Short Answer:

Temperature affects cavitation by changing the vapor pressure of the fluid. As the temperature increases, the vapor pressure also increases, which makes it easier for cavitation to occur even at higher pressures. This means bubbles can form more quickly in warmer fluids.

In hydraulic machines like pumps and turbines, higher temperatures raise the risk of cavitation damage. Civil engineers must carefully control fluid temperature, especially in hot climates or high-energy systems, to reduce the chances of cavitation and protect machine components from wear and failure.

Detailed Explanation

Effect of temperature on cavitation

Cavitation is a dangerous condition where vapor bubbles form in a liquid due to low pressure and then collapse suddenly, creating strong shock waves that damage internal surfaces of hydraulic machines. One of the key factors that affect cavitation is temperature, because it directly influences the vapor pressure of the fluid.

Vapor Pressure and Temperature
Vapor pressure is the pressure at which a liquid starts to boil and turn into vapor at a given temperature. As temperature increases, the molecules in the liquid gain more energy and move faster. This makes it easier for them to escape the liquid phase and form vapor bubbles.

So, when temperature goes up:

• Vapor pressure increases
• The fluid needs less pressure drop to start boiling
• Cavitation becomes more likely even at moderate flow conditions

In other words, at higher temperatures, the fluid does not need to reach very low pressures to form vapor bubbles. This is why hot water or hot fluids are more prone to cavitation than cold fluids under the same operating conditions.

How This Affects Hydraulic Machines

In pumps, turbines, and valves, fluid often passes through areas where pressure momentarily drops (like near impellers or nozzles). If the fluid is already at a high temperature:

• The local pressure may fall below the vapor pressure quickly
• Vapor bubbles form more easily
• These bubbles collapse as they move to higher pressure zones
• This collapse leads to surface pitting, metal fatigue, and erosion

This effect is even more severe in machines handling hot water, chemicals, or fluids in industrial or thermal power plants.

Examples in Civil Engineering Systems:

1. Pumping Systems in Hot Climates:
   In areas with high ambient temperatures, stored water can become warm. When pumped, it has a higher risk of cavitation if suction pressure is not maintained properly.
2. Hydroelectric Turbines:
   In power plants, water temperature can rise due to environmental factors or energy conversion. If not accounted for, cavitation may damage turbine blades.
3. Boiler Feed Pumps:
   These pumps handle hot water and are highly sensitive to temperature changes. Engineers must ensure enough suction head is maintained to avoid cavitation.

How to Control Cavitation Due to Temperature:

• Maintain adequate Net Positive Suction Head (NPSH)
• Use cooling systems or insulation to manage fluid temperature
• Avoid sudden pressure drops in the system
• Select materials that resist cavitation damage

Temperature-related cavitation is a major concern in systems that operate in hot conditions or thermal environments, and it must be controlled for safe and long-lasting machine performance.

Conclusion:

Temperature affects cavitation by increasing the vapor pressure of fluids, making bubble formation easier at higher temperatures. This raises the risk of damage in hydraulic machines like pumps and turbines. Proper design, monitoring, and temperature control are essential to avoid cavitation and ensure efficient performance in civil engineering systems.