Executive Summary : | Refrigeration is a critical technology for the comfort of human living space, food security, health, and allied domains. The environmental cost of refrigerants has become a grave concern since the discovery of atmospheric ozone depletion and greenhouse gas effects. The Montreal protocol and Kigali agreement seek to rapidly diminish the use of high Ozone Depleting Potential (ODP) and Global Warming Potential (GWP) refrigerants. Globally, there are concerted efforts to replace ecologically harmful refrigerants. India has put out the India Action Cooling Plan which recognizes the growing needs of refrigeration (about 8 times increase by 2038) and the power required (about 4.5 times increase) for cooling. The country aggressively seeks to replace environmentally harmful refrigerants with eco-friendly refrigerants and significant thrust is given to research and development of new technologies, indigenization (Atmanirbhar Bharath Campaign) and skill development (Skill India Campaign) in the field of refrigeration. Carbon-di-oxide, a natural gas with negligible ODP and GWP compared to the current refrigerants is a promising working fluid receiving significant research attention. Further, CO2 has very high volumetric cooling capacity resulting in compact systems. The ejector uses a motive fluid to entrain and compress a secondary fluid using energy and momentum augmentation in a varying area duct. It has no moving parts and functions solely due to the gasdynamic interactions causing mixing and shock waves, leading to the final pumping action. The introduction of a passive gasdynamic ejector can significantly reduce energy input and increase the Coefficient of Performance (COP) of the refrigeration system (~35% has been reported). With CO2 as the working fluid, the ejector works in either supercritical or transcritical domains where real gas effects become important. The performance of the Ejector Refrigeration System (ERS) is intimately linked to the mixing and shock structures in the ejector which has to be fundamentally understood to design high performance ejectors. Fundamental studies on the mixing process and shock structure in S-CO2 and T-CO¬2 nozzles and ejectors are limited. Our laboratory has successfully studied mixing and shocks experimentally in air ejectors leading to significant design correlations. In this proposal, we aim to conduct fundamental gas-dynamic experimental studies on S-CO2 and T-CO2 nozzles and ejectors to provide crucial design data and high fidelity validation data for CFD. A new experimental setup will be developed for CO2 ejector testing. This proposal will lead to the indigenous development and realization of low ODP and GWP refrigeration systems. Expert level manpower will be developed in S-CO2 and T-CO2 systems through the doctoral programme. |