Heat Exchanger Calculator

To calculate a heat exchanger, you need to determine the heat duty (Q = m × Cp × ΔT), calculate the log mean temperature difference (LMTD), and use the heat transfer equation (Q = U × A × LMTD) to find the required surface area. Input the fluid properties, flow rates, and temperatures for both hot and cold streams.

Counter-current flow has hot and cold fluids flowing in opposite directions, providing better heat transfer efficiency and higher LMTD. Co-current flow has both fluids flowing in the same direction, resulting in lower efficiency but simpler design. Counter-current is typically preferred for maximum heat transfer.

Typical U values vary by application: liquid-to-liquid (100-300 BTU/hr·ft²·°F), gas-to-liquid (5-50 BTU/hr·ft²·°F), gas-to-gas (2-10 BTU/hr·ft²·°F), and condensing steam (200-1000 BTU/hr·ft²·°F). These values depend on fluid properties, velocities, and heat exchanger design.

The heat transfer area is calculated using A = Q / (U × LMTD), where Q is the heat duty, U is the overall heat transfer coefficient, and LMTD is the log mean temperature difference. Ensure all units are consistent for accurate results.

Heat exchanger effectiveness is the ratio of actual heat transfer to the maximum possible heat transfer. It ranges from 0 to 1 (0% to 100%) and indicates how well the heat exchanger performs compared to an ideal infinite-area exchanger.

Specific gravity affects the mass flow rate calculation (mass flow = volumetric flow × density × specific gravity). This directly impacts the heat duty calculation since Q = mass flow × specific heat × temperature difference. Water has a specific gravity of 1.0 as reference.

The overall heat transfer coefficient depends on individual heat transfer coefficients on both sides, fouling factors, wall thermal conductivity, and wall thickness. Higher velocities, better fluid properties, and cleaner surfaces increase the U value.