any question about heat exchanger model

egry

hi,when i use heat exchanger model to calculate a three-dimension question, i set the heat exchanger core, the rows and the columns according to the help files. However,as i use fluent to calculate my case, the error happens that Macro ### : no cells;Macro ### has zero gas influx;NTU_hxc_macro_source: The macro face area too small. And the energy equation is not convergent. has somebody an idea about this question?thanks!