Condenser Design — Benzene Vapor Condensation

Problem

Design a horizontal shell & tube condenser to condense saturated benzene vapor using cooling water under the following operating conditions.

Hot fluid: Benzene Vapor
Mass flow rate: 12,000 kg/h
Condensing temperature: 95°C
Operating pressure: 1.2 bar
Latent heat of condensation: 394 kJ/kg
Cooling medium: Water
Cooling water inlet temperature: 30°C
Cooling water flow rate: 50,000 kg/h
Maximum allowable shell-side pressure drop: 0.5 bar
Maximum allowable tube-side pressure drop: 0.5 bar
Heat exchanger orientation: Horizontal
Design method: Bell–Delaware

Code

from processpi.units import *
from processpi.components import *
from processpi.streams import MaterialStream
from processpi.equipment.heatexchangers import HeatExchangerEngine


# ============================================
# DEFINE COMPONENTS
# ============================================

benzene = Benzene()
water = Water()


# ============================================
# DEFINE PROCESS STREAMS
# ============================================

hot_in = MaterialStream(
    "benzene_vapor_in",
    component=benzene,
    phase="vapor",
    temperature=Temperature(95, "C"),
    pressure=Pressure(1.2, "bar"),
    mass_flow=MassFlowRate(12000, "kg/h"),
)

hot_out = MaterialStream(
    "benzene_liquid_out",
    component=benzene,
    phase="liquid",
    temperature=Temperature(95, "C"),
)

cold_in = MaterialStream(
    "cw_in",
    component=water,
    phase="liquid",
    temperature=Temperature(30, "C"),
    pressure=Pressure(1, "bar"),
    mass_flow=MassFlowRate(50000, "kg/h"),
)

# Outlet temperature calculated automatically
cold_out = MaterialStream(
    "cw_out",
    component=water,
)


# ============================================
# CREATE CONDENSER MODEL
# ============================================

hx = HeatExchangerEngine(
    method="bell_delaware"
)

hx.fit(
    hx_type="condenser",

    hot_in=hot_in,
    hot_out=hot_out,

    cold_in=cold_in,
    cold_out=cold_out,

    latent_heat=394000,

    shell_dp=Pressure(0.5, "bar"),
    tube_dp=Pressure(0.5, "bar"),

    orientation="horizontal",
    mode="design",
)

results = hx.run()


# ============================================
# OUTPUT
# ============================================

print(results.summary())

# Complete engineering report
results.detailed_summary()

Output

Heat Exchanger Summary
==============================
Type                  : condenser
Type Selection        : explicit
Method                : bell_delaware
Heat Duty             : 1313.333 kW
Area                  : 41.783 m2
U Calculated          : 707.075 W/m2K
U Basis               : calculated
Tube Velocity         : 1.997 m/s
Shell Velocity        : 25.587 m/s
Tube Pressure Drop    : 84.059 kPa
Shell Pressure Drop   : 205.147 kPa
Tube Count            : 140
Tube Length           : 5.000 m
Status                : PRESSURE_DROP_FAILURE

Pressure Drop Assessment
------------------------------
Tube ΔP Limit        : 50.000 kPa
Tube ΔP Actual       : 84.059 kPa
Shell ΔP Limit       : 50.000 kPa
Shell ΔP Actual      : 205.147 kPa

Engineering Feasibility
------------------------------
Thermal Performance  : PASS
Hydraulic Performance: PASS
Pressure Drop        : FAIL

Engineering Insights
------------------------------
• Heat-transfer coefficient within acceptable range.
• Tube-side velocity 2.00 m/s is within the 0.6-2 m/s range.
• Shell-side velocity 25.59 m/s is within the 10-30 m/s range.
• Tube-side pressure drop exceeds allowable limit.
• Shell-side pressure drop exceeds allowable limit.

Warnings
------------------------------
• [ASSUMPTION_WARNING] Sieder-Tate (mu/mu_w)^0.14 taken as 1 on the shell side: no hot_wall_viscosity given
• [ASSUMPTION_WARNING] Sieder-Tate (mu/mu_w)^0.14 taken as 1 on the tube side: no cold_wall_viscosity given
• Tube-side pressure drop 84059.4 Pa exceeds limit 50000.0 Pa
• Shell-side pressure drop 205147.0 Pa exceeds limit 50000.0 Pa

Discussion

This example demonstrates the design of a horizontal shell & tube condenser using the Bell–Delaware shell-side analysis method.

Unlike a conventional heat exchanger, the hot process stream undergoes phase change from vapor to liquid. The required heat duty is therefore calculated primarily from the latent heat of condensation, while the cooling water absorbs the released energy.

The HeatExchangerEngine automatically performs:

Phase-change energy balance
Condenser sizing
Heat-transfer area calculation
Bell–Delaware shell-side corrections
Tube bundle sizing
Tube count optimization
Tube and shell velocity calculations
Hydraulic validation
Engineering assessment and recommendations

Design Results

Parameter	Value
Heat Exchanger Type	Condenser
Design Method	Bell–Delaware
Orientation	Horizontal
Heat Duty	1313.33 kW
Heat Transfer Area	41.78 m²
Calculated Overall U	707.08 W/m²·K
Tube Count	140
Tube Length	5.0 m
Tube Velocity	1.997 m/s
Shell Velocity	25.587 m/s

The calculated overall heat-transfer coefficient is within the expected range for a shell-and-tube condenser operating with water as the cooling medium.

The tube count is set so that the cooling water stays within the 0.6-2.0 m/s band of condenser service (1.997 m/s), and the benzene vapor crosses the shell at 25.59 m/s, within the 10-30 m/s vapor band. Both pressure drops exceed the 0.5 bar limits (84.1 kPa on the tube side, 205.1 kPa on the shell side), so the engine reports the status as PRESSURE_DROP_FAILURE instead of a feasible design.

Engineering Assessment

The thermal check passes, but the pressure-drop check fails on both sides, and the warnings list the two exceedances. The warnings also record that the Sieder-Tate viscosity ratio was taken as 1 on both sides because no wall viscosities were given.

For a complete engineering report, use:

results.detailed_summary()

To inspect every calculation performed by the engine, use:

results.trace()

For diagnostic information including warnings, optimization actions, and convergence details, use:

results.debug_summary()