Evaluating and Extending Computational Models of Rhythmic Syncopation in Music

In a heat exchanger apparatus comprising a main heat exchanger having a water box with a secondary heat exchanger inside the water box, the secondary heat exchanger includes two coupling tubes passing sealingly through a wall of the water box. The secondary heat exchanger is secured to the water box by means of these coupling tubes. Each coupling tube is carried on the secondary heat exchanger by being introduced into an access hole in the wall, and being secured in a base ring of the secondary heat exchanger. Each coupling tube has a deformable terminal portion which is upset so as to expand it radially in a hole formed in the base ring.