09 May 2011

Thermal Power Plant Interview Questions Answers 1

What are the main circuits in the Thermal Power Plant?

Answer:Thermal Power plant consists of four main circuits, they are:
  • Feed water and steam flow circuit
  • Coal and ash circuit
  • Air and gas circuit
  • Cooling water circuit

Steam power plant works on which cycle?

Answer: Steam power plant works on the principle of Rankine Cycle

What is the Thermal efficiency of steam power plant?

Answer: Thermal efficiency of steam power plant is defined as the ratio of heat equivalent of mechanical energy transmitted to the turbine shaft to the heat of combustion. Generally Thermal efficiency of the steam power plant will be in the range of 30-35%

What is the overall efficiency of the Thermal Power Plant or Steam Power Plant?

Answer: Overall efficiency of the system is defined as the ratio of heat equivalent of electrical output to the heat of combustion. Generally Overall efficiency of the steam plant will always be less than the thermal efficiency of the steam plant, it will be of the order of 29-33%
Overall efficiency of steam plant is determined by multiplying the thermal efficiency of the plant with efficiency of the generator (electrical efficiency)

Why the Thermal efficiency of the steam power plant is quite low?

Answer: In Steam power station, more than 50% of the total heat of combustion is lost as heat rejected to the condenser and the loss is unavoidable as the heat energy cannot be converted in to mechanical energy with out a drop in temperature. Steam in the condenser is at lowest temperature. This is the reason that the thermal efficiency of the power plant is quite low.

On what factors efficiency (thermal) of the steam plant depends?

Answer: Efficiency of the thermal plant depends on three factors, they are
  1. pressure of steam entering the turbine
  2. temperature of the steam entering the turbine
  3. pressure in the condenser
Thermal efficiency increases with increase in temperature and pressure of the steam entering the turbine. For this reason high temperature and pressure are used. Thermal efficiency is effectively increased by decreasing the pressure in the condenser, so pressure in the condenser is kept as low as possible.
Thermal efficiency also increases by reheating the steam between turbine stages


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