady state: Inlet: V = 30 m/s, h = 976.2 kJ/kg, s = 6.149 kJ/kg-K; Exit: h = 825.5 kJ/kg. Determine(a) The exit velocity.(b) The minimum specific entropy (s) possible at the exit.
A refrigerant flows steadily through an insulated tube, its entropy increases from 0.2718 kJ/kg-K at the inlet to 0.3075 kJ/kg-K at the exit. If the mass flow rate of the refrigerant is 0.2 kg/s and the pipe is insulated, determine (a) The rate of entropy generation within the pipe. (b) What-if
A wall separates a hot reservoir at 1000 K from a cold reservoir at 300 K. The temperature difference between the two reservoirs drive a heat transfer at the rate of 500 kW. If the wall maintains steady state, determine (a) Q⋅ (in kW), (b) W⋅ext (in kW), (c) dS/dt (in kW/K), (d) S⋅gen,univ.
A resistance heater operates inside a tank consuming 0.5 kW of electricity. Due to heat transfer to the ambient atmosphere at 300 K, the tank is maintained at a steady state. The surface temperature of the tank remains constant at 400 K. Determine the rate at which entropy (a) Leaves the tank. (b)
Heat is conducted through a slab of thickness 2 cm. The temperature varies linearly from 500 K on the left face to 300 K on the right face. If the rate of heat transfer is 2 kW, determine the rate of entropy transfer dS/dt (magnitude only) at the (a) Left. (b) Right faces. (c) Plot how the rate of
A 30 kg aluminum block cools down from its initial temperature of 500 K to the atmospheric temperature of 300 K. Determine the total amount of entropy transfer from the system's universe. Assume the specific internal energy of aluminum (in kJ/kg) is related to its absolute temperature (K) through u
Water is heated in a boiler from a source at 1800 K. If the heat transfer rate is 20 kW, (a) Determine the rate of entropy transfer into the boiler's universe. (b) Discuss the consequences of reducing the source temperature with respect to the boiler size and entropy transfer.
An insulated tank contains 50 kg of water at 30oC, which is stirred by a paddle wheel at 300 rpm while transmitting a torque of 0.2 kNm. Determine (a) The rate of change of temperature (dT/dt) (b) The rate of change of total entropy (dS/dt). (c) The rate of generation of entropy (Sgen) within the
A rigid insulated tank contains 1 kg of air at 300 K and 100 kPa. A 1 kW internal heater is turned on. Determine the rate of (a) Entropy transfer into the tank. (b) The rate of change of total entropy of the system. (c) The rate of generation of entropy within the tank. Assume s = lnT and u = T,
A rigid tank contains 10 kg of air at 500 K and 100 kPa while the surroundings is at 300 K. A 2 kW internal heater keeps the gas hot by compensating the heat losses. At steady state, determine the rate of (a) Heat transfer. (b) The rate of entropy generation (Sgen) inside the tank. (c) The rate of
A tank contains 50 kg of water, which is stirred by a paddle wheel at 300 rpm while transmitting a torque of 0.2 kNm. After the tank achieves steady state, determine (a) The rate of heat transfer. (b) The rate of entropy transfer into the atmosphere. (c) The rate of entropy generation in the tank's
A gearbox (a closed steady system that converts low-torque shaft power to high-torque shaft power) consumes 100 kW of shaft work Due to lack of proper lubrication, the frictional losses amounts to 5 kW, resulting in an output power of 95 kW. The surface of the grearbox is measured to be 350 K while
A closed steady system receives 1000 kW of heat from a reservoir at 1000 K and 2000 kW of heat from a reservoir at 2000 K. Heat is rejected to the two reservoirs at 300 K and 3000 K, respectively. (a) Determine the maximum amount of heat that can be transferred to the reservoir at 3000 K. (b) The
A tank contains 1 kg of air at 500 K and 500 kPa. A 1 kW internal heater operates inside the tank at steady state to make up for the heat lost to the atmosphere which is at 300 K. Determine (a) The rate of entropy transfer into the atmosphere. (b) The rate of entropy generation in the system's
A rigid tank contains 1 kg of air initially at 300 K and 100 kPa. A 1 kW internal heater is turned on. After the tank achieves steady state, determine (a) The rate of heat transfer. (b) The rate of entropy transfer into the atmosphere. (c) The rate of entropy generation in the tank's universe.
A closed chamber containing a gas is at steady state. The shaft transfers power at a rate of 2 kW to the paddle wheel and the electric lamp consumes electricity at a rate of 500 W. Using an energy balance determine (a) The rate of heat transfer. (b) If the surface temperature of the chamber is 400
A copper block receives heat from two different sources: 5 kW from a source at 1500 K and 3 kW from a source at 1000 K. It loses heat to atmosphere at 300 K. Assuming the block to be at steady state, determine (a) The net rate of heat transfer in kW. (b) The rate of entropy generation in the
An electric bulb consumes 500 W of electricity at steady state. The outer surface of the bulb is warmer than the surrounding atmosphere by 75oC. If the atmospheric temperature is 300 K, determine (a) The rate of heat transfer between the bulb (the system) and the atmosphere. Also determine the
An electric heater consumes 2 kW of electricity at steady state to keep a house at 27oC. The outside temperature is -10oC. Taking the heater inside the house as the system, determine (a) The maximum possible energetic efficiency of the heater. (b) The rate of entropy generation in the heater's
An electric adaptor for a notebook computer (converting 110 volts to 19 volts) operates 10oC warmer than the surroundings, which is at 20. If the output current is measured at 3 amps and heat is lost from the adapter at a rate of 10 W, determine(a) The energetic efficiency of the device.(b) The
At steady state, the input shaft of a gearbox rotates at 2000 rpm while transmitting a torque of 0.2 kN-m. Due to friction, 1 kW of power is dissipated into heat and the rest is delivered to the output shaft. If the atmospheric temperature is 300 K and the surface of the gearbox maintains a
A steam power plant produces 500 MW of electricity with an overall thermal efficiency of 35%. Determine (a) The rate at which heat is supplied to the boiler. (b) The waste heat that is rejected by the plant. (c) If the heating value of coal (heat that is released when 1 kg of coal is burned) is 30
A heat engine receives heat from a source at 2000 K at a rate of 500 kW, and rejects the waste heat to a medium at 300 K. The net output from the engine is 300 kW. (a) Determine the maximum power that could be generated by the engine for the same heat input. (b) Determine the thermal efficiency of
A Carnot heat engine with a thermal efficiency of 60% receives heat from a source at a rate of 3000 kJ/min, and rejects the waste heat to a medium at 300 K. Determine (a) The power that is generated by the engine. (b) The source temperature.
A heat engine operates between a reservoir at 2000 K and an ambient temperature of 300 K. It produces 10 MW of shaft power. If it has a thermal efficiency (ηth) of 40%, (a) Determine the rate of fuel consumption in kg/h if the heating value of the fuel is 40 MJ/kg. (b) If the heat engine is
A heat engine, operating between two reservoirs at 1500 K and 300 K, produces an output of 100 MW. If the thermal efficiency of the engine is measured at 50%, determine (a) The Carnot efficiency of the engine (in percent), (b) The rate of heat transfer into the engine from the hot source in MW, (c)
A heat engine receives heat from two reservoirs: 50 MW from a reservoir at 500 K and 100 MW from a reservoir at 1000 K. If it rejects 90 MW to atmosphere at 300 K, (a) Determine the thermal efficiency of the engine. (b) Calculate the entropy generated in kW/K in the engine's universe.
A heat engine produces 1000 kW of power while receiving heat from two reservoirs: 1000 kW from a 1000 K source and 2000 kW from a 2000 K source. Heat is rejected to the atmosphere at 300 K. Determine (a) The waste heat (heat rejected) in kW. (b) The entropy generation rate in kW/K in the system's
A heat engine, operating between two reservoirs at 1500 K and 300 K, produces 150 kW of net power. If the rate of heat transfer from the hot reservoir to the engine is measured at 350 kW, determine (a) The thermal efficiency of the engine, (b) The rate of fuel consumption in kg/h to maintain the
A solar-energy collector produces a maximum temperature of 100oC. The collected energy is used in a cyclic heat engine that operates in a 5oC environment. (a) What is the maximum thermal efficiency? (b) What-if Scenario: What would the maximum efficiency be if the collector were redesigned to focus
The Ocean Thermal Energy Conversion (OTEC) system in Hawaii utilizes the surface water and deep water as thermal energy reservoirs. Assume the ocean temperature at the surface to be 20oC and at some depth to be 5oC; determine (a) The maximum possible thermal efficiency achievable by a heat
You have been hired by a venture capitalist to evaluate a concept engine proposed by an inventor, who claims that the engine consumes 100 MW at a temperature of 500 K, rejects 40 MW at a temperature of 300 K, and delivers 50 MW of mechanical work. Does this claim violates the first law of
A utility company charges its residential customers 12 cents/kW.h for electricity and $1.20 per Therm for natural gas. Fed up with the high cost of electricity, a customer decides to generate his own electricity by using a natural gas fired engine that has a thermal efficiency of 35%. Determine the
A heat engine produces 40 kW of power while consuming 40 kW of heat from a source at 1200 K, 50 kW of heat from a source at 1500 K, and rejecting the waste heat to atmosphere at 300 K. Determine (a) The thermal efficiency of the engine. (b)What-if Scenario: What would the thermal efficiency be if
Two reversible engines A and B are arranged in series with the waste heat of engine A used to drive engine B. Engine A receives 200 MJ from a hot source at a temperature of 420oC. Engine B is in communication with a heat sink at a temperature of 4.4oC. If the work output of A is twice that of B,
A Carnot heat engine receives heat from a TER at TTER through a heat exchanger where the heat transfer rate is proportional to the temperature difference as QH = A(TTER-TH). It rejects heat to a cold reservoir at TC. If the heat engine is to maximize the work output, show that the high temperature
Two Carnot engines operate in series. The first one receives heat from a TER at 2500 K and rejects the waste heat to another TER at a temperature T. The second engine receives this energy rejected by the first one, converts some of it to work, and rejects the rest to a TER at 300 K. If the thermal
A reversible heat engine operates in outer space. The only way heat can be rejected is by radiation, which is proportional to the fourth power of the temperature and the area of the radiating surface. Show that for a given power output and a given source temperature (T1), the area of the radiator
A heat engine receives heat at a rate of 3000 kJ/min from a reservoir at 1000 K and rejects the waste heat to the atmosphere at 300 K. If the engine produces 20 kW of power, determine (a) The thermal efficiency (b) The entropy generated in the engine's universe.
A household freezer operates in a kitchen at 25oC. Heat must be transferred from the cold space at a rate of 2.5 kW to maintain its temperature at - 25oC. What is the smallest (power) motor required to operate the freezer.
To keep a refrigerator in steady state at 2oC, heat has to be removed from it at a rate of 200 kJ/min. If the surrounding air is at 27oC, determine (a) The minimum power input to the refrigerator. (b) The maximum COP.
A Carnot refrigerator consumes 2 kW of power while operating in a room at 20oC. If the food compartment of the refrigerator is to be maintained at 3oC, determine the rate of heat removal in kJ/min from the compartment.
An actual refrigerator operates with a COP that is half the Carnot COP. It removes 10 kW of heat from a cold reservoir at 250 K and dumps the waste heat into the atmosphere at 300 K. (a) Determine the net work consumed by the refrigerator. (b) What if Scenario: How would the answer change if the
A sport utility vehicle with a thermal efficiency (ηth) of 20% produces 250 hp of engine output while traveling at a velocity of 80 mph. (a) Determine the rate of fuel consumption in kg/s if the heating value of the fuel is 43 MJ/kg. (b) If the density of the fuel is 800 kg/m3, determine the fuel
An inventor claims to have developed a refrigerator with a COP of 10 that maintains a cold space at -10oC, while operating in a 25oC kitchen. Is this claim plausible? (1:Yes; 0:No)
A refrigeration cycle removes heat at a rate of 250 kJ/min from a cold space maintained at -10oC while rejecting heat to the atmosphere at 25oC. If the power consumption rate is 0.75 kW, determine if the cycle is (1: reversible; 2: irreversible; 3: impossible).
A refrigeration cycle removes heat at a rate of 250 kJ/min from a cold space maintained at -10oC while rejecting heat to the atmosphere at 25oC. If the power consumption rate is 1.5 kW, (a) Do a first-law analysis to determine the rate of heat rejection to the atmosphere in kW. (b) Do a second-law
In a cryogenic experiment a container is maintained at -120oC, although it gains 200 W due to heat transfer from the surroundings. What is the minimum power of a motor that is needed for a heat pump to absorb heat from the container and reject heat to the room at 25oC?
An air-conditioning system maintains a house at a temperature of 20oC while the outside temperature is 40oC. If the cooling load on this house is 10 tons, determine(a) The minimum power requirement.(b) What-if Scenario: What would the minimum power requirement be if the interior were 5 degrees
An air-conditioning system is required to transfer heat from a house at a rate of 800 kJ/min to maintain its temperature at 20oC.(a) If the COP of the system is 3.7, determine the power required for air conditioning the house.(b) If the outdoor temperature is 35oC, determine the minimum possible
A solar-powered refrigeration system receives heat from a solar collector at TH, rejects heat to the atmosphere at T0 and extracts heat from a cold space at TC. The three heat transfer rates are Q⋅H, Q⋅0 and Q⋅C, respectively. (a) Do an energy and entropy analysis of the system to derive an
Assume TH = 425 K, T0 = 298 K, TC = 250 K and Q⋅C = 20 kW in the above system of problem 2-5-36[GX]. (a) Determine the maximum COP of the system. (b) If the collector captures 0.2 kW/m2, determine the minimum collector area required.
A refrigerator with a COP of 2.0 extracts heat from a cold chamber at 0oC at a rate of 400 kJ/min. If the atmospheric temperature is 20oC, determine (a) The power drawn by the refrigerator. (b) The rate of entropy generation in the refrigerator's universe.
On a cold night a house is losing heat at a rate of 15 kW. A reversible heat pump maintains the house at 20oC while the outside temperature is 0oC. (a) Determine the heating cost for the night (8 hours). (b) Also determine the heating cost if resistance heating were used instead. Assume the price
A truck engine consumes diesel at a rate of 30 L/h and delivers 65 kW of power to the wheels. If the fuel has a heating value of 43.5 MJ/kg and a density of 800 kg/m3, determine (a) The thermal efficiency of the engine. (b) The waste heat rejected by the engine. (c) How does the engine discard the
On a cold night a house is losing heat at a rate of 80,000 Btu/h. A reversible heat pump maintains the house at 70oF, while the outside temperature is 30oF. Determine (a) The heating cost for the night (8 hours) assuming the price of 10 cents/kWh for electricity. Also determine (b) The heating cost
A house is maintained at a temperature of 20oC by a heat pump pumping heat from the atmosphere. Heat transfer rate through the wall and roof is estimated at 0.6 kW per unit temperature difference between inside and outside. (a) If the atmospheric temperature is -10oC, what is the minimum power
A house is maintained at a temperature TH by a heat pump that is powered by an electric motor. The outside air at TC is used as the low-temperature TER. Heat loss from the house to the surroundings is directly proportional to the temperature difference and is given by Q⋅ loss = U(TH -TC). (a)
A house is maintained at steady state (closed system) at 300 K while the outside temperature is 275 K. The heat loss (Q⋅C) is measured at 2 kW. Two approaches are being considered: (A) electrical heating at 100% efficiency and (B) an ideal heat pump that operates with Carnot COP. The price of
A house is maintained at a temperature of 25oC by a reversible heat pump powered by an electric motor. The outside air at 10oC is used as the low-temperature TER. Determine the percent saving in electrical power consumption if the house is kept at 20oC instead. Assume that the heat loss from the
A house is heated and maintained at 25oC by a heat pump. Determine the maximum possible COP if heat is extracted from the outside atmosphere at(a) 10oC,(b) 0oC,(c) -10oC.(d) -40oC.(e) Based on these results, would you recommend heat pumps at locations with a severe climate?
A Carnot heat engine receives heat at 800 K and rejects the waste heat to the surroundings at 300 K. The output from the heat engine is used to drive a Carnot refrigerator that removes heat from the cooled space at -20oC at a rate of 400 kJ/min and rejects it to the same surroundings at 300 K.
A reversible heat engine is used to drive a reversible heat pump. The power cycle takes in Q1 heat units at T1 and rejects Q2 heat units at T2. The heat pump extracts Q4 from a heat sink at T4 and discharges Q3 at T3. (a) Develop an expression for Q4/Q1 in terms of the four given temperatures. (b)
A heat engine with a thermal efficiency (ηth) of 35% is used to drive a refrigerator having a COP of 4. (a) What is the heat input to the engine for each MJ removed from the cold region by the refrigerator? (b) If the system is used as a heat pump, how many MJ of heat would be available for
A heat engine operates between two TERs at 1000oC and 20oC respectively. Two-thirds of the work output is used to drive a heat pump that removes heat from the cold surroundings at 0oC and transfers it to a house kept at 20oC. If the house is losing heat at a rate of 60,000 kJ/h, determine(a) The
Determine the rate of coal consumption by a thermal power plant with a power output of 350 MW in tons/hr. The thermal efficiency (ηth) of the plant is 35% and the heating value of the coal is 30 MJ/kg.
A heat engine is used to drive a heat pump. The waste heat from the heat engine and the heat transfer from the heat pump are used to heat the water circulating through the radiator of a building. The thermal efficiency of the heat engine is 30% and the COP of the heat pump is 4.2. Evaluate the COP
A furnace delivers heat at a rate of Q⋅H1 at TH1. Instead of directly using this for room heating, it is used to drive a heat engine that rejects the waste heat to atmosphere at T0. The heat engine drives a heat pump that delivers Q⋅H2 at Troom using the atmosphere as the cold reservoir. Find
A heat pump is used for heating a house in the winter and cooling it in the summer by reversing the flow of the refrigerant. The interior temperature should be 20oC in the winter and 25oC in the summer. Heat transfer through the walls and ceilings is estimated to be 2500 kJ per hour per oC
In 2003 the United States generated 3.88 trillion kWh of electricity, 51% of which came from coal-fired power plants. (a) Assuming an average thermal efficiency of 34% and the heating value of coal as 30 MJ/kg, determine the coal consumption in 2003 in tons. (b) What-if Scenario: What would the
Determine the fuel cost per kWh of electricity produced by a heat engine with a thermal efficiency of 40% if it uses diesel as the source of heat. The following data is supplied for diesel: price = $2.00 per gallon; heating value = 42.8 MJ/kg; density = 850 kg/m3.
A gas turbine with a thermal efficiency (ηth) of 21% develops a power output of 8 MW. Determine (a) The fuel consumption rate in kg/min if the heating value of the fuel is 50 MJ/kg. (b) If the maximum temperature achieved during the combustion of diesel is 1700 K, determine the maximum thermal
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