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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 study of the fins arrangement pattern of refrigerated display cabinet evaporator towards thermal performance improvementPublication . 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 an open multideck display cabinet with dual air curtain to evaluate the impact of the evaporator fins arrangement pattern on the overall thermal performance. Experimental laboratory tests were performed on climate class no. 3 (25 °C and 60%) with three different evaporator configurations. The thermal exchange area was the same among the three models to keep the aluminum fins and cooper tubes cost constant. The study investigates the increase on the operation time before defrost and the minimization of the latent thermal load due water condensation and freezing between the evaporator fins. Compared to the uniform fin pitch, it was possible to reduce 18% the frost mass and, thus, increasing the refrigeration time between defrosts and decreasing 14% the total heat load. However, an increase on the air (+0.6 °C) and product temperatures (+1.9 °C) due to an inefficient heat exchange, leads to new analysis and assessments related to the residence time between the fins and the airflow in order to keep the temperatures low at the refrigerated space and thus ensuring food safety.
- 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.