Experimental and Numerical quantitative evaluation of the thermal performance of refrigerated display cabinets with variation of air curtain thickness and porosity of the back panel

Open multideck display cabinets are widely used to expose perishable products in supermarkets and convenience stores. This paper reports the results of experimental tests performed according to ISO23953 in an open multideck refrigerated display cabinet to assess the impact on the thermal performance by varying the width of the discharge air grille and the perforation density of the back panel. The experimental laboratory tests were conducted for climate class n.° 3 (25° C and 60%). The results evaluation shows that the perforation density of the back panel and the width of discharge air grille alter significantly the thermal entrainment factor and the energy consumption of the equipment. The best performance configuration showed a 10% reduction of the cooling load. The analysis of the results provides valuable information for the development of these equipmentsinfo:eu-repo/semantics/publishedVersio

Experimental study of the interference in air curtains due to the parallel transfer in front of refrigerated display cases

Refrigerated display cases used to expose perishable food for sale in convenience stores and supermarkets are subject to human interference. Clients and repositories transit in front of display cases and frequently remove or place food products on the shelves depending on sales volume. This movement is part of the trade, although it has consequences on the display case performance. Each interference drags or breaks the air curtain resulting in the modification of air flow and promoting the ambient air thermal entrainment that consequently change the equipment's working conditions and increase 2% to 5% its energy consumption. This experimental study quantifies the air temperature increase and the energy consumption increase when there is an interference drag due to people inside the store passing parallel to the frontal opening of the display case. The tests were performed using a robotic mannequin that systematically transfers around the display case (5 minutes lap during 24 hours) and parallel to the frontal opening of the refrigerated display case with a translation velocity of 0.6 m/s. The results show that the products temperature increases 16% and the energy consumption increases 4.6% due to the air movement generated by the robotic mannequin transfer. These results are part of a more complex evaluation of the air curtain interference by humans to be used in the development of new products on an industrial scale.info:eu-repo/semantics/publishedVersio

Experimental comparison at open and closed vertical multidecks display cases at standard and tropical environmental conditions

This 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.info:eu-repo/semantics/publishedVersio

Relevant parameters on the energy efficiency of closed refrigerated multideck display cases

The application of closed refrigerated multideck display cases (CRDC) and electronic fans is slowly increasing in Brazilians supermarkets, following the international trend. In order to obtain energy savings, this paper reports the results of experimental tests performed in a CRDC according to ISO 23953 to evaluate the influence of (1) environmental conditions, (2) gaps between doors and (3) fans type on the overall performance of a display case. Experimental laboratory tests were performed on two different conditions of temperature and relative humidity of the ambient air (Tamb=25°C; amb=60% and Tamb=27°C; amb=70%), with electromagnetic and electronic fans, and with and without gaps between doors. The analysis and discussion of experimental results include the comparison of compressor energy consumption, total heat load, total condensed water collected on defrost periods and air and product temperatures. The experimental data analysis provides valuable information to set the operative parameters of the CRDC taking into account usual in-store conditions in Brazil.info:eu-repo/semantics/publishedVersio

Impact of different lighting configurations in energy consumption of glass doors multideck display cases

This paper reports the results of experimental tests performed in a glass doors multideck display case for medium temperature. This type of equipment considers a large reduction in the thermal load due the use of doors, however, a large part of the energy consumption is coming from the lighting. Experimental tests were performed with different types of lighting setup to measure the energy consumption and its consequent impact on the thermal load. The configurations tested were: fluorescent lamps and LED, both tested in horizontal (under the shelves) positioning and only LED were tested in vertical (next to the doors) positioning. Comparing with fluorescent lamps, experimental results show that LED illumination under the shelves reduces the direct energy consumption in 41% and the LED in vertical position results in 74% of energy economy. The illuminance depends on the position at which the measurement is made, LED illumination under the shelves results in a variation of -26 to +31% and LED in vertical position results in a variation of -50 to +422%. The LED illumination in vertical positioning is the best alternative to save energy and highlight the products exhibited.info:eu-repo/semantics/publishedVersio

Experimental study of the influence of consumers movement parallel to the frontal opening of a multideck display case on the evaporator's thermal performance

This paper reports the results of experimental tests performed according to ISO 23953 (climate class n° 3: 25ºC and 60%) in an open refrigerated multideck display case (ORDC) to evaluate the influence of consumers passing in front of its opening on the thermal performance of the evaporator. The consumers’ passage in front of the ORDC is simulated by a robotic mannequin: MARIA - Mannequin for Automatic Replication of the Interference in the Air curtain. Tests are performed for MARIA velocity's ranging from 0.2 ms-1 to 0.8 ms-1, with 0.2 ms-1 velocity steps for two conditions: mannequin moving towards or against the airflow of the test room. All tests are performed in an ORDC with dual air curtain. The results quantify the influence of MARIA translational velocity on the frost formation in the evaporator coil and how this phenomenon affects the evaporator's airflow, inlet and outlet temperatures and sensible and latent heat loads. The analysis of experimental data provides valuable information for evaporator design taking into account usual in-store conditions.info:eu-repo/semantics/publishedVersio

Experimental evaluation and qualitative increase of thermal load in open refrigerated display cases due to breakage of the air curtain

Open refrigerated display cabinets are used extensively in convenience stores and supermarkets in order to display perishable products meeting the criteria of food security. In Brazil, there are about 81 thousand stores using open or closed refrigerated display cabinets for products sale. The vertical open refrigerated display cabinet is the model that consumes more energy. About 81% its total consumption is due to the infiltration of outside air through the air curtain. The air curtain performance can be influenced by several factors, among which, the customers’ movement near the equipment frontal opening causing a perturbation in the air jet and increasing its energy consumption. Experimental tests were conducted in open and closed hours of a food store. The TEF increases by 22% and cooling load by 18% when the shop is open. The results comparison allows evaluating the thermal performance of the equipment among test cases for a real scenario.info:eu-repo/semantics/publishedVersio

Performance variation of vertical open refrigerated display cases in-situ operation and testing according to ISO and ASHRAE standards

Refrigerated display cases are an equipment widely used in sales environments, such as stores and super markets. Most equipment are open type since they provide a good marketing appeal. This type of equipment is used to expose perishable foods or chilled drinks. 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. With the aim to assist the development of new equipment that meet the test conditions established by testing standards and market needs, experimental tests were conducted comparing real operation conditions and test conditions following the testing standards ISO 23953/2005 and ASHRAE 72-2005. The experimental results show that test conditions required by standards are stricter than in-situ operation, providing higher conservation temperatures (56% increase) and energy consumption (17% increase). The experimental study considers an open vertical refrigerated display case that demands high electrical energy consumption due to its characteristics. The tests performed in the laboratory using a climatic chamber determine approximately 17% higher thermal load values than those of in-situ operation with remote refrigeration system. This condition arises from the different airflow conditions that are found inside stores when comparing with the conditions and patterns imposed by standards for equipment testing. This difference has a negative impact in the commercial scope since equipment manufacturers relate lower thermal load values than those determined in tests of similar models according to standards.info:eu-repo/semantics/publishedVersio

Influence of the test procedure for setting the external air movement on the thermal performance of open multideck display case

This 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.info:eu-repo/semantics/publishedVersio