How do you calculate the (regenerative) efficiency of a heat exchanger?

The efficiency of a heat exchanger indicates how efficiently heat is transferred between two media. Factors such as the inlet and outlet temperatures, the flow rate, the specific heat, the pressure drop and heat losses all play a part in this.

Due to negligible heat losses to the surroundings, the efficiency of a heat exchanger is practically 100 per cent; the heat released by the hot medium is absorbed in full by the cold medium. The regenerative capacity of a heat exchanger indicates the degree of heat recovery.
The regenerative capacity of a heat exchanger is the ratio of the actual capacity achieved to the theoretically maximum achievable capacity.

In practice, efficiency is not determined using a single fixed formula. Engineers use thermal calculations and simulations to assess the performance of a heat exchanger under specific process conditions. This provides a realistic picture of the heat transfer and the energy efficiency of the system.