Comparative Study of Wireless Versus Standard Thermocouples for Data Gathering and Analyses in Rotary Cookers

Abstract

The performance of a wireless temperature sensor was compared with that of a conventional thermocouple for gathering heat penetration data. A central composite rotatable design experimental design with three different processing conditions (glycerin concentration [70–100%], retort temperature [111.6–128.4C] and retort speed [4–24 rpm]) were employed using 307 × 409 cans containing the particulate fluid to compare the performance of the two devices. Experiments were performed in a fixed axial mode of rotation in a rotary cooker, and only liquid temperature was measured using both temperature sensors. The heating rate index, fh, cook value to lethality ratio, CO/FO, were evaluated and compared using a t‐test. Statistically there were no differences (P > 0.05) in the performance of the two systems with respect to the parameters tested; however, compared with conventional thermocouples, the wireless sensors were more stable, and more practical for use in rotary cookers especially for free axially rotating cans. PRACTICAL APPLICATIONS In order to meet the recent industrial demand to optimize the thermal process in rotary cookers, it is imperative that time‐temperature data during processing be accurately gathered. To gather temperature data in rotary retorts, standard thermocouples equipped with a slip ring assembly are used together with a data acquisition set up. A biaxially rotating can, as in continuous cooker simulators, would require two such slip rings: one at the can level and one at the retort level, making the data gathering more cumbersome. To assist in such scenarios, use of self‐contained “wireless” sensors is more practical. This study focuses on concerns about using wireless sensors due to their own volume influencing the temperature measurement at the critical control point. This study will demonstrate that wireless sensors could potentially replace standard thermocouples for the measurement of temperature for convection‐heated food in large size 307 × 409 cans.

Heat transfer phenomena during thermal processing of liquid particulate mixtures—A review

“…For data gathering under such situations, researchers have used self-contained wireless sensors which gather data continuously and transmit signals to a computer. Dwivedi and Ramaswamy (2010b) showed that there were no statistical differences between the performance of wireless systems compared to conventional systems and in fact, the wireless sensors were reported to be relatively more stable for rotary autoclaves especially for free axially rotating cans. By adopting wireless technology, 20-80% of the wiring costs in industrial application can be eliminated and also gives a chance of real time tracking of the free movement of particles (Wang et al, 2006).…”

“…Various techniques have been developed for monitoring particle temperatures during agitation. Depending on the purpose of collection of heat penetration data, these techniques may range from the use of normal thermocouples (Deniston et al, 1987;Meng, 2006;Sablani, 1996) to the use of other technologies like wireless sensors (Awuah et al, 2007b;Dwivedi and Ramaswamy, 2010b;Lesley, 1987;Wang et al, 2006), time-temperature indicators like liquid crystals (Balasubramaniam and Sastry, 1995;Stoforos and Merson, 1991;Zitoun andSastry, 1994) and, chemical (Van Loey et al, 1995;Hendrickx et al, 1995;Weng et al, 1992) and biochemical indicators (Pflug et al, 1980a(Pflug et al, , 1980bSilva et al, 1994). …”

“…Dwivedi and Ramaswamy (2010b) developed an innovative methodology to measure U and h fp under conditions where temperature monitoring is not possible. This methodology is particularly useful when an alternate mode of processing is available where particle-temperatures can be measured.…”

“…Dwivedi and Ramaswamy (2010b) coupled experimentally evaluated U from fluid temperatures (measured using wireless sensors) in the biaxial mode with values of ratio of U/h fp in fixed axial mode to compute h fp for the biaxial mode. This approach gave consistent results with the traditional approach of measuring both liquid and particular temperature.…”