An Exergy Based Unified Test Protocol for Solar Cookers of Different Geometries

Abstract

Abstract:It is good for the consumer to have solar cookers of various varieties in terms of geometrical designs, performance and price but it is a ch allenge to develop a u niform test standard for evaluating the thermal performance of the cookers irrespective of their geometrical construction. Due to the lack of uniform test protocol, consumer cannot compare the quantitative performance of the cookers of different configuration and become confused. For this end, we plotted graphs between exergy output and temperature difference, for solar cookers of different designs and it resembled a parabolic curve for each design. The peak exergy (vertex of the parabola), can be accepted as a measure of devices' fuel ratings. The ratio of the peak exergy gained to the exergy lost at that instant of time can be considered as the quality factor of the solar cooker. Besides, the exergy lost is found to vary linearly with temperature difference irrespective of the topology of the device and the slope of the straight line obtained through curve fitting represents the heat loss coefficient of the cooker. The proposed parameters can lead to development of unified test protocol for solar cookers of diversified designs.

Determination of Performance Measuring Parameters of an Improved Dual Paraboloid Solar Cooker

“…Further, the temperature difference gap at half peak power and its product Figure 19) efficiencies have substantially improved compared to the results reported for a single parabolic trough cooker, where maximum energy efficiency was 15.7% and maximum exergy efficiency was 1.25% [23]. Similarly, these parameters are substantial improvements over SK-14 and Sheffler-type parabolic solar cookers [25].…”

“…Further, it has been proposed that a plot between the exergy output power and δT, fitted with a second order polynomial, can be used to infer the peak exergy power of the device during a particular experiment [25]. The plot may also be used to infer the temperature difference gap between the temperatures corresponding to half exergy power points, on either side of the peak power point.…”

“…This value is by far the highest reported in literature, for any solar cooker. Table 4 summarizes the various exergy-based performance measuring parameters for these experiments and provides comparison of these parameters with those of other types of solar cookers [1,3,4,25].…”

“…Heat loss coefficient (W/K m 2 ) of the cooker is extracted by dividing the slopes of these curves by the aperture area of the cooker, while the specific heat loss coefficient (W/K kg m 2 ) is obtained by further division by the amount of water. The quality factor of the solar cooker may be evaluated by dividing the peak exergy gained to the exergy lost at that instant [25]. Figure 21 shows the graphs between the output exergy power E xo and the temperature difference δT.…”

The use of exergetic indicators in the food industry – A review

“…Another promising indicator is eco-exergy, a concept developed by Jørgensen (2007), in which the embodied information in living organisms in the form of DNA is assigned as potential energy work. Other less used indicators are the specific exergy destruction (Ducoulombier et al, 2007;Tambunan et al, 2010;Catton et al, 2011), the exergy loss rate (Pandey and Nema, 2011), the exergy-to-energy ratio , the exergy heating effectiveness (Akpinar, 2010b), the weighted mean overall exergetic efficiency (used in a country scale system) (Ahamed et al, 2011;Xydis et al, 2011), the exergetic factor, productivity lack, and relative irreversibility (Xiang et al, 2004), and peak exergy (used in solar drying analysis) (Kumar et al, 2012;Cuce and Cuce, 2013).…”