Chapter 8, Problem 8.9P

1. A geothermal-based trigeneration plant produces 2.5 MW of electricity, 1.8 MW of process heat, and 1.4 MW of cooling. Electricity is produced for a period of 7500 h, heating for 2500 h, and cooling for 2000 h per year. The energy of geothermal plant consumed in the plant is 4 × 107 kWh during an entire year period. Determine the annual average utilization factor of this plant.

6.7 A gas engine-based trigeneration plant delivers heat and power at the fol- lowing rates: • 90 kJ/s of heat for water heating and 110 kW of electricity over 12 h (5) a day 110 kW of electricity and 100 kJ/s of heat for absorption cooling over 12 h (t,) a day Plant overall efficiency in heating and power generation mode is EUF, = 87%, which in cooling and power generation mode is EUF, = 75%. The fuel in the gas engine is natural gas with an LHV of 49 MJ/kg. Calculate (i) the total useful energy production by the trigeneration plant in a day, (ii) the trigeneration plant average EUF value, and (iii) the monthly fuel energy and fuel requirements of the trigeneration plant.

In a steam power plant that operates based on a Rankine cycle, the operating pressures of the steam generator and the condenser are 10,000 and 10 kPa, respectively. If the turbine inlet stream is saturated vapor and the condenser outlet flow is saturated liquid, determine the specific heat transfers in the steam generator and the condenser, the specific work involved in the turbine and the pump, and the thermal efficiency and the BWR of the cycle. Also, if the power plant produces 250 MW power, determine the mass flow rate of the cycle’s working fluid.

1. A medium size power station is used to produce 30 MW net power for a refinery. The station uses steam as the operating fluid and operates according to the Carnot cycle between the pressure limits of 0.4 bar and 35 bar. Steam enters the boiler as a saturated liquid and leaves it as a dry saturated vapour. (i) List the name of the four processes in a generic Carnot cycle and state what type of energy transfer (work/heat) can be neglected in each process. (ii) Sketch a T-s diagram for the above cycle indicating the location of the four components required. (iii) Determine the dryness fraction of the steam that is fed to the condenser.

Problem 1 Calculate the thermal efficiency or coefficient of performance of the following cycles, and determine if the cycles are reversible, irreversible, or impossible. (a) A steam power cycle that receives thermal energy at a rate of 800 kW from a thermal source at 550°C and rejects thermal energy at a rate of 300 kW to a thermal sink at 50°C. (b) A heat pump that needs 10 kJ work input to deliver 120 kJ of thermal energy to a room at 27°C. The heat pump interacts with a low temperature reservoir at 5°C.

A steam power plant operates on a thermodynamic cycle in which water circulates through a boiler, turbine, condenser, pump, and back to the boiler. For each kilogram of steam (water) flowing through the cycle, the cycle receives 2100 kJ of heat in the boiler, rejects 1100 kJ of heat to the environment in the condenser, and receives 10 kJ of work in the cycle for stage one pump and another 10 kJ of work in the cycle for second stage one 1. Determine the work done by the steam in the turbine, in kJ/kg. 2. Determine the thermal efficiency for this cycle.

A heat pump cycle using water as the working fluid consists of a compressor, a condenser, an expansion valve, and an evaporator. Saturated vapor with mass flow rate of 1 kg/s at 0.5 MPa (state 1) enters the condenser and leaves it as saturated liquid at the same pressure (state 2). The pressure in the evaporator is 0.01 MPa. The condenser and the evaporator processes are isobaric. The compressor is adiabatic and reversible. The valve is adiabatic. A. List all the known information and assumptions. B. Determine the heat output of the condenser (QH) C. Determine the heat input of the evaporator(Qc) D. Determine the coefficient of performance of the heat pump. E. Determine the coefficient of performance of a Carnot heat pump running between the same temperatures TH and TC at the evaporator and condenser. F. Calculate the entropy generation in the compressor. G. Draw the TS diagram for the cycle on paper. (Hint: you must calculate T1, T2, T3, T4, h1, h2, h3, h4, s1, s2, s3, s4, and draw…

In a simple power cycle that uses water, the following conditions are met: The pressure in the boiler is 3 MPa and that of the condenser is 20 kPa. The steam that comes out of the boiler is saturated and at the condenser outlet there is saturated liquid. Considering that the turbine operates in a reversible adiabatic way, determine: a) output work of the cycle, b) heat transferred in the condenser, c) the efficiency of the cycle.

The gas turbine in the power generation building is a vital element of the performance and financial viability of the whole plant.  Investigate the principles of operation of the gas turbine and relate your findings to the design, running and maintenance of such a system.