Indirect Heat Exchanger

Indirect Heat Exchangers are thermal process units which transfer heat from an industrial burner into air that’s used to heat a product during baking. Working 24/7 to produce baked goods, these heat exchangers are under heavy thermal stresses which often leads to failure.

The baking industry have many types of baking ovens for varied purposes to achieve different types of bake. (See our white paper on baking comfort zones). Baking oven types can be divided between direct and indirect. Indirect baking ovens rely on a heat exchanger to distribute the heat in the oven and have no product of combustion in contact with the bake product which is a benefit with regards to health and safety.

Baker Perkins, Spooner Vicars, Buhler, GEA Imaforni and other manufacturers have adopted indirect heating ovens for many years.

A blue chip company got in contact with EnerTherm Engineering with a reliability problem on their fleet of ovens making biscuit. Each oven had 3 to 8 indirect heat exchangers and the reliability of each heat exchanger was a major concern and was impacting on running costs and down time. Each indirect heat exchanger was lasting only 12-18 months.

EnerTherm Engineering investigated the problem by simulating current design and evaluating the root cause of failure. Air flow and heat distribution in the heat exchanger was causing thermal stress and leading to heat exchanger tube failure.

EnerTherm Engineering have designed a new indirect heat exchanger using Computation Fluid Dynamics and FEA stress analysis, to ensure minimal thermal induced stress onto the tube header.

The overall efficiency of the heat transfer through the indirect heat exchanger was increased by 30%. The thermal induced stress was reduced to nil. The new unit will be built in the next few months and installed.