FREE, full-sized textbooks on heat transfer and heat exchanger design. You can download or view them as .pdf files right now. Interested? I've got two to share.
A Heat Transfer Textbook, 3rd edition by John H. Lienhard IV and John H. Lienhard V. This is a senior-level heat transfer textbook for mechanical engineers; I found it has the same basic topics as my heat transfer text from school. Conduction, convection, radiation, heat exchanger design, and an introduction to mass transfer.
There is a link to a solutions guide on the site, but they don't have it filled in yet.
Next up, the Wolverine Heat Transfer Databooks from Wolverine Tube, Inc., are for the detailed heat exchanger designer. These books are a huge resource. I'm no heat exchanger expert, but the books have been handy to dip into for the occasional fouling factor or piece of advice. You can read it all online.
Give a shout out if you find any juicy topics in either book. Enjoy!
P.S. If you're really into heat transfer and ready to spend some money, check out Process Heat Transfer by Kern. I have not read it, but independently I have had several old hands rave about it as one of the must-have "classics" on the subject.