The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform

Carmela Aprea - One of the best experts on this subject based on the ideXlab platform.

  • an experimental evaluation of the transcritical co2 refrigerator performances using an internal heat exchanger
    International Journal of Refrigeration-revue Internationale Du Froid, 2008
    Co-Authors: Carmela Aprea, Angelo Maiorino
    Abstract:

    Abstract The classical substances as hydrochlorofluorocarbons (HCFCs) used as working fluids in the vapour compression plants have to be replaced by new substances because of their ozone depletion potential and their greenhouse effect. Carbon dioxide (CO 2 ) is non-toxic, non-flammable, has zero ozone depletion potential and negligible global warming potential as refrigerant. Referring to a transcritical CO 2 cycle working as a classical “split-system” to cool air in residential applications, the aim of this paper is the evaluation of the energy performances using an internal heat exchanger. The experimental plant employs a semi-Hermetic Compressor, plate-finned tube type heat exchangers, a back pressure valve electronically controlled and an expansion valve. Besides it is possible to control the flash gas produced in the liquid receiver thanks to another semi-Hermetic Compressor linked to an inverter. An increase of the coefficient of performance has been found using the internal heat exchanger. The comparison of the coefficients of performance of two cycles, working with and without the internal heat exchanger, is discussed.

  • Performance evaluation of R22 and R407C in a vapour compression plant with reciprocating Compressor
    Applied Thermal Engineering, 2003
    Co-Authors: Carmela Aprea, Adriana Greco
    Abstract:

    Abstract In this paper, the problem of R22 phase-out in refrigeration plants is addressed. A comparison is performed between R22 and R407C. The latter seems to be a promising drop-in substitute for the former. Experimental tests are performed in a vapour compression plant with a reciprocating Compressor. The objective of this paper is to evaluate the Compressor performance using R407C in comparison to R22. The plant overall energetic performance is also evaluated. R22 performance is consistently better than that of its candidate substitute. The difference stems from the different irreversibilities of the plant components arising when using R22 and R407C, respectively. Specific attention is devoted to Compressor irreversibilities. Performance indices related to the semi-Hermetic Compressor are evaluated when using either refrigerant fluid. The investigation has revealed that R22 performs better than R407C mainly because of a better compression process due to a number of factors, including the facts that the isoentropic and volumetric efficiencies of the semi-Hermetic Compressor are better than that of R407C.

  • Performance evaluation of R22 and R407C in a vapour compression plant with reciprocating Compressor
    Applied Thermal Engineering, 2003
    Co-Authors: Carmela Aprea, Alessandra Greco
    Abstract:

    In this paper, the problem of R22 phase-out in refrigeration plants is addressed. A comparison is performed between R22 and R407C. The latter seems to be a promising drop-in substitute for the former. Experimental tests are performed in a vapour compression plant with a reciprocating Compressor. The objective of this paper is to evaluate the Compressor performance using R407C in comparison to R22. The plant overall energetic performance is also evaluated. R22 performance is consistently better than that of its candidate substitute. The difference stems from the different irreversibilities of the plant components arising when using R22 and R407C, respectively. Specific attention is devoted to Compressor irreversibilities. Performance indices related to the semi-Hermetic Compressor are evaluated when using either refrigerant fluid. The investigation has revealed that R22 performs better than R407C mainly because of a better compression process due to a number of factors, including the facts that the isoentropic and volumetric efficiencies of the semi-Hermetic Compressor are better than that of R407C. © 2002 Elsevier Science Ltd. All rights reserved.

E Torrella - One of the best experts on this subject based on the ideXlab platform.

  • experimental comparison between r152a and r134a working in a refrigeration facility equipped with a Hermetic Compressor
    International Journal of Refrigeration-revue Internationale Du Froid, 2015
    Co-Authors: R Cabello, Rafael Llopis, D Sanchez, I Arauzo, E Torrella
    Abstract:

    Abstract The EU Regulation 517/2014 has recently been approved in a further attempt to curb the effects of Global Warming. As a consequence, the refrigeration sector is moving towards refrigerants with a low Global Warming Potential (GWP100) in accordance with the limit fixed by these regulations (150). In this regard, the old refrigerant R152a attracts renewed interest due to its low GWP (138) and its similarity to R134a. The present work shows the results of using R152a in a vapour compression plant equipped with a Hermetic Compressor and an IHX designed for R134a. The refrigerant was replaced by a conventional “drop-in” process in order to carry out an energy comparison. The results have revealed an improvement in the COP with R152a up to 13% despite a reduction in the cooling capacity of about 10%. During the test campaign, R134a Hermetic Compressors have been shown to be capable of operating with R152a.

  • experimental evaluation of an internal heat exchanger in a co2 subcritical refrigeration cycle with gas cooler
    Applied Thermal Engineering, 2015
    Co-Authors: Rafael Llopis, Carlos Sanzkock, Ramón Cabello, D Sanchez, E Torrella
    Abstract:

    Abstract We present the experimental evaluation of an internal heat exchanger or suction-line/liquid-line heat exchanger in a CO2 subcritical refrigeration plant with gas-cooler. The plant, driven by a 1.5 kW CO2 semi Hermetic Compressor, uses brazed plate heat exchangers as condenser, evaporator and internal heat exchanger, an air finned tube gas-cooler and an electronic expansion valves. The evaluation (77 steady-states) covers evaporating temperatures from −40 to −25 °C and condensing temperatures from −15 to 0 °C, always at the nominal speed of the Compressor. Here, the effect of the internal heat exchanger on the main energy parameters is analysed, i.e., cooling capacity, COP and heat rejection at gas-cooler and condenser. Also, the effect of the internal heat exchanger in a cascade cycle is analysed theoretically. It has been concluded that the internal heat exchanger does not improve the performance of the subcritical cycle, but it could improve the energy performance if it is used inside a cascade refrigeration system.

Paulo X B Sousa - One of the best experts on this subject based on the ideXlab platform.

  • experimental analysis of a direct expansion solar assisted heat pump with integral storage tank for domestic water heating under zero solar radiation conditions
    Energy Conversion and Management, 2012
    Co-Authors: Jose Fernandezseara, Carolina Pineiro, Alberto J Dopazo, F Fernandes, Paulo X B Sousa
    Abstract:

    Abstract This paper deals with the experimental evaluation of the performance of a direct expansion solar assisted heat pump water heating (DX-SAHPWH) system working under zero solar radiation conditions at static heating operation mode of the storage tank. The DX-SAHPWH system includes two bare solar collectors as evaporator, a R134a rotary-type Hermetic Compressor, a thermostatic expansion valve and a helical coil condenser immersed in a 300 L water storage tank. The zero solar radiation and stable ambient air temperature working conditions were established by placing the solar collectors into a climate chamber. The analysis is based on experimental data taken from the DX-SAHPWH provided by the manufacturer and equipped with an appropriate data acquisition system. In the paper, the experimental facility, the data acquisition system and the experimental methodology are described. Performance parameters to evaluate the energy efficiency, such as COP and equivalent seasonal performance factors (SPFe) for the heating period, and the water thermal stratification in the storage tank are defined and obtained from the experimental data. Results from the experimental analysis under transient operating working conditions of the DX-SAHPWH system and its main components are shown and discussed. Lastly, the Huang and Lee DX-SAHPWH performance evaluation method was applied resulting in a characteristic COP of 3.23 for the DX-SAHPWH system evaluated under zero solar radiation condition.

Y.x. Xu - One of the best experts on this subject based on the ideXlab platform.

  • Experimental performance analysis on a direct-expansion solar-assisted heat pump water heater
    Applied Thermal Engineering, 2007
    Co-Authors: Y.-w. Li, Ruzhu Wang, Jingyi Wu, Y.x. Xu
    Abstract:

    A direct expansion solar assisted heat pump water heater (DX-SAHPWH) experimental set-up is introduced and analyzed. This DX-SAHPWH system mainly consists of 4.20 m2 direct expansion type collector/evaporator, R-22 rotary-type Hermetic Compressor with rated input power 0.75 kW, 150 L water tank with immersed 60 m serpentine copper coil and external balance type thermostatic expansion valve. The experimental research under typical spring climate in Shanghai showed that the COP of the DX-SAHPWH system can reach 6.61 when the average temperature of 150 L water is heated from 13.4 ??C to 50.5 ??C in 94 min with average ambient temperature 20.6 ??C and average solar radiation intensity 955 W/m2. And the COP of the DX-SAHPWH system is 3.11 even if at a rainy night with average ambient temperature 17.1 ??C. The seasonal average value of the COP and the collector efficiency was measured as 5.25 and 1.08, respectively. Through exergy analysis for each component of the DX-SAHPWH system, it can be calculated that the highest exergy loss occurs in the Compressor, followed by collector/evaporator, condenser and expansion valve, respectively. Further more, some methods are suggested to improve the thermal performance of each component and the whole DX-SAHPWH system. ?? 2006 Elsevier Ltd. All rights reserved.

Alessandra Greco - One of the best experts on this subject based on the ideXlab platform.

  • Performance evaluation of R22 and R407C in a vapour compression plant with reciprocating Compressor
    Applied Thermal Engineering, 2003
    Co-Authors: Carmela Aprea, Alessandra Greco
    Abstract:

    In this paper, the problem of R22 phase-out in refrigeration plants is addressed. A comparison is performed between R22 and R407C. The latter seems to be a promising drop-in substitute for the former. Experimental tests are performed in a vapour compression plant with a reciprocating Compressor. The objective of this paper is to evaluate the Compressor performance using R407C in comparison to R22. The plant overall energetic performance is also evaluated. R22 performance is consistently better than that of its candidate substitute. The difference stems from the different irreversibilities of the plant components arising when using R22 and R407C, respectively. Specific attention is devoted to Compressor irreversibilities. Performance indices related to the semi-Hermetic Compressor are evaluated when using either refrigerant fluid. The investigation has revealed that R22 performs better than R407C mainly because of a better compression process due to a number of factors, including the facts that the isoentropic and volumetric efficiencies of the semi-Hermetic Compressor are better than that of R407C. © 2002 Elsevier Science Ltd. All rights reserved.