Heat exchanger design

Skill a5c-ai/babysitter/library/specializations/domains/science/mechanical-engineering/skills/heat-exchanger-design

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Specialized skill for heat exchanger sizing, rating, and optimization per TEMA standards including shell-and-tube, plate, and air-cooled configurations

SKILL.md

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Heat Exchanger Design Skill

Purpose

The Heat Exchanger Design skill provides comprehensive capabilities for sizing, rating, and optimizing heat exchangers according to TEMA standards, enabling systematic thermal-hydraulic design of shell-and-tube, plate, and air-cooled heat exchanger configurations.

Capabilities

Shell-and-tube heat exchanger design and rating
Plate heat exchanger sizing
Air-cooled heat exchanger configuration
LMTD and effectiveness-NTU methods
Fouling factor consideration
Pressure drop calculations
HTRI Xchanger Suite integration
Thermal-hydraulic optimization

Usage Guidelines

Design Methods

LMTD Method

Log Mean Temperature Difference

LMTD = (ΔT1 - ΔT2) / ln(ΔT1/ΔT2)

Q = U × A × F × LMTD

Where:
F = Correction factor for non-counterflow
U = Overall heat transfer coefficient
A = Heat transfer area

LMTD Correction Factors
- One shell pass, 2/4/6 tube passes
- Two shell passes, 4/8 tube passes
- Crossflow configurations

Effectiveness-NTU Method

Effectiveness Definition

ε = Q_actual / Q_max
Q_max = Cmin × (Th,in - Tc,in)

NTU Calculation
```
NTU = UA / Cmin
Cr = Cmin / Cmax
```
Effectiveness Relations
- Counterflow: ε = (1-exp(-NTU(1-Cr)))/(1-Cr×exp(-NTU(1-Cr)))
- Parallel flow: ε = (1-exp(-NTU(1+Cr)))/(1+Cr)
- Shell-and-tube: Complex correlations by TEMA type

Shell-and-Tube Design

TEMA Designations

Front End	Shell	Rear End
A - Channel	E - One-pass	L - Fixed tubesheet
B - Bonnet	F - Two-pass	M - Fixed tubesheet
N - Channel	J - Divided flow	N - Fixed tubesheet
-	X - Crossflow	P - Outside packed
-	-	S - Floating head
-	-	U - U-tube

Tube Layout
- Triangular pitch (30°): Maximum tubes, poor cleaning
- Square pitch (90°): Mechanical cleaning possible
- Rotated square (45°): Higher turbulence
Baffle Design
- Segmental: 20-45% cut
- Double segmental: Reduced pressure drop
- No-tubes-in-window: Vibration mitigation

Plate Heat Exchanger

Plate Selection
- Chevron angle (25-65°): Trade-off h vs ΔP
- Plate spacing: 2-5 mm typical
- Pass arrangement: U or Z configuration
Design Considerations
- Maximum pressure: 25-30 bar typical
- Maximum temperature: 150-200°C (gaskets)
- Fouling service: Not ideal

Air-Cooled Heat Exchanger

Configuration
- Forced draft: Fan below bundle
- Induced draft: Fan above bundle
- Natural draft: No fan (limited duty)
Design Parameters
- Face velocity: 2.5-3.5 m/s
- Tube rows: 3-6 typical
- Fin density: 275-435 fins/m

Fouling Considerations

Service	Fouling Factor (m²K/kW)
Cooling water	0.2-0.35
River water	0.35-0.5
Fuel oil	0.5-0.9
Heavy hydrocarbons	0.35-0.7
Light hydrocarbons	0.1-0.2
Steam (clean)	0.05-0.1

Process Integration

ME-012: Heat Exchanger Design and Rating
ME-011: Thermal Management Design

Input Schema

{
  "design_type": "sizing|rating",
  "exchanger_type": "shell_tube|plate|air_cooled",
  "hot_fluid": {
    "name": "string",
    "flow_rate": "number (kg/s)",
    "inlet_temp": "number (C)",
    "outlet_temp": "number (C, for sizing)"
  },
  "cold_fluid": {
    "name": "string",
    "flow_rate": "number (kg/s)",
    "inlet_temp": "number (C)",
    "outlet_temp": "number (C, for sizing)"
  },
  "pressure_constraints": {
    "hot_side_max_dp": "number (kPa)",
    "cold_side_max_dp": "number (kPa)"
  },
  "fouling_factors": {
    "hot_side": "number (m2K/kW)",
    "cold_side": "number (m2K/kW)"
  }
}

Output Schema

{
  "duty": "number (kW)",
  "geometry": {
    "type": "string (TEMA designation or plate type)",
    "area": "number (m2)",
    "shell_diameter": "number (mm)",
    "tube_count": "number",
    "tube_length": "number (m)"
  },
  "thermal": {
    "LMTD": "number (C)",
    "F_factor": "number",
    "U_clean": "number (W/m2K)",
    "U_dirty": "number (W/m2K)"
  },
  "hydraulic": {
    "shell_side_dp": "number (kPa)",
    "tube_side_dp": "number (kPa)"
  },
  "performance": {
    "effectiveness": "number",
    "NTU": "number"
  }
}

Best Practices

Always include fouling factors appropriate for the service
Verify pressure drop constraints are met on both sides
Check for vibration potential in shell-and-tube designs
Consider maintenance access in configuration selection
Apply TEMA tolerances for manufacturing variations
Use conservative correlations for preliminary sizing

Integration Points

Connects with CFD Analysis for detailed flow distribution
Feeds into HVAC System Design for system integration
Supports Thermal Analysis for component-level design
Integrates with Process Design for plant-level optimization