Validating the results of numerical modeling compared to the results of another model
 

My question is about the subject of the validation process of the results of a numerical study, for example, via Ansys fluent. There is something I noticed in several articles on this topic and I did not understand it. I hope someone who has an explanation or an explanation for that would be kind enough to write it. The topic, in brief, is the numerically studied model, for example, a plate heat exchanger with new plates. To perform the validation process of the results of the numerical study, the results are compared with another numerical or experimental study of a plate heat exchanger that uses traditional chevron plates published in the scientific literature! I know that any change in the calculation grid changes the accuracy of the results, so the matter will be if the model is completely changed. Does anyone have an explanation or explanation for my understanding of this?
with thanks and respect