This article outlines a technique to predict the performance of the convection passes of pulverized coal boilers, where the heat exchangers are typically comprised of assemblies of U-tube elements. Therein a heat exchanger comprised of n U-tubes per assembly is modeled as 2n rows in the product gas flow direction, and the portions of the straight tubes making up each assembly are considered to be distinct passes in crossflow. It is assumed that in each pass the tube-side fluid is unmixed and the gas-side fluid is mixed, and likewise the gas-side fluid is mixed between passes. The model employs a straightforward approach to predict the performance of a single pass as a building block to predict the performance of the overall assembly.