N5 Power Machines condensers

ialegodi@gmail.com 082 396 7717 STEAM CONDENSORS The function of steam condenser is to: I. Create a region of low pressure into which the turbine or engine could exhaust II. Supply pure feed water to the hot well at a temperature nearly equal to that of exhaust steam Two types of steam condensers: I. The jet condenser II. The surface condenser M water  Mass Of cooling water; M steam  Mass of exhaust steam; hc hf @ t c (enthalpy of the condensate); t  rise in temperature of water ; x  dryness fractionof exhauststeam ; t1  inlet temperature of cooling water and t 2  outlet temperture of cooling water P 101,325 B r  M r  the pressure of the condenser 760 M steam hf  xhfg  hc  M water cp water t water while cp of cooling is 4,187 kJ / kg.K 1   2 temperature log difference  1  t c  t w(inlet )  2  t c  t w( outlet )  1  ln  2  If the steam is dry saturated which means the dryness fraction is 1 x  1 AIR PUMPS Function of air pumps: are being used to remove air from the condenser to maintain a vacuum in the condenser Two types of air pumps: I. The Edwards air pumps II. The rotary air pumps Air leakage R  Tair capacity of the air pump volume of air pump  Pair where Pa is called partial pressure of air pumps Possible questions: 1. Every hour a surface condenser processes 6 500 kg exhaust steam, which has a dryness fraction of 0, 83. Air leakage into the condenser is at a rate of 1, 2 kg/1000 kg of steam. The air pump suction and the condensate have a temperature of 31 C each. The barometer and vacuum gauge reading is 760 Downloaded from hlayiso.com

ialegodi@gmail.com 082 396 7717 mmHg and 662 mmHg respectively. The temperature of cooling water is increased by 21 C after it passes through the condenser. The specific heat capacity of water is 4 187 J/kg.K and gas constant for air is 0, 288 kJ/kg.K Calculate the following: 1.1. The mass of cooling water required by the condenser every minute 1.2. The capacity of air pump in m 3 / min 2. A steam turbine supplies a surface condenser with 6 800 kg of steam per hour, which is 25% wet. The barometer reading is 750 mm Hg and the manometer reading is 667 mm Hg. The condensate and the air pump suction has a temperature of 37, 7 C . The cooling water enters the condenser at 22 C and leaves at 42 C . The air leakage is 0, 8kg for every 1000 kg of outlet steam and the gas constant for air is 0,287 kJ/kg.K Calculate the following: 2.1. The mass of cooling water required by the condenser every minute 2.2. The capacity of air pump in m 3 / min 3. The condenser in Question 2 is fitted with an air-cooling section which lowers the temperature from 37, 7 C to 21,1 C . Calculate the following: 3.1. The new capacity of air pump in m 3 / min 3.2. The percentage of saving in pump volume 4. A surface condenser has a vacuum-meter reading of 689, 3 mm mercury and a barometer reading of 757 mm mercury. Wet steam with a dryness fraction of 0,93 is supplied to this condenser at a rate of 3 450 kg/hour. The cooling water enters the condenser at 20,5 C and leaves at 32,4 C and the condensate has a temperature 31 C . The specific heat capacity of the cooling water is 4,187 kJ/kg.K Calculate the following: 4.1. The pressure in the condenser 4.2. The mass of cooling water required by the condenser every minute Downloaded from hlayiso.com

ialegodi@gmail.com 082 396 7717 5. A surface condenser handles 4 520 kg of wet steam, with a dryness fraction of 0, 81 every hour. The barometer and vacuum meter readings are 760 mm Hg and 662 mm Hg respectively. The temperature of the condensate and the air pump suction is 39 C . Cooling water enters the condenser at 20 C and leaves at 35,5 C . The gas constant for air is 0, 288 kJ/kg.K and the S.H.C of water is 4, 187 kJ/kg.K Calculate the following; 5.1. The quantity of cooling water required in kg/min 5.2. The capacity of air pump required in m 3 / min 5.3. The capacity of the new air pump in m 3 / min if the air was cooled to 36, 2 C before being pumped from the condenser 6. Exhaust steam with a dryness fraction of 0, 89 enters a surface condenser, which has a vacuum of 699, 5 mm mercy and is condensed to water at a temperature of 34, 6 C . The barometer reading is 760 mm Hg. The suction temperature of the air pump is 34, 6 C and R for is 0, 287 kJ/kg.K Calculate the following: 6.1. The combined pressure of the steam and air in the condenser 6.2. The partial pressure of the air 6.3. The mass of air extracted for every kilogram of steam whilst considering that air and steam occupy the same volume 7. 2 450 kg of the exhaust steam is condensed per hour in a surface condenser, whilst air leaks into the condenser at a rate of 2,3 kg/h. 50 kg water is used to condense one kg of steam with a dryness fraction of 0,83. The condensate and air pump suction have a temperature of 36, 2 C . The barometer reading is 760 mmHg and vacuum gauge reading is 685 mmHg. The air pump has volumetric efficiency of 87% and R for air is 0, 288 kJ/kg.K and S.H.C for superheated steam is 2,1 kJ/kg C Calculate the following: 7.1. The combined pressure of the steam and air pump in the condenser 7.2. The partial pressure of the air 7.3. The air pump capacity in m 3 / hour 7.4. The rise in temperature of the cooling water FOR MORE EXERCISES TURN TO PAGE 148 [ACTIVITY 11.2] V.A.A HAAGNER Downloaded from hlayiso.com