Cryogenic heat exchangers for process cooling and renewable energy storage: A review

© 2019 The cryogenic industry has experienced remarkable expansion in recent years. Cryogenic technologies are commonly used for industrial processes, such as air separation and natural gas liquefaction. Another recently proposed and tested cryogenic application is Liquid Air Energy Storage (LAES). This technology allows for large-scale long-duration storage of renewable energy in the power grid. One major advantage over alternative storage techniques is the possibility of efficient integration with important industrial processes, e.g., refrigerated warehousing of food and pharmaceuticals. Heat exchangers are among the most important components determining the energy efficiency of cryogenic systems. They also constitute the necessary interface between a LAES system and the industrial process utilizing the available cooling effect. The present review aims to familiarise energy professionals and stakeholders with the latest achievements, innovations, and trends in the field of cryogenic heat exchangers, with particular emphasis on their applications to LAES systems employing renewable energy resources. Important innovations in coil-wound and plate-fin heat exchanger design and simulation methods are reviewed among others, while special attention is given to regenerators as a prospective component of cryogenic energy storage systems. This review also reveals that the geographical spread of research and development activities has recently expanded from well-established centers of excellence to rather active emerging establishments around the globe

Refrigerated warehouses as intelligent hubs to integrate renewable energy in industrial food refrigeration and to enhance power grid sustainability

© 2016 Elsevier LtdBackground Independence from fossil fuels, energy diversification, decarbonisation and energy efficiency are key prerequisites to make a national, regional or continental economy competitive in the global marketplace. As Europe is about to generate 20% of its energy demand from Renewable Energy Sources (RES) by 2020, adequate RES integration and renewable energy storage throughout the entire food cold chain must properly be addressed. Scope and approach Refrigerated warehouses for chilled and frozen foods are large energy consumers and account for a significant portion of the global energy demand. Nevertheless, the opportunity for RES integration in the energy supply of large food storage facilities is often neglected. In situ power generation using RES permits capture of a large portion of virtually free energy, thereby reducing dramatically the running costs and carbon footprint, while enhancing the economic competitiveness. In that context, there exist promising engineering solutions to exploit various renewables in the food preservation sector, in combination with the emerging sustainability-enhancing technology of Cryogenic Energy Storage (CES). Key findings and conclusions Substantial research endeavours are driven by the noble objective to turn the Europe's Energy Union into the world's number one in renewable energies. Integrating RES, in synchrony with CES development and proper control, is capable of both strengthening the food refrigeration sector and improving dramatically the power grid balance and energy system sustainability. Hence, this article aims to familiarise stakeholders of the European and global food preservation industry with state-of-the-art knowledge, know-how, opportunities and professional achievements in the concerned field

Etude expérimentale et modélisation par PC-SAFT du comportement des mélanges à base de CO2 et des huiles frigorifiques de type PAG et POE

International audienceIn this work we have measured densities of a synthetic PAG oil from 283.15 K to 333.15 K and solubilities of CO2 in this oil from 253 K to 333.15 K. Molecular weight of the lubricant was estimated using fast atom bombardment (FAB). Molecular weight and experimental densities were used to calculate characteristic parameters of PC-SAFT model for several commercial PAG oils. Transferable characteristic parameters were used for POEs. Saturated and compressed densities together with the phase behavior (solubility, vapourliquid equilibria, liquidliquid equilibria, vapourliquidliquid equilibria and miscibility) of CO2-PAG and CO2-POE systems were modelled with PC-SAFT using a kij interaction parameter linear with the temperature. Experimental data have been successfully represented with the present model, which was used to predict the phase diagram type in the mixtures of CO2 with PAG or POE lubricant oils

Numerical simulation of air humidity distribution in a refrigerated truck enclosure

This work was carried out in order to study the humidity treatment heterogeneity in a large closed cavity such as a refrigerated truck. Two configurations were investigated: an empty refrigerated truck with (i) a local and (ii) an average introduction of humidity source. The refrigerated truck was equipped with a membrane contactor device (desiccant device) placed at the evaporator inlet. Air temperature, velocity and humidity fields were obtained numerically using CFD Fluent software assuming a constant evaporator outlet temperature, air humidity and airflow. It was found that the warm zone is located near the refrigerated truck door where the velocity is weak and the air humidity is less treated by the desiccant device. It was observed a difference of 7% in the humidity average between the two studied cases: global and local introduction on humidity sources inside the refrigerated truck

Les déterminants de la pauvreté au Maroc : Etude économétrique

Depuis son indépendance, le Maroc s'est engagé à atteindre des objectifs visant à réaliser un taux de croissance économique élevé dans le but d'améliorer le niveau de vie de sa population, de ce fait, cet engagement permanent repose sur une stratégie qui vise à réduire le taux de pauvreté et à offrir une vie décente aux personnes vulnérables. Cependant, pour mettre en œuvre une stratégie efficace de lutte contre la pauvreté, il est essentiel de comprendre les facteurs qui contribuent à la pauvreté. À cet égard, Ce document vise à analyser la pauvreté au Maroc, à travers une étude économétrique de l’impact de l’éducation , de la croissance, de l’inflation et du chômage sur l’évolution de la pauvreté au Maroc, la modélisation ARDL nous a conduit à conclure que les chocs sur la variable de la dépense annuelle par personne (proxy de la pauvreté) à long terme peut se corriger avec une vitesse d’ajustement de presque 43% c'est-à-dire qu’à long terme les déséquilibres entre le proxy de la pauvreté et ses déterminants cités plus haut se compensent. Ainsi à court terme, le chômage, l’éducation et l’inflation ont un impact significatif et positif sur la pauvreté par contre une relation significative mais négative entre la croissance et la pauvreté. À long terme, la croissance, l’éducation et l’inflation n’ont aucun impact sur la pauvreté par contre le chômage exerce un effet positif sur la dépense annuelle par personne entre 1987 et 2018 au Maroc

Numerical study of airflow and temperature distribution in a loaded cold store

© 2018 EUROSIS-ETI. The aim of this study is to analyze the effects of ventilation and cooling power distribution on air temperature and products temperature levels in a cold store by means of computational fluid dynamics. The refrigerated space under study has a set of six fans and six heat exchangers (HEs) with different mass flow rates and blowing velocities arranged back to back at the middle of the domain. For this purpose, three cases have been simulated with different operating conditions involving various combinations between HEs and fans, while maintaining the same cooling power in the warehouse. In the author’s knowledge, very few articles have been written on airflow in loaded enclosures ventilated by several heat exchangers

Numerical study of airflow and temperature distribution in a loaded cold store

International audienceThe aim of this study is to analyze the effects of ventilation and cooling power distribution on air temperature and products temperature Ievels in a cold store by means of computational fluid dynamics. The refrigerated space under study has a set of six fans and six heat exchangers (HEs) with different mass flow rates and blowing velocities arranged back to back at the middle of the domain. For this purpose, three cases have been simulated with different operating conditions involving various combinations between HEs and fans, while maintaining the same cooling power in the warehouse. In the author's knowledge, very few articles have been written on airflow in loaded enclosures ventilated by several heat exchangers