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Schematic diagram of forced-convection ovens using hot air impinging jets in the (a) coating and converting and (b) bread baking industry
Context in source publication
Context 1
... a wide variety of forced convection ovens in the process industries the hot air jets emerge from an array of nozzles arranged perpendicular to the machine direction and transfer heat into the target products by convection from the hot air jets, radiation from the oven walls and conduction from its containers, see Figure 3 above. ...
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Citations
... Among the numerous heat transfer technologies developed, thermal transfer from hot air nozzles within convection ovens are extensively used, including the glass temper, product coating, and baking various food products to name few. With arrays of hot impingement air nozzles perpendicular to the surface of targeted product, heat is transferred onto it [2]. A typical schematic of convection oven with impinging hot air jets is presented in Figure 1. ...
... However, several challenges exist due to the amount of energy consumed, the complex thermo-physical processes involved and the difficulties in monitoring the phenomena inside the oven [1]. The increase of energy price, the limitations posed to the lead time in the coating and converting industries [2], drive the pursue of higher efficiency of thermal transfer in the industrial ovens. ...
... The application of jet impingement can also increase the coefficient which reflects the efficiency of thermal-transfer between the surface of product and the oven atmosphere as additional control [9]. The flow patterns followed by impinging hot air jets have three regions: free flow field; impingement, stagnation flow and radial flow areas, as shown in Fig. 3 [2]. ...
Drying, curing, baking are few of the manufacturing processes that require the use of impingement ovens. For the manufacturing of large batches typically continuous flow ovens are used that are part of an automated conveyor processing line. The retention time for a product to be treated in the oven usually drives the production efficiencies (i.e. energy usage or lead times). In many processing lines though, the ovens are not designed and run in the most efficient way, and as a result become the “bottleneck” process phase. In such ovens, usually the hot air is ejected from rows of nozzles perpendicularly to the moving product. In the most advanced designs the ovens are divided in zones, with each zone having different targeted operating temperature. The optimization of the manufacturing process is difficult to be experimentally determined due to several reasons: the length of the ovens and the complexity of the movement of the product in and out of the oven are the most challenging ones. The main objective of this paper thus is the development of a Computer Fluid Dynamics model for simulating the thermal - transfer efficiency of an existing hot-air convection oven used to produce continuous products. The model is used for the estimation of the maximum speed that the conveyor belt can be run, and further investigate possible improvements on the design of the oven for the reduction of the cycle time. The results can be useful during the overview of the actual production and manufacturing rules.
