Oven Door Research Articles

A study on the optimal design for preventing thermal deformation over the oven door

A study on the optimal design for preventing thermal deformation over the oven door

Must Have Been A Lie

Must Have Been A Lie

The simulation of the microwave shielding properties of the dual band pass frequency selective surface

Without proper caution, the microwave leakage from a microwave oven door can be harmful to users’ health. In practice, the leaked radiation has to be blocked while the visible light is allowed to pass for a visual inspection of the cooking progress inside the oven. To fulfil the requirements, the door design based on the principle of the frequency selective surface (FSS) was proposed and the gridded square loop pattern was chosen. In the simulation conducted by COMSOL Multiphysics software, the size of the proposed FSS was given as 40.7×40.7 mm with a dielectric thickness of 2.8 mm. Two important characteristics in terms of shielding effectiveness (SE) and optical transparency (OT) of the proposed FSS configuration at normal incidence were simulated and found to be 62.7 dB and 57.5%, respectively. The simulation results indicate that the proposed FSS is applicable to a safety design of a microwave oven door in suppressing the microwave leakage. Parametric studies on the characteristics due to geometrical dimensions and glass substrate thickness were also investigated. These parameters were found to affect the shielding and transmitting performances of the proposed FSS.

Transport of chlorinated paraffins (CPs) from baking oven doors into the food

Chlorinated paraffins (CPs) have been repeatedly detected in the kitchen environment. Especially baking ovens were contaminated with high CP amounts on the insides of the doors. To investigate if CPs could be transferred into baked food, we spiked self-synthesized single chain C12-CP and C15-CP standards onto the inside door of an unused, CP-free baking oven. Experiments were performed under different conditions to assess possible CP transportation pathways. Coconut fat was used as food simulant, the exhaust air was monitored with cellulose filter paper and remaining CPs were collected via cotton wipes. In all experiments, both C12- and C15-CPs could be identified in both the food simulant and the cellulose samplers. Mean transfer rates into the food simulant amounted to 2.2% for C12-CPs and 5.8% for C15-CPs. Baking of food in CP-containing baking ovens may perceptibly increase the CP intake of consumers.

Making Microwave Oven Doors Child Resistant to Protect Young Children From Severe Scalds.

Most severe child scalds in the United States involve food and beverages. The wide variety of burn mechanisms, however, makes prevention challenging. Over the past 15 years, we have worked toward protecting young children from 1 specific mechanism: children opening microwave oven doors themselves and spilling the heated contents, resulting in often severe scalds. In our published research, we documented the frequency and severity of these cases and the vulnerability of young toddlers to be burned in this way. We have presented our findings and ideas for prevention at multiple national meetings and enlisted college engineering students to design microwave doors that would thwart a young child from opening them. In 2017, we became active members of a national task group convened by Underwriters Laboratories to address this issue, and two authors became voting members on the Underwriters Laboratories Standards Technical Panel for microwave ovens. We worked with microwave manufacturers and others for >1 year to address concerns of the industry, including those related to potential impacts on older adults. This effort resulted in the task group proposing a change in the standard, requiring "two distinct actions" to open the door of a microwave oven. On September 17, 2018, the panel voted to pass the measure, which will require child-resistant doors for all new microwave ovens in 2023. This report highlights how research can inform and support child injury prevention advocacy. Children will now be protected from this type of scald as microwaves with child-resistant doors replace current models.

Three‐dimensional computational fluid dynamics modeling of baking of chhana podo (milk cake)

AbstractComputational Fluid Dynamics (CFD) modeling was used to study the air velocity distribution and analyze the unsteady heat transfer and temperature distribution pattern during baking of chhana podo (milk cake). At first, a 3‐D geometry of the baking oven was created, and discrete ordinates (DO) radiation model was employed to predict the distribution of temperature. The data on progressive changes in thermal properties of chhana podo dough during baking were fed into the CFD model. The DO model was found to be adequate to predict the distribution of temperature in the product, with root mean squared error (RMSE) of 1.122 and mean percent relative deviation modulus (%P) of 0.70. Similarly, the DO model was found to be adequate to predict the air temperature distribution in the oven, with RMSE of 1.842 and %P of 1.61. The distribution of air velocity inside the oven was predicted using k‐ω turbulence model. The air velocity near the oven door was 0.505 m/s, whereas it was 5.002 m/s near the fan. Simulation results provided some insights on the effect of spatial location on air velocity. The placement of chhana podo inside the oven was optimized based on this simulation. This CFD simulation has potential application in the design of ovens with enhanced heat transfer and thermal efficiency.Practical ApplicationsThe present work models the heat transfer during baking of chhana podo. Even though a lot of research works related to CFD to products such as bread are available, many studies have not comprehensively considered temperature distribution in the oven, air velocity distribution and heat transfer in the product. The thermo‐physical properties of the product were modeled with respect to temperature and given as inputs into the CFD model. The CFD simulation of air velocity distribution inside the baking chamber will be useful in optimizing the placement of product or dough for uniform baking. The air velocity and heat transfer simulations quantified the diffusion of heat inside the product. This CFD simulation study could be useful in optimization and design of baking ovens for various products. Also, simulation of the baking conditions of a product could be advantageous from the economic perspective.

Making microwave oven doors “child-resistant” to protect young children from severe scalds.

Making microwave oven doors “child-resistant” to protect young children from severe scalds.

621 Successfully Advocating to Make Microwave Ovens “child-resistant” to Protect Young Children from Severe Scalds

Abstract Introduction Scald burn injuries are the leading cause of burn-related emergency room visits and hospitalizations for young children. An increasing portion of these injuries occur when children are removing items from microwave ovens. Many of these occur on the face/chest and can have lifelong physical, functional, aesthetic and psychological consequences. Over the past 15 years we have published a series of studies supporting our advocacy for a change in microwave oven design to protect children from severe scalds. Requiring microwave oven doors to be more difficult for a child to open would help to protect young children from these types of burn injuries. Our analysis of the National Electronic Injury Surveillance System found an estimated 7000 young children were treated in US emergency departments over the last decade for burns suffered when the child opened a microwave oven door and spilled the heated contents. This report describes our continued research and advocacy to finally get a regulatory agency to pass a “child-safety” mechanism for opening microwave doors. Methods In the United States, microwave ovens must meet the published microwave standard administered by Underwriters Laboratories (UL 923). In 2013, we formally proposed a change in the standard which underwent a voting process by the Standards Technical Panel. Microwave makers are well represented on the panel. This attempt did not pass. We continued to publish focused research, presented at national meetings, enlisted engineering students to design “child-resistant” microwave doors to demonstrate feasibility, and created a video to put a face to the statistics. In 2017, we became active members of a National Task Group convened by UL, and two authors became voting members on the 17 member microwave Standards Technical Panel. A new proposal was introduced by the Association of Home Appliances Manufacturers requiring “two distinct actions” to make it more difficult for a young child to open a microwave oven door. Multiple concerns were addressed including those related to the impact on seniors. We lobbied members who appeared undecided. Results On September 17, 2018, the UL 923 STP voted by a narrow margin to pass the measure. In the future, new microwave ovens sold in the United States will be required to be made with “child-resistant doors”. Conclusions Research and advocacy work together to protect children. Child scald risk will be reduced as microwaves with child-resistant doors replace current models. Applicability of Research to Practice Our research demonstrated that very young children are able to open microwave ovens putting them at risk for burn injuries. We worked diligently through various advocacy channels to actively improve the safety of microwave ovens. With the approved changes for future microwave design requirements, research and advocacy have now resulted in practice changes.

High levels of medium-chain chlorinated paraffins and polybrominated diphenyl ethers on the inside of several household baking oven doors

Fat obtained by wipe tests on the inner surface of 21 baking ovens from Stuttgart (Germany) were analyzed for halogenated flame retardants (HFRs), namely polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE), dechlorane plus (DP), short- and medium-chain chlorinated paraffins (SCCPs, MCCPs), as well as polychlorinated biphenyls (PCBs). In ~50% of the samples chlorinated paraffins (CPs) were present in the mg/g fat range, i.e. three to four orders of magnitude higher concentrated than the sum of all other target compounds. In contrast the remaining ~50% of the samples were free of CPs, while the other HFRs were comparable in CP-positive and CP-negative samples. The exceptionally high concentrations and exclusive presence of CPs in half of the samples produced strong evidence that these compounds were released from the baking oven itself. This hypothesis was supported by detection of MCCPs at even higher concentrations in the inner components of one dismantled baking oven. The release of substantial amounts of HFRs from the oven casing during its use may contribute to human exposure to these compounds, especially MCCPs and SCCPs.

Design of Fractal- Based Bandstop Filter for Microwave Radiation Leakage Reduction

There is a continuing concern over the risks associated with the use of microwave ovens because of the probable effects of the radiation leakage on the health of the individuals. In this paper, a new microstrip bandstop filter BSF is presented, designed and measured as an attempt to reduce the radiation leakage from the domestic microwave ovens operating at 2.45 GHz. The proposed BSF is composed of fractal based open-loop resonators coupled with an open-stub transmission line. The open-loop resonators are in the form of modified Minkowski fractal geometry of the 1st iteration. The open stubs have been adopted to increase the selectivity of the filter stopband response. The suggested filter is designed at 2.45 GHz. Modeling and performance assessments of the proposed filter have been evaluated by means of the computer software technique CST Microwave Studio and the Sonnet EM simulator. Simulation results reveal that the modeled filter offers stopband response with high selectivity. A prototype of the proposed filter is fabricated. The size limitations of the microwave oven opening width have been taken into account. Good agreement has been found between measured and simulated results. Four arrays of such a filter have been implemented to cover the microwave oven door frame taking into consideration the opening dimensions such that it well fit it. Measured radiated electric fields from the oven show that it considerably reduces the leaked radiation. By suitable choice of substrate material and carrying out the required dimension scaling, the proposed design idea is flexible and can be generalized for use with a wide variety of microwave equipment in which microwave leakage represents a serious issue.

Research on Optimization Design of Lifting Mechanism of Hot Air Drying Room Gate

Artificial hand lifting device for the traditional hot air drying oven door is optimized by design UG software to provide power to the lifting device of hydraulic pump. Thus driving the working mechanism to realize linear reciprocating rotary motion. This improvement improves safety during drying efficiency and the drying room door landing, convenient on-site workers the operation, improve the operation environment.

An aspirating cooling system for regulating temperature of pyrolytic oven glass

The aim of this study is to investigate the design parameter effects of an aspirating cooling system on the outer surface temperature of a household pyrolytic oven glass. Pyrolytic ovens include complicated components, such as an oven door, a cross-flow fan and an aspirating cooling system, and their complex interactions should be investigated in detail. In this study, the oven door and cross flow fan and aspirating cooling systems were modeled as a three dimensional system using a computational fluid dynamics and heat transfer method to investigate the fluid flow and temperature distribution of outer surface of the oven door. The simulation model predicted the temperature distribution based on the cross flow fan speed, cross flow fan position and channel design of the aspirating cooling system. The numerical results were validated against results obtained from an experimental study. The computational results show that the rotational speed of the cross flow fan, the cross flow fan position and the channel design of the aspirating cooling system play important roles in affecting the outer surface temperature distribution of the oven glass of a pyrolytic oven.

The Influence of Sound Awareness on the Level of Sound Generated during Nursing Activity in a Pseudo-Ward

Sound generated in a ward can be classified into 1) generated by medical staff, 2) generated by patients and their visitors, and 3) others, such as from in-hospital broadcasting microphones and nurse calls. Among these sounds, the incidence from medical staff, in particular, is reportedly high. The study objective is to investigate whether sound awareness is effective in regulating the sound environment even in a busy situation, such as in a real clinical setting, and to examine the extent to which sound awareness affects sound level. Nursing students were asked to perform a series of nursing activities in a pseudo-ward, and the changes in the sound level generated during the nursing activities with or without time and sound awareness were examined. Under varying experimental conditions, the sound and time levels associated with the nursing activities were measured in the following order: condition 1, without sound or time awareness; condition 2, with time awareness but without sound awareness; and condition 3, with both sound and time awareness. The time to perform nursing activities was longer with sound awareness. However, when aware of time only, the sound level from nursing activities rose by 2.3 dB, whereas when aware of both time and sound, the sound level dropped by 3.0 dB. With both time and sound awareness, there is a distinct drop in the sound level from nursing activities, such as wagon handling, handling of items (trays, bowls), working at the sink, and opening and closing the microwave oven door. These results suggest that even in a pseudo-clinical setting it is possible to regulate the environmental sound through the environmental sound awareness of the medical staff, resulting in a drop in the sound level generated while performing nursing activities.

Hybrid equivalent source – 3D ray-launching simulation technique for deterministic estimation of radiated emissions of electrical appliances

In this work, a method for modeling the leaked radiofrequency radiation from electrical appliances is presented, with the aim of obtaining a model for a 3D ray-launching algorithm. The domestic microwave oven is the appliance under analysis, as it radiates a substantial amount of power and it is spread worldwide. The method uses numerical electromagnetic field simulations to obtain the exterior oven radiation. Due to the complexity of the metallic mesh of the oven door, a retrieval process has been implemented in order to accelerate the electromagnetic field simulation. This result is incorporated to a proprietary 3D ray-launching algorithm by obtaining equivalent radiation sources. Finally, the microwave oven leakage is obtained for the complete volume of an indoor scenario. The numerical results are then compared with experimental measurements, with good agreement. The proposed model is useful to predict accurately the leakage of the domestic microwave oven within a complete complex indoor scenario, aiding in further radioplanning considerations.

Identifying the source of perytons at the Parkes radio telescope

"Perytons" are millisecond-duration transients of terrestrial origin, whose frequency-swept emission mimics the dispersion of an astrophysical pulse that has propagated through tenuous cold plasma. In fact, their similarity to FRB 010724 had previously cast a shadow over the interpretation of "fast radio bursts," which otherwise appear to be of extragalactic origin. Until now, the physical origin of the dispersion-mimicking perytons had remained a mystery. We have identified strong out-of-band emission at 2.3--2.5 GHz associated with several peryton events. Subsequent tests revealed that a peryton can be generated at 1.4 GHz when a microwave oven door is opened prematurely and the telescope is at an appropriate relative angle. Radio emission escaping from microwave ovens during the magnetron shut-down phase neatly explain all of the observed properties of the peryton signals. Now that the peryton source has been identified, we furthermore demonstrate that the microwaves on site could not have caused FRB 010724. This and other distinct observational differences show that FRBs are excellent candidates for genuine extragalactic transients.

Estimation of radiofrequency power leakage from microwave ovens for dosimetric assessment at nonionizing radiation exposure levels.

The electromagnetic field leakage levels of nonionizing radiation from a microwave oven have been estimated within a complex indoor scenario. By employing a hybrid simulation technique, based on coupling full wave simulation with an in-house developed deterministic 3D ray launching code, estimations of the observed electric field values can be obtained for the complete indoor scenario. The microwave oven can be modeled as a time- and frequency-dependent radiating source, in which leakage, basically from the microwave oven door, is propagated along the complete indoor scenario interacting with all of the elements present in it. This method can be of aid in order to assess the impact of such devices on expected exposure levels, allowing adequate minimization strategies such as optimal location to be applied.

Contribution to the development of colorimetry as a method for the assessment of fire-damaged concrete

This study presents a new method of using colorimetry for post-fire assessment of concrete. Changes in concrete colour with temperature are related to chemical changes of cement and aggregates. Two concretes were studied: an ordinary concrete (OC) and a high-performance concrete (HPC). The difference between both concretes was the water–cement ratio. They were made with the same cement and the same riverbed aggregates. Small samples were heated with different target temperatures: 100, 200 ... 1000 °C. After each cooling period, a picture was taken with a flatbed scanner. Two types of colour image decomposition were then used: RGB (red, green and blue) and HSI (hue, saturation and intensity) to analyse the evolution of the colour of the concrete with temperature. The evolution of red, green and blue components with temperature was analysed and two parameters of colorimetric analysis in order to predict the maximum temperature reached by concrete during fire were proposed. As the results have shown, the blue colour histogram gradually widens at its base as the temperature increases. Parameter of colorimetric analysis 1 is the measurement of this width. Parameter of colorimetric analysis 2 is associated with the appearance of very light colours beyond 800 °C. Thus, the number of pixels with intensity of red or green or blue higher than 225 increases very significantly between 800 and 900 C. Parameter of colorimetric analysis 3 is the average hue of the image (in the HSI colour space). It was found that parameter of colorimetric analysis 3 decreases significantly with temperature. This corresponds to the reddening of concrete with temperature due to the oxidation of mineral containing iron. To validate the use of these parameters of colorimetric analysis for the post-fire analysis of concrete, small concrete slabs were heated. They were positioned in place of the oven door, thus providing a thermal gradient through their thickness. Images taken during the cooling process were analysed using the proposed parameters of colorimetric analysis.

Movable oven for bread baking intended for food preparation in Serbian army peace corps

An oven for baking bread in field conditions is assigned to units that are by their nature relatively stationary and whose size does not require a movable bakery. It is intended for baking bread in our units located in international missions with supply difficulties, since our units have a habit od consuming bread instead of biscuits. The oven is of a prefabricated type, adapted for use in all types of terrains, simple design which makes it possible to be, dismantled and easyly transported. Introduction Changes in the socio-political environment have shown that it is not cost- effective to have an army whose sole task in peacetime would be to prepare for any defense from external enemies. Engagement of the Serbian Armed Forces in tasks with foreign missions imposes the need for integrated nutrition with armed forces of other countries. Production of bread, which predominantly affects the eating habits of the Serbian Armed Forces, requires the investigation of a possibility of its production. In conditions of supply difficulties, the use of movable ovens for baking bread can contribute to a more regular supply of bread to Serbian Army members who participate in peacekeeping operations. Eating habits In the period of the Principality of Serbia, the dominant share in daily rations was bread, which can be attributed to the poor economic situation of the Principality of Serbia. The recipe for military bread dates from 1883. During World War II, the bread share military daily rations was 40%, while today it accounts for 18.5%. The assessement of bread requirements depends not only on its energy value and weight, which is undoubtely important, but also on eating habits. Field oven A movable field oven is designed for baking bread under various climatic and terrain conditions in all three missions of the Army. The oven capacity is 68 kg of bread in one serving, and the daily capacity is 1420 kg. The oven set consists of a prefabricated body, additional materials, supplies, equipment, tools and tents for protection when working in field conditions. The oven prefabricated body consists of the following parts: feet (front and back), sides (front and rear), tubes (connecting and separating), slats, carriers (transversal, front and the one of the oven door), oven door and chimney. Constructing an oven includes the preparation phase, assembling the prefabricated elements and masonry work. Handling during use includes making fire and baking bread. A 600 g loaf is baked in 25 to 30 minutes. Conclusion The diet of Army members should include semi-wholegrain bread made of 850-type flour that has a higher nutritional value compared to white bread. A field oven of a prefabricated type is suitable for baking bread in units located in international missions.

Emissions at Coke Plants: European Environmental Regulations and Measures for Emission Control

At coke plants several pollutants are formed during coking, which are released to ambient air. To protect human health and to avoid harmful impacts on ambient air quality effective control of coke oven emissions is most significant. At coke plants the main source of emissions of NOx, SO2 and particulate matter is the flue gas from combustion of cleaned coke oven gas in the battery underfiring. Hence, advanced processes for coke oven gas cleaning in the by-product plant, like scrubbing processes for desulfurization of coke oven gas, are important measures at coke plants to reduce emissions to air. Effective filter equipments are available to abate emissions of dust from coke pushing and coal charging. Fugitive emissions at the batteries from leaking oven doors, lids and ascension pipes as well as fugitive emissions in the by-product plant from leaking pipes, flanges and valves can be abated by effective sealings, smooth operation and regular maintenance of all equipments. Inside the European Union emissions at coke plants are regulated in EU-directives on basis of Best Available Techniques (BAT) and monitored regularly by stipulation of national and local authorities. This paper focuses on (1) Legal EU-regulations on abatement of coke oven emissions into air, (2) Modern emission control measures available nowadays at coke plants.

SU-E-T-112: Experimental Characterization of a Novel Thermal Reservoir for Consistent and Accurate Annealing of High-Sensitivity TLDs.

To develop and characterize a novel thermal reservoir for consistent and accurate annealing of high-sensitivity thermoluminescence dosimeters (TLD-100H) for dosimetry of brachytherapy sources. The sensitivity of TLD-100H is about 18 times that of TLD-100 which has clear advantages in for interstitial brachytherapy sources. However, the TLD-100H requires a short high temperature annealing cycle (15 min.) and opening and closing the oven door causes significant temperature fluctuations leading to unreliable measurements. A new thermal reservoir made of aluminum alloy was developed to provide stable temperature environment in a standard hot air oven. The thermal reservoir consisted of a 20 cm × 20 cm × 8 cm Al block with a machine-milled chamber in the middle to house the aluminum TLD holding tray. The thermal reservoir was placed inside the oven until it reaches thermal equilibrium with oven chamber. The temperatures of the oven chamber, heat reservoir, and TLD holding tray were monitored by two independent thermo-couples which interfaced digitally to a control computer. A LabView interface was written for monitoring and recording the temperatures in TLD holding tray, the thermal reservoir, and oven chamber. The temperature profiles were measured as a function of oven-door open duration. The settings for oven chamber temperature and oven door open-close duration were optimized to achieve a stable temperature of 240 0C in the TLD holding tray. Complete temperature profiles of the TLD annealing tray over the entire annealing process were obtained. A LabView interface was written for monitoring and recording the temperatures in TLD holding The use of the thermal reservoir has significantly reduced the temperature fluctuations caused by the opening of oven door when inserting the TLD holding tray into the oven chamber. It has enabled consistent annealing of high-sensitivity TLDs. A comprehensive characterization of a custom-built novel thermal reservoir for annealing high-sensitivity TLD has been carried out. It enabled consistent and accurate annealing of high- sensitivity TLDs which could significantly improve the efficiency of brachytherapy source characterizations. Supported in part by NIH grant R01-CA134627.