When I discard blood (20-40 mL) in a beaker containing bleach (400mL), I can feel that heat is produced in the beaker. What is the chemistry behind it? Will heat be produced due to Lysis of haem protein in RBCs? Or any other mechanism?
This reaction produces heat for the same reason as burning methane in oxygen. There's a lot of chemical energy stored in the reactants, and comparatively little in the products. The hypochlorite is oxidising the organic content of the blood - not just breaking proteins but then breaking down the amino acids too, as well as anything else that happens to be in the sample.