Define design cases
Set inlet conditions, required outlets, allowable pressure drops and operating scenarios.
Heat Exchanger Design
Translate process conditions into a traceable thermal duty, required surface area, pressure-drop target and practical exchanger specification.
Applications
Equipment and design questions
The calculation method and required detail depend on exchanger type, phase behavior, fluid properties and the project decision.
- Shell-and-tube exchanger preliminary sizing and rating
- Plate heat exchanger duty and area screening
- Economizer, air heater and waste-heat recovery checks
- Water, steam, thermal oil and process-fluid services
- Heating, cooling, condensation and evaporation duties
- Existing exchanger performance and bottleneck review
- Fouling allowance and cleaning-cycle sensitivity
- Normal, turndown, startup and maximum-duty cases
Calculation workflow
From process data to exchanger specification
The work separates what is known from what is assumed, then checks thermal performance and hydraulic limits together.
Verify the heat duty
Close hot- and cold-side energy balances with suitable temperature-dependent properties.
Select the method
Use LMTD, correction factors or effectiveness-NTU according to the available information.
Estimate U and area
Combine film coefficients, wall resistance and fouling to determine required surface area.
Check hydraulics
Review velocity, pressure drop, flow regime, maldistribution and likely fouling or erosion risk.
Test off-design cases
Check turndown, fouling, property uncertainty and changed flow or temperature conditions.
What you receive
Typical deliverables
- Thermal design basis and operating-case matrix
- Hot- and cold-side heat-balance calculations
- LMTD or effectiveness-NTU calculation
- Overall heat-transfer coefficient breakdown
- Required area and design-margin recommendation
- Preliminary velocity and pressure-drop checks
- Duty sheet with assumptions and limitations
- Comparison of existing or proposed alternatives
What is needed
Typical project inputs
- Fluid identities, compositions and phase information
- Inlet flow rates, pressures and temperatures
- Required outlet condition or thermal duty
- Allowable pressure drop on each side
- Fouling tendency and cleaning requirements
- Materials, corrosion and temperature constraints
- Existing exchanger geometry when performing a rating
- Applicable project specifications and design cases
Scope boundary
What the calculation scope includes
The exact deliverables are agreed before work begins. The table below prevents thermal sizing from being confused with detailed mechanical design.
| Scope | Status | Typical content |
|---|---|---|
| Thermal sizing | Included | Duty, temperatures, LMTD/NTU, U-value, required area and design margin. |
| Thermal rating | Included | Performance of a defined exchanger geometry at specified operating conditions. |
| Hydraulic screening | Included | Preliminary velocity and pressure-drop checks using available geometry. |
| Detailed geometry | By agreed scope | Tube size, length, passes, baffle concept or plate arrangement at preliminary level. |
| Mechanical design | Separate scope | Shell thickness, tubesheet stress, nozzle loads, supports, vibration and expansion design. |
| Code certification | Separate scope | ASME/TEMA compliance, certified drawings, fabrication responsibility and authority approval. |
Illustrative calculation
Preliminary water-to-water exchanger sizing
This teaching example demonstrates the calculation chain. It is not presented as a completed client project or a fabrication design.
Given conditions
Hot water: 2.0 kg/s, cooled from 90°C to 60°C. Cold water: heated from 25°C to 50°C. Assume cp = 4.18 kJ/kg·K, counter-current flow, U = 800 W/m²·K and correction factor F = 0.95.
Q = ṁh × cp × (Thi − Tho) = 250.8 kW
ṁc = Q / [cp × (Tco − Tci)] = 2.40 kg/s
ΔTlm = (40 − 35) / ln(40 / 35) = 37.44 K
A = Q / (U × F × ΔTlm) = 8.81 m²
Before selection, the assumed U-value must be replaced by a geometry-based coefficient and both pressure drops must be checked. Fouling, material, pass arrangement and off-design cases may change the required area.
Engineering limits
A heat balance is necessary, but not sufficient
An exchanger that meets duty can still fail the project if pressure drop is too high, velocity promotes erosion, flow distribution is poor, fouling is underestimated or thermal expansion is not accommodated.
Important: Final procurement and fabrication require verified properties, vendor geometry, mechanical design, applicable codes, materials review and independent safety approval.
Related system work
Use Thermal Design to establish the overall process duty, steam demand and heat-recovery target. Use this service when the decision concerns a specific heat exchanger.
Project enquiry
Need to size or rate a heat exchanger?
Share the process conditions, fluid information, allowable pressure drops and any existing exchanger geometry. CADBoostPro can review the data and propose a suitable calculation scope.
Discuss your exchanger project →Best first dataset
Provide one design case with both inlet conditions, at least one required outlet condition, flow rates and pressure-drop limits.