Latent heat thermal energy storage (TES) plays an important role in the advocation of TES in contrast to sensible energy storage because of the large storage energy densities per unit mass/volume possible at a nearly constant thermal energy. In the current study, a heat exchange device with a zigzag configuration containing multiple phase-change-materials (m-PCMs) was considered, and an experimental system was built to validate the model for a single PCM. A two-dimensional numerical model was developed using the ANSYS Fluent 14.0 software program. The energy fractions method was put forward to calculate the average Ste number and the influence of Re and Ste numbers on the discharge process were studied. The influence of phase change temperature among m-PCMs on the solidification process has also been studied. A new boundary condition was defined to determine the combined effect of the Re and Ste numbers on the discharging process. The modelling results show that for a given input power... [more]

Continuous processes with time delay, in general, have been represented by using first order models with time delay (FOMTD). For this models, the parameter can be graphically estimated by plotting the process response when a step is applied to the manipulated variable. For higher order process, the FOMTD have poor results and the second order models with time delay (SOMTD) are more suitable for identifying the process. Nevertheless there is no simple graphic method for estimating the parameters of the SOMTD.

This research presents a simple graphic method for estimating the second order model with time delay parameter. The method requires to read four point of the process response when a step change in the manipulated variable is applied. From these readings the values of the time delay, gain and time constants of the SOMTD model are estimated.

Moreover, in this research, and alternative approximation of the time delay is proposed, this to avoid unstable zeros on the controller e... [more]

Los procesos continuos con tiempo muerto, generalmente han sido representados utilizando modelos de primer orden con tiempo muerto (FOPDT). Para este modelo, los parámetros pueden ser estimados gráficamente utilizando la gráfica de la respuesta del proceso, al aplicársele un escalón en la manipulación del mismo. Para procesos de alto orden, los modelos FOPDT dan pobres resultados y los modelos de segundo orden con tiempo muerto (SOPDT) son los más indicados para responder a las necesidades de identificación. Sin embargo no existe un método gráfico sencillo para estimar los parámetros del modelo SOPDT.

En esta investigación se presenta un método gráfico sencillo para estimar los parámetros del modelo de segundo orden con tiempo muerto. El método consiste en la lectura de cuatro puntos de la gráfica de respuesta del proceso real al aplicársele un cambio tipo escalón en la manipulación. De esas lecturas se estiman los valores del tiempo muerto, de la ganancia, y de las constantes de t... [more]

This paper addresses the issues related to the rapid production of hydrogen from methane steam reforming by means of process intensification. Methane steam reforming coupled with catalytic combustion in thermally integrated microchannel reactors for the production of hydrogen was investigated numerically. The effect of the catalyst, flow arrangement, and reactor dimension was assessed to optimize the design of the system. The thermal interaction between reforming and combustion was investigated for the purpose of the rapid production of hydrogen. The importance of thermal management was discussed in detail, and a theoretical analysis was made on the transport phenomena during each of the reforming and combustion processes. The results indicated that the design of a thermally integrated system operated at millisecond contact times is feasible. The design benefits from the miniaturization of the reactors, but the improvement in catalyst performance is also required to ensure the rapid pr... [more]

Conventional high-pressure homogenization (HPH) is widely used in the pharmaceutical, chemical, and food industries among others. In general, its aim is to produce micron or sub-micron scale emulsions with excellent product characteristics. However, its energy consumption is still very high. Additionally, several limitations and boundaries impede the usage of high-pressure homogenization for special products such as particle loaded or highly concentrated systems. This article gives an overview of approaches that have been used in order to improve the conventional high-pressure homogenization process. Emphasis is put on the ‘Simultaneous Emulsification and Mixing’ process that has been developed to broaden the application areas of high-pressure homogenization.

Integrated process and control design approach for cyclic distillation columns is proposed. The design methodology is based on application of simple graphical design approaches, known from simpler conventional distillation columns. Here, a driving force approach and McCabe-Thiele type analysis is combined. It is demonstrated, through closed-loop and open-loop analysis, that operating the column at the largest available driving force results in an optimal design in terms of controllability and operability. The performance of a cyclic distillation column designed to operate at the maximum driving force is compared to alternative sub-optimal designs. The results suggest that operation at the largest driving force is less sensitive to disturbances in the feed and inherently has the ability to efficiently reject disturbances.

In this work, a distillation system is designed to purify dimethyl ether (DME) from its reaction by-products in the conversion of flare gas into a useful energy product. The distillation equipment has a size constraint for easy transportation, making process intensification the best strategy to efficiently separate the mixture. The process intensification distillation techniques explored include the dividing wall column (DWC) and a novel semicontinuous dividing wall column (S-DWC). The DWC and the S-DWC both purify DME to fuel grade purity along with producing high purity waste streams. An economic comparison is made between the two systems. The DWC is a cheaper method of producing DME however the purity of methanol, a reaction intermediate, is not as high as the S-DWC. Overall, this research shows that it is possible to purify DME and its reaction by-products in a 40-foot distillation column at a cost that is competitive with Diesel.