Heat Transfer Mechanisms in Conductive Hydro-Drying of Pumpkin (Cucurbita maxima) Pieces

Abstract

Pumpkin pieces were dehydrated by conductive hydro-drying using the Refractance Window (RW) technology. The water bath temperature was fixed at 90 ± 2°C and the drying was carried out for 5 h. This study evaluated the convective effects of heat transfer by natural convection (NC) and forced convection (FC) due to the air in the top of the sample and the conductive effects on a Mylar sheet (MY) and a Mylar sheet covered with aluminum foil (MY/AL). Temperatures were measured at three sample points (bottom, middle, and top) during drying. The highest and lowest average temperatures were observed in NC-MY and FC-MY, respectively. The highest and lowest drying rates were obtained in FC-MY/AL and NC-MY, respectively. Analysis of variance indicated that the convection and convection–film interaction were statistically significant. Heat transfer due to the different mechanisms in the involved systems (water, drying film, product, and air) was examined.

Keywords:

• Drying
• Moisture content
• Temperature distribution