Dry Cooler For Organic Rankine Cycle For Recovering Heat From Gas Turbine Exhaust
Dry Cooler for Organic Rankine Cycle for Recovering Heat from Gas Turbine Exhaust
In the ORC system, the dry cooler is mainly used to cool the working fluid after it has passed through the turbine. After extracting heat from the gas turbine exhaust and expanding in the turbine to generate power, the working fluid needs to be cooled and condensed back to a liquid state to complete the cycle. The dry cooler achieves this by dissipating heat from the working fluid to the surrounding air, without the use of water as a cooling medium, which is different from traditional wet cooling systems.
Advantages of Using a Dry Cooler
Water - saving: Since gas turbine power plants are often located in areas where water resources are scarce, the dry cooler's water - free cooling method helps to conserve water, which is a significant advantage. It can operate effectively in arid environments without relying on a large amount of cooling water, reducing the water consumption of the power plant and the associated costs and environmental impacts.
Less maintenance: Compared to wet cooling systems, dry coolers have fewer components that are prone to corrosion and fouling. There is no need to deal with issues such as water leakage, scale formation, and microbial growth in cooling towers. This results in lower maintenance requirements and costs, as there is no need for regular cleaning and chemical treatment of cooling water systems.
Compact design: Dry coolers usually have a more compact structure, which can save space in the power plant. This is beneficial for gas turbine power plants where the layout is relatively compact, allowing for a more efficient use of the limited installation space.
Design Considerations for Dry Coolers
Heat transfer capacity: The dry cooler must be designed to have sufficient heat transfer capacity to handle the heat load from the working fluid. This requires accurate calculation of the heat released by the working fluid during the condensation process, taking into account factors such as the flow rate, temperature, and thermodynamic properties of the working fluid, as well as the temperature and flow rate of the cooling air.
Air flow design: To achieve efficient heat transfer, a reasonable air flow design is crucial. This includes determining the appropriate fan type, size, and number to ensure that the cooling air can flow evenly through the heat exchanger of the dry cooler. The air flow rate and velocity should be optimized to maximize the heat transfer coefficient between the working fluid and the air, while minimizing the pressure drop of the air flow to reduce the power consumption of the fans.
Material selection: The materials used in the dry cooler should have good heat transfer performance, corrosion resistance, and mechanical strength. Common materials include aluminum alloy for the heat exchanger fins and tubes, as it has excellent thermal conductivity and relatively low weight. The frame and other components are usually made of stainless steel or other corrosion - resistant alloys to ensure the durability of the dry cooler in the harsh operating environment of the power plant.
Operational Challenges and Solutions
Cold - weather operation: In cold weather conditions, the performance of the dry cooler may be affected by issues such as icing and reduced heat transfer efficiency. To address this, some dry coolers are equipped with anti - icing devices, such as electric heaters or hot - air recirculation systems, to prevent ice formation on the heat exchanger surfaces. Additionally, the control system of the dry cooler can be adjusted to optimize the operation parameters according to the ambient temperature, such as reducing the air flow rate or increasing the bypass of the working fluid to maintain the normal operation of the system.
Dust and dirt accumulation: In dusty environments, dust and dirt can accumulate on the surface of the dry cooler's heat exchanger, reducing its heat transfer efficiency. Regular cleaning of the heat exchanger surfaces is necessary to maintain the performance of the dry cooler. This can be achieved through manual cleaning or the use of automatic cleaning systems, such as high - pressure air blowers or water - spray cleaning devices. In addition, installing dust - filtering devices at the air inlet of the dry cooler can help to reduce the amount of dust entering the system and prolong the cleaning interval.
