Advanced Exergy Analyses of a Solar Hybrid Food Dehydrator

Waseem Amjad,Furqan Asghar,Faisal Mahmood,Jun-Tae Kim,Muhammad Imtiaz Hussain,Syed Nabeel Husnain,Anjum Munir,Muhammad Ali Raza

doi:10.3390/en15041505

Waseem Amjad, Furqan Asghar + Show 6 more

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https://doi.org/10.3390/en15041505

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Abstract

In this study, for the first time an advanced exergy analysis was applied to a solar hybrid food dehydrator to find out the causes of the inefficacies and to assess the actual improvement potential. The dryer was integrated with an evacuated solar tube collector and gas burner as a heating sources. Drying experiments were performed using bell pepper at 55 °C under three heating options i.e., gas, solar and dual. The rates of exergy destructions were split into unavoidable (EdUN) and avoidable (EdAV) which further split into four parameters termed unavoidable endogenous (EdUN,EN), unavoidable exogenous (EdUN,EX), avoidable endogenous (EdAV,EX) and avoidable exogenous (EdAV,EN). Conventional exergy analysis revealed that drying chamber possess lower improvement potential rate (IP) than heating components while outcomes of advanced exergy analysis showed that both the design and system components interaction of heating unit imparted a major effect on its efficiency. Optimizing the operating conditions of the heating sources could reduce their higher amount of inefficiencies. The values of exergy efficiency for the overall system were calculated to be 86.66%, 84.18%, 83.74% (conventional) and 97.41%, 95.99%, 96.16% (advanced) under gas, dual and solar heating modes respectively.

Highlights

Received: 28 December 2021Dehydration is an energy intensive process
Exergetic factor for the drying chamber was lowered than that of heating component but it handled a significant amount of exergy in the system while possessing lower improvement potential rate (IP) than heating component i.e., 0.69 kW less in case I, 0.98 kW in case II and 1.59 kW in case III
It shows that amount of exergy handled effectively in the drying chamber due to uniform air distribution through inline perforation

Summary

Introduction

Inefficient use of drying medium (mostly hot air) is one of the major causes responsible for it. Batch type food drying process is most widely used where drying medium (hot air) and its uniform circulation in the drying chamber is considered more important to encounter challenge of high energy consumption [1]. Various designs for uniform airflow distribution have been reported to decrease energy consumption. Use of inline perforation along the entire length of the drying chamber for drying uniformity has been reported [2]. The concept of alternating airflow and swing air temperature was applied to a grain dryer to achieve drying homogeneity [3] while in another study the effect of combining hot air and microwave vacuum drying on drying uniformity of mango slices was assessed [4]

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