Use of Hydrogen and Fuel Cells for Refrigerated Transport

Benchmark refrigeration systems in the road transportation sector are powered by diesel, having operation costs of up to 6,000 €/y with the consequent increase of the goods cost. This chapter presents an alternative refrigeration system based on fuel cells (FC) and hydrogen as fuel, with higher efficiency, reduced costs and independent of diesel price fluctuations. Examples of the energy load profiles impact on the FC sizing, H2 consumption and system autonomy are presented as well as a description of the FC model and performance simulation results. The economical feasibility of this new refrigeration system linked to renewable energies is also analyzed and an economical assessment for different scenarios is presented.

Integration of Renewable Energy in Refrigerated Warehouses

Refrigerated warehouses are large energy consumers and account for a significant portion of the global energy demand. Nevertheless the opportunity for integration of renewable resources in the energy supply of large cold storage facilities is very often unjustifiably neglected, whereas the employment of renewable energy for many other industrial and comfort applications is actively promoted and explored. In that context, the purpose of this chapter is to bridge the existing gap by raising the public awareness of stakeholders, researchers, practicing engineers and policy makers about the availability of a number of smart engineering solutions and control strategies to exploit renewables of different nature (solar, wind, geothermal, biogas, etc.) in the food storage sector, as well as by calling the readers' attention to the specialised knowledge in the matter, which has been published so far.

Implementation of Thermal and Energy Improvements in Domestic Refrigeration

This chapter concisely discusses two case studies experiences on domestic refrigeration. One of the cases involves the theoretical and experimental analysis of the thermal profile in the compartments of a refrigerator, all this under the modeling and simulation through CFD, thus obtaining interesting results in terms of energy consumption. The second case is focus on the thermal and energy evaluation of new material proposed as thermal insulator, which was developed in a conventional way in the laboratory and presents convenient thermal features. Therefore, the guidelines for this chapter are aimed at finding mechanism that streamline the domestic refrigeration systems, without modifying its cooling performance.

Processes and Technological Systems for Freezing of Foodstuff

The principles and methods of holistic understanding of the foodstuff freezing process, as well as structure, functioning and development of refrigeration systems are set out in this chapter. It is meant for students, post-graduate students and experts working in the field of improvement of processes and devices of refrigerating productions. This chapter represents a great interest and for science officers as careful studying of the questions stated in it will relieve them of failures and repetition of the errors which were taking place in Russia, and will help them to choose ways for effective research work in the field of conservation of foodstuff by freezing.

Capillary Tube as an Expansion Device in a CO2 (R744) Transcritical Heat Pump System

Natural refrigerants which are ecologically safe and were in use extensively in the pre-CFC era are witnessing a revival of CO2 (R744). Inherently being a low critical temperature (31.2 ?C) refrigerant, the CO2 cycle based system operates in transcritical mode offers an opportunity to obtain an optimum operating condition. Capillary tubes which are extensively used in small size vapour compression systems work very differently in a CO2 transcritical heat pump system. In this chapter it is described that installation of a capillary tube having an appropriately designed length replacing an expansion valve will result in a natural adjustment of the gas cooler pressure, so that the system balance always shifts to a favourable COP direction; this is contrary to the scepticism that exists on the capability of a capillary tube to attain the optimal pressure operation. There is an optimal length of capillary tube for a given diameter at which the heat pump runs optimally.

Retrofitting of R404a Commercial Refrigeration Systems with R410a and R407f HFCs Refrigerants

This chapter presents an experimental analysis about the retrofitting of two commercial stationary refrigeration systems marketed by an Italian leading company of the sector. Such systems operate both at medium temperature (MT) and low temperature (LT) and they are originally designed to work with the high global warming potential (GWP) hydrofluorocarbon (HFC) R404a fluid (GWP = 3922). The purpose is to investigate the performances of HFCs R410a (GWP = 2088) and R407f (GWP = 1825) chosen as effective alternatives to HFC R404a, due to their compatibility, non-flammability and market availability. Furthermore, such fluids meet the EU restrictions in force in the next future for high GWP HFCs. The experimental analysis compares the performances, in terms of COP and cooling capacity, of R404a and the two identified alternatives under different operating conditions, i.e. chamber and condenser inlet air temperatures. In case of comparable performances, significant environmental benefits are introduced by the adoption of R407f and R410a in the MT and LT refrigeration systems.

Current and Future Trends of Refrigerants Development

In this chapter is addressed the thematic of refrigerants: its historical evolution; properties; legislation applied in the area and future trends. The first refrigerant being marketed on a large scale was ethyl ether (R610), in 1834. Since then, the evolution of the utilized refrigerants was stimulated, initially due to constructive issues in the refrigeration system and later to environmental issues. This evolution may be divided into four generations: 1st use of any fluid that worked; 2nd safety and durability of the equipment; 3rd ozone layer protection and 4th increase of global warming concerns. During the process of evolution many refrigerants were tested to understanding of their properties. Currently, environmental concerns are taken as guide in the search for new refrigerants. The most promising refrigerants to be used in future are the HFEs, HFOs and HFCs with low-GWP, natural refrigerants and blends between (HCs/HFCs and HFCs/HFOs) refrigerants.

New Mechanisms for Cryogenic Solid-Gas Sublimation Refrigeration

Sublimation is one phase change mechanism which usually happens under low-to-moderate temperatures and at the same time large amounts of latent heat is absorbed or released. Low temperature sublimation has been proposed in a lot of applications as one useful fast cooling/refrigeration mechanisms, such as medical cooling, food engineering, chemical synthesis, domestic cooling and many industrial sectors. In this brief chapter, the basic mechanisms of static sublimation process and sublimation two-phase flows are clarified and analyzed first, which covers the theoretical and physical problems of sublimation phase-change. Then the previous studies are classified into numerical modeling and experimental verifications. Representative refrigeration systems are also introduced and compared in this chapter, which may give useful indications for future innovations in this field. Future research focuses are also summarized and proposed in this chapter.

Ejector Refrigeration Cycles

This chapter describes a collaborative effort of US private companies and various departments of the US Government to investigate the possibility of improving the efficiency of HVAC systems by use of one and two-phase ejectors. It is anticipated that this technology, when fully developed will result in attractive, energy saving products that significantly improve the performance of commercial and residential chiller/air-conditioning systems, refrigeration plants, and heat pumps (geothermal and air-source). Although the literature describing ejector applications in refrigeration dates back to the year of 1900, the ejector use was always considered as controversial, because the previous research had resulted with only theoretical results and without visible, commercial products. The research on the ejector application is consistent with present directions in the HVAC industry and it will attract more attention and research funding in the future. A classification of thermodynamic cycles where ejectors can be applied composed by three distinctive “categories” is suggested.

Optimization of Natural Gas Liquefaction Process

This chapter provides a brief review of the developments in the optimization of Natural gas (NG) liquefaction techniques since 2001. NG liquefaction is energy intensive and small improvements in liquefaction efficiency brings huge cost benefits thus optimization is needed. To tackle the NG liquefaction optimization problem, two different optimization philosophies, i) deterministic and ii) stochastic, have been adopted. The limitations of the deterministic approach have paved the way for derivative-free stochastic approaches. Although both techniques work well for the reported problem, their application is limited to the specific problems and generalization is quite difficult. Therefore to overcome this problem, a third of the so called knowledge-inspired class have been evolved for NG liquefaction optimization. Thus, this chapter covers the major development that took place in NG liquefaction area and after reviewing the trends future research directions are given.