Traditional supermarket refrigeration systems have long piping system, fittings and joints causing substantial refrigerant losses. The refrigerant losses bring about high cost and environmental damage. Additionally, defrosting of air-coils is one of the most energy consuming processes in supermarket refrigeration systems to keep display cabinets under the required temperature. Various studies, though limited in scope, have been conducted by several researchers in order to provide efficient and environmentally friendly supermarket refrigeration technologies. The current study, therefore, presents numerical models for cascade and secondary coolant systems and new correlations for frost property. These models showed that energy savings from 17500 to 170000kWh per annum could potentially be achieved from a typical supermarket store. These systems also avoid the use of environmentally damaging refrigerants thereby attracting supermarket owners. Finally, a step-by-step exercise of the application of the secondary coolant model has been presented to completely design, select, evaluate and install such systems or retrofit the existing traditional refrigeration systems in supermarkets.
The survey from US Department of Energy showed that about one-third of energy consumption in US is due to air conditioning and refrigeration systems. This significant usage of electricity in the HVAC industry has prompted researchers to develop dynamic models for the HVAC components, which leads to implementation of better control and optimization techniques. In this research, efforts are made to model a multi-evaporator system. A novel dynamic modeling technique is proposed based on moving boundary method, which can be generalized for any number of evaporators in a vapor compression cycle. The models were validated experimentally on a commercial supermarket refrigeration unit. Simulation results showed that the models capture the major dynamics of the system in both the steady state and transient external disturbances. Furthermore the use of MEMS (microelectromechanical) based Silicon Expansion Valves (SEVs) have reportedly shown power savings as compared to the Thermal Expansion Valves (TEVs). Experimental tests were conducted on a supermarket refrigeration unit fitted with the MEMS valves to explain the cause of these potential energy savings. In this study an advanced cascaded control algorithm was also designed to control the MEMS valves. The performance of the cascaded control architecture was compared with the standard Thermal Expansion Valves (TEVs) and a commercially available Microstaq (MS) Superheat Controller (SHC). The results reveal that the significant efficiency gains derived on the SEVs are due to better superheat regulation, tighter superheat control and superior cooling effects in shorter time period which reduces the total run-time of the compressor. It was also observed that the duty cycle was least for the cascaded control algorithm. The reduction in duty cycle indicates early shut-off for the compressor resulting in maximum power savings for the cascaded control, followed by the Microstaq controller and then the Thermal Expansion Valves. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148111
Covering the simultaneous needs for cooling and heating in supermarkets by a proper utilization of vapour compression systems is an interesting possibility for significant energy savings. This is a major issue considering supermarket refrigeration systems consume a large amount of energy. The environmental concerns and regulations attached to refrigeration applications forced the implementation of new system solutions where natural refrigerants have been widely used. This book includes an analytic comparison of conventional supermarket refrigeration systems using R404A with refrigeration system solutions using natural refrigerants such as carbon dioxide and ammonia. This investigation points out the fact that systems running with natural refrigerants can compete with systems running with artificial refrigerants by using adequat heat recovery systems such as heat pump cascade, heat pump cascade for sub-cooling, fixed pressure system and de-superheater.
This book covers the fundamentals and applications of carbon dioxide vapor compression refrigeration thermodynamic cycles. In particular, it presents new application areas, such as making ice and snow in the Winter Olympic Games, food cooling and refrigeration. The book explores the physical and chemical characteristics of CO2 fluid, and the unique traits of its thermodynamic cycle. The contributors explain how CO2 refrigeration is a developing, eco-friendly technology, and emphasize its importance for refrigeration and air-conditioning in the current and future market. This book is a valuable source of information for researchers, engineers and policy makers looking to expand their applicable knowledge of high-potential refrigeration technology using carbon dioxide. It is also of interest to postgraduate students and practitioners looking for an academic insight into the industry’s latest eco-friendly technologies.
This book is devoted to the analysis and applications of energy, exergy, and environmental issues in all sectors of the economy, including industrial processes, transportation, buildings, and services. Energy sources and technologies considered are hydrocarbons, wind and solar energy, fuel cells, as well as thermal and electrical storage. This book provides theoretical insights, along with state-of-the-art case studies and examples and will appeal to the academic community, but also to energy and environmental professionals and decision makers.
The 2002 assessment report, produced under the Montreal Protocol on ozone depleting substances, finds that technical progress has been made by the refrigeration, air conditioning and heat pump industry to comply with requirements to phase out CFCs and in several applications, HCFCs as well. However, there is still a significant amount of installed refrigeration equipment still using CFCs and HCFCs, and so service demand remains high and is best minimised by preventive service, containment, retrofit, recovery and recycling.
Refrigeration, air conditioning, and heat pumps (RACHP) have an important impact on the final energy uses of many sectors of modern society, such as residential, commercial, industrial, transport, and automotive. Moreover, RACHP also have an important environmental impact due to the working fluids that deplete the stratospheric ozone layer, which are being phased out according to the Montreal Protocol (1989). Last, but not least, high global working potential (GWP), working fluids (directly), and energy consumption (indirectly) are responsible for a non-negligible quota of greenhouse gas (GHG) emissions in the atmosphere, thus impacting climate change.
The definitive text/reference for students, researchers and practicing engineers This book provides comprehensive coverage on refrigeration systems and applications, ranging from the fundamental principles of thermodynamics to food cooling applications for a wide range of sectoral utilizations. Energy and exergy analyses as well as performance assessments through energy and exergy efficiencies and energetic and exergetic coefficients of performance are explored, and numerous analysis techniques, models, correlations and procedures are introduced with examples and case studies. There are specific sections allocated to environmental impact assessment and sustainable development studies. Also featured are discussions of important recent developments in the field, including those stemming from the author’s pioneering research. Refrigeration is a uniquely positioned multi-disciplinary field encompassing mechanical, chemical, industrial and food engineering, as well as chemistry. Its wide-ranging applications mean that the industry plays a key role in national and international economies. And it continues to be an area of active research, much of it focusing on making the technology as environmentally friendly and sustainable as possible without compromising cost efficiency and effectiveness. This substantially updated and revised edition of the classic text/reference now features two new chapters devoted to renewable-energy-based integrated refrigeration systems and environmental impact/sustainability assessment. All examples and chapter-end problems have been updated as have conversion factors and the thermophysical properties of an array of materials. Provides a solid foundation in the fundamental principles and the practical applications of refrigeration technologies Examines fundamental aspects of thermodynamics, refrigerants, as well as energy and exergy analyses and energy and exergy based performance assessment criteria and approaches Introduces environmental impact assessment methods and sustainability evaluation of refrigeration systems and applications Covers basic and advanced (and hence integrated) refrigeration cycles and systems, as well as a range of novel applications Discusses crucial industrial, technical and operational problems, as well as new performance improvement techniques and tools for better design and analysis Features clear explanations, numerous chapter-end problems and worked-out examples Refrigeration Systems and Applications, Third Edition is an indispensable working resource for researchers and practitioners in the areas of Refrigeration and Air Conditioning. It is also an ideal textbook for graduate and senior undergraduate students in mechanical, chemical, biochemical, industrial and food engineering disciplines.
