Heat Exchangers Flashcards
What are co-current and counter-current flow in plate and frame heat exchangers?
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.
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?
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.
What are pressure drops?
Pressure Drops: The reduction in pressure as fluid flows through a heat exchanger.
Why are pressure drops higher in plate and frame heat exchangers?
Narrow Channels: Thin plates create narrow flow channels, increasing resistance.
High Surface Area: Large surface area for heat transfer leads to more friction.
Turbulent Flow: Designed to promote turbulent flow for better heat transfer, but this increases pressure drops.
Complex Flow Patterns: Multiple passes and turns increase resistance and pressure loss.
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.
Why Not Overly Large:
Efficiency: Oversized fouling factors can reduce heat transfer efficiency.
Cost: Larger heat exchangers are more expensive to build and maintain.
Space: Overly large units require more installation space.
Maintenance: Encourages proper maintenance and cleaning instead of relying on oversized designs to handle fouling.
What are common materials of construction for plate and frame heat exchangers?
Stainless Steel
Titanium
EPDM Rubber
What is AHRI 400 Certification?
A standard for performance certification of liquid-to-liquid heat exchangers set by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI).
Why is AHRI important?
Performance Assurance: Ensures heat exchangers meet specified performance criteria.
Reliability: Provides confidence in the product’s reliability and efficiency.
Standardization: Facilitates comparison and selection of heat exchangers from different manufacturers.
Compliance: Ensures compliance with industry standards and regulations.
How do flange connection sizes impact the size of a plate and frame heat exchanger installation?
Flow Capacity: Larger flanges accommodate higher flow rates, requiring larger heat exchangers.
Pressure Rating: Flange size affects the pressure rating; higher pressure systems need appropriately sized flanges.
Space Requirements: Larger flange connections increase the overall footprint and space needed for installation.
Piping Compatibility: Ensuring the flange sizes match existing piping systems is crucial for seamless integration.
