Steam condensers is a closed vessel used in steam power plants where exhaust steam from turbines is condensed into water (called condensate) by removing its latent heat using a cooling medium, usually cold water or air. This conversion plays a vital role in enhancing the overall efficiency of the power cycle and facilitates the reuse of feedwater, reducing water and fuel consumption. Steam condensers are typically installed after the turbine in a power plant and form a critical component of the Rankine cycle.
Functions of a Steam Condenser
Condensation of Exhaust Steam
- The primary purpose of a condenser is to condense low-pressure exhaust steam from the turbine by transferring its heat to a cooler medium.
- Condensation changes steam back to liquid water, which occupies much less volume and helps maintain continuous flow in the cycle.
Maintains Vacuum at Turbine Outlet
- When steam condenses, it creates a vacuum inside the condenser.
- This vacuum reduces the turbine’s exhaust pressure, allowing steam to expand more and do more work, increasing turbine efficiency.
Increases Thermal Efficiency
- Lower exhaust pressure and reuse of water both lead to a significant boost in the thermal efficiency of the power plant.
- The condenser helps maintain favorable conditions for a more efficient Rankine cycle.
Reduces Back Pressure on the Turbine
- Without a condenser, steam would be exhausted into the atmosphere, creating resistance (back pressure).
- This would reduce the turbine’s output.
- A condenser minimizes this back pressure, allowing maximum work extraction from the turbine.
Conservation and Reuse of Water
- The condensed water (condensate) is reused as feedwater for the boiler.
- This minimizes freshwater usage and treatment costs, making the process economical and eco-friendly.
Types of Steam Condensers
Surface Condenser (Non-Mixing Type)
Working Principle:
- Steam enters a shell and flows around tubes containing cold water.
- The steam does not come in contact with the cooling water. It condenses on the outer surfaces of the tubes, and the condensate is collected separately.
Construction:
- Comprises a shell, a bundle of tubes, baffles, and inlet/outlet ports for water and steam.
Advantages:
- Pure condensate is obtained.
- High vacuum levels can be maintained.
- Ideal for high-capacity and critical applications (e.g., thermal and nuclear plants).
Disadvantages:
- Higher initial cost.
- Complex design, requires regular maintenance.
Jet Condenser
Working Principle:
- The exhaust steam directly mixes with cooling water.
- Heat is transferred through direct contact, and the steam condenses instantly.
- The resulting warm water mixture is collected.
Types of Jet Condensers:
- Parallel Flow Jet Condenser
- Counterflow Jet Condenser
- Barometric Condenser
Advantages:
- Simpler and cheaper.
- Compact design.
Disadvantages:
- Condensate is not reusable without treatment.
- Not suitable for modern, large-scale plants due to lower efficiency.
Main Components of a Steam Condenser
Condensing Shell (Surface Condenser)
- A pressure vessel where steam enters and flows around the tubes.
- Designed to withstand vacuum conditions and direct steam flow.
Tube Bundle
- Contains multiple parallel tubes through which cold water flows.
- Provides the surface area needed for effective heat exchange.
- Often made of corrosion-resistant materials like stainless steel or copper alloys.
Cooling Water Inlet and Outlet
- Supplies cooling water from a river, cooling tower, or chiller.
- Removes heated water after it absorbs the steam’s heat.
Air Extraction System
- Removes non-condensable gases (e.g., air, CO₂, oxygen) that enter with steam or through leakage.
- Helps maintain the vacuum pressure inside the condenser.
- Usually includes steam jet ejectors or mechanical vacuum pumps.
Steam condensers play a vital role in the efficiency and sustainability of steam power systems. By converting exhaust steam back into water and maintaining a vacuum at the turbine outlet, they enhance the thermal efficiency of the entire cycle, reduce water consumption, and lower operating costs. Whether it’s a surface condenser for high-capacity power plants or a jet condenser for smaller, cost-effective setups, each type has its own unique advantages and applications. Understanding their design, function, and maintenance is crucial for ensuring the optimal performance and longevity of thermal systems in power generation and industrial processes.