Regenerative Heat Exchanger Matrix NTU Calculator

A regenerator stores heat cyclically within the solid matrix rather than transferring it continuously through a separating wall like a recuperator.

Thermal wheels provide extraordinary thermal compact surface densities (up to 2000 m2/m3) at low manufacturing cost.

The rotating matrix is alternately exposed to hot exhaust gas (storing heat) and cold incoming gas (releasing heat).

As rotation speed increases, matrix heat capacity rate Cr rises, making performance approach that of a pure counterflow recuperator.

At very low rotation speeds, matrix temperature swings cause significant thermodynamic effectiveness penalties.

Regenerator effectiveness (epsilon) indicates the percentage of maximum thermodynamic heat transfer recovered.

NTU_0 measures the nondimensional thermal sizing of the heat exchanger.

Matrix capacity ratio Cr* should ideally exceed 2.0 to 5.0 to operate near maximum recovery.

• Wheel RPM: Rotating too slowly reduces effectiveness; rotating too fast increases seal wear and carryover leakage.
• Stream capacity imbalance: Balanced streams (Ch = Cc) achieve symmetrical temperature swings across matrix sectors.
• Carryover leakage: Gas trapped in matrix voids rotates into the opposite stream, causing cross-contamination.

• Power plant boiler Ljungstrom flue gas air preheaters and industrial glass furnace regenerators.
• HVAC energy recovery ventilators (ERV) and Stirling engine thermal regenerator design.

• Assumes clean non-fouled matrix channels with uniform circumferential flow distribution.
• Does not account for mass carryover leakage between opposing fluid duct streams.