Energy and Exergy Analyses of Thin-Layer Drying of Potato Slices in a Semi-Industrial Continuous Band Dryer

Abstract

This article is concerned with the energy and exergy analyses of the continuous-convection drying of potato slices. The first and second laws of thermodynamics were used to calculate the energy and exergy. A semi-industrial continuous-band dryer has been designed and used for drying experiments. The equipment has a drying chamber of 2 m length and the inlet air used for drying is heated by gas power. The experiments were conducted on potato slices with thickness of 5 mm at three different air temperatures of 50, 60 and 70 C, drying air mass flow rates of 0.61, 1.22, and 1.83 kg/s and feeding rates of 2.31 Â 10 -4 , 2.78 Â 10 À4 , and 3.48 Â 10 À4 kg=s. The energy utilization and energy utilization ratio were found to vary between 3.75 and 24.04 kJ=s and 0.1513 and 0.3700, respectively. These values show that only a small proportion of the supplied energy by the heater was used for drying. The exergy loss and exergy efficiency were found to be in the range of 0.5987 to 13.71 kJ=s and 0.5713 to 0.9405, respectively, indicating that the drying process was thermodynamically inefficient and much energy was vented in the exhaust air. In addition, the results showed that the feeding rate and the temperature and flow rate of the drying air had an important effect on energy and exergy use. This knowledge will provide insights into the optimization of a continuous dryer and the operating parameters that causes reduction of energy consumption and losses in continuous drying.

Improving exergetic performance parameters of a rotating-tray air dryer via a simple heat exchanger

“…Exergy analysis utilizes the concepts of conservation of mass and energy together with the second law of thermodynamics. Several studies have been published on the use of exergy analysis for various drying processes and systems [13][14][15][16][17][18][19][20][21][22][23]. The outcomes of previously published researches indicate that drying processes can be satisfactorily designed and optimized using exergy analysis.…”

A Comparative Study on Exergetic Performance Assessment for Drying of Broccoli Florets in Three Different Drying Systems

“…[13][14][15][16][17] In these previous studies, the drying process was thermodynamically modeled by Dincer and Sahin, [14] and drying of different products such as wheat kernel, [18] pistachio, [13] red pepper slices, [15] potato, [16,19] apple slices, [20] pumpkin, [17] laurel leaves, [21,22] pasta, [23] green olive, [24] and mint, [25] was evaluated in terms of energetic and exergetic aspects using various drying devices, such as fluidized bed dryers, solar drying cabinets, cyclone-type dryers, convective-type hot air dryers, and heat pump dryers. In addition, other exergetic studies on drying also included a solar greenhouse, [26] a freeze-drying process, [27] a detailed review, [28] and mathematical modeling.…”

Exergy Analyses of Onion Drying by Convection: Influence of Dryer Parameters on Its Performance

“…Aghbashlo et al (2008) obtained values close to 87% and the values obtained for Khanali et al , 2013 varied between 65% and 74%, approximately. For a drying temperature equal to 343K, the exergy efficiency was about 73%, and these researchers found values about 67%.…”