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Dive into the research topics where J. Alberto Dopazo is active.

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Featured researches published by J. Alberto Dopazo.


Heat Transfer Engineering | 2012

Experimental Analysis of the Freezing Process in a Horizontal Plate Freezer With CO2 as Refrigerant in a Cascade Refrigeration System

José Fernández-Seara; J. Alberto Dopazo; Fracisco J. Uhía; Rubén Diz

An experimental evaluation of a cascade refrigeration system prototype using NH3 and CO2 as refrigerants has been performed. The prototype is used to supply a 9-kW refrigeration capacity to a horizontal plate freezer at an evaporation temperature of –50°C as design conditions. The prototype includes a specific control system and a data acquisition system. The article describes the prototype and the experimental program carried out to study the freezing process in the horizontal plate freezer. The experimental results include the freezing time, the temperature evolution in the product to be frozen, the refrigeration capacity of the facility, the electric power of the compressors, the coefficient of performance (COP) of the low- and high-temperature systems, and the overall system COP. The results obtained would confirm that the use of CO2 in plate freezers represents a viable alternative to refrigerants currently in use.


Heat Transfer Engineering | 2012

Condensation of R22 Retrofit Substitutes R417A, R422A, and R422D on Horizontal Smooth Tubes

Francisco J. Uhía; José Fernández-Seara; J. Alberto Dopazo; Rubén Diz

This article reports on the experimental research conducted to study the condensation of R22 retrofit refrigerants R417A, R422A, and R422D on Cu smooth tubes of 18.85 mm outside diameter. These retrofit substitutes are three-component mixtures. Experiments were carried out at vapor saturation temperature of 40°C and wall subcooling from around 1.8 to 16.7°C. The results clearly show the difference in behavior of the mixtures during condensation from that of a pure substance. A rapid increase of the heat transfer coefficients for low wall subcoolings was found. Comparisons of the condensation performance among the different refrigerant mixtures are also shown in the article.


Applied Thermal Engineering | 2009

Theoretical analysis of a CO2–NH3 cascade refrigeration system for cooling applications at low temperatures

J. Alberto Dopazo; José Fernández-Seara; Jaime Sieres; Francisco J. Uhía


International Journal of Refrigeration-revue Internationale Du Froid | 2011

Experimental evaluation of a cascade refrigeration system prototype with CO2 and NH3 for freezing process applications

J. Alberto Dopazo; José Fernández-Seara


Energy Conversion and Management | 2012

Experimental analysis of a direct expansion solar assisted heat pump with integral storage tank for domestic water heating under zero solar radiation conditions

José Fernández-Seara; Carolina Piñeiro; J. Alberto Dopazo; F. Fernandes; Paulo X.B. Sousa


International Journal of Refrigeration-revue Internationale Du Froid | 2010

Modelling and experimental validation of the hot-gas defrost process of an air-cooled evaporator

J. Alberto Dopazo; José Fernández-Seara; Francisco J. Uhía; Rubén Diz


International Journal of Refrigeration-revue Internationale Du Froid | 2010

Vapour condensation of R22 retrofit substitutes R417A, R422A and R422D on CuNi turbo C tubes

José Fernández-Seara; Francisco J. Uhía; Rubén Diz; J. Alberto Dopazo


Applied Thermal Engineering | 2014

On the performance of a vertical helical coil heat exchanger. Numerical model and experimental validation

José Fernández-Seara; Carolina Piñeiro-Pontevedra; J. Alberto Dopazo


International Journal of Refrigeration-revue Internationale Du Froid | 2010

Experimental analysis on pressure drop and heat transfer of a terminal fan-coil unit with ice slurry as cooling medium

José Fernández-Seara; Rubén Diz; Francisco J. Uhía; J. Alberto Dopazo


International Journal of Refrigeration-revue Internationale Du Froid | 2011

Experimental evaluation of an ejector as liquid re-circulator in an overfeed NH3 system with a plate evaporator

J. Alberto Dopazo; José Fernández-Seara

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