Size confers some thermal intertia. Surface area is where heat is lost. Surface area increases as the square of linear dimension. But volume increases as the cube. Therefore for things of similar shape, large things lose heat slower.
Big animals have great thermal inertia.
So big dinos could have been inertial homeotherms. Also this means that large things with high metabolic rates need to dump heat. But small things like shrews need to conserve it always. Sometimes birds with good insulation need to cool - air sac system. As the body cavity contracts, the mass of air in the posterior sacs is pushed into the lungs where gas exchange takes place.