ABSTRACT
In this chapter, first the vapor compression heat pumps are discussed. These heat pumps are not only the most studied type but also the most frequently implemented type, and there is a large body of experience in designing and applying these heat pumps for several applications in industry and in the built environment. Heat pumps and refrigeration cycles are the same except for what concerns which reservoir is at the application temperature. For this reason, the relevant topics for heat pumps are similar to the topics discussed in the Refrigeration Fundamentals course at the Delft University of Technology by Stolk (1990), with the main difference that the focus is on applications of heat pumps in the chemical process industry. It identifies the ideal (reference) cycle, the Carnot cycle, and discusses the different sources for a departure from the ideal cycle. The chapter further discusses the vapor recompression cycles, which are generally the preferred solutions for industrial applications. Both working principle and specific industrial applications are presented. Compression-resorption heat pumps combine the advantages of absorption cycles with the advantages of vapor compression cycles and are promising for applications with significant temperature glides both on the process stream application side and in the heat source side. The differences in comparison to the other mechanically driven heat pumps are discussed as well as the calculation procedure to predict their performance. Because CO2 as a
refrigerant has a limited environmental impact, transcritical CO2 heat pumps are popular these days and are also discussed in a dedicated section, which also describes when these cycles could be advantageous. These cycles show a large temperature glide in the application side, while the heat is absorbed from the heat source at constant temperature, making the cycle specifically interesting when such conditions exist in a chemical plant. Finally, the Stirling heat pump and its calculation method are discussed. As mentioned, these cycles have received a lot of attention because they are expected to perform significantly better than vapor compression cycles. Nevertheless, application up to now has been limited to niche markets for very low-temperature refrigeration cycles. The cycle is discussed with enough detail to allow simple modeling and performance prediction.
