| Water is a natural refrigerant, which is absolutely harmless to man and nature. It is easily available and incurs no problems with its disposal after use. Even though water is one of the oldest refrigerants, state of the art technology is required to use water as a refrigerant in compression refrigeration plants with turbocompressors.; To compare water (R718) to other refrigerants, a code is developed in which all refrigerants can be compared in a single p-h, T-s, or p-T diagram. Using the code, the COP isolines of water (R718) and any refrigerant can be generated in a graph to determine which refrigerant has a better COP for a certain evaporation temperature and temperature lift. In regard to using water (R718) as a refrigerant, some specific features complicate its application in refrigeration plants with turbocompressors. Because the cycle works under coarse vacuum, the volumetric cooling capacity of water vapor is very low. Hence, huge volume flows have to be compressed with relatively high pressure ratios. Therefore, the use of water (R718) as a refrigerant compared to classical refrigerants, such as R134a or R12, requires approximately 200 times the volume flow, and about twice the pressure ratio for the same applications.; To enhance the turbocompression and improve the efficiency of R718 cycles, the novel concept of 3-port condensing wave rotors integrated in R718 compression refrigeration cycles is investigated. The condensing wave rotor employs pressurized water to pressurize, desuperheat, and condense the refrigerant vapor, all in one dynamic process. The underlying phenomena of flash evaporation, shock wave compression, desuperheating, and condensation inside the wave rotor channels are described in a wave and phase-change diagram as part of internal flow analysis. A characteristic equation is developed for the determination of the pressure required for the high pressure inlet port when the low pressure port and the outlet are known. For the external analysis, the thermodynamic process is described in detail. Based on the described thermodynamic model, a computer program is generated to evaluate the performance of the R718 baseline and wave-rotor-enhanced cycles. The effect of some key parameters on the performance enhancement is demonstrated as an aid for optimization. A performance map summarizes the findings and shows optimum wave rotor pressure ratio and maximum relative performance improvement of R718 cycles by using the 3-port condensing wave rotor.; Experimental investigation of the flow inside a small size wave rotor is described in the last chapter. This experimental analysis is reported as a proof of concept for wave energy exchange in smaller sizes, which ultimately lead to micro wave rotors. Moreover, the Schlieren method is used for shock wave visualization. Based on the skills developed, Shlieren technique is recommended for flow visualization in channels of a condensing wave rotor. |
