Heat Exchanger Area

\[A=\frac{Q}{U\Delta T_{lm}}\]

Variables

Aheat transfer area (m²)

Qheat transfer rate (W)

Uoverall heat transfer coefficient (W/(m²·K))

LMTDlog mean temperature difference (K)

Description

What is this formula?

The heat exchanger area formula calculates the required surface area needed to transfer a specified amount of heat between two fluids.

When to use it

Use this equation during heat exchanger design, equipment sizing, process optimization, and thermal system analysis.

Example

A heat exchanger must transfer 800 kW of heat. The overall heat transfer coefficient is 500 W/(m²·K) and the log mean temperature difference is 40 K.

Formula:

A = Q / (U·LMTD)

Substitution:

A = 800000 / (500 × 40)

A = 800000 / 20000

Result:

A = 40 m²

The exchanger requires approximately 40 m² of heat-transfer surface area.

Applications

- Heat exchanger design

- Shell-and-tube sizing

- Plate heat exchanger sizing

- Condenser design

- Evaporator design

Note

This equation assumes steady-state operation and a known overall heat transfer coefficient. In practical design, engineers usually add a safety margin and account for fouling factors that increase the required area over time.