How to use Plate Heat Exchanger LMTD& Area Calculator
- Enter Hot fluid inlet temperature Th1 (°C) and adjust the options as needed.
- Run the tool and inspect its results, evidence and limitations.
- Copy or download the result, then verify it against the actual website, source data or business records.
Try a concrete example
Hot stream 85°C to 60°C (25°C drop), cold stream 20°C to 50°C (30°C rise), duty 150 kW: counter-flow terminal deltas are 35°C and 40°C, yielding LMTD of 37.45°C. With 0.00010 m²·K/W fouling, effective k is 3103 W/(m²·K), requiring 1.29 m² surface area. Using standard 0.06 m² plates, recommend 24 active chevron plates (26 total with end plates). Hot flow is 5160 kg/h (86 L/min); cold flow is 4300 kg/h (71.7 L/min).
How to interpret results
PHEs achieve high heat transfer rates due to chevron corrugations triggering intense three-dimensional turbulence at low Reynolds numbers. Counter-flow yields maximum log mean driving temperature; always incorporate fouling resistance margins to prevent thermal performance degradation.
Frequently asked questions
Why must heat exchanger sizing use Log Mean Temperature Difference (LMTD) instead of arithmetic mean?
Along the flow path, temperature differentials vary exponentially rather than linearly. Using arithmetic mean temperature difference overstates the true driving force by 15% to 40% when temperature spans are wide, yielding dangerously undersized surface areas that fail target process temperatures.
What advantages does counter-current flow offer over co-current flow?
In co-current flow, cold outlet temperature can never exceed hot outlet temperature. In counter-current flow, cold fluid can exit substantially hotter than hot fluid discharge (temperature cross) while maintaining uniform driving force, achieving larger LMTDs and reducing costly titanium or stainless plate requirements by 20% to 40%.
Why does fouling resistance degrade PHE performance more severely than shell-and-tube units?
PHE clean overall heat transfer coefficients reach 3000 to 6000 W/(m²·K), meaning clean thermal resistance (1/k) is tiny (~0.0002 m²·K/W). Adding even a thin scale film (Rf = 0.0001) increases total resistance by over 50%, slashing thermal duty by 30% to 40%. Always design with 15% to 25% area excess and schedule periodic CIP cleaning.
What is temperature approach, and what are the economic pitfalls of selecting it too tight?
Approach temperature is the difference between hot fluid exit and cold fluid inlet (or vice versa). While tight approaches (2°C~3°C) maximize heat recovery, as approach nears zero, LMTD vanishes, driving required plate surface area and equipment capital expenditure asymptotically high. Practical economic approach temperatures range between 3°C and 8°C.