Loading...
22 results
Search Results
Now showing 1 - 10 of 22
- Numerical experimental evaluation of the aerodynamic drag of the air curtain in Vertical Open Refrigerated Display CabinetsPublication . Nascimento, Samuel Mariano do; Heidinger, Gustavo Galdi; Gaspar, Pedro Dinis; Silva, Pedro Dinho daThis paper presents the experimental and numerical results of a set of air curtain evaluations in a Vertical Open Refrigerated Display Cases (VORDC) when subjected to external disturbances due to the transfer of people in front of the air curtain. Previous experimental studies identified that the stability of the air curtain depends on the climatic conditions and ambient air movement inside the stores. The ambient air and VORDC air curtain can be disturbed during the movement of people in front of the VORDC, causing a certain amount of cold air to flow out of the VORDC and consequently hot and humid air entering. It is not possible to quantify exclusively the increase in energy consumption due to the transfer of people in the real case, due to the other variables involved in the process. Thus, a robot (Automated Mannequin for Interference Reproduction in the Air Curtain - MARIA) was mounted on a rail placed around the VORDC, in a climate chamber with controlled environment according to climatic class (n. º 3: T=25°C; =60%). MARIA performed clockwise and counterclockwise movements around the VORDC, with velocities of 0.2 m.s-1 at 0.8 m.s-1, with a pitch of 0.2 m.s-1. For the numerical evaluation, a 3D CFD model was developed to predict and analyze the air flow and heat transfer in the air curtain and outside both ways, refrigerated space and ambient air due to transfer of a body parallel to the air curtain.
- Experimental study of the influence of consumers movement parallel to the frontal opening of a multideck display case on the evaporator's thermal performancePublication . 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 (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.
- Comparing open and closed vertical refrigerated display cabinets at mild and tropical external environmentsPublication . 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 refrigerated display cabinets (VORDC vs. VCRDC). Tests were performed at a mild climate class (n. º 3: T=25°C; φ=60%) and a tropical one (n. º 6: T=27°C; φ=70%). The direct energy consumption is 46% higher at VCRDC due to the heated glass doors frame and defrost heaters. The product simulator temperature is higher and more stable at VORDC. The highest product simulator temperature is lower (-1.4°C) at the VCRDC 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 heat load is 77% lower at the VCRDC. Thus, the estimated total energy consumption is reduced 42%. Given the current concerns with energy consumption and sustainability of the heat exchange processes, the VCRDC provide the best solution.
- Performance variation of vertical open refrigerated display cases in-situ operation and testing according to ISO and ASHRAE standardsPublication . Nascimento, Samuel Mariano do; Heidinger, Gustavo Galdi; Gaspar, Pedro Dinis; Silva, Pedro Dinho daRefrigerated 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.
- Experimental analysis to optimize the performance of air curtains and heat exchangersPublication . Nascimento, Samuel Mariano do; Heidinger, Gustavo Galdi; Gaspar, Pedro Dinis; Silva, Pedro Dinho daThis chapter reports an overview about experimental studies concerning the thermal performance of air curtains and heat exchangers installed in vertical open refrigerated display cases. The air curtain analysis shows the influence on the thermal performance by varying the width of the discharge air grille and the perforation density of the back panel by a mathematical model. The variation on 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. Focusing the influence of environmental conditions on the performance of the heat exchanger, a second mathematical model was developed to evaluate the total heat load, its partial components and the condensate water mass. This analysis provides valuable information to the design of the air curtain and heat exchanger based on in-store environmental conditions and airflow efficiency.
- Impact of different lighting configurations in energy consumption of glass doors multideck display casesPublication . Heidinger, Gustavo Galdi; Nascimento, Samuel Mariano do; Gaspar, Pedro Dinis; Silva, Pedro Dinho daThis 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.
- 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.
- Experimental quantitative evaluation of thermal performance in refrigerated displays case with variation of the thickness of the air curtain and perforation density of the back panelPublication . Nascimento, Samuel Mariano do; Heidinger, Gustavo Galdi; Gaspar, Pedro Dinis; Silva, Pedro Dinho daOpen 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 a 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 equipments.
- «
- 1 (current)
- 2
- 3
- »