Heat exchangers have already proven to be important devices for thermal systems in many industrial fields. In order to improve the efficacy of heat exchangers, nanofluids are recently employed as coolants in them. Regarding unique characteristics of nanofluids, research studies in this area have witnessed a remarkable growth. This paper reviews and summarizes recent investigations conducted on use of nanofluids in heat exchangers including those carried out on plate heat exchangers, double-pipe heat exchangers, shell and tube heat exchangers, and compact heat exchangers. Meanwhile, some fascinating aspects about combination of nanofluids with heat exchangers are introduced. In addition, the challenges and opportunities for future research are presented and discussed.
