Steam condensers

Condenser is one of the essential components of steam power plants as it facilitates condensation of steam at given conditions with minimum expenditure of energy and minimum loss of heat and finally gives condensate which can be recirculated by feed pump to boiler for steam generation. Condenser generally operates at pressure less than atmospheric pressure

1. Aldel Education Trust’s ST. JOHN COLLEGE OF ENGINEERING AND MANAGEMENT, PALGHAR (ST. JOHN POLYTECHNIC) DEPARTMENT OF MECHANICAL ENGINEERING SUB: THERMAL ENGINEERING (TEN) 22337 TOPIC: STEAM CONDENERS PREPARED BY:- Prof. Pranit Mehata Lecturer, SJCEM 7972064172

2. INTRODUCTION A condenser is a closed vessel in which steam is condensed by abstracting the heat and where the pressure is maintained below atmospheric pressure .

3. ELEMENTS OF STEAM CONDENSING PLANT

4. DALTON’S LAW OF PARTIAL PRESSURE It states that, “ The total pressure exerted by he mixture of air and water vapour is equal to the sum of pressures which each constituents would exerts , if it occupied the same space by itself.” Mathematically,  

5. CLASSIFICATION OF CONDENSER

6. PARALLEL FLOW JET CONDENSER In this both the steam and water enter at the top, and mixture is removed from the bottom. The condensate, cooling water and air flow downwards and are removed by air pump and condensate pump. The condensate pump delivers the condensate to the hot well.

7. COUNTER FLOW JET CONDENSER In this the exhaust steam enters at the bottom, flows upwards and meets the down coming cooling water. The vacuum is created by air pump place at the top of the condenser shell. Falling water meets the exhaust steam entering at the bottom and the condensation occurs.

8. HIGH LEVEL JET CONDENSER In this exhaust steam enters at the bottom, flow upwards and meets the down coming cooling water. These are provided at a high level with a long vertical discharge pipe.

9. EJECTOR CONDENSER In this the steam and water mix up while passing through a series of metal cones. Water enters at the top through a number of guide cones. Steam enters the condenser through NRV arrangement. In diverging cone, kinetic energy is partly transformed to pressure energy.

10. SURFACE CONDENSER It consists of a cast iron shell, cylindrical in shape, with the two ends covered by cover plates. The cold water is sent through the lower half section tubes and comes out through the upper half section tubes. Exhaust steam enters the shell at the top and flows down surrounding the cold water tubes. The condensate is removed at the bottom by an extraction pump

11. DOWN FLOW SURFACE CONDENSER Most general type of surface condenser. The exhaust steam enters at the top and flow downwards over the tubes due to force of gravity as well as suction of extraction pump fitted at bottom. Baffle is provided to prevent the entry of condensed steam into it. It also called as cross surface condenser.

12. CENTRAL FLOW SURFACE CONDENSER The exhaust steam enters at the top and flow downwards. The suction pipe of air extraction pump is placed in the centre. The steam flows radially inwards over the tubes towards the suction pipe. It gives access to the whole periphery of the tubes. Its an improvement over down flow surface condenser.

13. EVAPORATIVE CONDENSER In evaporative condenser, steam circulates in pipes surrounded by water spray. It is used when there is scarcity of cooling water. The cooling water is allowed to evaporate under a small partial pressure . This type of condenser works better in dry weather.

14. COMPARISON OF JET AND SURFACE CONDENSER Jet Condensers Surface Condensers Cooling water and steam are mixed up Cooling water and steam are not mixed-up Mixing type condensers Non-mixing type condensers Less suitable for high capacity plant More suitable for high capacity plant Condensate is wasted Condensate is reused Requires less quantity of water Requires large quantity of water Low maintenance cost High maintenance cost Condensing plant is simple and economical Condensing plant is complicated and costly More power is required for air pump Less power is required for air pump High power is required for water pumping Less power is required for water pumping

15. VACUUM MEASUREMENT A vacuum gauge is used to measure the vacuum in the condenser. The vacuum gauge has readings marked in cm of Hg. It represents the height at which a column of mercury, the upper surface of which is in communication with the cylinder, will stand when supported by barometric pressure. The vacuum is dependent upon the barometric pressure and the absolute pressure in the condenser. Absolute pressure = barometric pressure - vacuum gauge pressure Usually, the vacuum gauge readings are corrected to standard barometer reading of 76 cm of Hg.

16. VACCUM EFFICIENCY The ratio of actual vacuum to the ideal vacuum is known as vacuum efficiency. Mathematically, Actual Vacuum= Barometric pressure- Actual pressure Ideal vacuum= Barometric pressure-Ideal pressure  

17. CONDENSER EFFICIENCY The ratio of temperature rise of cooling water to the vacuum temperature minus inlet cooling water temperature is called as condenser efficiency. Mathematically, where, = Outlet temperature of cooling water = Inlet temperature of cooling water = Vacuum temperature  

18. CONDENSER PERFORMANCE

19. COOLING TOWER Water used for cooling becomes hotter after extracting heat from condenser steam and needs to be cooled down if it is to be recycled. Cooling tower is an artificial device used to cool hot cooling water coming out from the condenser.

20. TYPES COOLING TOWER In Natural draught, the circulation of air is produced by the pressure difference of air inside and outside the cooling tower. In Induced draught, the circulation of air is provided by means of the fans placed at the top of the tower. In Forced draught, the circulation of air is produced by means of fans placed at the bottom of the tower.

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