In this paper, a comprehensive review of the principles of different refrigeration methods covering the temperature range from 4 K to 300 K is presented. The methods covered are based on steady state systems, such as the Carnot cycle, the vapor compression cycles: basic, cascade, and mixed gas refrigeration cycles, and the recuperative type cryocooler cycles: Joule–Thomson cycle, Brayton cycle, and Claude cycle, and periodic systems such as the regenerative type cryocooler cycles: Stirling cycle, pulse tube cycle, and Gifford–McMahon cycle. The current state of technology and challenges for further improvements are briefly summarized. Some comparisons and assessments are provided for these methods. It is seen that among other things, the selection of a proper refrigeration method is dependent on the following principal factors: (i) the refrigeration capacity required, (ii) the temperature level, and (iii) the application environment. Even though more than one refrigeration method may be suitable for a given application, the selection is further guided by considerations such as cost, reliability, size/compactness, and unit power. An attempt has been made in this paper to (1) present in-depth relevant details to understand the current state of engineering and technology, (2) provide a handy document for refrigeration designers in the industry, and (3) present the guiding principles in the selection of refrigeration methods.

In the past ten years, one has seen rapid advancements in heat and mass transport applications in biology and medicine. The research activities have been shifted from fundamental development of better theoretical models accurately describing the thermal effect of local vasculature geometry and blood perfusion rate in the 1980s and 1990s to emphases on biotransport research with clear clinical applications and on how to utilize theoretical simulation and imaging techniques for better designing treatment protocols in those applications. This review will first describe briefly technical advancements in bioheat and mass transfer in the past several decades and then focus on two important applications in bioheat and mass transport covering different temperature ranges: hypothermia in brain injury and hyperthermia in tissue thermal damage. The contributions of nanotechnology, imaging tools, and multiscale modeling to the advancements will be discussed in the review.