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In previous investigations, the nonlinear hypothesis use the linear bounded maps. Nonlinear hypothesis are described as the combination of the first order terms, and after of the mentioned combination, one bounded map is applied to alter the result. This document proposes two nonlinear hypothesis which use different structures instead of using the linear bounded maps. They are termed as novel nonlinear hypothesis and second order nonlinear hypothesis and their goal is to improve the second order processes modeling. The proposed nonlinear hypothesis are described as the combination of the first order and second order terms. Since the delta parallel robot is a second order process, it is an excellent platform to prove the effectiveness of the two proposed hypothesis.

In this article, a fuzzy logic model is proposed for more precise hourly electrical power demand modeling in New England. The issue that exists when considering hourly electrical power demand modeling is that these types of plants have a large amount of data. In order to obtain a more precise model of plants with a large amount of data, the main characteristics of the proposed fuzzy logic model are as follows: (1) it is in accordance with the conditions under which a fuzzy logic model and a radial basis mapping model are equivalent to obtain a new scheme, (2) it uses a combination of the descending gradient and the mini-lots approach to avoid applying the descending gradient to all data.

In this paper, an evaluation of the performance and operating parameters of a hybrid compression/absorption chiller coupled with a low-capacity solar concentrator is presented. The study was carried out using energy and mass balances applied to each component of each system. The variables evaluated in the hybrid chiller were the cooling power, the supply power, the Coefficient of Performance (COP) of both cooling systems and the ratio between heat and power. The diameter and temperature of the hot spot as well as the performance of the dish collector were evaluated. The changed parameters were the heat removed by each refrigeration system, the condenser temperature, the evaporator temperature, the concentration ratio and the irradiance. Results have shown that the compression system can produce up to 53% more cooling power than the heat supplied to the hybrid system. Meanwhile, the absorption system produces approximately 20% less cooling power than the supplied heat. It has also been found that, for the cooling power produced by the hybrid cooler to be always greater than the heat supplied, the cooling power provided by the absorption system should preferably be between 20% and 60% of the total, with a Stirling engine efficiency between 0.2 and 0.3 and a condensation temperature from 28 to 37 &deg, C. Likewise, it has been found that the compression system can produce cooling power up to 3 times higher than the heat of the Stirling engine hot source, with Th = 200 &deg, C and &eta, s = 0.3. Finally, it has been found that, in a low-capacity solar concentrator, on a typical day in Mexico City, temperatures in the hot spot between 200 and 400 &deg, C can be reached with measured irradiance values from 200 to 1200 W/m2.

In this work, the performance of a single effect absorption cooling system fed by solar thermal energy is evaluated. The absorption chiller includes a membrane-based microchannel desorber using three types of nanoparticles: Al2O3, CuO, or carbon nanotubes (CNT). Correlations available in the open literature to calculate the thermal conductivity of nanofluids are reviewed. Using experimental data for the water-lithium bromide solution (H2O-LiBr) with Al2O3 and CNT nanoparticles, the most appropriate correlation for thermal conductivity is selected. Nanofluid properties are evaluated using a concentration of nanoparticles of up to 5% in volume. The largest increase in the desorption rate (7.9%), with respect to using pure H2O-LiBr solution, is obtained using CNT nanoparticles and the maximum concentration of nanoparticles simulated. The performance of the chiller is evaluated and the daily solar coefficient of performance (SCOP) for the solar cooling facility is obtained. The best improvement with respect to the conventional system (without nanoparticles) represents an increase in the cooling effect of up to 6%. The maximum number of desorber modules recommended, always lower than 50, has been identified. This research was funded by FEDER/Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investigación/_Proyecto (DPI2017-83123-R), and science research grant SIP20190076, by the National Polytechnic Institute of Mexico (IPN). A.Z. thanks CONACYT for the 740638 scholarship granted.

In this work, the numerical simulation of the non-isothermal steady co-extrusion fiber spinning with flow-induced crystallization is explored. The model is based on the formulation originally proposed by China et al. in which Newtonian and Phan-Thien-Tanner (PTT) fluids are considered the core and the skin layer, respectively. The polymeric flow rate fraction, Deborah dimensionless number and the PTTs parameters on the temperature, the velocity and the crystallization profiles are analyzed. The numerical results show: the temperature profile is sensitive to the polymeric layer flow rate and the deformation parameters (shear thinning and extensional), the tensile stress induced crystallization parameter has a strong influence at the onset of the process, increasing drastically temperature and crystallinity.

En este trabajo se muestran los resultados de la transferencia de calor y la caida de presion de una superficie extendida con aletas tipo espina y arreglo de tubos en V invertida. La superficie extendida se compone de un tubo de aluminio y una cinta con cortes, del mismo material, que forman aletas tipo espina al enrollarla al tubo. El tubo forma un serpentin con un arreglo de tubos tipo V invertida de acuerdo a la direccion del flujo de aire. La caracterizacion experimental de la superficie se realizo en un tunel de viento en el intervalo de velocidades del flujo de aire de 0.5 a 5 m/s, para un flujo constante de agua caliente con una temperatura de 40°C que circula en el interior del serpentin. En base a los resultados experimentales se determinaron las correlaciones para el calculo de la transferencia de calor y la caida de presion en la superficie extendida con aletas tipo espina y arreglo de tubos en V invertida. Se compararon los resultados de la transferencia de calor con los obtenidos por otros autores que han probado superficies extendidas con aletas tipo espina pero con un arreglo de tubos en linea. Se encontro que la superficie extendida con aletas tipo espina y arreglo de tubos en V invertida presento una mayor intensidad en el proceso de transmision de calor por conveccion forzada a velocidades menores a 1 m/s. Palabras Clave: superficie extendida, aletas tipo espina, arreglo de tubos en V invertida, transferencia de calor, caida de presion.

This work investigates experimentally the adiabatic absorption of ammonia vapour into ammonia–lithium nitrate solution using a full cone nozzle and an upstream single-pass subcooler. Data are representative of the working conditions of adiabatic absorbers in absorption chillers. The nozzle was located at three different heights inside the absorption chamber, separated 0.165, 0.205 and 0.225 m from the bottom liquid surface. The diluted solution mass flow rate was modified between 0.04–0.08 kg/s and the solution inlet temperature between 23.5 and 30.6 °C. This paper analyzes the influence of these variables on the absorption ratio, mass transfer coefficient, outlet subcooling and approach to equilibrium factor. A linear relation between the inlet subcooling and the absorption ratio is observed. The approach to equilibrium factor for the conditions essayed is always between 0.64 and 0.87. Mass transfer coefficients and correlations for the approach to equilibrium factor and the Sherwood number are obtained. Results are compared with other ones reported in the literature.

This paper presents the experimental assessment of the adiabatic absorption of ammonia vapour into an ammonia–lithium nitrate solution using a fog jet nozzle. The ammonia mass fraction was kept constant at 46.08% and the absorber pressure was varied in the range 355–411 kPa. The nozzle was located at the top of the absorption chamber, at a height of 205 mm measured from the bottom surface. The diluted solution flow rate was modified between 0.04 and 0.08 kg s −1 and the solution inlet temperature in the range 25.9–30.2 °C. The influence of these variables on the approach to adiabatic equilibrium factor, outlet subcooling, absorption ratio and mass transfer coefficient is analysed. The approach to adiabatic equilibrium factor for the conditions essayed is always between 0.82 and 0.93. Pressure drop of the solution entering the absorption chamber is also evaluated. Correlations for the approach to adiabatic equilibrium factor and the Sherwood number are given.

This paper presents the experimental heat transfer evaluation during subcooled and saturated boiling of ammonia–lithium nitrate solution in a fusion plate heat exchanger, acting as a vapor generator under operating conditions representative of single-effect absorption machines. The solution flow rate and outlet temperature were modified in the ranges of 0.041–0.083 kg/s and 78–97 °C, respectively. The region where vapor bubbles begin to arise is estimated using a correlation for the wall superheat required for the onset of nucleate boiling. Results show that subcooled boiling is present in the generator. The initial boiling temperature is about 3.1 °C lower than the saturation temperature. The influence of the heat and mass fluxes on the boiling heat transfer coefficient is analyzed. The paper offers a correlation for the Nusselt number, including the subcooled and saturated boiling regions.

This paper presents the thermal and pressure-drop experimental evaluation of a fusion plate heat exchanger (PHE) during boiling conditions of a solution of lithium nitrate in ammonia. The data are representative of the working conditions of generators in single-effect absorption chillers. The solution flow rate and outlet temperature were modified in the ranges of 0.041–0.083 kg/s and 78–95 °C, respectively. Correlations for single-phase-flow heat transfer are used to characterize the boiling heat transfer. The influences of the heat flux, mass flux and exit-vapour quality are analyzed. Boiling heat-transfer coefficients and correlations for the Nusselt number are obtained. Results are compared with Cooper’s and Ayub’s correlations for boiling heat transfer. Pressure drop in the solution side was also measured and one correlation was obtained to characterize the frictional pressure drop under boiling conditions.

Single-effect absorption refrigeration hybridized with mechanical vapor compression in a vapor circuit is known as the absorption cycle with an integrated booster compressor. In this study, the compressor is located between the evaporator and the absorber. This paper presents a numerical model of this cycle with ammonia-lithium nitrate solution as the working pair. It is based on UA−ΔTlm models for separate regions of plate-type heat exchangers. The results are offered as a function of external circuit flow parameters. Different pressure ratios of the compressor were tested for a wide range of hot water driving temperatures (55–95 °C), showing that low values are more beneficial. This cycle allows for working at lower driving temperatures than the single-effect cycle, with low electricity consumption. At the same driving temperature, the capacity is augmented with an increased compressor pressure ratio, thus allowing for demand matching of the cooling. This cycle, operating with hot water at 67 °C with a pressure ratio of 2.0, has the capacity of a single-effect absorption cycle at 94 °C. The electrical COP was found to be higher than that in an ammonia vapor compression cycle for comprehensive working conditions.

The hot water temperature that maximizes the overall instantaneous efficiency of a solar cooling facility is determined. A modified characteristic equation model is used and applied to single-effect lithium bromide–water absorption chillers. This model is based on the characteristic temperature difference and serves to empirically calculate the performance of real chillers. This paper provides an explicit equation for the optimum temperature of vapor generation, in terms of only the external temperatures of the chiller. The additional data required are the four performance parameters of the chiller and essentially a modified stagnation temperature from the detailed model of the thermal collector operation. This paper presents and discusses the results for small capacity machines for air conditioning of homes and small buildings. The discussion highlights the influence of the relevant parameters.