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

Background 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

Research of thermo-physiological comfort of single jersey knitted structures with method of thermo-vision analysis

The term comfort is defined as “the absence of displeasure or discom¬fort” or “a neutral state compared to the more active state of pleasure”. Cloth¬ing comfort includes three main consid-erations: psychological, sensorial and thermo-physiological comfort. The ther¬mo-physiological comfort, entails both thermoregula¬tion and moisture management. It is known that fiber type, yarn properties, fabric structure, finishing treatments and clothing conditions are the main factors affecting thermo-physiological comfort. In this paper, the influence of structural properties and characteristics of the fiber on the air and water vapor permeability, thermal properties (thermo-physiological comfort), of single jersey knitted fabrics was investigated. Thermal conductivity of knitted fabrics was determined according to new method of thermo-vision analysis developed by researchers. The main advantage of the method is the possibility of non contact determination of the temperature change rate coefficient of the knitted fabric. The results indicate more significant influence of structural characteristics on thermo-physiological comfort, compared with the characteristics of the fibers. Knitted fabric of 50/50%PAN/cotton with the highest density and mass per unit area has lower air and water vapor permeability, thermal conductivity and higher thermal resistance compared with knitted fabrics of 100% wool and 100% PAN. Key words: single jersey, thermo-physiological comfort, airpermeability, water vapor permeability,thermo-vision analysi

Termo-fiziološki komfor dvoslojnih pletenina

Toplotne i fiziološke komponente su primarne funkcionalne komponente odeće, zbog toga što odeća mora da obezbedi zaštitu od hladnoče i toplote, i mora da dozvoli transfer vlage i toplote kroz različite slojeve odeće. U radu su konstruirane i ispletene dvoslojne integrirane pletenine od pamučne pređe u apsorpivnom sloju (lice pletenine) i od poliamidnih odnosno poliesterskih filamenata u difuzijskom sloju (naličje pletenine). Ispitivan je uticaj sirovinskog sastava i strukturnih karakteristika pletenina na toplotna svojstva (toplotnu provodljivost, toplotnu apsorpciju i toplotnu otpornost), kao i propustljivost vodene pare i vazduha pletenina. Toplotna svojstva ispitivana su metodom dr Bok-a. Strukturne karakteristike imaju značajan uticaj na toplotna svojstva i propustljivost vode i vazduha. Dvoslojno - integrirane pletenine sa poliamidnom komponentom daju hladniji osečaj u dodiru sa kožom, zbog njihove manje vrednosti toplotne apsorpcije. Ključne reči: dvoslojne integrirane pletenine, termo-fizološki komfor, propustljvost vodene pare, propustljivost vazduha THERMAL-PHYSIOLOGICAL COMFORT OF INTEGRATED DOUBLE KNITTED FABRICS The thermal and physiological components which have historically been the primary functional component of clothes, since they must protect us from cold and heat and, simultaneously, have to allow an appropriate moisture and heat transfer through the different layers. In this paper, integrated double layer knitted structures have been constructed and knitted, using cotton yarn in absorption (face) and polyamide or polyester filaments in diffusion (back) layers of the fabrics. The influence of the raw material used and the structural characteristics of the knitted structure on the thermal properties (thermal conductivity, thermal absorptivity, thermal conductivity) and permeability to water vapour and air has been statistically investigated. The thermal properties of fabrics have been tested using method of dr Bok. The structural characteristics have significant influence on the thermal properties and water and air permeability. Double – layer knitted structures with polyamide filaments has given a colder feeling based on higher thermal absorptivity values. Key words: double-integrated knitted fabrics, thermal-physiological comfort, water vapour permeability, air permeabilit

The influence of structural properties and characteristics of the fiber on the physical-mechanical properties and thermo-physiological comfort of single jersey knitted fabrics

The most important properties of the majority of knitted fabrics are good stretchability and elasticity, and thus the resulting freedom of movement. They are able to adopt themselves to the body shape of the wearer and have good air permeability, offering high standard of wear comfort. In this paper, the influence of structural properties and characteristics of fiber on the thermal properties, air and water vapor permeability, as well on the physical-mechanical properties of single jersey knitted fabrics were investigated. Single jersey knitted fabrics are made of 100% wool, 50/50% acryl/cotton, and 100% acryl yarn. The thermal properties of knitted fabrics were measured by method of D-r Boc. Correlation and regression analysis were used for data processing. The results indicate that characteristics of the fibres have significant influence on the the physical-mechanical and thermal properties, while structural characteristics have significant influence on the air and water vapor permeability. Knitted fabrics made of 100%wool have the highest thermal resistance and warmer feeling and touch due to the lower thermal absortivity value, while knitted fabrics of 50/50% acryl/cotton gave a séance of coolness. On the other hand, density and cover factor have most important influence on air and water vapor permeability Key words: single jersey, thermo-physiological comfort, air permeability, water vapour permeabilit

Modelling and numerical simulation of the transport phenomena in water thermal energy storage tanks

Mathematical model for numerical simulation of the transient heat transfer and fluid flows in water thermal energy storage tanks is developed. The model allows analysis of the thermal fields in the accumulators at different schemes and modes of charging and discharging. It was verified and validated based on experimentally obtained information about the temperature stratification at charging of a thermal accumulator at a laboratory solar system. The proposed approach for numerical study of the thermal energy storage is convenient for parametrical estimation and improvement of the efficiency of the thermal systems

THERMAL LOADS AT TRANSPARENT STRUCTURES INTEGRATED IN TROMBE WALLS

This contribution presents thermal load stress analysis of insulating glass units (IGU) integrated in Trombe walls. It is based on modelling and numerical simulation of the heat transfer processes occuring in the construction. The boundary conditions are based on experimental data, obtained from an existing Trombe wall test module, situated at the Technical University of Sofia. The investigations are performed for different cases of IGU fixing in the Trombe wall. The temperature fields and the ensuing thermal stresses in the IGU at winter conditions, obtained from the simulations, are used to analyze the possibility of glass failure due to the internal pressure loads

Efficiency evaluation of water production from the atmospheric air in Vietnam

The analysis of extracting potable water from the humid ambient air has been done by using the model of vapor-compression refrigeration (VCR) system for the case study in Vietnam. The temperature and relative humidity of moist air in Danang province in Vietnam were recorded for a whole year. The typical day in each month of year with detailed values of temperature and relative humidity for 24 hours were presented and used to identify the production of water from the air. The results show that, the temperature at the outlet of air stream throughout evaporator of VCR system is about 13°C in which the energy consumption to produce 1 liter of water is lowest. Besides, the electricity consumption cost in Vietnam varies in a day with various tariffs: at the peak load, medium load and low load, depends on the time of the day. The production price for one liter of water is also considered and working plans are proposed for the system by the time of the day

An experimental study for drying Pisum sativum on an electric dryer and a heat pump dryer

A study of drying parameters on the drying process of Pisum Sativum bean was carried out. The effects of drying temperature of moisture air from 40°C to 80°C on the drying time and on the drying kinetics were demonstrated not only on conventional electric dryers but also on heat pump dryers. Besides, checking the steady operation of the heat pump dryer was also considered. The results show that, when temperature rises, the shorter time and the faster removal of moisture content can be obtained for both dryer systems. Drying in an electric heater at 80°C took only 1 hour 45 minutes, but the broken skin of pea seeds happened. The comparison of heat pump dryer and electric dryer was presented with the shorter drying time on heat pump than electric dryer as a result of removing water vapor from moisture air at the evaporator of heat pump, it led to the reduction of specific humidity of air entering the drying chamber. And the last impressive result which can be seen is that the drying rate of a heat pump is higher than an electric dryer at the same drying temperatures beside the energy consumption of electric dryer is 2.76 times as much as that of heat pump dryer

Heat transfer performance of R1234yf for convective boiling in horizontal micro-fin and smooth tubes

This study analyses the performance of heat transfer process which occurs in the convective boiling of Hydro fluoro Olefin (HFO) refrigerant, R1234yf, in horizontal tube. Heat transfer and pressure drop of R1234yf are analyzed and computed at the same working conditions on the same size of outer diameter of tube do = 9.52 mm with difference of inner surface, one is a smooth surface and microfin for other. The flow pattern maps were built at 5°C saturation temperature with 8.62 kW/m2 of heat flux, it is presented that flow pattern of helix flow occurs at very low mass flux and low quality, while at that condition on smooth tube the flow is still stratified wavy flow. The comparison of heat transfer performance between microfin and smooth tube would be evaluated on enhancement factor E, penalty factor P and efficiency index I. With the mass flux on the range G = 111 -- 333 kg/m2s for 5°C boiling temperature, the results show that, average value of E is 2.18; 1.45 of P and 1.54 of I. One more impressing thing is that, at the quality “x” larger than 0.8, the dryout phenomenon takes place on smooth tubes while microfin tubes do not have this phenomenon