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- Variation of the thermal performance of open multideck display case due to the procedure of setting the external air velocityPublication . Heidinger, Gustavo Galdi; Nascimento, Samuel Mariano do; Gaspar, Pedro Dinis; Silva, Pedro Dinho daThis paper reports the experimental results with an open multideck display case with dual air curtain. Manufacturers seek during the design phase of the equipment to certify its suitability to the testing standards with the lowest energy consumption and ensuring food safety. The testing standard ISO 23953 is usually followed to determine the thermal cooling load. The thermal cooling load depends on the procedure to set the external air velocity. According to ISO 23953, the mean horizontal air velocity, with the refrigerated display case switched off, shall be 0.2 m s-1. This paper reports experimental test results where the initial procedure of setting the air velocity followed two different methods. Considering that (1) the display case is initially switched off as required by ISO 23953 and (2) the display case is initially switched on and the external air velocity is adjusted to the required level using auxiliary fans. After reaching steady state conditions, the 24-hour tests began with the display case switched on.
- Impact of external air currents on the performance of open multideck display case evaporators in laboratory conditionsPublication . Heidinger, Gustavo Galdi; Nascimento, Samuel Mariano do; Gaspar, Pedro Dinis; Silva, Pedro Dinho daThis paper reports the experimental results with an open multideck display case with dual air curtain. Manufacturers seek during the design phase of the equipment to certify its suitability to the testing standards with the lowest energy consumption and ensuring food safety. The testing standard ISO 23953 is usually followed to determine the equipment's thermal cooling load. However, some manufacturers use different procedures to set the external air velocity. The thermal cooling load will depend upon it. According to ISO 23953, the mean horizontal air velocity, with the refrigerated display case switched off, shall be 0.2 m/s. Thus, this paper reports the experimental results of tests where the initial procedure of setting the air velocity was performed by two different methods: (1) with the display case cooling on (2) and switched off as required by ISO 23953. The comparison of experimental results for the two conditions (switched off relatively to switched on) provide the quantitative variation of frost formation (-24%) and condensed water (+180%) on the evaporator coil and how this phenomena affects the distribution and magnitudes of air velocity (+7%); inlet (+5.9°C) and outlet temperatures (+5.5°C); the components of the total sensible (+10%) and latent (+15%) heat loads; and the average product temperatures (+176%). The analysis of experimental data provides the necessary basis to conclude that the initial procedure how the air movement is set affects significantly the performance of the equipment under testing. The results show that air movement procedure defined in the standard, although providing a higher thermal cooling load, is the most appropriated since the equipment will be able to operate correctly under more demanding ambient conditions and thus its design provides a better thermal performance.
- Experimental evaluation of the thermal performance at different environmental conditions of a low temperature display case with built-in compressor and water-cooled condenserPublication . Heidinger, Gustavo Galdi; Nascimento, Samuel Mariano do; Gaspar, Pedro Dinis; Silva, Pedro Dinho daThis paper reports the results of experimental tests performed according to ISO 23953 in a vertical closed low temperature display case to evaluate the influence of the environment where it is installed (climatic class) in the energy consumption and thermal performance. The compressor and the condenser are attached to the display case and an external water circuit is used to provide air-chilled water to the condenser. The need for this type of equipment arises from the numerous small stores without air conditioning system and without space for placing a remote cooling rack. Keeping the external environment temperature constant and consequently the refrigerant condensing temperature, changing climatic class n.° 3 (Ta=25 °C and ϕa=60%) to n.° 6 (Ta=27 °C and ϕa=70%), the compressor energy consumption increases 8% to 10% and the highest temperature of the warmest product simulator increases +3.0 °C. At the same climatic class, the water temperature increases with the external environment temperature. The compressor energy consumption increases 13% and 8% when the refrigerant condensing temperature increases from 40 °C to 45 °C and from 45 °C to 50 °C, respectively. Thus refrigeration equipment with compressor and condenser attached is susceptible to the climatic variation of the internal and external environment. In applications with large climatic amplitude, the components must be designed to meet all the operating situations.
- Experimental comparison at open and closed vertical multidecks display cases at standard and tropical environmental conditionsPublication . Heidinger, Gustavo Galdi; Nascimento, Samuel Mariano do; Gaspar, Pedro Dinis; Silva, Pedro Dinho daThis paper reports the results of experimental tests performed according to ISO 23953 in vertical open and closed multideck display cases to evaluate the influence of double glass doors in the direct energy consumption, product simulator temperature, evaporator total condensed water mass, total heat load and total energy consumption. Tests were performed at climate classes n.º 3 (Ta = 25°C; a = 60%) and n.º 6 (Ta = 27°C; a = 70%). The direct energy consumption is 46% higher at the closed display case due to the heat load generated by the heated glass doors frame and defrost heaters. The product simulator temperature is higher and more stable at the open display case. The highest product simulator temperature is lower (-1.4°C) at the closed display case and less stable (+2.7°C variation) due to the opening doors period. The total mass of condensed water at the evaporator is reduced 87% and the total energy consumption is 58% lower at the closed display case. In conclusion, the estimated total energy consumption (compressor and components) is reduced at the glass doors display case. Thus, it is verified that the use of refrigeration equipment closed to ambient air is increasingly seen as the definitive solution, given the current concerns with energy consumption and sustainability of the heat exchange processes.
- Influence of the test procedure for setting the external air movement on the thermal performance of open multideck display casePublication . Heidinger, Gustavo Galdi; Nascimento, Samuel Mariano do; Gaspar, Pedro Dinis; Silva, Pedro Dinho daThis paper reports the experimental results with an open multideck display case with dual air curtain. Manufacturers seek during the design phase of the equipment to certify its suitability to the testing standards with the lowest energy consumption and ensuring food safety. The testing standard ISO 23953 is usually followed to determine the equipment's thermal cooling load. However, some manufacturers use different procedures to set the external air velocity. The thermal cooling load will depend upon it. According to ISO 23953, the mean horizontal air velocity, with the refrigerated display case switched off, shall be 0.2 m/s. Thus, this paper reports the experimental results of tests where the initial procedure of setting the air velocity was performed by two different methods: (1) with the display case cooling on (2) and switched off as required by ISO 23953. The comparison of experimental results for the two conditions (switched off relatively to switched on) provide the quantitative variation of frost formation (-24%) and condensed water (+180%) on the evaporator coil and how this phenomena affects the distribution and magnitudes of air velocity (+7%); inlet (+5.9°C) and outlet temperatures (+5.5°C); the components of the total sensible (+10%) and latent (+15%) heat loads; and the average product temperatures (+176%). The analysis of experimental data provides the necessary basis to conclude that the initial procedure how the air movement is set affects significantly the performance of the equipment under testing. The results show that air movement procedure defined in the standard, although providing a higher thermal cooling load, is the most appropriated since the equipment will be able to operate correctly under more demanding ambient conditions and thus its design provides a better thermal performance.