1. A boiler heats water from an initial temperature of 45 C to a final temperatu
ID: 2073415 • Letter: 1
Question
1. A boiler heats water from an initial temperature of 45 C to a final temperature of 600 C at a pressure of 15 MPa a. What is the initial state of the water? Give v, u, h and s b. What is the final state of the water? Give v, u, h ands c. How much heat is supplied to the water (per kg of water) by the boiler during this process? d. What is the cost to run the boiler for one day? Assume water flows through the boiler at a rate of 1 kg/s and that the boiler is fired by natural gas (S3.00 per million BTU's) 2. An isentropic turbine accepts steam at an initial temperature and pressure of 600 C and 15 MPa, and rejects steam at a final pressure of 9.6 kPa. a. What is the state of the steam at the turbine exit? Givex, v, u, h and s b. How much work does the turbine produce per kg of steam? c. What is the power output of the turbine at a steam flow rate of 1 kg/s? d. If electricity can be sold a 0.025 dollars per kWhr what is the value of the electrical power this turbine can produce in a day? 3. A condenser accepts steam from the turbine in problem 2 at a pressure of 9.6 kPa. Saturated water at the same temperature leaves the condenser a. Give P, v, u, h and s for the saturated liquid water leaving the condenser b. How much heat leaves the condenser per kg of steam? c. What is the heat transfer rater from the condenser, assuming a water flow of 1 kg/s,Explanation / Answer
1.
From steam tables,
Initial state: u = 186598 J/kg; v = 1.00335e-3 m3/kg; h = 201598 J/kg; s = 632.163 J/kg-K
Final state: u = 320920 J/kg; v = 0.0247236 m3/kg; h = 3.58e+6 J/kg; s = 6672.84 J/kg-K
Heat transfered in Control Volume is hfinal - hinitial = 3.3784e+6 J/kg
Total water heated in a day 86400 kg, thus heat used = 3.3784e+6 x 86400 = 2.92e+11 J
1 million BTU = 1.055056e+9 J, thus No. of Million BTU in 2.92e+11 = 276.68
Thus total cost = $3 * 276.68 = $830.03
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.