1,721,034 research outputs found
Secondary refrigerant systems for display cabinets applications
No full text3nd Plenary Meeting - EU Concerted Action on "The preservation of Frozen Food Quality and Safety throughout the Distribution Chain", Leeds, UK, September 199
Effect of dedicated mechanical subcooler size and gas cooler pressure control on transcritical CO2 booster systems
Full text linkDedicated Mechanical Subcooling (DMS) is one of the most investigated and effective strategies applied to increase the performance of CO2 commercial refrigeration systems in transcritical operation. Further performance benefits can be obtained by a reduction of the gas cooler pressure of the main cycle at transcritical conditions. In this work the most important parameters for the design and operation of such a system, i.e. the DMS cooling capacity, the subcooling degree and the gas cooler pressure, are considered and their effect on the annual energy use of the plant is estimated in warm and hot climate conditions by means of a validated model. DMS is also compared to the parallel compression scheme and subcooling performed through a water chiller dedicated to HVAC. DMS results to be the most effective solution among those investigated, and the choice of the best design and operating parameters allows further energy saving and cost reduction
SIZING AND CONTROL RULES OF DEDICATED MECHANICAL SUBCOOLER IN TRANSCRITICAL CO2 BOOSTER SYSTEMS FOR COMMERCIAL REFRIGERATION
Full text linkUse of Dedicated Mechanical Subcoolers gives rise to the need of an optimisation process involving gas cooler
pressure, activation and setpoint temperature values, subcooling degree and subcooler size, with the aim of
further improving the energy efficiency while considering costs.
In this paper a thermoeconomic analysis is performed on a commercial refrigeration plant, at four climate
conditions from warm to hot, with time-dependent refrigerating load depending on the location, resulting in
some design and control rules for the DMS.
In terms of energy efficiency, the size of the DMS appears to be more crucial at hot climate conditions
(difference up to 3.5 % in energy saving), with sizes ranging from 35% to 45% of the total cooling capacity.
Optimal control rules should be preferentially adopted at mild-warm conditions, suggesting to exploit the
highest subcooling rate available. The economic analysis shows that energy use is the most important cost
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FINITE ELEMENT THERMAL ANALYSIS OF SPECIAL BUILDING COMPONENTS
No full textThe Finite element method, which is usuaJly employed to study thermal conduction within soiid components, has been utilized to solve coupled conduction convection and long-wave radiation problems. As an example, the thermal behavior of special building envelope components under transient conditions is investigated, with the aim of establishing the rate of heat transfer due to the difference between the internal and external temperatures and to the absorption of the incoming solar radiation. The components considered in this paper consist of a two-pane glazing system, an open cavity with air circulation, and an opaque wall. Assuming a sinusoidal variation in the absorbed solar radiation, the temperature distribution and the heat transfers are estimated. Comparisons with standard components are illustrated, and the efficiency of the system has been determined as a function of the climatic data
Thermodynamic and economic seasonal analysis of a transcritical CO2 supermarket with HVAC supply through ice thermal energy storage (ITES)
Full text linkA real case of a supermarket where a CO2 refrigerating plant also supplies heating, air conditioning and hot water
is considered. Ice thermal energy storage (ITES) is used both as latent storage in summer and as sensible thermal
energy storage (TES) in winter to partially cover the space cooling/heating load of the supermarket. In particular,
it allows to reduce peaks in the electrical power use, when the refrigeration and HVAC systems are running at full
power together with ovens and heaters for meals. A thermodynamic analysis, including a detailed theoretical
model of the formation and melting of ice on the coils, is carried out to predict the behaviour of ITES during the
charging and the discharging phases. A daily energy analysis for both a winter and a summer typical day, and an
annual analysis are carried out for the whole system. In summer, two cases are evaluated, i.e. supplying the
whole AC demand in the morning or partially covering the AC demand to reduce the design capacity of the
reversible heat pump. In all cases, the use of ITES aimed at shaving electrical peaks leads to a higher electrical
energy use, also on an annual basis. However, the cost analysis reveals significant benefits, including a reduction
in the required capacity of the reversible heat pump, better exploitation of tariffs and the avoidance of installing
an electrical transformer in a dedicated room. This results in savings €58,699 over 10 years €47,888 over 15
years, making the choice of ITES more economically advantageous within the typical lifetime of these system
Retail dispaly: equipment and maintenance
No full textin: A PRACTICAL GUIDE TO THE COLD CHAIN FROM FACTORY TO CONSUMER, editor: R.L. Fuller, EU Concerted Action CT96-1180, Report
FIELD TESTS, MODEL VALIDATION AND PERFORMANCE OF A CO2 COMMERCIAL REFRIGERATION PLANT INTEGRATED WITH HVAC SYSTEM
Full text linkA fully instrumented CO2 trans-critical booster system with parallel compression, in operation in a small size supermarket in northern Italy, made available measured data that allowed monitoring its performance.
The entire refrigeration system of the supermarket, i.e. the Commercial Refrigerating Unit, the refrigerated display cabinets and cold rooms, have been modelled in TRNSYS with in-house types for all components. The comparison with the field data available from monitoring the plant allowed to thoroughly calibrate the model, spanning the operation conditions of a whole year. The validated model is a reliable and powerful tool, usable to predict the plant performance in several conditions and to evaluate the feasibility and effectiveness of the integration with DHW/HVAC systems. Measurements and simulations show that, at mild climate conditions, it is possible and effective to fully provide HVAC and refrigeration duties with a single all-in-one unit properly designed and operated
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