Here is a free Heat transfer book:
http://web.mit.edu/lienhard/www/ahtt.html
A Heat Transfer Textbook, 5th ed
John H. Lienhard IV, University of Houston
John H. Lienhard V, Massachusetts Institute of Technology
Copyright © 2000-2019, John H. Lienhard IV and John H. Lienhard V
This introduction to heat and mass transfer, oriented toward engineering students, may be downloaded without charge. The ebook is fully illustrated, typeset in searchable pdf format, with internal and external links.
Version 5.00, 17 August 2019, 784 pp, 26 MB, 8.5×11 in. (216 x 280 mm)
Please note that this material is copyrighted under U.S. Copyright Law. The authors grant you the right to download and print it for your personal use or for non-profit instructional use. Any other use, including copying, distributing or modifying the work for commercial purposes, is subject to the restrictions of U.S. Copyright Law and the Berne International Copyright Convention.