A novel outlet fitting for use in connection with a heat exchanger. The heat exchanger is used in the role of a quench exchanger for cooling cracking effluent and solves particular problems associated with gas-oil cracking applications and other heavy feed based applications wherein differences between process outlet temperature and coolant temperatures are larger than in, for example, naphtha and gas cracking applications. The specific solution is achieved through a novel outlet fitting for the quench exchanger that eliminates the need for a steam purge, addresses thermal stress issues and reduces pressure drop within the system. The outlet fitting includes internal insulation to avoid the need for a steam purge. In addition, the outlet fitting includes a low-angle diffuser with an angle of less than 7 degrees and preferably less than 5 degrees.