Expansion Tanks Flashcards
Why do we need expansion tanks in hydronic systems?
Absorb Expansion: Accommodate the expansion of fluid as it heats up, preventing excessive pressure.
Prevent Pressure Fluctuations: Maintain stable pressure within the system.
Protect Components: Prevent damage to pipes, valves, and other components from pressure changes.
What types of Expansion tanks are there
Diaphragm
Partial Acceptance Bladder
Full Acceptance Bladder
Plain Steel Tanks
What is the difference between air control and air removal, and why did Taco move away from plain steel tanks?
Air Control: Manages air within the system, keeping it in a controlled location like an expansion tank.
Air Removal: Eliminates air from the system using air separators and vents.
Taco moved away from plain steel tanks because:
Plain steel tanks are prone to corrosion.
Modern diaphragm or bladder tanks are more efficient, separating air from water and reducing maintenance needs.
What factors go into selecting an expansion tank?
System Volume: Total volume of fluid in the system.
Temperature Range: Maximum and minimum operating temperatures.
Pressure Requirements: System pressure and safety limits.
Type of Fluid: Properties of the fluid being used (e.g., water or glycol mix).
Tank Material: Compatibility with the system fluid and corrosion resistance.
Installation Space: Available space for installing the tank.
Type of Tank: Diaphragm, bladder, or compression tank based on system needs
What are passes in heat exchangers?
Single Pass
Two-Pass
Multi-Pass
What are the types of shell and tube heat exchangers?
Fixed Tube Sheet: Tubes are fixed to the shell; easy to clean outside but not inside.
U-Tube: Tubes are bent into a U shape; allows for thermal expansion.
Floating Head: One end of the tube bundle can move; easier to clean and accommodates thermal expansion.
Straight Tube: Tubes run straight through the shell; good for high-pressure applications.
What are the limitations of shell and tube heat exchangers?
Size and Weight: Can be large and heavy, requiring substantial support.
Cost: Can be expensive to manufacture and maintain.
Fouling: Susceptible to fouling, which reduces efficiency and requires regular cleaning.
Pressure Drops: Can experience significant pressure drops, affecting system performance.
Complex Maintenance: Cleaning and maintenance can be complex and time-consuming, especially for fixed tube sheet designs.
When should you use shell and tube heat exchangers?
High Pressure
Large Heat Transfer Area
Versatile Fluids
Thermal Expansion
Efficiency
What are co-current and counter-current flow in plate and frame heat exchangers, and why use one over the other?
Co-Current Flow: Fluids flow in the same direction.
Advantages: Simpler design and lower pressure drops.
Disadvantages: Less efficient heat transfer compared to counter-current.
Counter-Current Flow: Fluids flow in opposite directions.
Advantages: Higher efficiency and better temperature gradients.
Disadvantages: More complex design and potentially higher pressure drops.
Why choose co-current flow over counter-current flow, in plate and frame heat exchangers?
Co-Current Flow:
Advantages: Simpler design, lower pressure drops.
Disadvantages: Less efficient heat transfer.
Counter-Current Flow:
Advantages: Higher efficiency, better temperature gradients.
Disadvantages: More complex design, potentially higher pressure drops.
What are passes in heat exchangers, and why use single pass?
Passes: The number of times fluid flows back and forth through the heat exchanger
Why Use Single Pass:
Simplicity: Easier design and construction.
Lower Pressure Drop: Reduced pressure drop compared to multi-pass.
Maintenance: Easier to clean and maintain.
Why does the temperature approach matter for a plate and frame heat exchanger?
Temperature approach is the difference between the outlet temperature of one fluid and the inlet temperature of the other. It matters because:
Efficiency: A smaller temperature approach indicates higher efficiency in heat transfer.
System Performance: Affects overall system performance and energy consumption.
Design Optimization: Helps in selecting the right size and type of heat exchanger for optimal operation.
Why are pressure drops higher in plate and frame heat exchangers?
Narrow Channels
High Surface Area
Turbulent Flow
Complex Flow Patterns
What are fouling factors and why don’t we build in overly large ones?
Fouling Factors: Allowances made for the accumulation of deposits that reduce heat exchanger efficiency over time.
Efficiency
Cost
Space
Maintenance
Materials of Consturction
Stainless Steel
Titanium
Hastelloy
Nitrile Rubber
EPDM Rubber
