ALFA LAVAL CB27 18H 24H 34H 40H 50H 50M 60H 70H 70M 100H

Chiller Brazed Plate Heat Exchanger Replacemnet	Brass Plate Heat Exchanger
Keyword	Alfa Laval Brazed Type Heat Exchanger
Plate Number	10–150 Plates
Thickness A (mm)	8 + (2.40 × n) mm
Dimension LWH (mm)	311 × 111 × A mm
Center Distance (mm)	50 mm / 250 mm
Weight (kg)	1.5 + (0.118 × n) kg
Volume (L) Q1Q2 Side / Q3Q4 Side	0.048 L / 0.048 L per channel
Designed Pressure	Max 40 bar (depending on version)
Designed Temperature	-196°C ~ +225°C
Plate Materials	Stainless Steel 316L / Copper Brazing
Capacity	Up to 55 kW

How to Size an Alfa Laval CB27 Brazed Plate Heat Exchanger Based on Flow Rate and Temperature Program

Selecting the correct Alfa Laval CB27 brazed plate heat exchanger starts with understanding the actual operating conditions of the system. In most HVAC, heat pump, boiler, and industrial cooling projects, sizing is mainly based on four factors:

• Flow rate
• Inlet and outlet temperatures
• Heat load (kW)
• Allowable pressure drop

For replacement projects, matching only the model number is usually not enough. Engineers and maintenance contractors should also verify the original temperature program, flow conditions, and pressure requirements to avoid undersizing or excessive pressure drop after installation.

This guide explains the basic CB27 sizing process in practical engineering terms commonly used in field applications.

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1. Collect Basic Operating Data

Before starting the calculation, confirm the following information for both hot and cold sides:

• Inlet temperature
• Outlet temperature
• Flow rate
• Fluid type and concentration
• Maximum working pressure
• Acceptable pressure drop

Typical media include:

• Water
• Chilled water
• Glycol solutions
• Thermal oil
• Standard HVAC circulation fluids

For glycol or special process fluids, concentration and viscosity should also be confirmed because they directly affect heat transfer performance and pressure drop.

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2. Calculate Heat Duty

The first step is calculating the required heat transfer capacity.

For liquid systems, the standard heat balance equation is:

Q = ṁ × cp × ΔT

Where:

• Q = heat duty (kW)
• ṁ = mass flow rate
• cp = specific heat capacity
• ΔT = temperature difference

In practical HVAC and heating projects, the hot side and cold side heat duty should remain approximately balanced. A small safety margin is normally added to compensate for fouling and heat loss over time.

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3. Convert Flow Rate to Heat Capacity

When flow rate is given in m³/h instead of kg/s, the calculation becomes:

Q = ρ × V̇ × cp × ΔT

Where:

• ρ = fluid density
• V̇ = volumetric flow rate

This method is commonly used for chilled water systems, boiler loops, and heat pump circulation calculations.

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4. Calculate LMTD

The CB27 uses a counterflow plate arrangement, which improves heat transfer efficiency and reduces required surface area.

The log mean temperature difference is calculated as:

ΔTlm = (ΔT₁ − ΔT₂) / ln(ΔT₁ / ΔT₂)

In real projects:

• Higher LMTD → smaller required heat transfer area
• Lower approach temperature → more plates required

This is one of the main reasons why two systems with the same kW load may require different plate counts.

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5. Estimate Required Heat Transfer Area

Once heat duty and LMTD are known, estimate the required heat transfer area:

A = Q / (U × ΔTlm)

Where:

• A = required heat transfer area
• U = overall heat transfer coefficient

For standard water-to-water applications, the overall heat transfer coefficient is often estimated between:

3,000–7,000 W/m²·K

Actual values depend on:

• Flow velocity
• Fluid viscosity
• Fouling conditions
• Plate geometry
• Glycol concentration

In field replacement work, underestimated fouling is one of the most common reasons for insufficient heating performance after installation.

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6. Check CB27 Capacity Range

After estimating the required heat transfer area, compare the result with the CB27 operating range.

Typical checks include:

• Required plate count
• Maximum flow rate
• Pressure drop
• Connection size
• Pressure rating

The CB27 is generally suitable for medium-capacity heating and cooling systems and supports flow rates up to approximately 14.5 m³/h depending on operating conditions and plate configuration.

If the required heat transfer area exceeds the CB27 range, a larger model or different plate configuration may be necessary.

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7. Typical Sizing Workflow

In most practical projects, engineers follow this sequence:

1. Confirm inlet and outlet temperatures
2. Confirm flow rate or heat load
3. Calculate heat duty
4. Calculate LMTD
5. Estimate required heat transfer area
6. Check pressure drop
7. Select plate count
8. Verify final selection with manufacturer software

This process is commonly used for:

• Boiler replacement projects
• Heat pump sizing
• Chiller circulation systems
• Hydronic heating loops
• Industrial process cooling

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8. Example Calculation

Operating Conditions

Hot side: 60°C → 45°C, water, flow rate 10 m³/h Cold side: 25°C → 40°C

Step 1 – Calculate Heat Duty

Q = 1000 × (10/3600) × 4.18 × (60 − 45) ≈ 174 kW

Step 2 – Calculate LMTD

• ΔT₁ = 60 − 40 = 20°C
• ΔT₂ = 45 − 25 = 20°C
• Since both ends are equal: LMTD = 20°C

Step 3 – Estimate Heat Transfer Area

Assuming U = 4,500 W/m²·K:

A = 174,000 / (4,500 × 20) ≈ 1.93 m²

At this stage, the calculated area and flow rate are checked against the CB27 plate range and allowable pressure drop.

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9. Final Selection Notes

For final sizing confirmation, always verify:

• Plate count
• Pressure rating
• Connection size
• Pressure drop
• Fluid compatibility

For corrosive or special fluids, provide:

• Fluid name
• Concentration
• Maximum temperature
• Chloride content

In replacement projects, it is also important to check whether the original exchanger suffered from:

• Internal scaling
• Fouling
• Copper brazing corrosion
• Excessive pressure cycling

These factors often affect actual field performance more than theoretical sizing calculations alone.

For critical applications, final model selection should always be confirmed using official Alfa Laval selection software or detailed thermal calculation data.

Direct Contact Channels:

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