Performance of a convective, infrared and combined infrared- convective heated conveyor-belt dryer

Abstract

A conveyor-belt dryer was developed using a combined infrared and hot air heating system that can be used in the drying of fruits and vegetables. The drying system having two chambers was fitted with infrared radiation heaters and through-flow hot air was provided from a convective heating system. The system was designed to operate under either infrared radiation and cold air (IR-CA) settings of 2000 W/ m 2 with forced ambient air at 30°C and air flow of 0.6 m/s or combined infrared and hot air convection (IR-HA) dryer setting with infrared intensity set at 2000 W/m 2 and hot at 60°C being blown through the dryer at a velocity of 0.6 m/s or hot air convection (HA) at an air temperature of 60°C and air flow velocity 0.6 m/s but without infrared heating. Apple slices dried under the different dryer settings were evaluated for quality and energy requirements. It was found that drying of apple (Golden Delicious) slices took place in the falling rate drying period and no constant rate period of drying was observed under any of the test conditions. The IR-HA setting was 57.5 and 39.1 % faster than IR-CA and HA setting, respectively. Specific energy consumption was lower and thermal efficiency was higher for the IR-HA setting when compared to both IR-CA and HA settings. The rehydration ratio, shrinkage and colour properties of apples dried under IR-HA conditions were better than for either IR-CA or HA.

Microwave pyrolysis of biomass for bio-oil production: Scalable processing concepts

“…The conveyor belt system has been widely used throughout the drying and food processing industries [74][75][76]. To integrate a conveyor belt into a continuous microwave processing system while maintaining high and even power densities across the cavity geometry, a tunnel applicator was proposed by incorporating a 'self-cancelling' reflection step (see Figure 10) [77].…”

Recent advances of novel thermal combined hot air drying of agricultural crops

“…IR technology provides improved efficiency for electrical energy conversion into heat, increased surface heating uniformity, decreased net heating time, increased retention of product quality attributes, significant reduction in energy demand, and simple equipment set-up (El-mesery & Mwithiga, 2015;Sadin, Chegini, & Khodadadi, 2014). However, the most common application of IR heating involves combined IR and HAD.…”

Effect of IR intensity and air temperature on exergy and energy at hybrid infrared-hot air dryer

“…The hybrid IRHA technique accelerates the drying process, increases product quality and improves drying efficiency [5]. Most agricultural products have been successfully dried using this system including mushroom slices [3], blackberry leaves [6], jujube slices [7], onion slices [8], apple slices [9], peas [10], stale breads [11], and potato slices [12]. Lutovska et al [13] and Zhu and Jiang [14] performed their research on drying of peas and sweet potatoes, respectively.…”