-This review reports research on liquid impingement jets and the abilities, limitations and features of this method of heat transfer. Some available and important correlations for Nusselt number are collected here. Also we demonstrate the capability of nanofluids to be applied in heat transfer processes involved liquid impingement jets.

A new impingement oven was designed and tested for its thermal and quality performance for baking of thin flat bread. The test facility was instrumented to monitor and record during the baking process. Bread temperature and weight loss were recorded on-line during baking at oven temperatures of 150, 175, 200, 225, and 250 C and 1, 2.5, 5, 7.5, and 10 m/s jet velocities, respectively. Image processing was used for monitoring the bread volume and surface color changes during baking. Better baking conditions were obtained with the impingement oven in comparison with the conventional direct fired ovens. Experiments showed that a higher jet velocity can be used for flat bread baking at lower oven temperatures and yield shorter baking times for the same quality product. For very thin breads (such as the Iranian breads), results show that conduction heat transfer from the bottom surface of the tray must also be considered along with the convective heat transfer from the jets in selection of optimal operating parameters. It is noted that desirable baking conditions, e.g., good browning, uniform color, high volume increase, etc., can be achieved in a well-designed and operated impingement oven in shorter baking times compared to the conventional ovens.

This study presents the successful application of the bees algorithm (BA) for optimal design of a cross‐flow plate fin heat exchanger by offset strip fins. The ε – NTU method is used to approximate the heat exchanger effectiveness and pressure drop. Two different objective functions including the minimization of total annual cost (sum of investment and operational costs) and total number of entropy generation units for certain heat duty required under given space constraints are considered as targets of optimization separately. Based on the applications, seven design parameters (heat exchanger length at hot and cold sides, fin height, fin frequency, fin thickness, fin‐strip length, and number of hot side layers) are selected as optimization variables. Two examples from the literature are presented to illustrate the efficiency and accuracy of the proposed algorithm. Results showed that the BA can detect an optimum configuration with higher speed (short computational time) and accuracy compared to the imperialist competitive algorithm (ICA) and the genetic algorithm (GA). © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(5): 427–446, 2014; Published online 3 October 2013 in Wiley Online Library (http://wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21087

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An artificial neural network (ANN) was developed to model the effect of baking parameters on the quality attributes of flat bread; i.e., crumb temperature, moisture content, surface color change and bread volume increase during baking process. As the hot air impinging jets were employed for baking, the baking control parameters were the jet temperature, the jet velocity, and the time elapsed from the beginning of the baking. The data used in the training of the network were acquired experimentally. In addition, using the data provided by ANN, a multi-objective optimization algorithm was employed to achieve the baking condition that provides the quality of the bread in all aspects simultaneously.